WO2000046605A2 - Scattering parameter calibration system and method - Google Patents
Scattering parameter calibration system and method Download PDFInfo
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- WO2000046605A2 WO2000046605A2 PCT/CA2000/000087 CA0000087W WO0046605A2 WO 2000046605 A2 WO2000046605 A2 WO 2000046605A2 CA 0000087 W CA0000087 W CA 0000087W WO 0046605 A2 WO0046605 A2 WO 0046605A2
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/28—Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
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- the present invention is related to the field of scattering (or "S") parameter measurement instruments, such as a vector network analyzer (or "VNA").
- S scattering
- VNA vector network analyzer
- a novel calibration methodology for such instruments is disclosed that minimizes the number of calibration steps required to fully calibrate the measurement instrument so that the S parameters of a multi-port device under test (or "DUT") can be accurately measured.
- a multi-port device is characterized by its number of ports, referred to throughout this application as n, where n is 2 or greater.
- the S matrix is composed of a plurality of S parameters.
- S parameters are the standard method for device characterization over a very wide range of frequencies, from less than 1 MHz to above 40 GHz. These parameters are used because they are easily determined, they provide directly relevant measures of device performance, and they are well defined for any type of device. If other device representations are required, such as impedance or admittance parameters, then these can be readily deduced from the measured S parameters.
- Scalar analyzers determine the amplitudes of the S parameters only, whereas vector analyzers (or VNAs) determine both the amplitudes and the phases. Scalar analyzers are far less flexible and far less accurate than vector analyzers, and are only employed in low-grade applications where equipment cost is a driving factor. Although the present system and method is generally applicable to VNA test instruments, the teaching of this application may also apply to other types of instruments that characterize S parameters (or other equivalent measurements) for a multi-port DUT.
- VNAs Vector network analyzers
- VNAs Commercial vector network analyzers
- These types of VNA systems include a signal generator and a combination of splitters and directional couplers that connect the two measurement ports of the VNA (Port 1 and Port 2) to its amplitude and phase detection circuitry (samplers).
- Typical VNAs have three or four samplers, the number of samplers affecting the accuracy and cost of the instrument.
- a typical device to be characterized by such a VNA may have two or more ports
- a an //-component vector containing the amplitudes of the waves incident on the device ports
- a is the incident voltage wave amplitude
- b is the outgoing voltage wave amplitude
- V is the voltage
- / is the input current
- Z is the normalizing impedance, all for the i'th port under test.
- the port-normalizing impedances ( Z ) are typically chosen to be equal to the
- the basic concept in this known procedure is to use a mathematical model of the test system, with a certain number of unknown terms usually 12), which desc ⁇ be all of the main error contributions. Initially, a sequence of n easurements is performed on a set of calibration components with accurately known S parameters. The values of the unknown model terms can be determined from these measurements, and the model can then be used to eliminate errors from subsequent device measurements. After correction, the device S parameters have an accuracy comparable to that of the original calibration components despite any imperfections in the test hardware.
- DUTs have more than two electrical ports. However, they must also be measured with two-port VNAs.
- the simplest procedure is to make measurements between two ports, e.g., i and , with the other ports terminated with accurate loads. This serves to determine the S,-,-, S
- the full S matrix for the multi-port device can be determined.
- This procedure has many disadvantages, however, such as: (1 ) a large number of separate measurements must be made, with the hardware being reconfigured at each stage; (2) it assumes that accurate terminations are available, which may not be true at all frequencies; and (3) reconfiguration of the hardware between measurements is impractical when components are being tested in thermal or thermal vacuum (TV AC) chambers. Because of these disadvantages, as well as others, full characterization of a multi-port device (particularly for large n) is rarely done.
- the switch box contains at least as many test ports as there are electrical ports on the DUT. Any test port on the switch box can be connected to either port of the two-port analyzer. In operation, two test ports are usually active, and are coupled to the analyzer, and the remainder are terminated in the switch box.
- any of the transmission paths can be measured automatically without reconfiguring the hardware. This greatly speeds up measurements, and allows testing to be performed in thermal or TVAC chambers.
- calibrating an S parameter measurement system for a multi-port DUT at present typically involves calibrations only across the test paths required for measuring the most important S parameters (typically /. paths are required).
