US20010001543A1 - Frequency-voltage conversion circuit and receiving apparatus - Google Patents
Frequency-voltage conversion circuit and receiving apparatus Download PDFInfo
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- US20010001543A1 US20010001543A1 US09/757,793 US75779301A US2001001543A1 US 20010001543 A1 US20010001543 A1 US 20010001543A1 US 75779301 A US75779301 A US 75779301A US 2001001543 A1 US2001001543 A1 US 2001001543A1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D7/00—Transference of modulation from one carrier to another, e.g. frequency-changing
- H03D7/16—Multiple-frequency-changing
- H03D7/165—Multiple-frequency-changing at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature
- H03D7/166—Multiple-frequency-changing at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature using two or more quadrature frequency translation stages
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
- H03D3/007—Demodulation of angle-, frequency- or phase- modulated oscillations by converting the oscillations into two quadrature related signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/14—Demodulator circuits; Receiver circuits
- H04L27/144—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements
- H04L27/152—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements using controlled oscillators, e.g. PLL arrangements
- H04L27/1525—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements using controlled oscillators, e.g. PLL arrangements using quadrature demodulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/14—Demodulator circuits; Receiver circuits
- H04L27/156—Demodulator circuits; Receiver circuits with demodulation using temporal properties of the received signal, e.g. detecting pulse width
- H04L27/1563—Demodulator circuits; Receiver circuits with demodulation using temporal properties of the received signal, e.g. detecting pulse width using transition or level detection
Abstract
In a frequency-voltage conversion circuit, integrating means gives a predetermined slope for rising or falling of a rectangular pulse signal. First comparing means compares an output value of the integrating means with a threshold value, and produces a pulse signal line having a pulse width corresponding to frequency of the rectangular pulse signal. Storing means stores and retains the threshold value. Smoothing means smooths the pulse signal line, and produces a voltage value corresponding to the frequency of the rectangular pulse signal. Second comparing means compares the voltage value with a reference voltage, and charges and discharges electric charge for the storing means on the basis of the comparison result.
Description
- This invention relates to a frequency-voltage conversion circuit and a receiving apparatus applicable for a direct conversion receiver which receives and demodulates a FSK Frequency Shift Keying) signal.
- A superheterodyne method and a direct conversion method are generally used in a FSK (Frequency Shift Keying) receiver. In each method, demodulation is carried out by the use of the known F-V (Frequency-Voltage) conversion.
- Referring to FIG. 1, description will be made about a related direct conversion receiver using the F-V conversion.
- In a Weber receiver illustrated in FIG. 1 the direct conversion receiver, a base-band cross signal is brought up to intermediate frequency (namely, up-conversion is conducted), and the F-V conversion is performed.
- The FSK signal sent from a receiver (not shown) is received by an
antenna 101, is amplified by ahigh frequency amplifier 102, and is given tomixers - A
local oscillator 107 produces an oscillation signal. The oscillation signal is shifted with π/2 by the use of a π/2shifter 105, and is given to themixer 103. Further, the frequency signal from thelocal oscillator 107 is directly given to themixer 104. - Low pass filters (hereinafter, abbreviated as LPFs)106 and 108 are connected to the
mixers mixers LPSs - Each of the
LPFs LPFs mixers conversion portion 130. - In this case, the up-
conversion portion 130 is composed ofmixers local oscillator 113, a π/2 shifter, and anadder 112, as illustrated in FIG. 1. - With this structure, the
