CN102081108B - Reduce the signal acquiring system of the probe load of equipment under test - Google Patents

Abstract

The present invention relates to reduce the signal acquiring system of the probe load of equipment under test.A kind of signal acquiring system has signal acquisition probe, and described signal acquisition probe has the probe tip circuit being coupled to resistance center conductor signal cable.The compensation system that the resistance center conductor signal cable of signal acquisition probe is coupled in signal processing equipment via the input node in signal processing equipment and input circuit.Signal acquisition probe and signal processing equipment have the time constant of mismatch at input node, and the system that wherein compensates provides zero pole point to keep flatness in signal acquiring system frequency bandwidth.

Description

Reduce the signal acquiring system of the probe load of equipment under test

Cross-Reference to Related Applications

This part continuation application requires the U.S. Patent Application Serial of JIUYUE in 2009 submission on the 30th The priority of number 12/571,236.

Technical field

The present invention relates generally to from equipment under test collection (acquire) signal and more specifically relates to And a kind of use has and reduces the signal acquisition probe (probe) of electric capacity and reduce equipment under test The signal acquiring system of load.

Background technology

Traditional passive voltage probe 10 is general by the resistance-capacitance parallel-connection network at probe tip 14 Network 12 (is shown as R in FIG_TAnd C_T) composition, this resistance-capacitance parallel network 12 via Resistance center conductor signal cable (resistive center conductor signal cable) 16 couplings Close to the compensation circuit 18 compensated in box.Compensate circuit 18 and there is resistive element R_C1And R_C2 And capacity cell C_C。R_C1Connect and R with cable 16_C2With variable condenser C_CSeries connection. Compensate circuit 18 and be coupled to such as oscillograph, frequency spectrum analyser, logic analyzer etc Measure test instrunment 22 input circuit 20.Usually, oscillographic input circuit 20 wraps Include and be shown as R_TSAnd C_TSInput resistance-capacitance network 24, its with provide with 10 to 20 pico farads (pf) the switch input attenuation circuit of the oscillograph input impedance of the 1M Ω that electric capacity is in parallel is (not Illustrate) it is associated.The defeated of preamplifier 26 is coupled in the output of switch input attenuation circuit Enter.Oscillograph is calibrated to provide the nominal from the oscillographic output being input to preamplifier Flat frequency response transmission function.

Compensating circuit 18 provides the resistance of cable 16 and electric capacity termination (termination) with Littleization reflects and has, to measuring test instrunment 22 offer, the biography that nominal flat frequency responds Delivery function.Compensated variable capacitance device C_CIt is that user is adjustable with at independent channel oscilloscope Electric capacity and the electric resistance partial pressure ratio of probe is mated during the change of input capacitance.Resistive element R_C1Carry Termination matching (wherein cable for resistance cable 16 in high frequency with oscillograph input Z₀≈155Ω).With variable condenser C_CThe R of series connection_C2Improve the electric capacity in oscillograph to bear Cable termination in load.

Needle point resistance R_T, cable termination resistor R_C1With input resistance R_TSFor DC to low Frequently input signal forms potentiometer attenuation network.In order to adapt to the input signal of wide frequency ranges, Use across needle point resistive element R_TBranch (shunt) needle point capacitor C_TAnd across end Connecting resistance element R_TSInput capacitor C_TSWith branch terminating capacitor C_CCompensate resistance to divide Depressor attenuation network.In order to obtain the potentiometer of correct compensation, probe tip resistance-capacitance is in parallel The time constant of network 12 is necessarily equal to include C_cableAnd C_CTerminating resistor-electric capacity parallel-connection network The time constant of network 24.

Correctly terminate this resistance cable 16 with the characteristic impedance of resistance cable 16 to require to compensation Network 18 adds relatively large shunt capacitance C_C.This is in addition to cable body capacitance C_CABLEOutside. Such as, by the manufacture of Tektronix company and the P2222 10X of sale of Beaverton, Oregon The needle point resistance R of passive probe_TWith electric capacity C_TIt is selected as being given to the oscillograph input of 1M Ω The 10X decile (divide) of impedance.Ignore the minimum needle point electric capacity of any other parasitic capacitance C_TIt it is cable body capacitance C_CABLE、C_CWith C_TS/ 9th of sum.For above-mentioned parameter For, C_TNeedle point electric capacity be about 8pF to 12pf.(it is C to input capacitance_TWith C_CABLE、 C_CWith C_TSSum connect) by the drives being monitored and therefore represent probe circuit is added The tolerance of how many loads.

Fig. 2 illustrates another passive voltage probe and oscillograph configuration, wherein preamplifier 28 It is configured to current amplifier.This configuration has the probe with Fig. 1 and oscillograph configuration is identical Restriction.Probe has the compensation circuit in probe compensation box and oscillograph is defeated at oscillograph Enter place and there is the traditional 1M Ω resistance in parallel with the electric capacity of 10 to 20pf.Existing passive voltage The major defect of probe and oscillograph configuration is the output of heart conductor signal cable in electrical resistance Midband and quite a few of high-band frequency signal code at place are terminated capacitor C_CPoint Road is to ground.Further, since before resistance center conductor signal cable is terminated at oscillograph input, So the parasitic capacitance of oscillographic input circuit serves as non-end extra current being shunted to ground Connect transmission line.

Probe tip electric capacity and resistance center conductor signal cable affect the total of traditional passive probe Body bandwidth.And, probe tip input due to low capacity reactance in parallel with high input resistance and Low input impedance is presented to equipment under test under high frequency.Reduce probe tip electric capacity to improve electric capacity Reactance requires that the miscellaneous part value of regulation divider network is to maintain the network compensated.Previously, this Realized by the resistance in raising probe tip.But, this improves the dividing potential drop of network Ratio, result is applied to the decay of the signal of probe to be increased.Being input to oscillographic reduction signal can Compensating with the gain by raising oscillograph input circuit, this causes the increase of noise on signal Thus reduce the overall signal to noise ratio of instrument.

Exist and provide relatively high impedance and the specific type of decay to 50 ohm of input oscillographs Passive probe.Z₀Probe has and is coupled to the relatively low defeated of 50 ohm of lossless coaxial cables Enter resistance (5000 ohm or less).Electric capacity at probe tip is generally less than by probe Parasitic capacitance produce 1pf.In the particular embodiment, probe tip resistance is 450 Europe Nurse, is coupled to oscillographic 50 ohm of inputs via 50 ohm of lossless coaxial cables, and this produces 10X passive divider network.Be input to the voltage of this probe compared with traditional passive probe by It is restricted in the size of input resistor.Additionally, low input resistance may give DC signal Caused multi load.