- the present invention overcomes the problems noted above and satisfies the needs in this field for a system and method of calibrating an S parameter measurement instrument (such as a vector network analyzer) in which the number of calibrations required to fully characterize the error model of an //-port system is n/2 calibrations for an even number of ports and (/?+l )/2 calibrations for an odd number of ports.
- S parameter measurement instrument such as a vector network analyzer
- the number of calibrations required to fully characterize the error model of an //-port system is n/2 calibrations for an even number of ports and (/?+l )/2 calibrations for an odd number of ports.
- Each test port in the system is involved in at least one full calibration, thus n/2 test paths are fully calibrated.
- the error terms of the applicable error model are calculated. These error terms are then decoupled from the associated test path into error parameters that are localized to the individual test ports of the test path.
- the error model for each test port can then be treated independently from the other test ports.
- the error terms for the test paths that are not calibrated are then constructed using the localized error parameters for the individual test ports.
- This calibration methodology provides a significant reduction in steps from the normal number of calibrations [//(//- 1)/2], and is less than that currently used for a partial calibration [//].
- a method of calibrating a scattering (S) parameter measurement system to characterize a multi-port device having // ports, wherein n is greater than or equal to 2, and the measurement system has at least n test ports, the method includes the following steps: (1) selecting n/2 test port pairs by assigning each of the n test ports to at least one of the n/2 test port pairs, wherein each test port pair is characterized by an error model comprising a plurality of error terms; (2) conducting a full calibration on each of the n/2 test port pairs and storing the S parameter measurements resulting from the full calibrations in a memory associated with the S parameter measurement system; (3) calculating the error terms of the error model for each of the n/2 test port pairs using the S parameter measurements taken during the full calibrations, and storing these error terms in the memory associated with the S parameter measurement system; (4) decoupling the error terms associated with the n/2 test port pairs into error parameters that are local to the individual test ports of the test port pairs, and storing these local
- Another aspect of the invention provides a method of calibrating an S parameter measurement system having /; test ports, wherein a test path between any two test ports is characterized by an error model having a plurality of error terms, the method comprising the steps of: calibrating n/2 test paths to determine the error terms for these test paths, wherein each test port participates in at least one of the n/2 calibration test paths; decoupling the error terms associated with the n/2 test paths into error parameters that are localized to a particular test port; and constructing the error terms for the non-calibrated test paths using the local error parameters for each of the test ports.
- Still another aspect of the invention provides a method of calibrating a vector network analyzer test system including a two-port vector network analyzer coupled to a 2-to-n switch matrix test set having two input ports coupled to the two ports of the vector network analyzer and // test ports, the method comprising the steps of: (a) selecting n/2 test paths for full calibration from the [n(n- 1 )]/2 possible paths through the test system, each test port participating in at least one test path, wherein each path through the test system is characterized by an error model including a plurality of error terms; (b) calibrating the n/2 test paths and measuring S parameters for these paths; (c) calculating the error terms for the n/2 test paths from the measured S parameter data; (d) decoupling the error terms from the respective n/2 test paths into error parameters that are local to one or the other of the test ports that comprise the respective test path; and (e) constructing the error terms for the non-calibrated test paths using the local error parameters for the individual test ports.
- an apparatus includes: an S parameter measurement system having // test ports for measuring the S parameters of a multi-port device, the S parameter measurement system having errors that must be corrected by calibration; and a calibration control system for calibrating the [n(n-l)]/2 possible test paths between the n test ports of the S parameter measurement system, and thus minimizing the errors, each test path being characterized by an error model having a plurality of error terms.
- the calibration control system includes software instructions for ( 1 ) calibrating n/2 test paths to determine the error terms for each of the paths, wherein each test port participates in at least one of the n/2 test paths; (2) decoupling the error terms associated with the calibrated test paths into error parameters that are localized to one of the test ports in the respective test path; and (3) constructing the error terms for the non-calibrated test paths using the localized error parameters for each of the test ports.
- Still another aspect of the invention provides a calibration system for use with an S parameter measurement instrument having // test ports, wherein a test path between any two test ports is characterized by an error model having a plurality of error terms, the calibration system comprising: means for calibrating n/2 test paths to determine the error terms for each of the paths, wherein each test port participates in at least one calibration test path; means for decoupling the error terms associated with the calibrated test paths into localized error parameters associated with the test ports; and means for constructing the error terms for the non-calibrated test paths using the localized error parameters associated with the test ports.
