JPH02302130A - Frequency conversion circuit, phase correction device used therefor, variable phase shifter used for relevant phase correction device and television receiver using the same frequency conversion circuit - Google Patents

Abstract

PURPOSE:To cancel image signals independently of the accuracy of phase of a local oscillator by providing a circuit correcting the error of phase of two signals from the local oscillator with respect to 90 deg.. CONSTITUTION:Phase shifters 19, 20 give the phase difference of 90 deg. to the output of a 1st mixer 17 and a 2nd mixer 18, a synthesizer 21 synthesizes the outputs of the phase shifters 19, 20 and outputs an intermediate frequency signal. A phase correction device 22 correcting the signal phase difference to 90 deg. is provided on the output stage of a local oscillator 16. Thus, the local oscillation signal with the phase difference of 90 deg. accurately is fed to the mixers 17, 18. Moreover, the image signal component phase difference is corrected to be 180 deg., thereby sufficiently ensuring the image attenuation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a frequency conversion circuit used in a wireless communication device.

[Conventional technology]

Conventionally, as a circuit configuration for canceling image signals in a television receiver, IE, International Solid States, Funferens (1987), pp. 216-217 (I
EEE, InternationalSol
id-8tate C1rcuits Conference
(1987) pp. 216-217), two signals obtained by dividing the original oscillation signal of the oscillator by 1/2 and having a phase difference of 90° are used as local oscillation signals to generate an image. Circuit configurations for canceling signals are known.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, the error for the phase difference of 90'' between the two signals obtained from the local oscillator directly appears as a decrease in the amount of image signal cancellation.Specifically, the phase error is 1.2.
'The amount of cancellation of -40dB is -30d at phase skin 43.6°
It drops to B. This is based on the assumption that there is no amplitude error, so it is thought that it will actually be lower.

In the conventional example, when integrated into an IC, the phase difference between the two outputs of the local oscillator may have an error of 4 to 5 @ due to element variations, and there was a problem that a sufficient amount of image signal cancellation could not be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a frequency conversion circuit having an image signal suppression ability that ensures a sufficient amount of image signal cancellation regardless of the phase accuracy of the output of a local oscillator.

[Means to solve the problem]

In order to achieve the above object, a phase corrector is provided to correct the phase difference between the two outputs of the local oscillator to 90'.

[Effect]

The phase corrector detects an error with respect to the 90° phase difference between the two signals, and operates to correct the phase difference between the two signals to 90° using the detected signal.

〔Example〕

A first embodiment of the present invention will now be described with reference to FIG. In FIG. 1, 11 is an input terminal, 12 is a bandpass filter that selects a received signal, and 13 is a bandpass filter 1.
a high frequency amplifier for amplifying the signal selected by 14;
is a divider that divides the output of the high frequency amplifier 13 into two signals,
15 is a resonator, 16 is a local oscillator that outputs two signals whose phases are 90° different from each other than the output of the resonator 15, and 17 is a first oscillator that mixes one output of the distributor 14 and one output of the local oscillator 16. 18 is a second mixer that mixes the other output of the distributor 14 and the other output of the local oscillator 16; 19.20 is the first mixer 17 and the second mixer 18;
21 is a synthesizer that combines the outputs of the phase shifters 19 and 20 and outputs an intermediate frequency signal, 22 is an output terminal, and 23 is a first phase corrector. , is.

Before explaining the operation in FIG. 1, the image signal suppressing operation in the conventional frequency conversion circuit capable of suppressing image signals shown in FIG. 2 will be explained.

In FIG. 2, parts designated by the same numbers as in FIG. 1 perform the same functions as in FIG.

Among the signals input to the first mixer 17 and the second mixer 18, the desired signal that has passed through the bandpass filter 12 is expressed as=Eg・5in(ωst+Qs)・=(
1) The image signal that could not be removed by the band pass filter 12 is 6; = E 1-sin (ωit + Qi)
”・(2), and the signal from the local oscillator 16 input to the first mixer 17 is aL□=EL−sin(ωLt+Qt,)・
-c3) Local oscillator 16 input to second mixer 18
The signal from aLa=EL-sin(ωLt+QL+) ・-
(4).