USP 6,483,284 shown in Fig. 3 teaches the broadband probe using pole zero cancellation. With resistor R_tabWith capacitor C_tabThe resistor R of series connection_tipWith capacitor C_tipParallel probe Needle point network detects from the signal of equipment under test and via intimate lossless coaxial cable 40 Signal is coupled to compensate network.Capacitor C_tabRepresent the trace on such as circuit board, coaxial electrical Electric capacity in the needle point circuit of cable etc.Cable termination resistor R_eIt is connected in series in cable Between 40 and the reversed input terminal of operational amplifier 42.Non-inverting input is coupled to jointly. That connect between the input terminal and lead-out terminal of operational amplifier 42 is resistor R_fbAnd electricity Container C_fbParallel combination, wherein resistor R_pkWith C_fbSeries connection.Needle point resistor in parallel R_tipWith capacitor C_tipCreate zero point and resistor R_tabWith capacitor C_tabCombination create pole Point.Limit is by the resistor R compensated in network_fbWith capacitor C_fbCreate and zero point is by resistance Device R_pkWith capacitor C_fbCreate.The zero point created in probe tip network and limit are by compensating Pole and zero in network offsets.End user device is coupled in the output compensating network, all Such as oscillograph etc..The time constant of this teaching two RC networks of statement must be equal so that zero Point and pole cancellation and probe have constant-gain.And, operational amplifier 42 is broadband A part for probe circuit rather than a part for end user device.

Summary of the invention

Thus, the present invention is that a kind of signal with signal acquisition probe and signal processing equipment is adopted Collecting system.Signal acquisition probe has the probe tip being coupled to resistance center conductor signal cable Circuit.Resistance center conductor signal cable is coupled to the input node of signal processing equipment.Input Node is also coupled to the compensation system being arranged in signal processing equipment via input circuit.Letter Number acquisition probe and signal processing equipment have (mismatched) of mismatch at input node Time constant, the system that wherein compensates provides zero pole point to in signal acquiring system frequency bandwidth Keep flatness.

Compensation system has input amplifier and the input being coupling in input amplifier and output Between the feedback loop circuit that is associated.Feedback loop circuit can be configured with variable resistance and electric capacity Element and input amplifier can be configured to current amplifier.Variable resistance and capacity cell May be embodied as having resistance value and capacitance for setting corresponding resistor and capacity cell Multiple depositors.Feedback loop circuit can pass through resistive element and the resistance of the first series coupled (it is with second and the at least the first variable gain voltage source of element and capacity cell series coupled The resistive element of three series coupled and capacity cell are in parallel) implement.Feedback loop circuit can also Including the second variable increasing with the resistive element of the second series coupled and capacity cell series coupled Benefit voltage source.

The input circuit of signal processing equipment preferably provides resistance center conductor signal cable Resistance and electric capacity termination in the attenuator circuit of at least one.Input node is coupled to signal road Footpath, the other end of this signal path is coupled to the resistance unit that the input of neighbouring input amplifier is arranged Part is to form the transmission line of termination.On-off circuit be disposed in signal processing equipment for via Attenuator circuit input node be selectively coupled to compensation system and for additional resistance- Capacitance fade network is optionally coupling between input node and attenuator circuit.

Probe tip circuit has at least the first resistive element in parallel with capacity cell.Probe pin Point circuit can also have multiple first resistive elements in parallel with multiple capacity cells to be formed High voltage signal acquisition probe.One or more capacity cells have the scope at 2 to 5 pico farads Interior effective capacitance.

A kind of calibration process for signal acquiring system comprises the following steps: use signals collecting Probe and signal processing equipment gather the digital value of wideband content signal as alignment of waveforms；? The wideband content signal in being stored in signal processing equipment is determined at common location on waveform At least the first measurement error value between reference calibrations waveform and alignment of waveforms；According in common position At least the first measurement error value at the place of putting determines error factor；And measurement error because of In multiple depositors in the feedback loop circuit of the input amplifier that son is applied to compensation system The suitably register value of feedback loop depositor.Then for alignment of waveforms and calibration reference waveform Each follow-up common location determines measurement error value and error factor.Alternatively, by Determine at the common location on waveform that at least one in time location and frequency location sets Wideband content signal reference calibrations waveform in being stored in signal processing equipment and alignment of waveforms Between multiple first measurement error value, and according on multiple first measurement error value and waveform Common location determine error factor.Having been directed towards alignment of waveforms and calibration reference wave After last common location in shape determines measurement error value and error factor, gather width Frequently the new digital value collection of content signal is as alignment of waveforms.By new alignment of waveforms and control gauge Model compares to examine this calibration.If this calibration is in calibrating standard, then storage input is put The register value in multiple depositors in the feedback loop circuit of big device and show calibration process Successful result.

If alignment of waveforms is not in calibrating standard, it is determined that whether calibration process alreadys more than repeatedly For time (iteration time) limits value.If calibration process is not above iteration time limit Value processed, then the common location on waveform is set to initial position.Then for alignment of waveforms and Each common location or multiple common location of calibration reference waveform determine one or more measurement Error amount and error factor.Having been directed towards on alignment of waveforms and calibration reference waveform After rear common location determines measurement error value and error factor, gather wideband content letter Number new digital value collection as alignment of waveforms.New alignment of waveforms is compared with calibrating standard Relatively to examine this calibration.If new alignment of waveforms is not the most in calibrating standard and calibrates Journey has timed out, then multiple in the feedback loop circuit of input amplifier before being stored in calibration process Initial value in depositor, and show the unsuccessful result of calibration process.

The digital value gathering wideband content signal includes signal acquisition probe as alignment of waveforms It is attached to the additional step of signal processing equipment.In signal processing equipment detection signal acquisition probe The presence or absence of probe memory, and if probe memory existence, probe storage The storage content of device is loaded in signal processing equipment.Signal processing equipment detection is stored in probe The existence of the probe correction constant in memorizer, and probe correction constant is applied to input puts The suitable register value in multiple depositors in the feedback loop circuit of big device.If signals collecting Probe does not has probe memory, then nominal register value is applied to the feedback loop of input amplifier Multiple depositors in circuit.

Can be by using fast Fourier transform the numeral of wideband content signal alignment of waveforms Value is converted into frequency domain representation and the common frequency position on waveform determines and is being stored in letter The frequency domain representation of the wideband content signal reference calibrations waveform in number process instrumentation and alignment of waveforms Frequency domain representation between measurement error value, implement calibration process in a frequency domain.Wideband content is believed The frequency domain representation of number reference calibrations waveform is stored as frequency-domain waveform.

When combining appended claims and accompanying drawing and reading, by the following detailed description aobvious and It is clear to the target of the present invention, advantage and novel feature.

Accompanying drawing explanation

Fig. 1 is the representative schematic diagram of prior art passive probe.

Fig. 2 is the representative schematic diagram of another prior art probe circuit.

Fig. 3 is the representative schematic diagram of other prior art probe circuit.

Fig. 4 is the block diagram of the signal acquiring system according to the present invention.

Fig. 5 is the representative frame according to the signal processing equipment in the signal acquiring system of the present invention Figure.

Fig. 6 is the representative schematic diagram of the signal acquiring system according to the present invention.

Fig. 7 illustrates the signal acquiring system compensated with and without feedback cross (crossover) Representative frequency response.

Fig. 8 A and 8B illustrates the calibration process flow process of the signal acquiring system for calibrating the present invention Figure.

Fig. 9 is the representative schematic diagram of the attenuator circuit in the signal acquiring system of the present invention.

Figure 10 is the signal of the high voltage signal acquisition probe in the signal acquiring system of the present invention Figure.

Figure 11 is the alternative embodiment of the signal acquiring system of the present invention.

