JPH10126300A - Mixer circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mixer circuit, having no deterioration in distortion characteristics at the time of gain control by using a frequency converting circuit which has small deterioration in distortion characteristics at the time of gain control and also using a buffer circuit for a local oscillation signal with the large drive power. SOLUTION: The local oscillation signal from a local oscillator 101 is passed through coupled capacitors 102 and 103 and inputted to the buffer circuit 101 for the local oscillation signal. The inputted local oscillation signal is amplified by a differential amplifier circuit by two-stage constitution and inputted to a frequency-converting circuit 192. An RF signal inputted between RF signal input terminals 178 and 179 is converted into an intermediate frequency signal by the frequency-converting circuit 192 with the local oscillation signal and outputted to an intermediate-frequency output terminal 153. Gain control is controllable with a voltage applied to a gain control voltage signal input terminal 173. For increasing the gain control quantity, the resistance values of resistances 166 and 167 for gain control quantity adjustment are made large, and for making the gain control quantity small, the resistance values of the resistances 166 and 167 are made small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixer circuit used for a tuner circuit of a receiver for mobile communication such as TV, CATV, satellite broadcasting, satellite communication, and cellular telephone.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a conventional mixer circuit.
This mixer circuit includes a local oscillator 501, a buffer circuit 591 for a local oscillation signal, and a frequency conversion circuit 592.

A local oscillation signal buffer circuit 591 has local oscillation signal input terminals 504 and 505 and a power supply terminal 540 common to a frequency conversion circuit.
The next stage has a source follower type buffer circuit configuration.

The first-stage differential amplifier circuit includes amplification transistors 517 and 518, a current source transistor 519, a current value setting resistor 520, and bleeder resistors 511 and 512.
And bias resistors 513 and 514. The load resistors 515 and 516 are connected to the drains of the amplifying transistors 517 and 518, respectively, and the connection point where the sources of the transistors 517 and 518 are connected in common is:
A current source transistor 519 whose gate is grounded is connected, and grounded via a current value setting resistor 520. A bleeder resistor 5 is connected to the gates of the transistors 517 and 518.
The voltages divided by 11 and 512 are applied via bias resistors 513 and 514, respectively. Further, the drains of the amplifying transistors 517 and 518 are connected to the gates of the transistors 535 and 536 of the source-follower type buffer circuit of the next stage via coupling capacitors 521 and 522, respectively.

The next-stage source-follower type buffer circuit includes transistors 535 and 536 and a current source transistor 53.
7, 538, bleeder resistors 531 and 532, and bias resistors 533 and 534.
35, current source transistor 537 and transistor 5
36 and the current source transistor 538 are connected in series. The gates of the current source transistors 537 and 538 are grounded and the sources are commonly connected, and are grounded via a current value setting resistor 539.

The voltages divided by the bleeder resistors 531 and 532 are applied to the gates of the transistors 535 and 536, respectively.
Is applied. The connection point between the transistor 535 and the current source transistor 537 and the connection point between the transistor 536 and the current source transistor 538 are connected to the gate of the frequency conversion transistor of the frequency conversion circuit 592, respectively.

As described above, the local oscillation signal buffer circuit 591 amplifies the local oscillation signal input between the local oscillation signal input terminals 504 and 505 by the first-stage differential amplifier circuit, and the next-stage source-follower type buffer. The signal is input to the frequency conversion circuit 592 via the circuit. The local oscillation signal input between the local oscillation signal input terminals 504 and 505 is input from the local oscillator 501 via the coupling capacitors 502 and 503. The power of the local oscillation signal buffer circuit 591 is supplied from a power supply terminal 540.

The frequency conversion circuit 592 includes an intermediate frequency output terminal 556, a power supply terminal 540 common to a local oscillation signal buffer circuit, a transformer 557, a gain control voltage signal input terminal 569, and RF signal input terminals 577 and 578. Have. An intermediate frequency signal is output to a terminal 556 of the transformer 557, the power supply side winding has an intermediate tap, and the power supply side winding has frequency conversion transistors 558 and 55.
9, 560, and 561 are connected, and the power supply voltage is supplied from a power supply terminal 540 common to a buffer circuit for a local oscillation signal via a transformer 557.

