JPH0374965B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circuit configuration of a mixer circuit that converts a microwave band signal frequency.

(Prior art) In a low frequency band, a differential amplifier circuit is constructed using bipolar transistors, but in that case, in order to improve the nonlinearity of the voltage vs. current characteristic between the base and emitter, the As shown in FIG. 3, series resistors 353 and 354 must be added to the emitters of bipolar transistors 351 and 352, respectively. The deterioration of the noise figure caused by these resistors 353 and 354 is coupled with the fact that bipolar transistors have a higher noise figure than GaAs-FETs in the microwave band. It was becoming.

On the other hand, GaAs-FETs have long been used in amplifiers and mixers as devices that can obtain high gain in the microwave band. An example of a mixer using GaAs-FET is a single GaAs-FET as shown in Figure 4.
-FET was used to generate a signal with the frequency of the sum or difference of a pair of input signals by utilizing distortion characteristics. In FIG. 4, 401 is a drain power supply terminal, 402 and 403 are signal input terminals,
406 is a signal output terminal, 430 is a GaAs-FET,
431 is a load resistor.

(Problems to be Solved by the Invention) The configuration described above has the drawbacks of a lack of isolation between the pair of input signals, and a lack of separation between the pair of input signals due to the presence of three different frequencies in a single device. The drawback was that part of the input signal was output to the terminal.

In addition, in conventional mixers, when a correction circuit is added to correct leakage of the local oscillation signal to the output terminal, the transmission output generated by mixing the local oscillation signal with the intermediate frequency signal also leaks to the local oscillation side terminal. , this signal is sent to the output terminal through a correction circuit. Since the delay time is significantly different between this leakage output and the output of the normal signal, there is a drawback that echo distortion occurs in the transmission characteristics.

In order to eliminate these drawbacks, a mixer circuit has recently been proposed in Japanese Patent Application Laid-Open No. 100617/1983, which uses FETs as elements of the balanced mixer to improve the degree of balanced separation. However, this circuit does not particularly prevent deterioration of balance due to a decrease in the output level on the positive phase side of the differential amplifier, so its effect is insufficient.

The purpose of the present invention is to eliminate such drawbacks and to obtain a large degree of separation between a pair of input signal terminals, by providing a pair of differential amplifier circuits at the output terminals of each amplifier circuit to mutually cancel out the leakage components. It is an object of the present invention to provide a mixer circuit using GaAs-FETs, which eliminates the above-mentioned drawbacks by connecting the mixer circuit in this manner, and is configured such that both of the above-mentioned pair of input signals can be suppressed to a sufficiently low level at the output terminal.

(Means for Solving the Problems) The mixer circuit according to the present invention is based on GaAs-FETs, and includes first to tenth GaAs-FETs and first and second resistors.

The sources of the first and second GaAs-FETs are commonly connected, and the first resistor is connected to the common source connection point.

The third GaAs-FET has its gate connected to the gate of the second GaAs-FET, and its source connected to the first and second GaAs-FET.
The source is connected to the common source connection point of the GaAs-FET and the first resistor.

The first resistor has one end connected to the source common ground point and the other end connected to the ground potential point.

The fourth and fifth GaAs-FETs are connected to the first
The source is connected to the drain of a GaAs-FET.

The sixth GaAs-FET has its source connected to the drain of the second GaAs-FET, and the source of the sixth GaAs-FET is connected to the drain of the second GaAs-FET.
The gate of the fourth GaAs-FET is connected to the gate of the fourth GaAs-FET.
The drain is connected to the drain of the drain.

The seventh GaAs-FET has its source connected to the drain of the second GaAs-FET, and the fourth GaAs-FET
The gate is connected to the gate of the fifth GaAs-FET.
The drain is connected to the drain of the drain.

The eighth GaAs-FET has its source connected to the second resistor, and its drain connected to the gates of the fifth and sixth GaAs-FETs.

The ninth GaAs-FET has its source connected to the source of the eighth GaAs-FET and the second resistor, and its drain connected to the gates of the fourth and seventh GaAs-FETs.

The second resistor includes eighth and ninth GaAs-
It is connected between the source of the FET and the ground potential point.

The 10th GaAs-FET has its gate connected to the gate of the 9th GaAs-FET, and the 8th and 9th
The source is connected to a common connection point between the source of the GaAs-FET and the second resistor.