mixer 109 is given with an oscillation signal from thelocal oscillator 113. Further, the oscillation signal from thelocal oscillator 113 is shifted with π/2 by a π/2shifter 111, and is given to themixer 110. - Signals multiplied by the
mixers adder 112 Alternatively, the multiplied signals may be subtracted by a subtracter (not shown). An output signal of theadder 112 is converted by the use of adelay detection portion 114. - In the above-mentioned Weber
receiver 131, a carrier wave frequency of the received FSK signal is defined as π/2 π while frequency deviation is defined as ±Δω/2 λ. In this condition, the received FSK signal SrFSX is represented by the following equation. - SrFSK=cos(ω±Δω)t
- In this event, when the output signal SOSC1 of the
local oscillator 107 is defined as SOSC1=sin ωt, the output signals SMIX3 and SMIX4 of themixers - SMIX3=cos (ω±Δω)t·cos ωt =½{cos (ω±Δω+ω)t+cos (ω±Δω·ω) t}=½{cos (2ω±Δω)t+cos (±Δωt)}
- SMIX4=cos(ω±Δω)t·sin ωt =½{sin (ω±Δω+ω)t+sin (ω±Δω·ω)t}=½{sin (2ω±Δω)t+sin(±Δωt)}
- First terms of these equations are removed by the
LPFs LPFs - SLPF6=½{cos(Δωt)} (1)
- SLPF8=½{sin(Δωt)} (2)
- In this case, when calculation is carried out without
limiter amplifiers conversion portion 130 is modified as follows. Herein, it is to be noted that the output signal of thelocal oscillator 113 is defined by SOSC 2=sin ω2t. - Vout=½{cos (Δωt) sin ω2t)} ±½{sin (Δωt) cos ω2t)}=½{sin (ω2±Δω)} (3)
- From the above-mentioned result, the base band signal I, Q is converted to a signal having frequency deviation of ±Δω/2π when the intermediate frequency ω2/2π is defined as a center.
- Subsequently, when the
limiter amplifiers LPF 106 and themixer 109 or between theLPF 108 and themixer 110, the condition is explained as follows. - When inputs into the
mixers limiter amplifiers - S LPF6 .=k{cos(Δωt)}+⅓·cos (3Δωt) +⅕·cos (5Δωt)+. . .} (1′)
- S LPF8 .=k{sin (ω2±ω)t +⅓·sin(3(ω2±Δω)t +⅕·sin (5(ω2±Δω)t)+. . .} (2′)
- Namely, the output Vout′ of the up-
conversion portion 130 is similarly considered to be the modification of the above-mentioned equation (3). Thereby, the following equation is introduced. - Vout=k{sin (ω2±ω) t +⅓·sin (3(ω2±Δω)t +⅕·sin(5(ω2±Δω)t)+. . .} (3′)
-
- Consequently, it is found out that the conversion-up becomes possible even when the
limiter amplifiers LPF 106 and themixer 109 or between theLPF 108 and themixer 110. - Although the Weber
receiver 131 has been suggested as a SSB (Single Side Band) receiver, it is found out that the Weberreceiver 131 is applicable as the FSK receiver, as explained above. - The output signal of the
adder 112 is given to thedelay detection portion 114, and the F-V conversion is carried out in thedelay detection portion 114. - In FIG. 2, a detail structure of the
delay detection portion 114 is illustrated. Further, a timing chart showing change (waveform) of each signal of each portion in thedelay detection portion 114 is illustrated in FIG. 3. - A signal VA from the
adder 112 is converted into output signals VB and VC by removing amplitude demodulation components by the use of alimiter amplifier 119. - Subsequently, the output signals VB and VC are converted into signals VD and VE having desired slopes at rising through common-
emitter transistors comparators reference voltage 126. - In this event, the
transistors current sources capacitors - Moreover, the signals VF and VG are converted into a signal VH via an AND gate (namely logical product). Thereby, pulse signal line, which has constant amplitude and constant delay time τ is formed, as illustrated in FIG. 3.
- Finally, the pulse signal line VH is integrated by a
LPF 125, and converted into a voltage value VI corresponding to frequency. Further, the obtained voltage VI is converted into a logic data signal consisting of “1” and “0” by a converter (not shown). - In FIG. 4, frequency spectrums are illustrated so as to explain the above-mentioned structure. In an intermediate stage in the FIG. 4, center frequency between frequency of “1” and frequency of “0” becomes carrier wave frequency.