Frequency conversion transistors 558 and 559
Are connected in common, the connection point is connected to a series connection of an RF buffer transistor 562 and a current source transistor 570, the sources of the frequency conversion transistors 560 and 561 are connected in common, and the connection point
Buffer transistor 563 and current source transistor 57
One series connection is connected. The gates of the current source transistors 570 and 571 are grounded, the sources are commonly connected, and are grounded via a current value setting resistor 572. Further, between the source of the RF buffer transistor 562 and the source of the RF buffer transistor 563, a series connection in which a resistor 565 and a resistor 566 are connected to both ends of a resistor 564 and a gain control transistor 567, respectively, is connected in parallel. The gate of the transistor 567 is connected to a gain control voltage signal terminal 569 via a gate protection resistor 568.

The gates of the frequency conversion transistors 558 and 561 and the frequency conversion transistors 559 and 5
The gates 60 are commonly connected, and the voltage divided by the bleeder resistors 551 and 552 is applied to each connection point via bias resistors 553 and 554, respectively. Further, voltages divided by bleeder resistors 573 and 574 are applied to the gate of the RF buffer transistor 562 and the gate of the RF buffer transistor 563 via bias resistors 575 and 576, respectively.

As described above, the mixer circuit shown in FIG. 5 includes an RF signal input terminal 577,
The intermediate frequency signal is supplied to the intermediate frequency output terminal 5 by the local oscillation signal from the local oscillator 501 which is input through the RF signal input between 78 and the local oscillation signal buffer circuit 591.
Output to 56. This mixer circuit can perform gain control by applying a voltage to the gain control voltage signal input terminal 569 to change the drain-source resistance of the gain control transistor 567.

[0012]

As in the mixer circuit shown in the above-mentioned prior art, the drain of a gain control transistor
When gain control is performed by changing the resistance between the sources, the channel resistance between the drain and the source changes non-linearly with respect to the gate voltage, and the distortion characteristic deteriorates particularly at the point where the channel resistance changes abruptly. There is.

In the prior art shown in FIG. 5, resistors are inserted at both ends of the gain control transistor 567, and a resistor is added in parallel with the series connection to reduce the non-linearity of the channel resistance between the drain and the source. By suppressing it, the deterioration of the distortion characteristic at the time of gain control is improved. However, in the above mixer circuit, since a resistor is inserted in series and parallel with the gain control transistor, the rate of change of the channel resistance of the gain control transistor becomes dull, and the gain control amount becomes insufficient, resulting in a good distortion characteristic and a sufficient gain control amount. Was difficult to achieve.

Further, in the mixer circuit, frequency conversion transistors 558, 559, to which a local oscillation signal is input,
Since the gates of 560 and 561 have a capacitance of about 1 pF, the source follower type buffer circuit composed of the transistors 535, 536, 537, and 538 of the local oscillation signal buffer circuit 591 has insufficient driving capability, and the frequency conversion circuit The local oscillation signal waveform inputted to 592 is disturbed,
In particular, when the current flowing through the frequency conversion circuit 592 is large, or when the frequency conversion transistors 558, 559, 560,
When the gate size of 561 is increased, there is a problem that the driving capability is insufficient and the noise characteristics and the distortion characteristics are deteriorated.

[0015]

In order to solve the above-mentioned problems, the present invention provides first gain control to the sources of the RF buffer transistors 562 and 563 of the frequency conversion circuit 592 of the conventional mixer circuit shown in FIG. A drain of a first gain control transistor connected in parallel with the amount adjustment resistor, and a drain of a second gain control transistor connected in parallel with the second gain control amount adjustment resistor; The sources of the first and second gain control transistors are commonly connected, a fourth current source transistor is connected to the connection point, and the source of the fourth current source transistor is connected via a fourth current value setting resistor. It was configured to be grounded. Further, the gates of the first and second gain control transistors are commonly connected via third and fourth resistors, respectively, and a gain control voltage terminal is provided.