The signals input from the distributor 14 to the first and second mixers 17 and 18 are frequency-converted by being mixed with the signals output from the local oscillator 16, respectively. The intermediate frequency signal components of the signals frequency-converted by the first and rj second mixers 17 and 18 are respectively eLiX (
as+eH) and eLzX(e3+s;).

The intermediate frequency signal component of the output of the first mixer 7 is Es-EL/2 ・cos((ωt-ωs)t+Q
t-Qs)+Ei-Ez/2・cos((ωL-ωH)
t+Qz-Qi)=EslE L/211cos
(ωmt + Q engineering) + Ei - Er, /2・cos (ωmt
+Q2) -(5) The intermediate frequency signal component of the output of the second mixer 8 is E s-E L/2 ・cos((<I) L-Qs
)t+QL-Qs+7)+Ei-Et/2・cos((
Qz cv;)t+QLQi+τ)=Es-EL/2
・cos(ω+at+Q,+T)+Ei”Et/2・
cos (ωmt+Qz)...(6
) However, ωL-ωS=ωm, ωL-ωi=-ωm, +
13111 is the intermediate frequency, Qt = QL Qs,
Qz = -QL +Qi.

In the above equations (5) and (6), each first term is the desired signal intermediate frequency component element sx t fs, and the second term is the image signal component element i1. fi, is.

FIG. 3 shows the respective phase relationships.

Next, the outputs of the first and second mixers 17, 18 are passed through phase shifters 19, 20 to the outputs of the first and second mixers 17, 18, respectively.

1ψ phase can be changed. However, Todoroki φ − Todoroki ψ =] “
...(7) The intermediate frequency signal components of the outputs of the phase shifters 19 and 20 are respectively Es-Et/2・cos(ω+et+Q1+＾φ)+E
i-Et/2・cos(ωmt+Q,+Aφ')-(
8) E s−E L/ 2・cos (ωmt+Q1+
Ding+＾φ)+E s−E L/ 2 ・cos(ωm
t+ Q2--7+ aψ)-(9). the above(
8), (9), each first term is the desired signal intermediate frequency component tfB2. The second term is the image signal component element i, , fii.

Figure 4 shows the respective phase relationships.

As is clear from the phase relationship in FIG. 4, the desired signal intermediate frequency components are in phase and the image signal components are in opposite phase.
By combining, only the image signal can be suppressed.

Here, if an error occurs in the image signal component phase difference of the outputs of the phase shifters 19 and 20 relative to 180°, the amount by which the image signal is suppressed by the synthesizer 21 decreases. Using this amount as the image cancellation amount, FIG. 5 shows the relationship between the image signal component phase difference and the error for 180°. From Figure 5, when the phase error increases from 1.2° to 3.6°, the amount of image cancellation is 10
dB deterioration.

Hereinafter, the reason why the image signal component phase difference of the output of the phase shifter 19, 20 causes an error with respect to 180 degrees and the embodiment shown in FIG. 1 for correcting the error will be described.

When the phase difference between the two outputs of the local oscillator 16 is 90° and there is a phase error of δ, the intermediate frequency component in the output of the mixer 17.18 is Es-EL/2・cos(ωmt
+Q□+ aφ)+Ei-Et/2・cos(ωmt+
Q2+ aφ)・(9)Es−EL/2・cos(ω
mt+Q, +(-H+aδ)+1ψ). Above (9
), In equation (10), the first term is the desired signal intermediate frequency component B19 fs, the second term is the image signal component 41t fxx, and the one phase error δ appears as it is at the outputs of the mixers 17 and 18.

FIG. 6 shows the respective phase relationships.

Therefore, the image signal component phase difference of the outputs of the phase shifters 19 and 20 produces a phase error for 180°.

The embodiment shown in FIG. 1 is a frequency conversion circuit capable of correcting the image signal component phase difference of the outputs of the phase shifters 19 and 20 to 180°.

That is, by providing the phase corrector 22 that corrects the signal phase difference to 90° at the output stage of the local oscillator 16,
Local oscillation signals with a phase difference of 0° are sent to mixers 17 and 18.
The image signal component phase difference can be corrected to 180°, and a sufficient amount of image attenuation can be ensured.

As explained above, according to this embodiment, the local oscillator
This has the advantage that it is possible to configure a frequency conversion circuit capable of suppressing image signals that is not affected by the output phase difference accuracy.

FIG. 7 is a block diagram showing the second embodiment.