- a method for calibrating a four-sampler vector network analyzer test system having n test ports comprising the steps of: conducting a full calibration on one test path consisting of two of the n test ports; conducting reflection calibrations only on each of the remaining n-2 test ports that did not participate in the full calibration; and constructing an error model for each of the test paths that were not fully calibrated using error data from the full calibration on the one test path and the reflection calibrations on the remaining test ports.
- the present invention overcomes the disadvantages of presently known calibration systems and methods for characterizing multi-port devices using a vector network analyzer (or other type of S parameter measurement instrument), and also provides many advantages. Not all of these advantages are simultaneously required to practice the invention as claimed, and the following list is merely illustrative of the types of benefits that may be provided, alone or in combination.
- FIG. 1 is a block diagram of a preferred four-sampler, two-port vector network analyzer test system incorporating a calibration control system according to the present invention, wherein the VNA is coupled to a hypothetical four-port DUT via a switch matrix test set.
- FIG. 2 is a mathematical model of the scattering matrix [S A ] and the forward error parameters for the preferred 12-term error model, shown in signal flow-graph form.
- FIG. 3 is a mathematical model of the scattering matrix [S A ] and the reverse error parameters for the preferred 12-term error model, shown in signal flow-graph form.
- FIG. 4 is a flowchart of a preferred series of steps for calibrating an n-port S parameter measurement system such as shown in Figure 1.
- FIG. 5 is a flowchart of a preferred series of steps for decoupling the forward and reverse error tracking terms in the 12-term error model.
- FIG. 6 is a plot showing the zero-frequency phase extrapolation step utilized by the methodology of the present invention to resolve the sign ambiguity in the square root calculation that results from decoupling the forward and reverse error tracking terms.
- Figure 1 sets forth a block diagram of a four- sampler, two-port vector network analyzer test system 10 incorporating a calibration control system according to the present invention, wherein the VNA 10 is coupled to a hypothetical four-port DUT 50 via a switch matrix test set 30. Note that although a four- sampler VNA 10 is shown, the present invention can be utilized with any type of vector network analyzer, or any other type of S parameter measurement system using vector error correction.
- the preferred four-sampler VNA test system 10 includes a microprocessor 12 coupled to a memory 14, which together control the signal generation and measuring circuitry 16-24 used to characterize the DUT 50.
- the microprocessor 12 could be any type of embedded microprocessor, microcontroller, DSP, ASIC, etc., as would be apparent to one of ordinary skill in this art.
- the memory 14 preferably contains the calibration control system of the present invention, and is preferably a permanent solid state memory, such as a flash ROM, EEPROM, ROM, etc. But, alternatively, the memory 14 could be a hard disk, floppy disk, RAM, or any other type of memory storage medium. Indeed, the memory 14 could be located external to the VNA 10 itself.
- a PC or workstation could be coupled to the VNA 10 using industry standard control bus structures such that the VNA 10 is controlled by the external PC or workstation.
- the calibration control system could be stored in the permanent memory (i.e., hard disk, CD-ROM, etc.) of the PC or workstation, or it could be loaded from a removable memory device.
- the signal generation and measu ⁇ ng circuitry 16-24 used to characterize DUTs includes signal source generator 16, transfer switches 18, splitters 20, variable attenuators
- Samplers A and B measure the reflected and transmitted waves, when power is incident on Port 1 , and vice versa when power is incident on Port 2.
- Samplers Rl and R2 measure the incident waves on Port 1
- VNA VNA
- the operation and control of these components will not be described in detail, as they are apparent to one of ordinary skill in the art of network analyzers. But it should be noted that the overall operation of the VNA 10 is preferably controlled by microprocessor 12, in conjunction with the calibration control system, which is preferably stored in memory 14. This calibration system and methodology are described in more detail below in connection with Figures 4-6. For more information regarding the general operation of vector network analyzers, refer to
- VNA calibration system shown in Figure 1 is setup in an example configuration for measuring the S parameters of a hypothetical four-port device 50.
- This example device will be used in discussing the preferred calibration methodology set forth below. It should be noted that this particular VNA system 10 can, of course, be used to measure the S parameters of any type of DUT with four ports or less. The example device is chosen for simplicity in explaining the concepts and benefits of the preferred methodology.
- the purpose of the test set 30 is to provide for automatic switching between the two ports (Port 1, Port 2) 26, 28 of the VNA 10 and the four test ports (P1-P4) 52-58, which are connected to the device ports (J 1 -J4) during the taking of actual S parameter measurements.