With this configuration, in the conventional example shown in FIG. 5, both ends of the gain control transistor 567 have the same potential so that no DC current flows, whereas the first and second gain control transistors 567 do not flow. The non-linearity of the channel resistance between the drain and source is improved by the
Deterioration of distortion characteristics during gain control can be suppressed.

Further, the conventional frequency conversion circuit 59 shown in FIG.
The output stage of the buffer circuit 591 of the local oscillation signal input to the second transistor 2 is connected to transistors 535, 536, 537 and 538.
Fifth from the source follower type buffer circuit composed of
The differential amplifier circuit includes a sixth load resistor, first and second amplifying transistors, a fifth current source, and a fifth current setting resistor.

Since the fifth and sixth load resistors can use relatively low values of about several tens of ohms to about 100 ohms, the output impedance of the buffer circuit for the local oscillation signal can be reduced, and the frequency of the next stage can be reduced. The effect of the gate capacitance of the conversion circuit 592 can be reduced. Accordingly, particularly when the current flowing through the frequency conversion circuit 592 is large, or when the frequency conversion transistors 558, 559, 56
Even when the gate sizes of 0 and 561 are large, the driving capability is not insufficient, and good noise characteristics and distortion characteristics can be obtained.

Further, a capacitor which can be ignored for the RF signal and has a low impedance for the local oscillation signal is connected between the drains of the RF buffer transistors 562 and 563 of the frequency conversion circuit 592. A local oscillation signal leaked through the transistor for use is attenuated, and a local oscillation signal is prevented from leaking into an RF buffer transistor to which an RF signal is input, thereby reducing conversion loss and improving noise characteristics.

Further, by adding an RF amplifier circuit having a differential configuration having gain control means similar to that of the frequency conversion circuit at a stage preceding the RF signal input terminals 507 and 508, the gain of the RF amplification circuit is increased similarly to the frequency conversion circuit. It is possible to obtain a mixer circuit in which the distortion characteristic during control is less deteriorated and which has good conversion gain and noise characteristics.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of a mixer circuit according to the present invention will now be described with reference to FIG.
This will be described with reference to FIG. The tuner circuit according to the present embodiment includes local oscillation signal input terminals 104 and 105, a power supply terminal 150,
F signal input terminals 178 and 179 and intermediate frequency output terminal 1
55, a local oscillation signal buffer circuit 191, and a frequency conversion circuit 192.

The local oscillation signal buffer circuit 191 has a power supply terminal 150 common to the frequency conversion circuit 192, and local oscillation signal input terminals 104 and 105. The buffer circuit for the local oscillation signal has a two-stage differential amplifier circuit configuration, and the first-stage differential amplifier circuit includes load resistors 115 and 116.
, Amplifying transistors 117 and 118, a current source transistor 119, a ground resistor 120, a current value setting resistor 121, bleeder resistors 111 and 112, bias resistors 113 and 114, and coupling capacitors 122 and 123. ing. The load resistor 115 and the amplifying transistor 11
7, a load resistor 116 and an amplifying transistor 118 series-connected body are connected in parallel, grounded via a current source transistor 119 and a current value setting resistor 121, and constitute a differential amplifier circuit. The gates of the amplification transistors 117 and 118 are connected to the bleeder resistors 111 and 112, respectively.
Is applied via bias resistors 113 and 114, and the gate of the current source transistor 119 is grounded via a ground resistor 120.

Similarly to the first-stage differential amplifier circuit, the next-stage differential amplifier circuit includes load resistors 135 and 136, amplifying transistors 137 and 138, a current source transistor 139 (second current source), and a gate. It has a ground resistor 140, a current setting resistor 141, bleeder resistors 131 and 132, bias resistors 133 and 134, and coupling capacitors 142 and 143. The load resistor (first load resistor) 135 and the amplifying transistor (ninth transistor) 137 are connected in series, and the load resistor (second load resistor) 136 and the amplifying transistor (tenth transistor) 138 are connected. A series-connected body is connected in parallel, grounded via a current source transistor 139 and a current value setting resistor 141, and forms a differential amplifier circuit.