In this embodiment, in the frequency conversion circuit shown in FIG. 2, when the phase difference between the two outputs of the local oscillator has a phase error of Δδ with respect to 90°, the image signal component position of the output of the phase shifter 19 and 20 is A circuit is provided to correct the phase difference to 180'.

In FIG. 7, 24 is a second phase corrector, and the parts designated by the same numbers as in FIG. 1 have the same functions as those in FIG. 1, so their explanation will be omitted.

As mentioned above, the phase difference between the two outputs of the local oscillator 16 is 90
', mixer 17,1
The phase relationship between the desired signal intermediate frequency component and the image signal component of the output of No. 8 is as shown in FIG.

Even if an attempt is made to correct the phase difference between the image signal components at the outputs of the mixers 17 and 18 to 90'', the phase error cannot be directly detected because the image signal components are attenuated by the bandpass filter 12.

Since the signal component detectable at the output of the mixer 17,18 is the desired signal intermediate frequency component, the mixer 17,1
The second phase corrector 24 provided at the output stage of B detects the phase difference between the desired signal intermediate frequency components and operates to correct the phase difference between the image signal frequency components to 90'.

From FIG. 6, the phase error of the desired signal intermediate frequency component with respect to 90° has the same magnitude as the phase error of the image signal component with respect to 90°, but the direction of rotation is opposite. Therefore, the second phase corrector 24 detects the phase error with respect to 90° of the desired signal intermediate frequency component of the eight outputs of the mixers 17 and 18,
The phase of the outputs of mixers 17 and 18 is changed by the detected phase amount, and the phase error with respect to 90' of the desired signal intermediate frequency component is changed to 90'.
By rotating the image signal component in the opposite direction to the direction in which it is to be corrected, the phase difference of the image signal component is corrected to 90". As a result, the phase difference of the image signal component of the 8 forces of the phase shifter 19° and 20 is 180°. Therefore, a sufficient amount of image attenuation can be secured.

As explained above, according to this embodiment, the same effects as the embodiment shown in FIG. 1 can be obtained.

FIG. 8 is a block diagram showing a third embodiment of the present invention. In FIG. 8, parts designated by the same numbers as in FIGS. 1 and 7 perform the same functions as in FIGS. 1 and 7.

In this embodiment, the first phase corrector 23 in the embodiment shown in FIG. 1 and the second phase corrector 24 in the embodiment shown in FIG.
This is a frequency conversion circuit equipped with both of the following, and its operation is similar to that of the first and second embodiments.

FIG. 9 shows the first phase corrector 2 in FIGS. 1 and 8.
FIG. 3 is a block diagram showing a specific example of No. 3;

In FIG. 9, 31.32 is an input terminal, 33.34 is an output terminal, 35.36 is a first and second variable phase converter that varies the phase of the input signal by a control voltage, and 37.
38 is a detection terminal, 39 and 40 are control terminals, and 41 is a phase detector that detects the phase difference between two input signals and generates a voltage at the control terminals 39 and 40 according to the phase difference.

The operation will be explained below. The signals input to the input terminals 31 and 32 are outputted to the output terminals 33 and 34 via the first and second variable phase shifters 35 and 36, and are also output to the phase detector 4.
1 is input. The phase detector 41 detects a phase error with respect to 90'' of the phase difference between the two input signals, and outputs the signal to the control terminal 3.
At 9.40, the control voltage necessary for the variable phase shifters 35 and 36 to operate so that the phase difference of the eight forces approaches 90° is generated. In this way, the first and second variable phase shifters 3
By feeding back a voltage corresponding to the phase difference between the signals output from the output terminals 33 and 36 to the first and second variable phase shifters 35 and 36, the phase difference between the two signals output to the output terminals 33 and 34 can be adjusted. It operates to maintain the angle at 90°.

According to this specific example, the phase difference between the two signals can be maintained at 90''.

FIG. 10 is a block diagram showing a specific example of the second phase corrector 24 in FIGS. 7 and 8. FIG.

In Figure 10, parts indicated by the same numbers as in Figure 9 have the same functions as in Figure 9, and 42 and 43 have the same functions as the first and second variable phase shifters, respectively. The operation of the third and fourth variable phase shifters will be explained below. Of the two signals input to the second phase corrector 24 having a phase error with respect to the phase difference of 90°, the signal input to the input terminal 31 is phase-compared via the first variable phase shifter 35. It is also supplied to the output terminal 33 via the third variable phase shifter 42. On the other hand, the signal input to the input terminal 32 is supplied to the phase detector 41 via the second variable phase shifter 36, and is also supplied to the output terminal 34 via the variable phase shifter 43.