Detailed description of the invention

With reference to Fig. 4, it is shown that adopt according to the signal of the probe load reducing equipment under test of the present invention The high level block diagram of collecting system 50.Signal acquiring system 50 has and includes resistance center conductor signal The signal acquisition probe 52 of cable 54.Signal cable is coupled to the input of signal processing equipment 58 Node 56.Input node 56 is also coupled to the Acquisition Circuit 60 in signal processing equipment 58. Acquisition Circuit 60 generates the digital value of the input signal from signal acquisition probe 52.Input letter Number digital value be coupled to controller 62 for processing further.Controller 62 can be number Word value is coupled to process circuit 64 for formatted digital value and the digital value formatted Display is on display device 66.

In traditional probe-system of Oscillograph, for flat frequency and phase response to signal Every grade of path compensates.Calibrate oscillograph to provide nominal flat frequency to ring Should.Signal acquisition probe is attached to oscillograph and uses the termination in probe and compensate circuit Calibration probe is to produce the nominal flat frequency response relative to oscillograph input.Obtained by Probe-system of Oscillograph have signal acquisition probe and oscillograph input time constant coupling with Probe system of Oscillograph bandwidth produces flat frequency response.In the present invention, signal is adopted The collection probe 52 high frequency input impedance at equipment under test is by reducing signal acquisition probe 52 Input capacitance and be enhanced.The obtained structure of the present invention makes the spy of signal acquisition probe 52 Pin needle point circuit and the time constant of circuit of the input node 56 across signal processing equipment 58 Mismatch.Compensation system 68 in Acquisition Circuit 60 provides and makes to be produced by the time constant of mismatch Signal acquiring system 50 frequency response planarization zero pole point pair.

Below by describing the signal processing equipment 58 of the present invention about digital oscilloscope, such as show Ripple device, logic analyzer, Aristogrid etc..The signal that Fig. 5 depicts as the present invention is adopted The high level block diagram of the digital oscilloscope 100 of a part for collecting system 50.Usually, oscillograph 100 include multiple signalling channel, are wherein connected to from quilt in the input of each signalling channel Measurement equipment (DUT) gathers various types of signal acquisition probes 105,110 of the signal of telecommunication, all Such as passive and active voltage probes, current probe etc..Oscillograph 100 signalling channel input coupling Close corresponding signalling channel Acquisition Circuit 115,120.Corresponding Acquisition Circuit 115,120 Come its corresponding input letter according to the sampling clock provided by internal sample clock generator 122 Number sample.

Acquisition Circuit 115,120 all includes preamplifier, analog to digital conversion circuit, triggering electricity Road, withdrawal device (decimator) circuit, support acquisition memory etc..Acquisition Circuit 115, 120 operation time can with certain one or more measured signal of sample rate digitized thus produce One or more samplings being adapted for controller 125 accordingly or processing circuit 130 use Stream.In response to the order received from controller 125, Acquisition Circuit 115,120 changes preposition Amplifier feed-back value；Trigger condition, withdrawal device function and other collection relevant parameters.Gather Its corresponding obtained sample streams of 115,120, circuit is sent to controller 125.

Trigger circuit 124 to be illustrated as separating with Acquisition Circuit 115,120, but this area Skilled artisans appreciate that it can be inside Acquisition Circuit 115,120.Trigger circuit 124 Trigger parameter is received from controller 125 in response to user's input, such as activation threshold value level, Postpone (hold off), post trigger collection etc..Trigger circuit 124 and regulate Acquisition Circuit 115,120 with the digital sample from DUT capture measured signal.

Controller 125 operates to locate the one or more of reason Acquisition Circuit 115,120 offer The sample streams that gathers thus generate the corresponding fluxion of sampling that is associated to one or more sample streams According to.That is, every lattice (per division) expected time and every lattice volt display parameters are given, control Device 125 processed operate with amendment or the initial data that is associated with the sample streams gathered of rasterizing from And produce and there is every lattice expected time and the corresponding Wave data of every lattice volt parameter.Controller 125 normalization can also have every lattice unexpected time, every lattice volt and every lattice current parameters Wave data thus produce have expectation parameter Wave data.125 Wave datas of controller There is provided to and process circuit 130 for being subsequently presented on display device 135.

The controller 125 of Fig. 5 preferably includes processor 140, supports circuit 145 and storage Device 155, described processor 140 is such as by motorola inc's system of Schaumburg, IL The PowerPC making and selling^TMProcessor.Processor 140 is (all with conventional support circuitry 145 As power supply, clock circuit, cache memory, buffer/expander etc. and auxiliary are held The circuit of the software routines that row is stored in memorizer 155) cooperation.Like this, it is contemplated that make herein Some process steps discussed by software process may be implemented within hardware, such as with Processor 140 cooperates to perform the circuit of each step.Controller 125 also with input/output (I/O) circuit 150 docks.Such as, I/O circuit 150 can include that keypad, instruction set Standby, touch screen or other be suitable to the device that provides user to input to controller 125 and export. Controller 125 operation of adaptive Acquisition Circuit 115,120 in response to such user input To perform various data acquisitions, to trigger, process and display communication and other functions.It addition, User's input can be used to trigger automatic calibration function or adaptive display device 135, logic is divided Analysis or other operating parameters of other data acquisition equipments.

Memorizer 155 can include volatile memory, such as SRAM, DRAM and its His volatile memory.Memorizer 155 can also include non-volatile memory devices (such as Disc driver or tape-shaped medium's etc.) or programmable storage (such as EPROM etc.). Signal source 157 generates the wideband content signal for probe compensation.Being preferable to carry out in the present invention In example, wideband content signal is rapid edge square wave.Alternatively, signal source 157 can be Contour (leveled) frequency conversion sine wave generator.

Although the controller of Fig. 5 125 is depicted as being programmed to execute the various of the foundation present invention Control the general purpose computer of function, but the present invention can be with the most such as special IC (ASIC) hardware is implemented.Like this, processor 125 as described herein is intended to by extensively Free burial ground for the destitute is construed to be equivalently performed by hardware, software or by a combination thereof.

Fig. 6 is the representative schematic diagram of the signal acquiring system 200 according to the present invention.In Fig. 5 Same element in figure 6 by labelling in the same manner.Signal acquisition probe 105 has and comprises probe The detecting head 202 of needle point circuit 204, resistance center conductor signal cable 212 and resistor unit Part 216.Probe tip circuit 204 has and the resistive element of capacity cell 208 parallel coupled 206, capacity cell 208 is connected with resistive element 210.For typical 10X probe, electricity Hold element 208 electric capacity in the range of 2-5 pico farad (pf) with to equipment under test provide low defeated Enter electric capacity.Probe tip circuit 204 is coupled to one end of resistance center conductor signal cable 212. The other end of resistance center conductor signal cable 212 is coupled to numeral via resistive element 216 and shows The BNC input node 214 of one of the signal acquisition circuit 115,120 in ripple device 100.Electricity Resistance center conductor signal cable preferably has the resistance center conductor that resistance is 39 Ω/ft Coaxial cable.Resistance center conductor signal cable 212 have by shown in capacitor 213 over the ground Electric capacity.BNC input node 214 is coupled to on-off circuit 220, this on-off circuit 220 and then There is provided signal acquisition probe 105 to the coupling of input circuit 226.Resistive element 216 and input Circuit 226 (is illustrated as being composed in parallel with capacity cell 229 by resistive element 227 typically Attenuator circuit) in resistive element 231 combine, make resistance center conductor signal cable 212 Terminate with its characteristic resistance impedance.In a preferred embodiment of the invention, resistance center conductor letter The termination capacitor of number cable 212 is of about 40pf and terminating resistor is of about 150 Ω.It addition, 1.2 meters of resistance center conductor signal cables 212 have the direct-to-ground capacitance of about 40pf by chance.Electricity The direct-to-ground capacitance of resistance center conductor signal cable 212 can be held by changing the length of cable Change places change.Resistive element 216 has the resistance value of 100 Ω and resistive element 231 has The resistance value of 50 Ω.Resistive element 231 is physically possible near as current amplifier The input of input amplifier 238, to reduce BNC input node 214 and input amplifier 238 Between the non-terminated parasitic capacitance of signal traces.BNC and signal traces are here assumed to be It is designed to the characteristic impedance of 50 Ω correctly to be terminated by resistive element 231.Input circuit 226 also make resistance center conductor signal cable 212 terminate with its characteristic capacitance impedance.