The amplification transistors 137 and 138
The voltage divided by the bleeder resistors 131 and 132 is applied to the gates of the current source transistor 139 via the bias resistors 133 and 134, and the gate of the current source transistor 139 is grounded via the grounding resistor 140.

The local oscillation signal input between the local oscillation signal input terminals 104 and 105 is applied to the amplifying transistor 117,
Amplified by 118 and coupled capacitances 122 and 12 respectively
The signal is input to the gates of the amplifying transistors 137 and 138 at the next stage through 3. The input local oscillation signal is amplified by the amplifying transistors 137 and 138, and passes through the coupling capacitors 142 and 143, respectively.
Output to

The frequency conversion circuit 192 includes a power supply terminal 150 common to a buffer circuit for local oscillation signals, RF signal input terminals 178 and 179, an intermediate frequency output terminal 155, a gain control voltage signal input terminal 173, and an output transformer 156. have. Further, the frequency conversion circuit 192 includes frequency conversion transistors 157, 158, 159, and 160,
A noise characteristic improving capacitor 161, RF buffer transistors 162 and 163, a gain controlling transistor 164,
165, gain control amount adjusting resistors 166 and 167, current source transistor 168, grounding resistor 169, gate protection resistors 171 and 172, and bleeder resistors 151 and 15
2, 174, 175 and bias resistors 153, 154,
176 and 177.

An intermediate frequency output terminal 155 is connected to the output side winding of the transformer 156, the power supply side winding has an intermediate tap, and one input of the power supply side winding has a frequency conversion transistor (the Drain of transistor 157 and transistor for frequency conversion (third transistor) 1
A drain 59 is connected and outputs a first intermediate frequency signal. The other input of the power supply side winding is connected to the drain of the frequency conversion transistor (second transistor) 158 and the drain of the frequency conversion transistor (fourth transistor) 160 to output a second intermediate frequency signal. The first and second intermediate frequency signals are combined and output from the output winding.

Further, a power supply voltage is supplied from a power supply terminal 150 common to the local oscillation signal buffer circuit via an intermediate tap of the power supply side winding. The sources of the frequency conversion transistors 157 and 158 and the sources of the frequency conversion transistors 159 and 160 are commonly connected, respectively.
They are connected to the drains of RF buffer transistors 162 and 163 (fifth and sixth transistors), respectively.

RF buffer transistors 162 and 163
, A gain control transistor (seventh transistor) 164 and a gain control amount adjusting resistor (first resistor)
166 and a gain control transistor (eighth
Transistor 165 and a gain control amount adjusting resistor (second
167 are connected in parallel, and are grounded via a current source transistor 168 and a current value setting resistor 170.

Further, the RF buffer transistor 162,
A noise characteristic improving capacitor 161 is connected between the drains of the current source transistor 163 and the ground of the ground resistance 1.
69 is grounded. Gain control transistor 16
4 and 165 are connected to a gain control voltage signal terminal 173 via resistors 171 and 172, respectively.

Frequency conversion transistors 157 and 160
And the gates of the frequency conversion transistors 158 and 159 are connected in common, respectively, and the bleeder resistor 151,
The voltages divided by the respective resistors 152
It is applied through 53 and 154.

Further, the RF buffer transistor 162,
163 have RF signal input terminals 178, 1
79 and the bleeder resistors 174, 17
5 are applied to the bias resistors 17 respectively.
6, 177 are applied.

The operation of the above mixer circuit will now be described.
The local oscillation signal from the local oscillator 101 has a coupling capacitance of 10
The local oscillation signal is input to the buffer circuit 191 via the second and the third signals 103. The input local oscillation signal is amplified by a two-stage differential amplifier circuit and input to the frequency conversion circuit 192.