- the switch matrix 30 is coupled to the VNA 10 by ports A (32) and B (34) and to the DUT 50 by switch matrix ports PI ' (36), P2' (38), P3' (40), and P4' (42).
- the switch matrix ports Pl'-P4' are, in turn, coupled to the actual test ports (P1-P4), where the calibrations are conducted, via test cables C1-C4. It should be noted tnat the switch matrix 30 operation can be controlled by microprocessor 12, or it could be controlled by an external PC or workstation that may also be controlling the VNA 10.
- FIG. 2 is a mathematical model of the scattering matrix [S A ] and the forward error parameters of the preferred 12-term error model
- Figure 3 is the same for the reverse parameters of the 12-term error model.
- S A scattering matrix
- Figure 3 is the same for the reverse parameters of the 12-term error model.
- These figures represent the error model in signal flow graph form
- Each test port path through the S parameter measurement system is characterized by two twelve-term error models, one model for each of the two senses in which the pair of test ports may be connected to Ports 1 and 2 of the analyzer.
- These models are based on the assumption that the wave amplitudes detected at the samplers are linear functions of the wave amplitudes at the device ports. This assumption means that non-linear effects in the instrument are not included, neither are repeatability effects associated with switches, cables and RF connectors However, these models do accurately describe all the major error contributions in the test hardware.
- the forward error model 60 shown in Figure 2 includes an input section 62, a
- the DUT section 64 and an output section 66 The input section is composed of error parameters e 00 , e 0 , en and e ⁇ / coupled between nodes ao, a/, bo and b ⁇ , an RF in signal, and a measured S component S UM -
- the output section is composed of error parameters e 22 and ej2 coupled between nodes a 2 , b 2 and b 3 , and a measured S component S 21M .
- the DUT section is composed of the actual S parameters Sn 1 , SU A , S- 7 . 4 and S? 2 ) , and a single through leakage error parameter e? ⁇ .
- the reverse error model 70 shown in Figure 3 includes an input section 76, a DUT section 74 and an output section 72.
- the input section is composed of error parameters e '33, e '23, e ' 22 and e '32 coupled between nodes a '2, a ' 3 , b '? and b ' 3 , an RF in signal, now on the Port 2 side of the model, and a measured S component S 22 ⁇ .
- the output section 72 is composed of error parameters e 'n and e ' 01 coupled between nodes a '1, b O and b ' /, and a measured S component S/ 2 ⁇ .
- the DUT section is composed of the actual S parameters SHA, S/z.. 21A and S22A, and a single through leakage error parameter e ' o3-
- the present inventors have discovered, however, that by making two minor assumptions regarding the VNA test hardware (as shown in Figure 1), the error terms for all possible test paths can be determined by calibrating only n/2 paths, where each test port participates in at least one calibration path.
- the calibration system decouples the error terms into e ⁇ or parameters that are local to each of the n test ports.
- the error terms for the paths that are not calibrated are then mathematically constructed using the local error parameters for the respective test ports associated with the path.
- This decoupling process includes a novel sign ambiguity determination method for calculating and resolving the square root of the forward and reverse reflection tracking terms (ETR, ERR), which are needed to effectively localize the forward and reverse transmission tracking terms (ETF, ERF).
- the first assumption of the prefe ⁇ ed calibration procedure is as follows - Assumption 1: with the exception of the leakage terms EXF, EXR, a ly fundamental error parameter in the error model is local to the port to which it refers, and is independent of the choice of the other port.
- test port P4 (58) were connected to Port 1 26 of the VNA, then its local e ⁇ or parameters, e 0 ⁇ , e / o, eoi, en, e n, and e'n would be independent of which of the other test ports P1-P3 was connected to Port 2 (28) of the analyzer.
- test ports are independent in this sense, then a standard calibration procedure has a great deal of redundancy. It is, in part, by eliminating this redundancy that the number of required test port interconnections can be reduced. It should be noted that no particular assumptions are required for the leakage terms EXF, EXR. These terms are determined by transmission measurements with all test ports disconnected (and usually terminated). The instrument can therefore cycle through all the paths automatically and determine the leakage terms without manual intervention.
- Equations (4-12) reveal an issue with this scheme that requires an additional assumption to reduce the number of full calibration steps to a minimum.