On-off circuit 220 has for selecting via 226 probe tip circuit 204 of input circuit Selecting property be coupled to compensation system 224 or probe tip circuit 204 and input circuit 226 it Between couple the booster resistor-capacitor composed in parallel by resistive element 230 and capacity cell 232 The switch element 222 of attenuation network 228.Resistance-capacitance attenuator network 228 provides requiring The backwards compatibility of the classical signal acquisition probe of the oscillograph input impedance of 1M Ω.Switch element 222 relay switches preferably receiving switch command from controller 125.

Signal acquisition probe 105 preferably has information (the such as probe class comprised about probe Type, serial number etc.) memorizer 234, and probe correction data can also be comprised.Visit Pin memorizer 234 is preferably by the Maxim Integrated Products of Sunnyvale, CA The line EEPROM that company manufactures under part number DS2431 and sells.Probe memory 234 It is coupled to controller 125 via Integrated Service Digital Network letter/power line 236.Alternatively, probe memory 234 can be via such as I²C bus, the multi-thread communication bus of Firewire bus etc and control Device 125 processed communicates.

Resistance and the electric capacity termination of resistance center conductor signal cable 212 are moved to signal processing Instrument 100 significantly reduces and is branched out at the output of heart conductor signal cable 212 in electrical resistance Midband and high-band frequency signal code amount to ground.Resistance center conductor in prior art In signal cable passive voltage probe, midband and high-frequency band signals at the output of probe cable Quite a few (about 2/3rds) of electric current are defeated according to termination capacitor and the oscillograph of cable The parasitic capacitance that enters and shunted to ground by the terminating capacitor in probe compensation box.Additionally, it is existing The resistance center conductor signal cable of technology is terminated in the compensation box of probe, and this causes serving as Parasitic capacitance in the oscillograph input of non-terminated tap (stub), thus further additional Shunt current is to ground.In the present invention, the resistance in input circuit 226 and electric capacity termination are with electric The input series connection of resistance center conductor signal cable 212 and input amplifier 238, causes the most more Big electric current flows in the input of amplifier.Probe tip electric capacity can be reduced to 2-5pf's In the range of value, this reduce the intermediate frequency at the output of heart conductor signal cable 212 in electrical resistance Band and high-band frequency signal code.This reduction of signal code is provided to input current and puts Overall the increasing of the signal code of big device is offset so that signal to noise ratio is equivalent to existing passive electrical Pressure probe.It addition, terminate from BNC input node 214 to the signal of input amplifier 238 The resistive element 231 in path combines the stray inductance of this signal path and electric capacity substantially signal Path changeover becomes the transmission line of termination, and this reduces the signal code amount shunting to ground further.? Resistance and capacitance cable termination move to terminate at instrument in oscillograph 100 and signal path In result be at the output of heart conductor signal cable 212 in electrical resistance more than 50% midband It is coupled to input amplifier 238 and owing to inputting at BNC with high-band frequency signal code Eliminate non-terminated tap between node 214 and input amplifier 238 and make the band of signal acquiring system Wide increase.

The terminating resistor of resistance center conductor signal cable 212 and electric capacity are for given cable class Type is fixed value, and the direct-to-ground capacitance of resistance center conductor signal cable 212 is with the length of cable And change.In a preferred embodiment of the invention, the end of resistance center conductor signal cable 212 Connect electric capacity and be about 40pf and terminating resistor is about 150 Ω.It addition, in 1.2 meters of resistance Heart conductor signal cable 212 has the direct-to-ground capacitance of about 40pf by chance.Resistance center conductor The direct-to-ground capacitance of signal cable 212 can be easily altered by changing the length of cable. Resistive element 206 in probe tip circuit 204 has value and the capacity cell of 9.75M Ω 208 values with 3.4pf.Capacitance is less than typically having the electric capacity in the range of 8 to 14pf Existing resistance center conductor passive voltage probe.Reduce the input capacitance at probe tip just to subtract The little capacitive load of equipment under test, causes broader probe bandwidth.Use the probe of face amount The time constant of needle point circuit 204 is 33.15 microseconds.Across BNC input node 214 time Between constant should mate the time constant of probe tip circuit 204.To in input circuit 226 Capacity cell 229 applies to limit, because its electric capacity should build-out resistor center conductor signal cable The termination capacitor of 212.Therefore, the electric capacity of capacity cell 229 is 40pf.Resistance center conductor The direct-to-ground capacitance of signal cable 212 is 40pf, and it needs to add termination capacitor to.At BNC Electric capacity obtained by input node 214 is 80pf.Probe tip circuit 204 time constant is removed With the summation capacitance of the direct-to-ground capacitance of resistance center conductor signal cable 212 and termination capacitor 80pf value, it should the value of the 414.4k Ω of the resistive element 227 in generation input circuit 226. But, to the needs with the backwards compatibility of conventional probe with to directly driving oscillograph input Demand requires that oscillograph input capacitance is in the range of 10-20pf.In oscillographic input Parasitic capacitance is about 2pf.The optimal value of the effective capacitance of capacity cell 229 and 232 is preferred Ground is between 10 and 12pf.The value of capacity cell 229 is set to 40pf with build-out resistor The electric capacity of center conductor signal cable 212.The value of capacity cell 232 needs to be of about 13.3pf To produce the effective capacitance of about 10pf.Capacity cell 229 with the ratio of capacity cell 232 is 3: 1, it is desirable to resistive element 227 with the 1: 3 of resistive element 230 ratio.Resistive element 227 He The value of 232 needs to add up 1M Ω for backwards compatibility, causes resistive element 227 to have The value of 250k Ω and resistive element 232 have the value of 750k Ω.Input circuit 226 and resistance The obtained time constant of-capacity attenuator network 228 is 10 microseconds.For being set as 10 The time constant of the input circuit 226 of microsecond, normal across the time of BNC input node 214 Number is nominally 20 microseconds (80pf × 250k Ω) and the time of probe tip circuit 204 is normal Number is 33.15 microseconds.Compensating circuit 224 and have separate zero pole point pair, it compensates across showing The mismatch time constant of the BNC input node of ripple device 100.