The RF signal input between the RF signal input terminals 178 and 179 is converted into an intermediate frequency signal by the local oscillation signal input to the frequency conversion circuit 192, and is output to the intermediate frequency output terminal 155. Note that the gain control can be controlled by the voltage applied to the gain control voltage signal input terminal 173. If the gain control amount is to be increased, the resistance values of the gain control amount adjusting resistors 166 and 167 are increased, and the gain control is performed. To reduce the amount, the gain control amount adjusting resistor 16 is used.
6, 167 may be reduced.

In the embodiment of FIG. 1, the gates of the current source transistors 119, 139, and 168 are set to several tens of Ω to prevent parasitic oscillation due to stray capacitance of the transistors.
It is grounded via a resistor of about 0Ω.

According to the above-described structure, since a direct current flows through the gain control transistor, the non-linearity of the channel resistance between the drain and the source is improved, so that the deterioration of the distortion characteristic during the gain control is suppressed. be able to.

Further, by making the output stage of the buffer circuit for the local oscillation signal a differential amplifier circuit, the output impedance of the buffer circuit is reduced, and the influence of the gate capacitance of the next-stage frequency conversion circuit is reduced. As a result, even when the current flowing through the frequency conversion circuit is large or when the gate size of the frequency conversion transistor is large, the driving capability is not insufficient, and good noise characteristics and distortion characteristics can be obtained.

Further, the RF buffer transistor 162,
By connecting a capacitor between the drains of the RF buffer transistor 163 and suppressing leakage of a local oscillation signal into the RF buffer transistor, conversion loss can be reduced and noise characteristics can be improved.

Second Embodiment Next, a second embodiment of the mixer circuit of the present invention will be described with reference to FIG. Components performing the same operation as in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The mixer circuit according to the second embodiment is characterized in that the output stage of the buffer circuit for the local oscillation signal is changed from a differential amplifier circuit to a source follower circuit, as compared with the mixer circuit according to the first embodiment. The transistors 215 and 216, the current source transistors 217 and 218, the ground resistor 219, the current value setting resistor 220, the bleeder resistors 211 and 212, and the bias resistors 213 and 214 are different from the first embodiment.

The output stage of this buffer circuit includes transistors 215, 217 and 216.
And the transistor 218 are connected in series. The gates of the transistor 217 and the transistor 218 are grounded via the ground resistor 219, and the source is grounded via the current value setting resistor 220. The above transistor 21
5 and the gate of the transistor 216 are connected to the bleeder resistor 21.
1 and 212 are applied via bias resistors 213 and 214, respectively. The connection point between the transistor 215 and the transistor 217 and the connection point between the transistor 216 and the transistor 218 are connected to the gate of the frequency conversion transistor of the frequency conversion circuit 192, respectively.

With such a configuration, even when the driving capability of the buffer circuit is small, such as when the frequency conversion circuit current is small and the gate input capacitance of the frequency conversion transistor is small, the noise characteristics and distortion characteristics are not deteriorated. In the case where there is no driving capability, even if the output stage of the buffer circuit is a source follower circuit as in the second embodiment, there is no shortage of driving capability.
Since the current can be made smaller than that of the differential amplifier circuit, the power consumption of the buffer circuit can be reduced.

[Embodiment 3] Next, a third embodiment of the present invention will be described with reference to FIG. Components performing the same operation as in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The mixer circuit of the third embodiment is different from the mixer circuit of the first embodiment in that the RF signal input terminal 1
This embodiment is characterized in that an RF amplifier circuit 360 having a differential configuration having gain control means similar to that of the first embodiment is added to the stage preceding to the stages 78 and 179. The RF amplification circuit 360 includes load resistors 333 and 334 and amplification transistors 335 and 336.
, Gain control transistors 337 and 338, gain control amount adjusting resistors 339 and 340, current source transistor 341, current value setting resistor 343, and ground resistor 342.
, Gate protection resistors 348 and 349, and bleeder resistor 3
44, 345, bias resistors 346, 347, RF
Signal input terminals 350 and 351 and coupling capacitors 331 and 33
Two.