- In FIG. 5, characteristic obtained the
delay detection portion 114 is illustrated. In the above-mentioned example, demodulation sensitivity KD is defined as KD=2τ V [V/Hz]. Consequently, the characteristic is affected by variation of τ and V. Herein, it is to be noted that τ represents delay time while V indicates output amplitude of the signal VH. - Moreover, the delay time τ is inversely proportional to variation of the constant
current sources capacitors - Specifically, the demodulation sensitivity is fluctuated by variation of manufacturing condition. In addition, Further, F-V conversion output amplitude is varied in the direct-conversion method using the F-V conversion. As a result, receiving condition may be deteriorated.
- Further, the power supply voltage is restricted from the same reason, and reneality of the F-V conversion is degraded. In consequence, receiving condition is also degraded.
- It is therefore an object of this invention to provide a frequency-voltage conversion circuit which is capable of correcting manufacturing variation and change with time caused by the variation.
- It is another object of this invention to provide a frequency-voltage conversion circuit which is capable of demodulating a FSK signal with stable and high sensibility and linearity.
- In a frequency-voltage conversion circuit according to this invention, integrating means gives a predetermined slope for rising or falling of a rectangular pulse signal.
- First comparing means compares an output value of the integrating means with a threshold value, and produces a pulse signal line having a pulse width corresponding to frequency of the rectangular pulse signal.
- Storing means stores and retains the threshold value. Smoothing means smooths the pulse signal line, and produces a voltage value corresponding to the frequency of the rectangular pulse signal.
- Second comparing means compares the voltage value with a reference voltage, and charges and discharges electric charge for the storing means on the basis of the comparison result.
- In this case, the integrating means comprises a constant current device which produces constant current, and a static capacitance device which stores the current.
- With such a structure, the second comparing means discharges the electric charge from the storing means when the voltage value is higher than the reference voltage.
- On the other hand, the second comparing means charges electric charge for the storing means when the voltage value is lower than the reference voltage.
- FIG. 1 is a block diagram showing a related direct conversion receiver using F-V conversion;
- Fig. 2 is a connection diagram showing a detail structure of the
delay detection portion 114 illustrated in FIG. 1; - FIG. 3 is a timing chart showing change (waveform) of each signal of each portion in the
delay detection portion 114 illustrated in FIG. 1; - FIG. 4 is diagram showing frequency spectrums for explaining function of the direct-conversion receiver;
- FIG. 5 is a characteristic diagram showing characteristic obtained by the
delay detection portion 114 illusrated in FIG. 1; - FIG. 6 is a block diagram showing a structure of a receiver according to a first embodiment of this invention;
- FIG. 7 is a connection diagram showing a detail structure of the
delay detection portion 14 illustrated in FIG. 6; - FIG. 8 is a timing chart showing change (waveform) of each signal of each portion in the
delay detection portion 14 illustrated in FIG. 6; - FIG. 9 is a characteristic diagram showing difference of F-V conversion characteristic (demodulation sensitivity) due to difference of threshold level VTH16;
- FIG. 10 is a connection diagram showing a detail structure of a
delay detection portion 14 in frequency-voltage conversion circuit according to a second embodiment of this invention; and - FIG. 11 is a timing chart showing change (waveform) of each signal of each portion in the delay detection portion illustrated in FIG. 10.
- Hereinafter, description will be made about embodiments of this invention with drawings.
- (First embodiment)
- Referring to FIG. 6, description will be made about a first embodiment of this invention.