Compensation system 224 has the input amplifier 238 as current amplifier, and wherein it is anti- Input mutually and be coupled to attenuator circuit 226 via termination resistor 231 and non-inverting input is coupled to Ground.The input amplifier 238 of compensation system 224 has feedback loop circuit 240, this feedback loop Circuit 240 include scalable feedback resistor 242, adjustable resistor and capacity cell and Adjustable gain element.The value of adjustable resistor, capacitor and booster element is many by changing The register value of individual depositor controls.The feedback loop of resistive element 242 sets DC and low frequency Gain.Regulation is by resistive element 250 and capacity cell 252 and resistive element 254 and electric capacity The serial Feedback ring of element 256 composition is to form separate pole and zero pair.Capacity cell 252 With 256 total capacitance set midband gain and the shunt conductance of resistive element 250 and 254 Set high-frequency gain.Can by the pole and zero of element 250 and 252 time constant to being formed Independently to be adjusted with the time constant to being formed of the pole and zero by element 254 and 256 Joint.Regulate these time constants with for by intermediate frequency in other parts of circuit and the mistake of high-frequency gain This part joining the residual error caused provides flatness correction.Resistive element 244, capacity cell 246 With the variable gain voltage source as form of the variable gain amplifier 248 to have gain " K " Serial Feedback ring affect the gain in the arrowband between low-frequency band and medium-band frequencies, it is adjusted Save with being somebody's turn to do for the residual error caused by other part medium and low frequencies of circuit and the mismatch of intermediate-frequency gain Part provides flatness correction.Controller 125 via be used for loading adjustable resistor, electric capacity and Four line serial peripheral interface buses 258 of the register value of booster element and feedback loop circuit 240 Communication.

Fig. 7 illustrates the representativeness of the signal acquiring system 200 compensated with and without feedback cross Frequency response 260,262.Electric capacity in the probe tip circuit 204 of signal acquiring system 200 The electric capacity of element 208 is reduced, and this improves high frequency input impedance.Probe tip circuit 204 In reduce electric capacity result in across input node 214 with the resistance combining input circuit 226 The time of the time constant mismatch of the direct-to-ground capacitance capacitor 213 of center conductor signal cable 212 Constant.This has broken and has wherein compensated each of signal path for flat frequency and phase response Conventional probe-the oscilloscope architecture of level.The time constant of mismatch produces the peak near 8KHz Value 264.In frequency response 262 low ebb near 60MHz 266 with by termination components, Resistive element 216 and 231 and capacity cell 229 produce, resistance center conductor signal electricity Round reflection in cable 212 is relevant, only the multiple resistance of resistance center conductor signal cable 212 Anti-approximation.Feedback loop circuit 240 provides feedback cross to compensate to peak value 264 and low ebb 266. In the feedback loop circuit 240 of input amplifier 238 by change adjustable resistor element 244, In the gain " K " of adjustable capacitive element 246 and variable gain amplifier 248 any two Individual register value corrects 8KHz peak value 264.Low ebb 266 near 60MHz by The electric capacity of the capacity cell 208 lower than the electric capacity of same capacitor in conventional probe causes, and And by change the register value of capacity cell 252 and 256 and resistive element 250 and 254 with Form separate pole and zero to correcting.The total capacitance of capacity cell 252 and 256 sets Midband gain (10KHz to 10MHz) and the electricity in parallel of resistive element 250 and 254 Lead the gain being set on 200MHz.

Resistive element 244 and capacity cell 246 in the feedback loop of input amplifier 238 produce Zero pole point pair in signal acquiring system 200, in its generation frequency response near 8KHz Enough degree of freedom that peak value 264 can be flattened.Anti-with what any gain " K " was connected Feedback ring in zero pole point pair interpolation can by " K " be set as plus or minus eliminate peak value or Low ebb.The transmission function of low-frequency band (DC to midband AC) is illustrated by equation 1 below:

$H\left(\mathrm{j\ω}\right)=-\left(\frac{R_{242}\·(C_Z\·A_Z\·T_Z)}{{\mathrm{TA}}_P\·C_P}\right)$ (equation 1)

Wherein

C_ZExpression suppressed zero:

(C₂₄₆·R₂₄₄·jω+1)

A_ZExpression attenuator zero point:

(C₂₂₉·R₂₂₇·jω+1)

T_ZExpression needle point zero point:

(C₂₀₈·R₂₀₆·jω+1)

C_PRepresent and correct limit:

$\left(\begin{array}{c}(C_{252}+C_{256})\·R_{242}\·\mathrm{j\ω}+C_{246}\·R_{244}\·\mathrm{j\ω}+C_{246}\·K\·R_{242}\·\mathrm{j\ω}+\\ (C_{252}+C_{256})\·C_{246}\·R_{242}\·R_{244}\·{\left(\mathrm{j\ω}\right)}^2+1\end{array}\right)$

TA_p(R₂₂₇+R₂₀₆+C₂₁₂·R₂₂₇·R₂₀₆·jω+C₂₂₉·R₂₂₇·R₂₀₆·jw+C₂₀₈·R₂₂₇·R₂₀₆J ω) table Show needle point/attenuator limit:

This third-order system has makes institute by those parts in regulation feedback loop circuit 240 Three limits are had to align with all three zero point enough degree of freedom of (line up with), thus The random mismatch of permission time constant on the either side of input node 214.R₂₄₄、C₂₄₆ Or " K " if component values they one of be set; could be solved.For most of realities Actual value, suppressed zero " C on the real axis of zero pole plot_Z" position be set equal to needle point / attenuator limit " TA_p" position set C₂₄₆In the case of produce R₂₄₄Value or Set R₂₄₄In the case of produce C₂₄₆Value.To correction limit " C_P" equation factorisation (factor) and the smaller in two limits it is set equal to needle point zero point " T_Z" basis The R solved₂₄₄And C₂₄₆Value and produce the value of " K ".Alternatively, use equal to attenuator Zero point " A_Z" higher solve limit come to correction limit " C_P" the just generation of equation factorisation The value of " K ".

Midband AC is illustrated to the transmission function of high-frequency AC by equation 2 below:

$H\left(\mathrm{j\ω}\right)=-\left(\frac{A}{B+C}\right)$ (equation 2)

Wherein A is equal to:

$\frac{1}{(\frac{1}{(R_{250}+\frac{1}{C_{252}\mathrm{j\ω}})}+\frac{1}{(R_{254}+\frac{1}{C_{256}\mathrm{j\ω}})})}$

B is equal to:

$(R_{216}+R_{231}+\frac{1}{C_{229}\mathrm{j\ω}})\·[\cos (\mathrm{\β}\·l)+Y_0\·j\·\sin (\mathrm{\β}\·l)\·(R_{210}+\frac{1}{C_{208}\mathrm{j\ω}})]$

C is equal to:

$\cos (\mathrm{\β}\·l)\·(R_{210}+\frac{1}{C_{208}\mathrm{j\ω}})+Z_0\·j\·\sin (\mathrm{\β}\·l)$

And The electrical length of 1=cable.

For determining at midband AC to high-frequency AC by the analysis transmitting function of cable Use 2 port microwave theories, specifically ABCD or transmission matrix.Making of transmission matrix With allowing to use the measurement data of cable, because S parameter can be easily transformed into T parameter. Transmission function is set up by solving port voltage.2 port methods easily solve probe tip, The transmission function of cable and attenuator.By electric current being sued for peace at summing junction and assuming defeated Enter amplifier 238 for ideal operational amplificr to solve the active electrical in signal acquiring system 200 Road.