- This issue relates to the fact that the error parameters e/o, e 32 , and e ' 23 , e '01 do not appear individually, but in the combinations ETF (e / o * e 32 and ETR (e '23 * e '01) which are refe ⁇ ed to as "the transmission tracking terms.” Indeed, no measurement on calibration standards alone can determine these e ⁇ or parameters in isolation.
- e'oi i , which can be localized to one of the test ports in the test path.
- the ERR parameters e ' 32 and e'oi are identical to e ?2 and e O ⁇ , except that the Y terms are missing. Since these terms cancel out in the final equations (see equations 31 and 32, below), it is only necessary to determine the ratios defined by e ' 32 and e'oi in order to properly construct the non-calibrated test paths.
- test ports (P1-P4) be calibrated in pairs in such a way that each test port is included in at least one pair.
- the interconnection scheme could therefore be (PI, P2), (P3, P4) for the hypothetical four- port test system shown in Figure 1, although any other physically convenient pairing could be used.
- PI, P2 the test ports
- P3, P4 the test ports
- a full 12-term calibration procedure is performed.
- calibration measurements are made with the ports of the network analyzer (Port 1, Port 2) connected to the test ports (P1-P4) in both possible senses.
- reflection measurements are made of each test port in its terminated state.
- the total number of operations performed by the test technician is exactly the same as for a conventional 12- term calibration, but in this case the analyzer performs considerably more measurements on each calibration component.
- the e ⁇ or terms for paths 1 and 3 (P1-P2, P3-P4) are then known from the actual measurements on these test ports.
- each test port in any path can be treated independently of the others.
- the e ⁇ or terms for the remaining paths (2, 4, 5 and 6) can be constructed from the localized e ⁇ or parameters for the two ports in the respective path. This procedure is described in more detail below.
- Figures 4-6 describe in more detail the method steps carried out by an S parameter measurement system programmed to function according to the present invention.
- Figure 4 is a flowchart of a prefe ⁇ ed series of steps for calibrating an //-port S parameter measurement system such as shown in Figure 1.
- Figure 5 is a flowchart of a prefe ⁇ ed series of steps for decoupling the forward and reverse e ⁇ or tracking terms in the 12-term e ⁇ or model.
- Figure 6 is a plot showing the zero-frequency phase extrapolation step utilized to resolve the sign ambiguity in the square root calculation of the forward and reverse reflection tracking terms.
- the prefe ⁇ ed method discussed herein is applicable to any RF measurements made using a VNA (or other equivalent device) for characterizing the S parameters of a DUT.
- VNA or other equivalent device
- the discussion of the prefe ⁇ ed method is limited to the 12-term e ⁇ or model shown in Figures 2 and 3, but it is equally valid for other e ⁇ or models.
- the invention is capable of many distinct implementations. It can be implemented as a method of operation. It can be implemented as a system or apparatus including computer software (or firmware) programming for executing the preferred method of operation.
- each path is characterized by two twelve-term e ⁇ or models, which are chosen for each of the two possible ways of connecting the chosen test ports (P1-P4) to the VNA 10. This would normally require twelve full two-port calibrations to be performed as shown in Table 1.0, set forth below. However, because the measurements for a given pair of test ports are performed automatically, both senses can be calibrated in one operation and thus, only six pairs of ports need to be connected in order to fully calibrate the system. Thus, according to the conventional methodologies, for an n-port system //(//- 1 )/2 such pairings are required. Table 1.0 - Conventional Calibration Path Connectivity for a Four-Port Device
- n/2 2 connections, P1-P2 and P3-P4, since the VNA can automatically measure in both directions.
- the missing eight calibrations are constructed using e ⁇ or data from those taken. Note that for devices with an odd number of ports the required number of port pairings is (n+l)/2 rather than n/2.
- This methodology is preferably implemented as software instructions stored in the memory 14 of the VNA 10. These software instructions can be installed into the VNA memory via a floppy disk or other transportable medium, or they may be permanently installed in the VNA memory, such as in a ROM, Flash ROM, EEPROM, or other type of memory device.
- the first step of the method 80 is to select the desired n/2 test port pairings.
- Each test port must participate in at least one pairing.
- This full calibration step can be done according to several well-established and published techniques, such as SOLT (Short Open Load Through), LRM (Line Reflect Match) or TRL (Through Reflect Line), or can be done using any other suitable combination of calibration components.