First and second variable phase shifters 35, 36 and phase detector 4
1, the operation of correcting the phase difference to 90' is similar to the specific example shown in FIG.

Further, the third phase shifter 42 is controlled by the control voltage from the control terminal 40, and the fourth phase shifter 43 is controlled by the control voltage from the control terminal 39 (input terminal 31
and 32 to change the phase of the signal and output it to output terminals 33 and 34. This amount of phase change is the same as the phase error of the signals input to the input terminals 31 and 32 with respect to 90 degrees, and the phase rotation direction is opposite to the direction in which the phase difference is corrected to 90 degrees. By performing the above operation, the second phase correction winding 22
As described in the embodiment shown in the figure, it operates to detect the phase difference between the desired signal intermediate frequency components and correct the phase difference between the image signal components to 90°.

According to this specific example, it is possible to detect the phase difference between the desired signal intermediate frequency components and correct the phase difference between the image signal components to 90'.

FIG. 11 shows the phase detector 41 in FIGS. 9 and 10.
FIG. 2 is a circuit diagram showing a specific example.

In Figure 11, 37.38 is a detection terminal, 53.54
is an unbalanced-balanced circuit, 55, 56, 57° 58.59,
60 is a FET that constitutes an analog multiplication circuit, 61.62
63 is a drain resistor, 63 is a constant current source, 64 is a power supply voltage application terminal, 65 and 66 are low-pass filters for extracting the DC component of the signal, and 39 and 40 are control terminals.

The signal input to the detection terminal 37 is sent to the unbalanced-balanced circuit 53.
are applied to the gates of FETs 55, 58 and 56, 57 as two signals having a phase difference of 180°. Similarly, the signal input to the detection terminal 38 is applied to the gates of FETs 59 and 60, respectively, via the unbalanced-balanced circuit 54.

The phase of the signal input to the detection terminal 37 is
If it is 90″ ahead of the phase of the signal input to
Control terminal 39. ．． When the same standard voltage is generated at 40 and the lead is smaller than 90°, a voltage higher than the standard voltage is generated at the control terminal 39, a voltage lower than the standard voltage is generated at the control terminal 40, and the lead is smaller than 90°. If it is larger than 906, a voltage lower than the standard voltage is generated at the output terminal 39 and a voltage higher than the standard voltage is generated at the control terminal 40.

FIG. 12 shows the variable phase shifter 35 in FIGS. 9 and 10.
, 36, 42, and 43. FIG.

In FIG. 12, 71 is the output impedance of the signal source, 72 is the load resistance, and 73 is the F constituting the source common circuit.
ET, 74 is a source resistance, 75 is a variable means for varying the drain-source voltage (hereinafter referred to as Vd5) of the FET 73, 7
6 is an input terminal, and 77 is an output terminal.

The signal input to the input terminal 76 has its phase reversed at the output terminal 77, and the signal source output impedance 71 and the FE
Gate-drain junction capacitance of T73 (hereinafter referred to as Cgd)
, the phase changes by "Q" due to the RC circuit formed by the gate-source junction capacitance.

By the way, the cgci of the FET 73 and the gate-drain voltage (hereinafter referred to as Vgd) of the FET 73 have a relationship as shown in FIG. Therefore, if the variable means 75 is adjusted so that Vgd is set at point A in FIG. 13, and then the variable means 75 is adjusted to reduce Vds, Vgd will also be reduced, and as shown in FIG. Point A moves to point A', and as Cgd becomes larger, Todoroki Q becomes larger. Furthermore, when the variable means 75 is adjusted to increase Vds, Vgd also increases, point A moves to point A#, and Cgd decreases, so ΔQ
becomes smaller.

As explained above, in this specific example, the amount of phase shift can be continuously varied by voltage control.

FIG. 14 shows the variable phase shifter 35 in FIGS. 9 and 10.
, 36, 42, and 43. FIG. In FIG. 14, parts indicated by the same numbers as in FIG. 12 perform the same functions as in FIG. 12. The variable phase shifter shown in FIG. 14 has a common source circuit of the variable phase shifter shown in FIG. The operation is the same except that it is replaced with a source follower circuit.