When the time delay of the transmission function instruction cable of equation 2 causes probe time constant and attenuator Between limit between constant separately.Traditionally, by selection, limit is set on top of each other Probe circuit time constant value compensates this limit separately.This has used in probe cable The lattice network compensated in box of the other end and realize.But, this and signal acquiring system 200 Concept is inconsistent, is wherein reduced in probe tip circuit 204 by reduction probe tip electric capacity Load capacitance and probe compensation circuit be present in signal acquiring system.

These limits can be in alignment with each other by improving needle point resistance, but this makes probe-signal The overall frequency response of process instrumentation system is impaired (suffer).Solve medium-band frequencies response flat Other traditional solutions of smooth property require regulation cable data or remove the electric capacity in attenuator With regulated attenuator time constant.Remove the too many electric capacity in attenuator and make the noise gain of system Impaired and require that input amplifier 238 has higher gain bandwidth.The present invention is by anti- Zero pole point in feedback loop circuit 240 is to being divided into two zero pole point to (capacity cell 252,256 And resistive element 250 and 254) increase the zero pole point in transmission function to compensate separately Limit.

Low-frequency band (DC to midband AC) and midband AC are to the transmission function of high-frequency AC Above analysis assume to there is not parasitic capacitance or inductance and input amplifier 238 is to have nothing The ideal amplifier of limit gain bandwidth.For in the equation 2 of midband AC to high-frequency AC Resistive element 210,231,250 and 254 is and corresponding capacity cell 208,229,252 Damped resistor with 256 series connection.Under these frequencies (midband AC is to high-frequency AC) Assume capacity cell 208,229,252 and 256 conductance ratio big DC resistive element 206, 227 and 242 is much higher, thus causing midband scope transmission function is 208,229,252 Function with the capacity ratio of 256.

Should be appreciated that and will exist due to the high-frequency loss caused because of the Kelvin effect on cable and post Give birth to the limit caused and from the various interconnection in system 200 and the inductance peak value in earth lead Zero point.Input amplifier 238 will have the Phase delay of limited bandwidth and non-zero.These Additive effect is considered needing in final design and will affect the alternative pack of system 200 Value.

The resistance in the feedback loop circuit 240 of input amplifier 238 and electricity is changed by electronics The register value of the gain " K " holding element and variable voltage amplifier realizes the present invention's The active compensation of signal acquiring system 200.Probe memory 234 can be loaded with and signal Representative value (such as input resistance, decay factor, dynamic range, the band that acquisition probe is associated Width, host resistance (host resistance) etc.).Probe memory 234 can also be in work Factory-run school is loaded with the calibration constants being associated with this particular probe on time.Calibration constants is with defeated Enter the register value that the existing register value in the feedback loop circuit 240 of amplifier 238 combines.

Wideband content signal from signal source 157 is internally provided to arrive during factory calibrated At least one signalling channel of oscillograph 100.Wideband content signal is as CAL REFERENCE WAVEFORM (calibration reference waveform) is characterized and is stored in oscillograph In memorizer 155.The waveform characterized can be wideband content signal at the time location selected Digitized range value.Alternatively, the waveform of sign can be stored as with amplitude, skew, Rise time, excessively washout time domain mathematical table that often (overshoot aberration) etc. is associated Reaching formula, it will generate the digital waveform of CAL REFERENCE WAVEFORM.Additionally Alternative is by performing the gathered digital time domain data of wideband content signal quickly Fourier transformation (FFT) and characterize CAL REFERENCE WAVEFORM in a frequency domain.

Oscillograph memorizer 155 is loaded with specific error factor table of a series of time. Each table definition leaves the reference time position on CAL REFERENCE WAVEFORM Time location.Each table has measurement error field and error factor field, wherein surveys Each record of amount error field has corresponding record in error factor field.Replaceable Ground, oscillograph memorizer 155 can be loaded with the specific error factor of a series of frequency Table, wherein the numerical data of wideband content signal has used FFT to be switched to frequency domain.Often Frequency location on individual table definition CAL REFERENCE WAVEFORM.Each table has Measurement error field and error factor field, wherein each record of measurement error field exists Error factor field has corresponding record.It addition, multiple special time error factor tables Can be stored in oscillograph memorizer 155.These tables comprise and leave the multiple of reference time Time location.These tables have time location and associated measurement error field and measurement error Combination because of son field.

Fig. 8 A and 8B illustrates the calibration process of the signal acquiring system 200 for calibrating the present invention Flow chart.Before calibration signal acquisition probe 105, to not attaching signal acquisition probe 105 Signalling channel perform DC signal path compensate.In step 270 signal acquisition probe 105 It is attached to one of signalling channel of oscillograph 100.Oscillograph 100 detects signal in step 271 The existence of acquisition probe memorizer 234 and in step 272 reads probe memory 234 Hold.If oscillograph 100 is not detected by the existence of signal acquisition probe memorizer 234, then It is conventional probe in step 273 by attached probe identity.If probe memory 234 has Just like the probe correction constant described in step 274, then in step 275, probe correction is normal Number combines with the register value of the feedback loop circuit 240 of input amplifier 238.

User is connected to wideband content signal source 157 also the other end of signal acquisition probe 105 And step 276 use display device 135 and instrument controlling part (it can include I/O circuit, Such as keyboard, mouse etc.) initiate the probe correction to signalling channel.Oscillograph 100 exists Step 277 gathers the digital value of wideband content signal as CAL WAVEFORM (calibration ripple Shape).Alternatively, institute's collection digital value of wideband content signal can use FFT to be turned Change to frequency domain.As represented by step 278, measure at the time selected or frequency location Between the CAL WAVEFORM and the CAL REFERENCE WAVEFORM that are gathered Error amount.Can also measure at the time of multiple selections or frequency location and to be gathered Multiple mistakes between CAL WAVEFORM and CAL REFERENCE WAVEFORM Difference.Access error factor table in step 279, the time wherein selected or frequency meter with One or more selection times of the measurement error value used or frequency are corresponding.In step 280, The error factor corresponding with the error amount measured is applied to suitable feedback loop depositor Register value.The following value of error factor: this value is multiplied by feedback loop circuit 240 Actual registers value to generate new register value.In step 281, determine measurement error value Whether at final time or the frequency location of CAL REFERENCE WAVEFORM.If Calibration process is not in final time or the frequency position of CAL REFERENCE WAVEFORM Put, then this process returns to step 278 and determines at next time selected or frequency location It is in the survey between CAL WAVEFORM and CAL REFERENCE WAVEFORM Amount error amount.

If calibration process has determined that at CAL WAVEFORM and CAL Last measurement error value between REFERENCE WAVEFORM, then as in step 282 Shown in, the new of digital value performing wideband content signal gathers and digital value is stored as CAL WAVEFORM.In step 283 by the CAL WAVEFORM just gathered and calibration Specification is compared to determine new CAL WAVEFORM whether in calibrating standard.School Quasi-specification includes examining: CAL WAVEFORM low-frequency compensation is measured in specification, peak-to-peak short Phase is not normal less than the span when the setting compared with CAL REFERENCE WAVEFORM Setting percentage ratio in degree, peak-to-peak the most not normal less than with CAL REFERENCE Setting percentage ratio in the different set time span that WAVEFORM compares, and when rising Between within the setting time compared with CAL REFERENCE WAVEFORM.If it is new CAL WAVEFORM meets calibrating standard, then as shown in step 284, and input amplifier The register value of the feedback loop circuit 240 of 238 is saved for particular probe and signalling channel school Accurate.In step 285, export to inform the user by the display on display device 135 and calibrated Journey by and calibration process terminate.