- A FSK (Frequency Shift Keying) signal transmitted from a transmitter (not shown) is received via an
antenna 1, is amplified by a high-frequency amplifier 2 ,and is given tomixers - An oscillation signal from a
local oscillator 7 is shifted with 2/π by a 2/π shifter 5. The shifted signal is given to themixer 3 while the oscillation signal from thelocal oscillator 7 is directly given to themixer 4. - The
mixers mixers LPFs - Each of the
LPFs LPFs mixers conversion portion 30. - The up-
conversion portion 30 is composed of a mixer 9, amixer 10, alocal oscillator 13, a 2/π shifter 11, and anadder 12. The mixer 9 is given with an oscillation signal from thelocal oscillator 13. On the other hand, the oscillation signal from thelocal oscillator 13 is shifted with 2/π by the 2/π shifter 5. The shifted signal is given to themixer 10. - Signals multiplied by the
mixers 9 and 10 are added by the use of anadder 12. Alternatively, the multiplied signals may be subtracted by a subtracter (not shown). - The
reference numeral 32 represents a switch which switches a signal obtained by aWeber receiver 31 with an output signal of thelocal oscillator 13. Thereference numeral 14 indicates a delay detection portion which F-V converts an output signal of theswitch 32. Further, thereference numeral 18 represents a control portion which controls theswitch 32 and thedelay detection portion 14. - The
switch 32 gives the output signal of thelocal oscillator 13 into thedelay detection portion 14 when a control signal S18 is put into “H” (high level). On the other hand, theswitch 32 gives the output signal of theadder 12 into thedelay detection portion 14 when the control signal S18 is put into “L” (low level). - In FIG. 7, a signal VA (rectangular pulse signal) from the
above adder 12 is removed amplitude modulation components thereof by alimiter amplifier 19, and is converted into output signals VB and VC respectively. - Subsequently, the output signals VB and VC are converted into signals VD and VE having desired slopes at rising through common-
emitter transistors - Further, the signals VD and VE are converted into signals VF and VG by
comparators - In this event, the
transistors current sources capacitors comparators capacitor 16, and is given with an output signal of aVI amplifier 15. - Further, the signals VF and VG are converted into a signal VH via an AND gate (logical product). Thereby, a pulse signal line VH, which has constant amplitude and constant delay time τ, is formed, as illustrated in FIG. 8.
- The pulse signal line VH is integrated by a
LPF 25, and is converted into a voltage value VI corresponding to frequency. - Further, the voltage value VI is compared with a reference voltage 17 (VREF). An output signal of the VI amplifier 15 is supplied as a reference voltage of the
comparator - With such a structure, when the control signal S18 is put into “L” (low level), the
switch 32 selects the output of theadder 32. Consequently, theVI amplifier 15 is put into an off-state (namely, an output terminal is opened). Consequently, electric charge (threshold level VTH16) of thecapacitor 16 is retained or kept. - On the other hand, when the control signal S18 is put into “H” (high level), the
switch 32 selects the output signal of thelocal oscillator 32. As a result, theVI amplifier 15 is put into an on-state. Thereby, feedback in thedelay detection portion 14 is activated. - As mentioned above, the signal VA from the
delay detection portion 14 is removed the amplitude modulation components thereof by thelimiter amplifier 19, and is converted into the signals VB and VC. In this event, the signals VB and VC have phases reverse to each other. - Subsequently, the output signals VB and VC are converted into signals VD and VE by the common-
emitter transistors comparators comparators - Further, the signals VF and VG are converted into a signal VH by via the AND gate. Thereby, pulse signal line VH having the constant amplitude and the constant delay time τ is formed, as described before.