- SOLT Short Open Load Through
- LRM Line Reflect Match
- TRL Through Reflect Line
- each method relies upon measuring certain calibration components in order to solve the e ⁇ or contributions in the standard 12-term model (or whatever other model is being used).
- 12 independent measurements at the test ports must be made.
- a typical procedure involves reflection measurements on three known impedance standards at each of the two test ports (6 measurements), transmission and reflection measurements on a through connection with known properties (4 measurements), and transmission measurements with the test ports disconnected and terminated with matched loads (2 measurements).
- the measured S parameters are stored at step 84.
- This data can be stored in the memory 14 of the VNA 10, or it could be transferred to a PC or workstation that is controlling the calibration system.
- the full calibration process continues (86, 82) until each of the selected n/2 test port pairs is calibrated and the respective S parameters are stored 86.
- Control of the calibration system then passes to step 90, in which the measured S parameters gathered during the calibration process (82) are used to calculate the error terms (EDF, ESF, ELF, EXF, ERF, ETF, EDR, ESR, ELR, EXR, ERR, and ETR) associated with each test port pair.
- error terms EDF, ESF, ELF, EXF, ERF, ETF, EDR, ESR, ELR, EXR, ERR, and ETR
- e ⁇ or terms are computed by solving the standard 12-term e ⁇ or model equations (4-12), and these values are then stored in the system at step 88.
- control of the calibration system passes to step 92, ir which the error terms associated with the test port pairings are decoupled into error parameters that are localized to the individual test port to which they are associated by virtue of the independence assumption.
- These local e ⁇ or parameters are then stored per test port for use in constructing the e ⁇ or model for the non-measured paths.
- the e ⁇ or terms are decoupled from the port pair into localized e ⁇ or parameters associated with just one of the test ports.
- the first way relates to the transmission tracking terms (ETF. ETR), and is more thoroughly described below in connections with Figures 5 and 6.
- the second way (which is less complex than the first) relates to the remaining error terms. These terms are decoupled from the port pairing by disassociating the term from the port path that is calibrated and by associating the error parameters that comprise the term with one of the respective test ports that form the path.
- test port pairing P1-P2 where PI is connected to Port 1 of the analyzer and P2 is connected to Port 2 (i.e., path 1.)
- the e ⁇ or terms EDF. ESF, ERF, ELF, EDR, ESR, ERR and EER can be decoupled from the test path (path 1) into the local e ⁇ or parameters e ⁇ , e//, e/ ⁇ * eoi, e22, e ' 33 , e '2 2 . e ' 23 * e ' 32 and e ' // by disassociating these terms from the test port pairing (path 1), and associating the local parameters with the individual test ports (PI or P2).
- FIG. 5 a flowchart is set forth showing a preferred series of steps for decoupling the forward and reverse e ⁇ or tracking terms into local error parameters. This decoupling operation separates the e ⁇ or tracking terms into localized
- test ports are reciprocal 104
- step 106 in which the complex square root of the ERE and ERR terms is calculated using data from step 108 to resolve the sign ambiguity of these square root terms (step 108 is described in more detail below.)
- step 110 Having resolved the sign ambiguity of the square root of ERE and ERR, control passes to step 110, in which the e ' 32 and e'oi e ⁇ or parameters are calculated according to the following equations:
- I ⁇ J - are local e ⁇ or parameters associated with the other test port in the path to be VERE constructed.
- Equations (31) and (32) thus express ETF and ETR as products of error parameters which can be explicitly determined and are localized to a particular test port.
- FIG. 6 is a plot showing the zero- frequency phase extrapolation step.
- the X-axis of the plot 124 shows frequency in Hz, and the Y-axis shows phase, measured in degrees.
- the data plots 126, 128 show the ERE (or ERR) data for two test ports (as solid lines), and the extrapolated data as dashed lines. These curves 126, 128 are extrapolated to 0Hz using a straight line fit.
- This information is computed at step 108.
- step 98 the error model for each of the non-measured paths is constructed using the e ⁇ or parameters stored in step 94 for the individual test ports. For example, using the calibration data from path 1 (P1-P2) and path 3 (P4-P3), the e ⁇ or model for path 5 (P1-P3) can be constructed as shown in Table 3.0.
- the isolation terms (EXF, EXR) between test ports can be ignored in most applications. If the isolation terms are required, then they are measured with the test ports disconnected, so no additional calibration is needed.