In the above configuration, the present invention provides the first and third
A high frequency signal of the first frequency is applied from the common gate connection point of the GaAs-FET, and the ninth and tenth GaAs
-A high-frequency signal of the second frequency is applied from the common connection point of the gates of the FETs, and the fourth and sixth GaAs-
A third high-frequency signal having a frequency that is the sum or difference of the high-frequency signals of the first and second frequencies can be extracted from the common drain connection point of the FET or the common drain connection point of the fifth and seventh GaAs-FETs. It is configured so that it can be done.

(Example) Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a mixer circuit according to the present invention. In FIG. 1, 101 is a power supply terminal, 102 is a first frequency signal input terminal, 103 is a second frequency signal input terminal, 10
6, 107 are signal output terminals, 104,
105 are bias terminals, 110 to 11
9 are GaAs-FETs, and 120 to 126 are resistors. A pair of GaAs-FET11
0 and 111 are differential amplifier circuits for the first frequency signal, and a phase sending output is obtained on the drain side of the GaAs-FET 110, and a positive phase output is obtained on the drain side of the GaAs-FET 111. The GaAs-FETs 116 to 119 forming the dual differential amplifier circuit have GaAs-
Connect the output of FET110 to load resistor 120 and connect the output of GaAs-FET111 to load resistor 121.
or by connecting the output of GaAs-FET 110 to load resistor 121.
2 of connecting the output of 11 to the load resistor 120.
It performs switching operations between two modes. The second frequency signal applied to the input terminal 103 is applied to GaAs-FETs 113 and 11 forming a differential amplifier circuit.
4 to form a dual differential amplifier circuit.
It controls switching of the outputs of the GaAs-FETs 116 to 119. The signals applied to the first and second signal input terminals 102 and 103 are balanced together to form a dual differential circuit.
119, so the output terminals 106, 10
There is little leakage to 7. Generally, when the value of the resistor 125 is small, in a differential amplifier circuit using GaAs-FETs 110 and 111, the positive phase output appearing at the drain of GaAs-FET 111 tends to be lower than the negative phase output appearing at the drain of GaAs-FET 110. In such a case, the dual differential amplifier circuits 116 to 1
This deteriorates the balance of the signal applied to the terminals 19 and causes leakage to the output terminals 106 and 107.

In the present invention, a GaAs-FET 112 is added, and the signal on the positive phase side of the first frequency applied to the input terminal 102 is corrected by applying it to the resistor 125.
Since the signal is output to the drain of the GaAs-FET 111, deterioration in balance due to a drop in the level on the positive phase side, which tends to occur in differential amplifier circuits using GaAs-FETs, is prevented. A GaAs-FET 115 is also added to GaAs-FETs 113 and 114 forming a differential amplifier circuit for amplifying the second frequency to improve balance. The differential amplifier circuit consisting of GaAs-FETs 113 to 115 not only improves an unbalanced signal to a balanced signal, but also amplifies the second frequency signal and forms a dual differential amplifier circuit.
It also serves to prevent the signals present at ports 16 to 119 from leaking to the input terminal 103.
Even when viewed from the input terminal 102, the input terminal 103
GaAs-FET110~1 although not as much as it looks from the outside
Since the differential amplifier circuit consisting of 12 has a buffer effect, the GaAs-
It functions to prevent signals present in FETs 116 to 119 from leaking out.

In the circuit shown in FIG. 1, if a local oscillation signal is input from the input terminal 103 and a high frequency signal is added from the input terminal 102, the cross-modulation characteristics of the high frequency signal can be improved. In FIG. 1, by inserting a resistor 124 and increasing the local oscillation signal level to be applied to the input terminal 103,
The waveform during the switching operation of 16 to 119 can be made rectangular, and the cross modulation characteristics of high frequency signals can be further improved. Further, it is assumed that the mixer circuit according to the present invention receives a local oscillation signal from an input terminal 103, receives an intermediate frequency signal from an input terminal 102, and obtains an output from an output terminal 106 or an output terminal 107. By adding a compensation circuit whose phase and level are variable between the output terminals 106, 107 and the input terminal 103, the cross-modulation characteristics of the transmission signal are excellent, and the leakage of local oscillation signals to the output terminals 106, 107 is prevented. A transmission mixer with low heat and thermal noise is constructed.