- Finally, the pulse signal line VH is integrated by the
LPF 25, and is converted into the voltage value VI corresponding to the frequency of the signal VA. - The voltage value VI is compared with the reference voltage VREF. As a result of the comparison, when the voltage value VI is higher than the reference voltage VREF, the output of the
VI amplifier 15 is put into “L”. Thereby, electric charge off thecapacitor 16 is discharged. In consequence, the threshold level VTH16 is lowered or reduced. - On the other hand, when the voltage value VI is lower than the reference voltage VREF, the output of the
VI amplifier 15 is put into “H”. Thereby, electric charge of thecapacitor 16 is charged. Thereby, the threshold level VTH16 is increased. - In the first embodiment, the delay time τ is adjusted on the condition that the control signal S18 is put into “H”. Thereby, the voltage value VI from the
delay detection portion 14 is converged to the reference voltage VREF. In this event, frequency given to thedelay detection portion 14 is equal to center frequency of a second FSK signal. - On the other hand, when the control signal S18 is put into “L”, a normal receiving state appears. In this case, frequency given to the
delay detection portion 14 is equal to the second FSK signal. Therefore, the control signal S18 is put into “H” during signal receiving wait state or during signal receiving state unnecessary to receive a signal. - The above-mentioned delay time τ is inversely proportional to current variation of the constant
current source capacitor comparator - In this embodiment, when the voltage value VI is higher than the reference voltage VREF, the delay time τ becomes higher than a value to be essential. In this case, the
VI amplifier 15 discharges electric charge of thecapacitor 16 so as to reduce VTH16. Thereby, the delay time τ becomes low. In consequence, the voltage value VI is reduced, and the voltage value VI is finally is converged to VREF. - On the other hand, when the voltage value VI is lower than the reference voltage VREF, the delay time τ becomes lower than the value to be essential. In this event, the
VI amplifier 15 charges electric charge of thecapacitor 16 so as to increase VTH16. Thereby, the delay time τ becomes high. Consequently, the voltage value VI is increased, and the voltage value VI is finally is converged to VREF. - In FIG. 9, F-V conversion characteristic (demodulation sensibility) is illustrated in accordance with difference of the threshold levels VTH16.
- Herein, it is to be noted that each straight line A, B and C in FIG. 9 corresponds to each level A, B and C illustrated in FIG. 8.
- The voltage value VI is equal to a voltage corresponding to center frequency of the second FSK signal. Therefore, the voltage corresponding to the center frequency is compatible with the reference voltage VREF. Thereby, variation of the demodulation sensibility is substantially eliminated, and the F-V conversion characteristic is corrected as the straight line B illustrated in FIG. 9.
- When the receiving sate becomes normal by putting the control signal S18 into “L”, the reference voltage VREF is used as reference voltage of a comparator or an A/D (Analog/Digital) converter given with the voltage VI, and thereby, corresponds to center frequency of accurate second FSK signal.
- (Second embodiment)
- Referring to FIG. 10, description will be made about a second embodiment of this invention. Herein, it is to be noted that the same reference numeral is attached to the same portion as each portion illustrated in FIG. 7.
- In the second embodiment, a current control portion27 is controlled by the use of a control signal S18 from the
control portion 18. The current control portion 27 compares the voltage value VI with the reference voltage VREF, and controls constantcurrent sources - With such a structure, when the control signal S18 is put into “L”(low level), current value of the constant
current source local oscillator 13 selected by theswitch 32 is given thereto. Thereby, the current control portion 27 is put into an on-state. Consequently, the feedback becomes active. - In this event, a signal VA is removed amplitude modulation components thereof by the
limiter amplifier 19, and is converted into signals VB and VC. The signals VB and VC are given with desired slopes corresponding to current values determined by constantcurrent sources - Further, the signals VD and VE are converted into signals VF and VG by
comparators - Further, logic product (negative logic product) is carried out for the signals VF and VG through an AND
gate 24. Thereby, pulse signal line VH is generated, as illustrated in FIG. 11. - In the pulse signal line VH, amplitude and delay time τ are constantly kept. This signal line VH is integrated by a
LPF 25, and is converted into voltage value VI corresponding to the frequency of the signal VA. - In this case, the voltage value VI is compared with the reference voltage VREF. As the result of the comparison, when the voltage value VI is higher than the reference voltage VREF, the current control portion 27 controls so as to increase current value of the constant
current source - On the other hand, when the voltage value VI is lower that the reference voltage VREF, the current control portion 27 controls so as to reduce the current value of the constant
current source - More specifically, when the control signal S18 is put into “H” (namely, the feedback is in an active state), the delay time τ is adjusted. Further, the F-V converted voltage value VI is converged into the reference voltage VREF. On the other hand, when the control signal S18 is put into “L”, normal receiving state appears.
- Therefore, the control signal S18 is put into “H” so as to perform the feedback during signal receiving wait state or during signal receiving state unnecessary to receive a signal.