- step 100 control of the system passes to step 100, where a DUT 50 is attached to the system for actual S parameter measurements.
- these measured S parameters ( _S" ) for the DUT 50 can be co ⁇ ected to give the actual S parameters (S A ) by solving the standard equations given above (4-12) using the e ⁇ or data stored at steps 88 and 96.
- S A the actual S parameters
- the VNA system can be calibrated by performing a full two-port calibration between test ports P2-P4 and two reflection calibrations, one on test port PI using 3.5mm calibration standards and one on test port P3 using TNC calibration standards.
- the full twelve-term e ⁇ or models can then be constructed from the e ⁇ or terms gathered during the calibration of the system.
- test ports PI and P3 52, 56
- test ports P2-P4 Path 6
- the e ⁇ or parameters for each of the ports are determined by decoupling and localizing the parameters so that each port can be treated independently from the others.
- the e ⁇ or terms for path P1-P3 can be constructed using the measured e ⁇ or parameters from the partial calibrations of ports 1 and 3, and the full calibration of path P2-P4. In a similar manner the four remaining combinations of test ports P1-P2, P1-P4, P2-P3 and P3-P4 can be constructed.
- a and AT are calculated based on e ⁇ or parameters from P2-P4 they are, in fact, independent of the test ports they are measured from and can be applied universally to all of the other test ports. In this manner an n-port system can be calibrated using one full two-port calibration and n-2 reflection calibrations, which is again a significant reduction from the n/2 case.
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Application Number | Priority Date | Filing Date | Title |
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CA002361666A CA2361666C (en) | 1999-02-02 | 2000-02-01 | Scattering parameter calibration system and method |
EP00901456A EP1181562B8 (en) | 1999-02-02 | 2000-02-01 | Scattering parameter calibration system and method |
DE60034121T DE60034121T2 (en) | 1999-02-02 | 2000-02-01 | METHOD AND DEVICE FOR STREUPARAMETER CALIBRATION |
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US09/241,704 | 1999-02-02 | ||
US09/241,704 US6300775B1 (en) | 1999-02-02 | 1999-02-02 | Scattering parameter calibration system and method |
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WO2000046605A2 true WO2000046605A2 (en) | 2000-08-10 |
WO2000046605A3 WO2000046605A3 (en) | 2001-11-29 |
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PCT/CA2000/000087 WO2000046605A2 (en) | 1999-02-02 | 2000-02-01 | Scattering parameter calibration system and method |
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US (1) | US6300775B1 (en) |
EP (1) | EP1181562B8 (en) |
CA (1) | CA2361666C (en) |
DE (1) | DE60034121T2 (en) |
WO (1) | WO2000046605A2 (en) |
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Cited By (7)
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US7113891B2 (en) | 2004-05-12 | 2006-09-26 | Agilent Technologies, Inc. | Multi-port scattering parameter calibration system and method |
GB2426067A (en) * | 2005-05-12 | 2006-11-15 | Agilent Technologies Inc | Power calibration for a multi-port vector network analyser |
WO2007014280A2 (en) * | 2005-07-25 | 2007-02-01 | University Of Florida Research Foundation, Inc. | System, device, and methods for embedded s-parameter measurement |
WO2007014280A3 (en) * | 2005-07-25 | 2007-06-28 | Univ Florida | System, device, and methods for embedded s-parameter measurement |
CN111257814A (en) * | 2020-03-05 | 2020-06-09 | 西北工业大学 | Straight-through-short circuit calibration method of vector network analyzer |
US11894882B2 (en) | 2020-08-07 | 2024-02-06 | Rohde & Schwarz Gmbh & Co. Kg | Measurement system and measurement method |
CN112051534A (en) * | 2020-08-31 | 2020-12-08 | 中电科仪器仪表有限公司 | External device and method for improving measurement and calibration precision of microwave network |
Also Published As
Publication number | Publication date |
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WO2000046605A3 (en) | 2001-11-29 |
DE60034121D1 (en) | 2007-05-10 |
DE60034121T2 (en) | 2007-11-08 |
CA2361666A1 (en) | 2000-08-10 |
EP1181562B8 (en) | 2007-06-27 |
CA2361666C (en) | 2005-11-01 |
EP1181562B1 (en) | 2007-03-28 |
US6300775B1 (en) | 2001-10-09 |
EP1181562A2 (en) | 2002-02-27 |
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