Note that the variable means 27 for varying Vds in FIGS. 12 and 14 operates in accordance with the control voltage from the control terminals 39 and 40.

According to this specific example, the amount of phase shift can be made variable by voltage control, and a phase shifter with low output impedance can be constructed.

FIG. 15 shows the variable phase shifter 35 in FIGS. 9 and 10.
, 36, 42, and 43. FIG.

In FIG. 15, parts indicated by the same numbers as in FIG. 12 perform the same functions as in FIG. 12, and 78 is an FE.
Variable means for varying the gate-source voltage (hereinafter referred to as Vgs) of T73, 79 is a power supply voltage application terminal.

By adjusting the variable means 78, the Vg of the FET 73
After adjusting d to point A in FIG. 13, the variable means 7
8 to increase Vgs, FET73
(7) Vgd becomes smaller, and the point A in FIG.
Point A in the diagram moves to point A'. In Figure 13, point A moves to point A'.
The operation of changing the amount of phase shift by moving to point ' or point A# is the same as the specific example shown in FIG.

FIG. 16 shows the variable phase shifter 35 in FIGS. 9 and 10.
, 36, 42, 43 according to the fourth embodiment.

In FIG. 16, parts indicated by the same numbers as in FIG. 15 perform the same functions as in FIG. 15.

The variable phase shifter shown in FIG. 16 is obtained by replacing the common source circuit of the variable phase shifter shown in FIG. 15 with a source follower circuit, and the operation is the same.

Figure 17 shows the Vg of the FET in Figures 15 and 16.
FIG. 7 is a circuit diagram showing a specific example of variable means 78 for making s variable.

In FIG. 17, 81 is a source follower FET, 82
is a level shift diode, 83 is a current source FET, 84
85 is a source diode, 85 is a power supply voltage application terminal, 86 is a control voltage application terminal, 87 is an input terminal, and 88 is an output terminal.

A signal input to the input terminal 87 is outputted from the output terminal 88 via the FET 81 and the level shift diode 82. Here, if the voltage applied to the control voltage application terminal 86 is increased, the FET 81 and the level shift diode 82
The current flowing through the output terminal 88 increases, and the DC range of the signal taken out from the output terminal 88 decreases. Conversely, when the voltage applied to the control voltage application terminal 86 is reduced, the DC component of the signal taken out from the output terminal 88 becomes larger. Therefore, the output terminal 88 is connected to the FET in FIGS. 15 and 16.
This specific example is connected to the gate of 73 in Figs. 15 and 16.
By using it as a variable means 78 for varying Vgs in the figure, a circuit that can vary the amount of phase shift by voltage control can be configured.

FIG. 18 is a block diagram showing an example in which the embodiment of FIG. 1 is applied to a television receiver.

In FIG. 18, 25 is an intermediate frequency amplifier, 26 is a demodulator that demodulates the intermediate frequency signal, 2'7 is an output terminal that outputs the demodulated signal, and 28 is the magnitude of the signal demodulated by the demodulator 26. A to control the gain of a high frequency amplifier by checking the
GC circuit 29 is a channel selection control circuit. Furthermore, the area within the broken line is the frequency conversion circuit of the embodiment shown in FIG.

The signal output from the synthesizer 21 is amplified by an intermediate frequency amplifier, demodulated by a demodulation circuit 24, and taken out from an output terminal 25 as a video signal.

In the example shown in FIG. 18, the embodiment shown in FIG. 1 is used as the frequency conversion circuit, but the embodiment shown in FIG. 7 or the embodiment shown in FIG. 8 may also be used.