A series connection of a load resistor 333, an amplification transistor 335 and a gain control amount adjusting resistor 339, and a series connection of a load resistor 334, an amplification transistor 336 and a gain control amount adjustment resistor 340 are connected in parallel. Connected, the current source transistor 341 and the current setting resistor 3
It is grounded via 43.

The gain control amount adjusting resistors 339 and 340
Have gain control transistors 337 and 33, respectively.
8 are connected in parallel to form a differential amplifier circuit. Further, the gate of the current source transistor 341 is connected to the ground resistor 34.
2, and the gain control transistors 337, 3
38 gates are gate protection resistors 348, 349, respectively.
To the gain control voltage signal input terminal 173.

The amplification transistors 335, 336
The voltages divided by the bleeder resistors 344 and 345 are applied to the gates by bias resistors 346 and 347, respectively. Then, the RF signal input terminals 350 and 351
The RF signal input by the amplifier transistors 335, 3
36 and output to the frequency conversion circuit by the coupling capacitors 331 and 332.

Since the direct current flows through the gain control transistors 337 and 338 in the same manner as the frequency conversion circuit, the non-linearity of the channel resistance between the drain and the source is improved. Deterioration of distortion characteristics can be suppressed.

As described above, by using the same gain control configuration as that of the frequency conversion circuit in the RF amplifier circuit, a mixer circuit with little deterioration in distortion characteristics and good gain characteristics and noise characteristics during gain control can be obtained.

Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIG. Components performing the same operation as in the third embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The mixer circuit of FIG. 4 is different from the mixer circuit of the third embodiment in that the output stage of the buffer circuit for the local oscillation signal is changed from a differential amplifier circuit to a source follower circuit. 416, current source transistors 417 and 418, a ground resistor 419, a current value setting resistor 420, bleeder resistors 411 and 412, and bias resistors 413 and 414 are different from the third embodiment.

In the output stage of this buffer circuit, a transistor 415 and a current source transistor 417 and a transistor 416 and a current source transistor 418 are connected in series, respectively. The gates of the current source transistors 417 and 418 are connected in common, and While being grounded, the sources of the current source transistors 417 and 418 are grounded via the current value setting resistor 420.

The voltages divided by the bleeder resistors 411 and 412 are applied to the gates of the transistor 415 and the current source transistor 416, respectively.
14. The connection point between the transistor 415 and the current source transistor 417 and the transistor 41
6 and the current source transistor 418 are connected to the gates of the frequency conversion transistors of the frequency conversion circuit 192, respectively.

With this configuration, even if the driving capability of the buffer circuit is small, such as when the frequency conversion circuit current is small and the gate input capacitance of the frequency conversion transistor is small, the noise characteristics and distortion characteristics are not deteriorated. In this case, even if the output stage of the buffer circuit is a source follower circuit as in the fourth embodiment, there is no shortage of driving capability, and the current can be made smaller than that of the differential amplifier circuit. Power consumption can be reduced.

As an example of the effect of the embodiment of the present invention, FIG. 6 shows a gain control amount with respect to the gain control amount of the mixer circuit shown in the conventional example of FIG. 5 and the mixer circuit shown in FIG. From the figure, it can be seen that the configuration of the embodiment of the present invention has a smaller change in the gain control amount with respect to the gain control voltage and a smaller rate of change in the drain-source channel resistance than the conventional gain control circuit.

FIG. 7 shows the distortion characteristics with respect to the gain control voltage of the mixer circuit shown in the conventional example of FIG. 5 and the mixer circuit shown in FIG. As shown in the figure, by using a gain control circuit through which a DC current flows in the gain control transistor, it is possible to suppress the deterioration of the distortion characteristic during the gain control.