If new CAL WAVEFORM is unsatisfactory for calibrating standard, then in step 286 high-ranking officers Current lapse of time of quasi-process compares with iteration time limits value.If calibration process Current lapse of time is not above iteration time limits value, then in step 287 by new CAL The time of REFERENCE WAVEFORM or frequency location are reset to starting position and really Determine between CAL REFERENCE WAVEFORM and new CAL WAVEFORM Measurement error value, determines error factor and error factor is applied to input amplification The register value of the multiple depositors in the feedback loop circuit 240 of device 238.If calibration process Lapse of time exceed iteration time limits value, then as shown in step 288, feedback loop electricity The initial register values on road 240 is set to described register value.Initial register values can be It is applied in the case of there is no any probe correction at the beginning of the depositor in feedback loop circuit 240 In the case of beginning nominal value or the most calibrated probe and signalling channel combination first The register value of front calibration.Step 289 by the display output on display device 135 to Non-calibrated state and the calibration process of family notice probe-combination of channels terminate.

With reference to Fig. 9, it is shown that such as the decay electricity implemented in the signal acquiring system 200 of the present invention The representative schematic diagram on road 226.Attenuator circuit 226 preferably multistage decay ladder (ladder) 300, the most each attenuation grade have input current node 302A, 302B, 302C, 302D、302E.In a preferred embodiment, multistage decay ladder 300 have Pyatyi 304A, 304B、304C、304D、304E.Five attenuation grades are merely possible to example and various number The level of amount may be implemented within multistage decay ladder 300 without departing from claimed invention Scope.Input current to multistage decay ladder 300 is adopted from signal via BNC input 214 Collection probe 105 receives.Input current each attenuation grade 304A, 304B, 304C, 304D, At each input current node 302A, 302B, 302C, 302D, 302E of 304E suitable Sequence ground divides.Each node electric current Part I by attenuator switch 306A, 306B, 306C, 306D, 306E are coupled to input amplifier 238 or are coupled to ground and its of electric current More than be partly coupled to next attenuation grade.Such as, the input electricity of electric current input node 302A is entered Stream is divided so that the electric current of 3/4ths is coupled to input amplifier 238 by the first attenuation grade Or be coupled to ground and the current coupling of 1/4th to next attenuation grade 304B input current joint Point 302B.Enter 1/4th electricity of electric current input node 302B of the second attenuation grade 304B Stream be divided in case total input current of multistage decay ladder 300 3/16ths by second Level 304B be coupled to input amplifier 238 or be coupled to ground and 1/16th is coupled to next The input current node 302C of attenuation grade 304C.The electric current entering the 3rd attenuation grade 304C is defeated / 16th electric current of ingress 302C is divided so that multistage decay ladder 300 the most defeated Enter electric current 3/64ths are coupled to input amplifier 238 or coupling by third level 304C Close and input current node that 1/64th is coupled to next attenuation grade 304D 302D.Enter input current node 302D 1/64th electric current be divided so that one Half electric current is coupled to input amplifier 238 by fourth stage 304D or is coupled to ground and half Electric current is coupled to input amplifier 238 by level V 304E or is coupled to ground.

The vertical gain inputted by user sets to be explained for activating and going by controller 125 Activate attenuator switch 306A, 306B, 306C, 306D, 306E.By each attenuation grade 304A, The electric current of 304B, 304C, 304D, 304E can be individually coupled to input amplifier 238 Input or can be combined and be applied to the defeated of input amplifier 238 by multistage electric current Enter.When implement " " coupling time, input current is not coupled to input amplifier 238.Decay 226 electric currents of circuit scale (scale) dynamic range to input amplifier 238.

The input impedance of the attenuator circuit 226 of signal acquiring system 200 is than existing passive voltage It is low that probe is estimated.The compensation compensated in the box electricity of prior art probe as shown in Figure 1 The shunt impedance on road 18 is the series impedance in signal acquiring system 200 now.Adopt with signal Collection probe 105 and the optional resistance-capacitance attenuator network 228 of attenuator circuit 226 series connection Interpolation improve input resistance and reduce oscillographic input capacitance with allow tradition nothing Source voltage probe is used together with signal acquiring system 200.

With reference to Figure 10, it is shown that for implementing the highvoltageprobe 400 of signal acquiring system 200 The schematic diagram of signal acquisition probe 105.Highvoltageprobe 400 has and comprises probe tip circuit The detecting head 202 of 402.Probe tip circuit 402 has and the resistive element 410 being connected in series With 412 and multiple electricity being connected in series of capacity cell 414,416 and 418 parallel coupled Resistance element 404,406,408.Probe tip circuit is coupled to resistance center conductor signal cable One end of 212, wherein the other end of signal cable 212 is via signal cable termination circuit 420 It is coupled to the BNC input 214 of one of branch attenuator circuit 422 and signal acquisition circuit 115. Cable termination circuit 420 has with the resistive element 426 connected with resistive element 430 and electric capacity The resistive element 424 of element 428 parallel coupled.Branch attenuator circuit 422 has and electric capacity unit The resistive element 432 of part 434 parallel connection.Branch attenuator circuit 422 is used as have probe tip electricity A part for the divider network on road 402.In a preferred embodiment, probe tip circuit 402 Total series resistance be of about 40M Ω and shunt resistance element 432 is 1M Ω, this causes Carry out dividing by the ratio of 40: 1 and from defeated to input amplifier 238 of probe tip circuit 402 The complete attenuation factor gone out is the 50 selection decay factors being multiplied by attenuator circuit 226.Probe tip The divider network of circuit 402 and branch attenuator circuit 422 reduces at coaxial cable 212 High voltage potential at output is to provide the user factor of safety.Resistance center conductor signal cable 212 have dielectric and skin loss, and it can pass through resistive element 426 and capacity cell 428 in parallel with resistive element 424 compensate.

Use the compensation system 224 with input amplifier 238 and feedback loop circuit 240 Describing signal acquiring system 200, this feedback loop circuit 240 includes separate pole and zero To and resistive element 244, capacity cell 246 and to have the variable increasing of gain " K " Benefit amplifier 248 is the serial Feedback ring in the variable gain voltage source of form.Consider various replacing The embodiment changed, wherein Figure 11 representatively shows an alternate embodiment.Compensating The circuit of the signal acquiring system 200 before system 224 is identical with Fig. 6.From previously The mutual component of accompanying drawing is in fig. 11 by labelling in the same manner.The compensation system 224 of Fig. 6 figure Compensation system 500 in 11 is replaced.Compensation system 500 has input amplifier 238 with anti- Feedback loop circuit 502, this feedback loop circuit 502 has in the feedback loop circuit 240 replacing Fig. 6 Resistive element 254 and capacity cell 256, resistive element 504, capacity cell 506 and To have the variable gain amplifier of gain " L " the variable gain voltage source 508 as form Serial Feedback ring.Comprise resistive element 244, capacity cell 246 and variable gain voltage source (K) The feedback loop of 248 compensates low-frequency band intersection 264 (Fig. 7) and comprises resistive element 504, electricity The feedback loop holding element 506 and variable gain voltage source (L) 508 compensates high frequency band intersection 266 (Fig. 7).The interpolation in the second variable gain voltage source 508 provides another degree of freedom, and it allows Use in the case of the time constant not changing series resistance and capacity cell 504 and 506 and increase Benefit " L " regulates zero pole point pair.Resistance and capacity cell 504,506 and variable gain voltage The serial Feedback ring in source (L) 508 combines series resistance element 250 and capacity cell 252 is adjusted Joint is to be the residual error caused by the mismatch of intermediate frequency and high-frequency gain in other parts of circuit This part provides flatness correction.