〔Effect of the invention〕

According to the invention, the phase of the two signals from the local oscillator is
Since a circuit is provided for correcting the error relative to the angle, the image signal can be canceled out regardless of the phase accuracy of the local oscillator.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
3 is an explanatory diagram showing the phase relationship between the intermediate frequency signal components of the signals obtained from the first and second mixers in FIG. 2, and FIG.
The figure is an explanatory diagram showing the phase relationship of intermediate frequency signal components of the signal obtained from the phase shifter in Fig. 2, and Fig. 5 is an explanatory diagram showing the phase relationship of the intermediate frequency signal component of the signal obtained from the phase shifter in Fig. 2. 6 is an explanatory diagram showing the phase relationship between the intermediate frequency signal components of the signals obtained from the first and second mixers in FIG. 2 when there is a phase error. 7 is a block diagram showing a second embodiment of the present invention, FIG. 8 is a block diagram showing a third embodiment of the present invention, and FIG. 9 is a block diagram showing the first phase correction in FIGS. 1 and 8. 10 is a block diagram showing a specific example of the second phase corrector in FIGS. 7 and 8. FIG. 11 is a block diagram showing a specific example of the second phase corrector in FIGS. 9 and 10. A circuit diagram showing a specific example of a detector, FIG.
13 is a characteristic diagram showing the relationship between the gate-drain junction capacitance and the gate-drain voltage of the FET 73 in FIG. 12, FIG. 14 is a circuit diagram showing a second specific example of the variable phase shifter in FIGS. 9 and 10, and FIG. 15 is a circuit diagram showing a third specific example of the variable phase shifter in FIGS. 9 and 10. 16 is a circuit diagram showing a fourth specific example of the variable phase shifter in FIGS. 9 and 10, and FIG. 17 is a specific example of the variable means in FIGS. 15 and 16. FIG. 18 is a block diagram showing an example in which the embodiment of FIG. 1 is applied to a television receiver. 16... Local oscillator, 17... First mixer, 18
...Second mixer, 19.20...Phase shifter, 21.
...Synthesizer, 22...first phase corrector. Laugh 1 Figure Atsushi 2 Figure 3 Here Figure 4: ″f-゛2 Figure 5 'O-1 Kaotsu Figure 72 Tail! 3 Figure 18

Claims (1)