FIG. 2 is a block diagram showing a frequency converter according to an example of application of such a mixer circuit. In FIG. 2, 242 is an intermediate frequency amplification circuit, 241 is an intermediate frequency signal input terminal, 243 is a local oscillation circuit, 247 is a mixer circuit shown in FIG. 1, 245,
246 is a correction circuit that can vary the phase and level, 245 is a semi-fixed inductance,
246 is a semi-fixed resistor. In order to improve the cross-modulation characteristics of the transmission characteristics, the level of the intermediate frequency signal is sufficiently reduced and used within a small signal level range with good linearity. In such a case, the local oscillation level becomes relatively high, and even if the mixer circuit has excellent balance characteristics, the amount of leakage of the local oscillation signal at the output terminal becomes noticeable. In order to correct this, a correction circuit consisting of an inductor 245 and a resistor 246 is provided, and correction is made at the same level and in opposite phase to the local oscillation signal present at the output terminal, thereby further reducing the amount of leakage of the local oscillation signal. be able to.

In the case of Fig. 2, a differential amplifier circuit made of GaAs-FET operates as a buffer amplifier at the input terminal 203 to which the local oscillation signal is applied, and the level of the transmission signal leaking toward the local oscillation circuit is set to a sufficiently small value. Therefore, the echo distortion described above becomes sufficiently small.

(Effects of the Invention) As explained above, in the present invention, in order to obtain a large degree of separation between a pair of input signal terminals, a pair of differential amplifier circuits is installed at the output terminal of each amplifier circuit so that leakage components are mutually canceled out. By connecting it to , the balance is improved and even-order cross-modulation distortion is reduced. Furthermore, each GaAs-FET
Since it is a DC direct-coupled type, it is suitable for monolithic ICs, and has the effect of easily achieving high reliability in addition to miniaturization.

In particular, GaAs-
By adding FETs to each of the high frequency signal input terminal and the local oscillation signal input terminal, the degree of separation between each input and output terminal is further increased.

Furthermore, in the present invention, the source series resistance is omitted by using GaAs-FET, so noise is generated less, and even if the intermediate frequency signal level is reduced in order to improve the cross-modulation characteristics of the transmission characteristics, the noise is not included in the output terminal. Thermal noise and local oscillation signal level caused by this can be kept sufficiently low.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a mixer circuit according to the present invention. FIG. 2 is a block diagram showing an embodiment of a frequency conversion device to which the mixer circuit shown in FIG. 1 is applied. FIG. 3 is a circuit principle diagram showing an example of a differential amplifier circuit constructed using a conventional technique using bipolar transistors. FIG. 4 is a circuit diagram showing an example of a mixer circuit using GaAs-FETs according to the prior art. 110-119,430...GaAs-FET, 1
20～126,246,351,352,431
... Resistor, 351, 352 ... Bipolar transistor, 242 ... Intermediate frequency amplification circuit, 243
... Local oscillation circuit, 245 ... Inductor, 24
7...Mixer circuit, 101 to 107, 202, 2
03,206,207,241,244,401
~403,406...Terminal.

Claims (1)

[Claims] 1 The first and second
a GaAs-FET and a gate connected to the gate of the first GaAs-FET;
a third GaAs-FET whose source is connected to a common source connection point of the GaAs-FET; a first resistor connected between the common source connection point and a ground potential point; fourth and fifth GaAs-FETs whose sources are connected to the drains of the second GaAs-FET, whose sources are connected to the drains of the second GaAs-FETs, whose gates are connected to the gates of the fifth GaAs-FETs, and whose sources are connected to the drains of the second GaAs-FETs; a sixth GaAs-FET whose drain is connected to the drain of the fourth GaAs-FET, and a source connected to the drain of the second GaAs-FET,
a seventh GaAs-FET having a gate connected to the gate of the fourth Ga-As-FET and a drain connected to the drain of the fifth GaAs-FET;
and an eighth GaAs-FET whose drain is connected to the gate of the sixth GaAs-FET;
A ninth GaAs-FET whose source is connected to the source of the GaAs-FET and whose drain is connected to the gates of the fourth and seventh GaAs-FETs, and the sources of the eighth and ninth GaAs-FETs are grounded. a second resistor connected between the potential point and the ninth GaAs
- a tenth device having a gate connected to the gate of the FET and a source connected to a common connection point of the sources of the eighth and ninth GaAs-FETs and the second resistor;
GaAs-FET, and the first and third
A high frequency signal of the first frequency is applied from the common gate connection point of the GaAs-FET, and the ninth and tenth
A high frequency signal of the second frequency is applied from the common gate connection point of the GaAs-FET, and the fourth and sixth
A third high frequency signal having a frequency that is the sum or difference of the high frequency signals of the first and second frequencies from the common drain connection point of the GaAs-FETs or the common drain connection point of the fifth and seventh GaAs-FETs. GaAs-
Mixer circuit using FET.