[0057]

According to the present invention, the use of a frequency conversion circuit with little deterioration in distortion characteristics during gain control and the use of a buffer circuit for a local oscillation signal having a large driving capability allow the deterioration in distortion characteristics during gain control. And a mixer circuit with a small number of components can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment according to the present invention.

FIG. 3 is a circuit diagram showing a third embodiment according to the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment according to the present invention.

FIG. 5 is a circuit diagram showing an example of a conventional mixer circuit.

FIG. 6 is a diagram showing a difference in gain control amount characteristics with respect to a gain control voltage between a conventional mixer circuit and an embodiment according to the present invention.

FIG. 7 is a diagram showing a difference in a distortion characteristic with respect to a gain control amount between a conventional mixer circuit and an embodiment according to the present invention.

[Explanation of symbols]

101, 501: Local oscillator, 191, 591: Local oscillation signal buffer circuit, 104, 105, 504, 505155: Local oscillation signal input terminal, 150: Power supply voltage terminal, 192, 592: Frequency conversion circuit, 178, 179, 350, 351, 577, 578 ... R
F signal input terminal; 173, 569: Gain control voltage signal input terminal; 155: Intermediate frequency signal output terminal.

Claims (4)

[Claims] A local oscillation signal input means, a local oscillation signal buffer circuit, a frequency conversion circuit, and an RF signal input means, wherein the input RF signal and a local oscillation signal are transmitted through a local oscillation signal buffer circuit. A mixer circuit for outputting an intermediate frequency signal by inputting a local oscillation signal from an oscillation signal input means to a frequency conversion circuit, wherein the frequency conversion circuit connects sources of first and second transistors in common, and A differential circuit in which the drain of a fifth transistor is connected to a common connection point, and a differential circuit in which the sources of third and fourth transistors are connected in common and the drain of a sixth transistor is connected to the common source connection point And a first current source. The gates of the first and fourth transistors are connected in common to serve as an input terminal for a first local oscillation signal. The gates of the first and third transistors are commonly connected to form an input terminal for a second local oscillation signal, the drains of the first and third transistors are commonly connected to form a first intermediate frequency signal output terminal, and the second and fourth transistors are connected. Of the fifth and sixth transistors are connected to the first and second RF signal input terminals, respectively. The source of a fifth transistor is connected to the first current source via a first resistor, and the source of a sixth transistor is connected to a second resistor for gain control means of the double-balanced frequency conversion circuit. , The seventh and eighth transistors are connected in parallel to the first and second resistors, respectively, and the gates of the seventh and eighth transistors are respectively connected to the third and the third resistors. No. 4. A mixer circuit, wherein the mixer circuit is commonly connected via a resistor of No. 4 and a gain control voltage terminal is provided. 2. The mixer circuit according to claim 1, wherein a capacitor is connected between the drains of said fifth and sixth transistors. 3. The buffer circuit for a local oscillation signal according to claim 1,
First and second load resistors are connected to the drains of the first and the tenth transistors, respectively, the sources of the ninth and tenth transistors are commonly connected, and a second current source is connected to the common source connection point. The drains of the ninth and tenth transistors are connected to the input terminals of the first and second local oscillation signals via the first and second coupling capacitors, respectively, and the gates of the ninth and tenth transistors are respectively connected to the third terminal. 3. The mixer circuit according to claim 1, wherein said mixer circuit is a differential amplifier circuit having an input terminal for a fourth local oscillation signal. 4. An RF signal input means, wherein third and fourth load resistors are respectively connected to drains of eleventh and twelfth transistors, and sources of the eleventh and twelfth transistors are commonly connected. A third current source is connected to the common connection point, and drains of the eleventh and twelfth transistors are connected to input terminals of the first and second RF signals via third and fourth coupling capacitors, respectively. A differential amplifier circuit having gates of eleventh and twelfth transistors as input terminals of third and fourth RF signals, respectively, and gain control means using a gain control voltage provided in said differential amplifier circuit. Item 4. The mixer circuit according to any one of Items 1 to 3.