- The delay time τ is inversely proportional to variation of the current value of the constant
current source capacitor comparator - In this embodiment, when the voltage value VI is higher than the reference voltage VERF, the delay time τ is becomes larger than a value to be essential. In such a case, the current control portion 27 controls so as to increase the current value of the constant
current source - On the other hand, when the voltage value VI is lower than the reference voltage VERF, the delay time τ is becomes lower than the value to be essential. In this case, the current control portion 27 controls so as to reduce the current value of the constant
current source - Herein, it is to be noted that the voltage value VI is a voltage which corresponds to center frequency of the second FSK signal. Therefore, the voltage corresponding to the center frequency is made to be compatible with the referential voltage VREF. Thereby, variation of demodulation sensibility is substantially eliminated. Further, the F-V conversion characteristic is corrected as the straight line B illustrated in FIG. 9 When the control signal S18 is put into “L” and is in the normal receiving state, the reference voltage VREF is used as the reference voltage of a comparator or a A/D converter which is supplied with the voltage value VI, and thereby, accurately corresponds to the center frequency of the second FSK signal.
Claims (15)
1. A frequency-voltage conversion circuit, comprising:
integrating means which gives a predetermined slope for rising, or falling of a rectangular pulse signal;
first comparing means which compares an output value of the integrating means with a threshold value and which produces a pulse signal line having a pulse width corresponding to frequency of the rectangular pulse signal;
storing means which stores and retains the threshold value;
smoothing means which smooths the pulse signal line and which produces a voltage value corresponding to the frequency of the rectangular pulse signal; and
second comparing means which compares the voltage value with a reference voltage and which charges and discharges electric charge for the storing means on the basis of the comparison result.
2. A circuit as claimed in , wherein:
claim 1
the integrating means comprises;
a constant current device which produces constant current, and
a static capacitance device which stores the current.
3. A circuit as claimed in , wherein:
claim 1
the second comparing means discharges the electric charge from the storing means when the voltage value is higher than the reference voltage.
4. A circuit as claimed in , wherein:
claim 1
the second comparing means charges electric charge for the storing means when the voltage value is lower than the reference voltage.
5. A frequency-voltage conversion circuit, comprising:
integrating means which gives a predetermined slope for rising or falling of a rectangular pulse signal;
comparing means which compares an output value of the integrating means with a threshold value and which produces a pulse signal line having a pulse width corresponding to frequency of the rectangular pulse signal;
smoothing means which smooths the pulse signal line and which produces a voltage value corresponding to the frequency of the rectangular pulse signal; and
a current control portion which compares the voltage value with a reference voltage and which changes the slope of the rising or the falling of the rectangular pulse signal on the basis of the comparison result.
6. A circuit as claimed in , wherein:
claim 5
the integrating means comprises;
a constant current device which restricts current to a predetermined value, and
a static capacitance device which stores the current.
7. A circuit as claimed in , wherein the
claim 6
the current control portion compares the voltage value with the reference voltage and changes current restricting value by the constant current device on the basis of the comparison result.
8. A circuit as claimed in , wherein:
claim 7
the current control portion increases the current restricting value by the constant current device when the voltage value is higher than the reference voltage.
9. A circuit as claimed in , wherein:
claim 7
the current control portion reduces the current restricting value by the constant current device when the voltage value is lower than the reference voltage.
10. A receiving apparatus having at least an oscillator, and an up-conversion portion which includes a first mixer connected to the oscillator, a second mixer connected to the oscillator via a 2/π shifter, and an adder for adding output signals of the first and second mixers, comprising:
a switch which selects either one of an output signal of the oscillator and an output signal of the adder;
a delay detection portion which converts the selected signal between frequency and voltage so as to produce a voltage value; and
control portion which controls the switch and the delay detection portion.
11. An apparatus as claimed in , wherein:
claim 10
the control portion gives a control signal into the switch and the delay detection portion.
