JPS62186605A - Frequency converter - Google Patents

Abstract

PURPOSE:To improve the isolation between the input and output and the frequency conversion loss by using a three terminal FET as a frequency conversion element. CONSTITUTION:After an IF signal is fed to a hybrid circuit 12 and distributed into two signals having a phase difference of 180 deg. to each other, the signals are impressed to gates G of FETs 10, 11. further, a local oscillation signal impressed to a rat race type hybrid circuit 4 is distributed and impressed to drains D of the FETs 10, 11. A bias voltage Vg is impressed to each gate G of the FETs 10, 11 and sources S are connected to ground. Then the IF signal is impressed to the gates G and th local oscillation signal is impressed to the drains D and a frequency conversion signal is outputted via the circuit 4.

Description

[Detailed Description of the Invention] [Summary] In a frequency converter, first and second
A relatively low frequency signal with a phase difference of 180 degrees is applied to the gates of the microwave field effect transistors, and a local oscillation signal input from the first terminal of the rough trace hybrid circuit is applied to each drain in the same phase. , the frequency conversion outputs obtained from each drain are combined in phase from the fourth terminal (2) to improve conversion loss and crowd isolation.

[Industrial application field]

The present invention relates to an improvement in a frequency converter used, for example, in an up-converter of a microwave band transmitter.

Advances in semiconductor technology have led to the development of microwave field effect transistors (hereinafter abbreviated as PET) that operate in the several tens of Gllz band, making it possible to use them as frequency conversion elements in the microwave band instead of microwave diodes. .

Therefore, there is a need for a frequency converter that uses this FET and has improved conversion loss and input/output isolation.

[Conventional technology]

FIG. 3 shows a circuit diagram of a conventional example.

In the figure, an intermediate frequency signal input from a terminal IN is divided in phase by a hybrid circuit 1 and applied to diodes 2 and 3. Further, the local oscillation signal is applied to the first terminal (2) of the rough trace type hybrid circuit 4 via a capacitor.

In this rat race type hybrid circuit 4, a signal applied to the first terminal (■) is distributed to the second terminal (■) and the third terminal (■).
The local oscillation signal applied to the first terminal ■ appears at the second terminal ■, but does not appear at the fourth terminal ■. It is applied to the diodes 2 and 3 from the third terminals ■ and ■.

Also, since there is a 180 degree phase difference between the propagation from the third terminal ■ to the fourth terminal ■ and the propagation from the second terminal ■ to the fourth terminal ■, the diodes 2 and 3 are reversely connected. By connecting in the direction, the frequency conversion signal generated by this diode is
The in-phase signal is synthesized at terminal ■ and output.

Here, the bias voltages -V and +V are applied to the choke coil 7.
The conversion efficiency is improved by flowing a predetermined diode current in addition to the diode 2.3 through the diode 8. or,
5.6 is a short stub that is grounded at high frequency, and 9 is a choke coil.

[Problem that the invention seeks to solve]

However, frequency converters using diodes have the following problems.

■Since the diode 2.3 is a two-terminal element, the local oscillation signal is transmitted to the second. It passes through the third terminals ■ and ■ to the input side, and the input/output isolation is poor.

■ Frequency conversion loss is large because a diode is used as the frequency conversion element.

[Means for solving problems]

As shown in Fig. 1, the above problem is caused by a hybrid circuit 12 that divides the input signal whose frequency is to be converted into two signals with a phase difference of 180 degrees, a gate to which the output of the hybrid circuit is input, and a grounding circuit. first and second FETs 10.11 each having a source which is input with a local oscillation signal and a drain into which a local oscillation signal is input and a frequency conversion signal is output; a first terminal [1] to which the local oscillation signal is input; second and third terminals [2] connected to the drains of the first and second FETs;
] and [3], and the frequency conversion signals with a phase difference of 180 degrees output from the drains of the first and second PETs are
This problem is solved by the frequency converter of the present invention, which is constituted by a rat race type hybrid circuit 4 having a fourth terminal 4 which is phase-shifted by 0 degrees and synthesized in the same phase.