[Claims] 1. Each of them has a frequency that differs from the frequency of the input signal by an amount of the intermediate frequency, and 2. Their phases differ by approximately 90° from each other.
a local oscillator that outputs one signal; a first mixer that mixes the input signal with one of the two signals output from the local oscillator to convert the frequency of the input signal; and a first mixer that converts the frequency of the input signal; a second mixer that converts the frequency of the input signal by mixing it with the other of the two signals output from the local oscillator; A frequency conversion circuit comprising a phase shifter that creates a 90° phase difference between signals, and a synthesizer that combines two signals output from the phase shifter, the two signals output from the local oscillator. The phase difference between two signals is 9
A frequency conversion circuit characterized in that a first phase corrector correcting to 0° is provided between the local oscillator and the first and second mixers. 2. Each signal has a frequency that differs from the frequency of the input signal by an amount equal to the intermediate frequency, and their phases differ by approximately 90°.
a local oscillator that outputs one signal; a first mixer that mixes the input signal with one of the two signals output from the local oscillator to convert the frequency of the input signal; and a first mixer that converts the frequency of the input signal; a second mixer that converts the frequency of the input signal by mixing it with the other of the two signals output from the local oscillator; A frequency conversion circuit comprising a phase shifter that provides a 90° phase difference between signals, and a synthesizer that synthesizes two signals output from the phase shifter, wherein the first and second mixers A second phase corrector is provided between the first and second mixers and the phase shifter for correcting to 90° a phase difference between image signals included in two signals respectively output from the mixer. A frequency conversion circuit featuring: 3. Each signal has a frequency that differs from the frequency of the input signal by an amount equal to the intermediate frequency, and their phases differ by approximately 90° 2.
a local oscillator that outputs one signal; a first mixer that mixes the input signal with one of the two signals output from the local oscillator to convert the frequency of the input signal; and a first mixer that converts the frequency of the input signal; a second mixer that converts the frequency of the input signal by mixing it with the other of the two signals output from the local oscillator; A frequency conversion circuit comprising a phase shifter that creates a 90° phase difference between signals, and a synthesizer that combines two signals output from the phase shifter, the two signals output from the local oscillator. The phase difference between two signals is 9
A first phase corrector for correcting to 0° is provided between the local oscillator and the first and second mixers, and the image contained in the two signals output from the first and second mixers, respectively. A frequency conversion circuit characterized in that a second phase corrector for correcting a signal phase difference to 90° is provided between the first and second mixers and the phase shifter. 4. In the first phase corrector used in the frequency conversion circuit according to claim 1 or 3, the phase of one of the two signals output from the local oscillator is changed, and at the same time, a first variable phase shifter whose phase shift amount is varied by a first control voltage supplied; Detecting the phase difference between two signals output from a second variable phase shifter whose phase shift amount is varied by a second control voltage supplied with the phase shift amount, and the first and second variable phase shifters. and a phase detector that supplies two voltages as the first and second control voltages according to the detection results. 5. In the second phase corrector used in the frequency conversion circuit according to claim 2 or 3, the position of the desired signal contained in the two signals output from the first and second mixers, respectively. Detect the phase difference and select 2 according to the detection result.
a phase detection means for outputting two voltages as first and second control voltages; and a phase detection means for changing the phase of the image signal included in the signal output from the first mixer, and outputting a phase shift amount at that time. a first variable phase shifter that is varied by the first control voltage, and a phase shifter that changes the phase of the image signal included in the signal output from the second mixer, and the amount of phase shift at that time; a second variable phase shifter that is varied by the second control voltage that is output. 6. The phase corrector according to claim 5, wherein the phase detection means changes the phase of the signal output from the first mixer, and the amount of phase shift at that time is determined by the first control voltage. changing the phase of the signal output from the third variable phase shifter and the second mixer;
a fourth variable phase shifter whose phase shift amount is varied by the second control voltage; and a desired signal contained in the two signals respectively output from the first and second variable phase shifters. a phase detector that detects a phase difference between the signals and outputs two voltages as the first and second control voltages according to the detection result. 7. In the variable phase shifter used in the phase corrector according to claim 4, 5 or 6, a source of an FET whose gate is connected to the input terminal via an impedance and whose drain is connected to the output terminal. a grounding circuit and the FET
a variable means for varying the voltage between the drain and source of the FET, and by varying the voltage between the drain and source of the FET by the variable means, the voltage between the gate and drain of the FET is varied; A variable phase shifter characterized in that the phase of a signal output from the output terminal is varied with respect to the phase of the signal input from the input terminal. 8. In the variable phase shifter used in the phase corrector according to claim 4, 5 or 6, a source of an FET whose gate is connected to the input terminal via an impedance and whose source is connected to the output terminal. a follower circuit and the FE
Variable means for varying the voltage between the drain and source of T;
and the drain of the FET is controlled by the variable means.
By varying the voltage between the sources, the voltage between the gate and drain of the FET is varied, and the phase of the signal output from the output terminal relative to the phase of the signal input from the input terminal is varied. A variable phase shifter characterized by: 9. The variable phase shifter according to claim 7 or 8, wherein the variable means comprises means for varying the gate bias voltage of the FET. 10. In the variable phase shifter used in the phase corrector according to claim 4, 5 or 6, the first variable phase shifter has a gate connected to the input terminal via an impedance and a drain connected to the output terminal. It consists of a FET source common circuit, and variable means for varying the voltage between the gate and source of the first FET, and the variable means causes the first FET to be grounded.
By varying the voltage between the gate and source of the ET,
A variable device characterized in that the voltage between the gate and drain of the first FET is varied to vary the phase of the signal output from the output terminal relative to the phase of the signal input from the input terminal. Phase shifter. 11. In the variable phase shifter used in the phase corrector according to claim 4, 5 or 6, a source of an FET whose gate is connected to the input terminal via an impedance and whose source is connected to the output terminal. It consists of a follower circuit, and variable means for varying the voltage between the gate and source of the first FET, and the variable means causes the first FET to
By varying the voltage between the gate and source of the first FET, the voltage between the gate and drain of the first FET is varied, and the phase of the signal output from the output terminal relative to the phase of the signal input from the input terminal is varied. A variable phase shifter characterized in that the phase is variable. 12. The variable phase shifter according to claim 10 or 11, wherein the variable means includes a second FET whose gate is connected to the drain of the first FET and whose drain is connected to a positive power supply; It is constructed by connecting a plurality of diodes in series, and one end of the anode is connected to the second FE.
a diode array connected to the source of T and whose other end, the cathode, is connected to the gate of the first FET and the voltage controlled current source, and is applied to the control voltage application terminal of the voltage controlled current source. By varying the voltage,
A variable phase shifter, characterized in that the voltage between the gate and source of the first FET is variable. 13. A television receiver characterized by using the frequency conversion circuit according to claim 1, 2 or 3.