The transmission function of low-frequency band (DC to midband AC) is illustrated by equation 3 below:

$H\left(\mathrm{j\ω}\right)=-\left(\frac{R_{242}\·(C_Z\·A_Z\·T_Z)}{{\mathrm{TA}}_P\·C_P}\right)$ (equation 3)

Wherein C_ZIt is suppressed zero, A_ZIt is attenuator zero point, T_ZIt is needle point zero point, and TA_pBe as Needle point defined in equation 1/attenuator limit, and C_PIt is the correction limit being given by:

$\left(\begin{array}{c}(C_{252}+L\·C_{506})\·R_{242}\·\mathrm{jw}+C_{246}\·R_{244}\·\mathrm{jw}+C_{246}\·K\·R_{242}\·\mathrm{jw}+\\ (C_{252}+L\·C_{506})\·C_{246}\·R_{242}\·R_{244}\·{\left(\mathrm{jw}\right)}^2+1\end{array}\right)$

When L is equal to 1 and C₅₀₆Represent original C₂₅₆Time, this transmission function is reduced to original Embodiment equation.This transmission function has enough degree of freedom to compensate needle point circuit 204, electricity Resistance center conductor signal cable 212 and the mismatch time constant of attenuator circuit 226, such as Fig. 6 Original embodiment equation 1 as.

Midband AC is substantially the same with equation 2 to the transmission function of high frequency, wherein B and C Identical with equation 2 shown below:

$H\left(\mathrm{j\ω}\right)=-\left(\frac{A}{B+C}\right)$ (equation 2)

A is modified to include in the molecule " L ":

$\frac{1}{(\frac{1}{(R_{250}+\frac{1}{C_{252}\mathrm{j\ω}})}+\frac{L}{(R_{504}+\frac{1}{C_{506}\mathrm{j\ω}})})}$

Wherein L is set to 1, and " A " is equivalent to " A " in equation 2.

As the compensation system 224 of Fig. 6, adjustable resistor, capacitor and booster element Value by change multiple depositors register value control, its middle controller 125 load can Regulation resistance, electric capacity and the register value of booster element.

It will be appreciated by a person skilled in the art that can be to the embodiment described above of the present invention Details make many change without departing from its ultimate principle.Such as, input amplifier 238 is not It is limited to inverting amplifier and permissible in the case of without departing from the scope of claimed invention Use non-inverting amplifier.And, compensation system 224 can be implemented with multistage amplifier, Wherein one or more amplifiers provide gain and one or more amplifier to provide feedback to hand over Fork compensates.It addition, unenforced any compensation can be moved in using input amplifier 238 Move in signal path the some levels after more, such as in single-ended-to-difference conversion or variable gain stages Afterwards.It should also be noted that the step in the calibration process of signal acquiring system 200 need not with Definite order as described and claimed is performed, and the change of order of steps can be It is carried out without departing from the case of claims of the present invention.Equally, limit except lapse of time Outside the iteration count calibration that can be used to stop do not restrain attempt.Present invention preferably uses Depositor change the resistance in the feedback loop circuit of compensation system and capacity cell resistance and Capacitance.It is contemplated, however, that, adjust the resistance in signal acquiring system by precision laser And capacitive element, it may not be necessary in feedback loop circuit, use depositor.The scope of the present invention Therefore should only be defined by the following claims.

Claims (12)

1. a signal acquiring system, including:

Having the signal acquisition probe of probe tip circuit, described probe tip circuit is coupled to electricity Resistance center conductor signal cable, wherein said probe tip circuit has time constant；And

Having the signal processing equipment of input node, described input node is coupled to signals collecting to be visited The resistance center conductor signal cable of pin, wherein said probe tip circuit time constant and leap The time constant of the input node of described signal processing equipment is not mated, and described resistance center Conductor signal cable substantially crosses over the resistance of input node of described signal processing equipment at it Being terminated with in capacitance characteristic impedance, wherein said input node is coupled to cloth via input circuit Putting the compensation system in signal processing equipment, wherein said compensation system provides zero pole point pair, It compensates described unmatched time constant, to keep flat in signal acquiring system frequency bandwidth Smooth property.

2. signal acquiring system as claimed in claim 1, the system that wherein compensates also includes input Amplifier, described input amplifier have be coupling in input amplifier input and output between Be associated feedback loop circuit.

3. signal acquiring system as claimed in claim 2, wherein said signal processing equipment is also Including the transmission line of termination, it has signal path, one end coupling of wherein said signal path To input node, the other end is coupled to the resistive element that the input of neighbouring input amplifier is arranged.

4. signal acquiring system as claimed in claim 2, wherein input amplifier includes electric current Amplifier.

5. signal acquiring system as claimed in claim 2, the wherein said feedback loop electricity that is associated Road includes resistive element and capacity cell.

6. signal acquiring system as claimed in claim 5, the wherein described phase of input amplifier Association feedback loop circuit also includes variable resistor element and variable-capacitance element, plurality of deposits Device sets the variable resistor element and the respective resistivity values of variable-capacitance element and capacitance selected.

7. signal acquiring system as claimed in claim 6, the wherein described phase of input amplifier Association feedback loop circuit also includes resistive element and the first resistive element and capacity cell series connection coupling At least the first variable gain voltage source, the resistive element of the second series coupled and the electric capacity unit closed Part and the resistive element of the 3rd series coupled and capacity cell, wherein resistive element and One resistive element and the first variable gain voltage source of capacity cell series coupled and the second and Resistive element and the capacity cell of the 3rd series coupled are connected in parallel to each other in the input of input amplifier And between output；

Wherein, described first resistive element be positioned at described at least the first variable gain voltage source and institute State between capacity cell.

8. signal acquiring system as claimed in claim 7, the wherein described phase of input amplifier Association feedback loop circuit also includes the resistance with the second series coupled and capacity cell series coupled The second variable gain voltage source.

9. signal acquiring system as claimed in claim 1, wherein input circuit also includes decay Circuit.

10. signal acquiring system as claimed in claim 9, also includes being arranged in signal processing On-off circuit in instrument, for selecting the input node of signal processing equipment via attenuator circuit Selecting property it is coupled to compensation system and for additional attenuator circuit is optionally coupling in Between input node and the attenuator circuit of signal processing equipment.

11. signal acquiring systems as claimed in claim 1, wherein probe tip circuit also wraps Include at least the first resistive element in parallel with capacity cell.

12. signal acquiring systems as claimed in claim 11, wherein capacity cell has 2 Electric capacity in the range of 5 pico farads.