[Effect]

In the present invention, the drain conductance of PET 10.11 is changed by an intermediate frequency signal manually applied to the gate, so when a local oscillation signal with a higher frequency than this intermediate frequency signal is applied to the drain, this local oscillation signal is amplitude modulated. A frequency-converted signal is output from the drain. Therefore,
Only the frequency-converted signal is extracted using the rat race type hybrid circuit 4, but since a three-terminal element PET is used, input/output isolation is improved, and the power of the frequency-converted signal is also improved and increased.

shows a frequency conversion characteristic diagram.

First, in FIG. 1, the intermediate frequency signal to be frequency-converted is applied to the hybrid circuit 12 via the capacitor C1 and divided into two signals with a phase difference of 180 degrees. capacitor C4,
Added via C5.

Furthermore, the local oscillation signal applied to the first terminal ■ of the rough trace type hybrid circuit 4 via the capacitor C2 is as follows.
It is distributed and applied to the drains D of the first and second FETs 10.11 through the second terminal (2) and the third terminal (3).

Here, a bias voltage Vg is applied to each gate G of FETl0.11 via a choke coil 13.14, and a source S is grounded. And gate G
An intermediate frequency signal is applied to the drain D, a local oscillation signal is applied to the drain D, and a frequency conversion signal is passed through the second terminal ■, the third terminal ■, and is synthesized and outputted at the fourth terminal ■. Ru.

At this time, the leakage of the local oscillation signal becomes a 180 degree phase difference and is canceled out at the fourth terminal ■, as in the conventional example, and between the fourth terminal ■, the third terminal ■, and the fourth terminal ■. Second terminal ■
The phase difference between them is 180 degrees, so the intermediate frequency signal is
By distributing the 80 degree hybrid circuit I2, F
The outputs of ETs 10 and 11 are combined in phase.

In this way, since a three-terminal FET is used as the frequency conversion element, input/output isolation is improved compared to the conventional one.

In addition, a stub is provided for the second terminal ■ and the third terminal ■,
At the fourth terminal (2), the power of the frequency conversion signal is maximized and the power of the local oscillation signal is minimized. Furthermore, when the drain voltage of the FET is used at Ov, the drain voltage supply path via the hybrid circuit 4 is not required, so one choke is not required compared to the conventional example.

Next, Fig. 2 shows the frequency conversion characteristics of the frequency converter of Fig. 1, but the frequency of the intermediate frequency signal is 900M! (z, when the frequency of the local oscillation signal is approximately 13.4 GIlz and a frequency conversion signal with a conversion frequency of approximately 14.3 GHz is obtained, the power of the local oscillation signal is 11.5 dBo+, 10.0
dBm.

The relationship between the converted power and the intermediate frequency signal power when set to 7.5 dBn+ and 5.0 dBm is shown.

As shown in the figure, for example, the power of the local oscillation signal is 11°5d.
Bm, the conversion loss is approximately 4 dB, approximately 4 dB lower than the conventional example.
Improved.

〔Effect of the invention〕

As explained in detail above, according to the present invention, the three-terminal P
Since the ET is used as a frequency conversion element, there is an effect that frequency conversion loss and input/output isolation are improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a frequency conversion characteristic diagram of FIG. 1, and FIG. 3 is a circuit diagram of a conventional example. In the figure, 4 is a rough trace type hybrid circuit, 10 and 11 are microwave field effect transistors, and 12 is a hybrid circuit. 14≦Mon no Tokogeya 4 da 1〃F1 No. 6 To] 1 Sonojima Fl Sekisho 9 SanjJ dBm 1st TogAf) National liquid color Shitagogonno・↓Acupuncture? chair/to live story +
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Claims (1)

[Claims] A hybrid circuit (12) that divides an input signal whose frequency is to be converted into two signals with a phase difference of 180 degrees, a gate G to which the output of the hybrid circuit is input, and a grounded source. first and second microwave field effect transistors (10
, 11), a first terminal [1] into which the local oscillation signal is input, and a first terminal [1] to which the local oscillation signal is input.
and second and third terminals [2] and [3] connected to the drain of the second microwave field effect transistor,
A rat having a fourth terminal [4] that further shifts the phase of the frequency conversion signals of 180 degrees outputted from the drains D of the first and second microwave field effect transistors by 180 degrees and synthesizes them in the same phase. Race type hybrid circuit (4
) A frequency converter comprising: