JPH01288004A - mixer - Google Patents

Abstract

PURPOSE:To obtain the characteristic of the mixer employing a dual gate FET with no adjustment and to attain a semiconductor integrated circuit by providing a circuit controlling a gate voltage so as to give a constant current between a source and a drain. CONSTITUTION:A 2nd gate is connected to a constant voltage such as a ground potential (ground). Moreover, an active bias circuit 7 is provided to vary the bias of a 1st gate 1 in a way that the bias current between the drain and ground is made constant. Then a drain bias of 3-5V is given to a GaAs dual gate FET employing at a microwave band and an active bias circuit fixing the drain-ground current to 1-2mA is provided. Thus, the conversion gain of the output is always maximized and the mixer is operated without any adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mixer for a signal synthesis circuit used in communication equipment.

BACKGROUND OF THE INVENTION In recent years, communication information networks have expanded, and new media such as satellite communications are attracting attention. Mixers are indispensable for these communication devices in order to change the signal frequency and perform modulation and demodulation.

Conventionally, diodes have been used in mixers of communication equipment using microwaves on U)(F band plates.

In particular, 10αh band mixers used for satellite broadcasting, satellite reception, etc. have been using GaAs diodes.

However, when integrating these discrete elements, the diode mixer requires a large filter, making it unsuitable for integration.

Recently, dual gate FETs have been attracting attention as an element that does not require this filter.

FIG. 3 is a circuit diagram of a mixer using conventional dual gate FETs. 1 is the first gate, 2 is the second gate,
3 is a drain. The first of dual gate FET4
The gate 1 and the second gate 2 serve as signal input terminals, and the drain 3 serves as an output terminal for mixed signals. To make this mixer work, it is necessary to apply a bias.5.
10°11 is the bias end. The conversion gain of the mixer is
Among these biases, this can be obtained by particularly adjusting the biases of the first gate and the second gate.

It has always been the case that the output voltage of the variable voltage generator 6 is adjusted so that the gain is maximized. However, adjusting while looking at high frequency characteristics such as gain is time-consuming and requires the addition of an adjustment circuit and the need to change circuit constants, making it difficult to integrate. was there.

Invention or Problem to be Solved As mentioned above, a mixer using dual FETs requires a bias circuit that adjusts while monitoring the conversion gain, and also has the disadvantage that such adjustment is necessary. It had Furthermore, there was a problem that it could not be integrated.

In view of the above drawbacks, the present invention provides a mixer that eliminates the need for such adjustment and further includes a fixed bias circuit.

Means for Solving the Problems In order to solve the above problems, the mixer of the present invention is configured with a circuit that allows a constant current to flow between the source and the drain by feeding the gate voltage.

Function: With this configuration, the conversion gain is always stably maintained at the maximum bias condition, eliminating the need for adjustment.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a dual FE in an embodiment of the present invention.
FIG. 3 is a diagram showing a circuit diagram of a T mixer. 4 is a dual gate FET, 1 is a first gate, 2 is a second gate, and 3 is a drain. The two gates serve as signal input terminals, and the drain serves as a mixing signal output terminal. 5, 10.11 is a bias end. In the present invention, the second gate is connected to a constant voltage.
For example, earth. Further, an active bias circuit 7 is installed to vary the bias of the first gate so that the bias current between the drain and the ground is constant. In GaAs dual-gate FETs used in the microwave band, the drain bias is set to 3 to 5 μ;
An active bias circuit is provided to fix the current between the drain and ground at 1-2 mA. According to the embodiment, the output conversion gain is always the maximum, and operation is possible without adjustment.

FIG. 2 is a diagram showing a circuit diagram of a dual gate FET mixer with an active bias circuit according to an embodiment of the present invention. A specific example of an active bias circuit attached to the dual gate FET mixer of FIG. 1 is shown.

9 is a transistor, and 8.12 is an external bias terminal.

When the resistance value of the active bias circuit is set, feedback is activated and the first gate bias is automatically adjusted so as to keep the current between the drain and ground constant.

Although the circuit here adjusts the first gate bias, it is of course also possible to adjust the second gate bias.

Dual Goo) FET4 is GaA in the microwave band.
a MES FET is used, and around 16 ru is 800
~300 μm, around 10 GHz, 600~2
A gate width of 0.00 μm is used; in both cases, a drain-to-ground current of 1 to 3 mA is optimal.

As described above, if the active bias circuit is used to produce high frequency characteristics by the current, no adjustment is required and integration becomes possible.

Further, although the explanation has been made using a mixer, it goes without saying that the present invention can also be applied to a modulator using a dual gate FET.

As described above, the effects of the invention enable a mixer using dual gate FETs to exhibit characteristics without adjustment, and furthermore, enables integration into a semiconductor integrated circuit.

As described above, 1. It has great practical effects in terms of circuit simplification, miniaturization, and high performance.

[Brief explanation of the drawing]

FIG. 1 shows a dual game (FE) in an embodiment of the present invention.
A circuit diagram of a T mixer, FIG. 2 shows a dual FET with an active bias circuit in one embodiment of the present invention.
Mixer circuit diagram, Figure 3 is a conventional dual FE
It is a circuit diagram of a mixer using T. 1...First gate, 2...Second gate, 3...Drain, 4...Dual
Gate, FET, 5...Bias end, 6...
...Variable voltage generator, 8...External bias end, 9
...Transistor, 10.11 ・Mountain/bias end, 12...External bias end.

Claims (1)

[Claims] A mixer characterized by comprising a circuit that flows a constant current between a source and a drain by controlling the voltage of one gate of a dual gate FET.