12. An apparatus as claimed in , wherein:
claim 11
the control portion selects the output signal of the oscillator when the control signal is put into a first level while the control portion selects the output signal of the adder when the control signal is put into a second level different from the first level.
13. An apparatus as claimed in , wherein:
claim 12
the first level is equal to a high level while the second level is equal to a low level.
14. An apparatus as claimed in , wherein:
claim 10
the oscillator produces a rectangular pulse signal having a predetermined frequency.
15. An apparatus as claimed in , wherein: the receiving apparatus includes a Weber receiver.
claim 10
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JP35381398A JP3204233B2 (en) | 1998-11-30 | 1998-11-30 | Frequency-voltage conversion circuit, receiver, and method of controlling frequency-voltage conversion characteristics |
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US09/450,331 US6252438B1 (en) | 1998-11-30 | 1999-11-29 | Frequency-voltage conversion circuit and receiving apparatus |
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US7479812B1 (en) * | 2005-05-27 | 2009-01-20 | National Semiconductor Corporation | Producing a frequency-representative signal with rapid adjustment to frequency changes |
US20080007983A1 (en) * | 2006-06-28 | 2008-01-10 | Honeywell International, Inc. | Frequency-to-voltage converter with analog multiplication |
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US4383230A (en) * | 1979-09-24 | 1983-05-10 | Manzolini David B | Voltage tuned active filter and circuitry simulating a capacitance and an inductance |
JPS57204629A (en) * | 1981-06-12 | 1982-12-15 | Nec Corp | Control circuit of pulse width |
US4675580A (en) * | 1985-09-30 | 1987-06-23 | Rca Corporation | Parabolic voltage generating circuit |
US5757219A (en) * | 1996-01-31 | 1998-05-26 | Analogic Corporation | Apparatus for and method of autozeroing the input of a charge-to-voltage converter |
JPH10163877A (en) * | 1996-11-28 | 1998-06-19 | Sony Corp | Threshold control circuit of multi-valued comparator for demodulation circuit |
US6118984A (en) * | 1997-04-08 | 2000-09-12 | Acer Peripherals, Inc. | Dual conversion radio frequency transceiver |
-
1998
- 1998-11-30 JP JP35381398A patent/JP3204233B2/en not_active Expired - Lifetime
-
1999
- 1999-11-29 US US09/450,331 patent/US6252438B1/en not_active Expired - Lifetime
-
2001
- 2001-01-11 US US09/757,793 patent/US6433591B2/en not_active Expired - Lifetime
Cited By (8)
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US20030090574A1 (en) * | 2001-10-30 | 2003-05-15 | Seaman Mark D. | Systems and methods for providing automated delivery of digital images |
US20030222702A1 (en) * | 2002-04-04 | 2003-12-04 | Christian Bjork | Quadrature switching mixer with reduced leakage |
US20030236083A1 (en) * | 2002-04-04 | 2003-12-25 | Magnus Wiklund | Linearity improvement of Gilbert mixers |
WO2003085819A3 (en) * | 2002-04-04 | 2004-02-19 | Ericsson Telefon Ab L M | Linearity improvement of gilbert mixers |
US7054609B2 (en) | 2002-04-04 | 2006-05-30 | Telefonaktiebolaget Lm Ericsson (Publ) | Linearity improvement of Gilbert mixers |
US7672659B2 (en) | 2002-04-04 | 2010-03-02 | Telefonaktiebolaget L M Ericsson (Publ) | Mixer with feedback |
US20100194484A1 (en) * | 2009-02-04 | 2010-08-05 | Hiroshi Deguchi | Oscillator circuit and memory system |
US8008978B2 (en) * | 2009-02-04 | 2011-08-30 | Kabushiki Kaisha Toshiba | Oscillator circuit and memory system |
Also Published As
Publication number | Publication date |
---|---|
US6433591B2 (en) | 2002-08-13 |
US6252438B1 (en) | 2001-06-26 |
JP3204233B2 (en) | 2001-09-04 |
JP2000165460A (en) | 2000-06-16 |
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