JP2834168B2 - Distributed amplifier - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distributed amplifier that operates to obtain high output in a wide band.

[Prior Art] FIG. 4 shows, for example, "A Monolithic Gallium Arsenic 1-13 GHz Traveling Wave Amplifier", IEETransactions, MTT
—Vol. 30, No. 7, July 1982, pp. 976-981 (“A Mon
olithic GaAs 1-13GHz Traveling-Wave Amplifier ", I
EEE Trans., Vol. MTT-30, No. 7, July 1982, pp. 976-98
1 is a circuit diagram showing the conventional distributed amplifier shown in 1), in which 1 is an input terminal, 2 is an output terminal, 3 is a field effect transistor (hereinafter referred to as FET), 4 is an input terminal of FET3, 5 is the output terminal of FET3, 6 is the ground terminal of FET3,
7 is an input-side termination resistor circuit, 8 is an output-side termination resistor circuit, 9 and 11 are distributed constant lines, and 10 is a phase adjustment line.

In such a distributed amplifier, the distributed constant line 9
And a capacitance Cgs between the gate and the source of the FET 3 disposed adjacently, a pseudo distributed constant line having a characteristic impedance Zg is formed, and the input-side terminating resistor circuit 7 forms an input-side coupling circuit P. . Further, a pseudo distributed constant line is formed by the drain-source capacitance Cds of each of the FET cells, the phase adjusting line 10 and the distributed constant line 11, and the output side termination circuit 8 and the output side coupling circuit Q
Is configured.

Next, the operation will be described. The microwave power input from the input terminal 1 propagates through each distributed constant line 9 in the direction of the input-side termination resistor circuit 7. Most of the microwave power propagating in this way is sequentially distributed to each FET 3,
Amplified. On the other hand, unnecessary microwave power not distributed to each of the FETs 3 is absorbed by the input-side terminating resistance circuit 7. For this reason, the input-side coupling circuit P having the above configuration can generally obtain good input reflection characteristics over a wide band without using a matching circuit.

On the other hand, the microwave power input to each FET3
And propagates in the direction of the output terminal 2 via the phase adjusting line 10 and the distributed constant line 11. In addition, since the electric lengths in the respective propagation paths from the input terminal 1 to the output terminal 2 are selected to be equal, the microwave power amplified by each FET 3 is sequentially combined by the output side coupling circuit, and 2 is output. With the configuration of the output side coupling circuit, good output reflection characteristics can be obtained over a wide band as in the case of the input side.

By the way, as a general method for increasing the output of the distributed amplifier as described above, there are methods of increasing the number of FETs 3 arranged periodically or increasing the gate width of each FET 3. According to the above document, the gain G of the distributed amplifier is approximately Can be expressed as Here, αg is the attenuation constant per unit length of the gate side circuit, lg is the gate side line length per unit cell of FET3, Zg is the characteristic impedance of the gate side line, and gm is FET3
And n is the number of FET3. From the above equation, the gain does not increase monotonically with n, , The gain no longer increases. Therefore, even if the number of FETs 3 is further increased, the gain does not increase, and as a result, the output of the amplifier does not increase. When the gate width of each FET 3 is increased, the gate-source capacitor Cgs increases, the cutoff frequency of the amplifier decreases, and it is impossible to obtain an output over a wide band.

[Problems to be solved by the invention]

Since the conventional distributed amplifier is configured as described above, in order to increase the output, it is necessary to increase the gate width of each FET3 or increase the number of FET3, and accordingly, the amplifier is shut down. There have been problems in that the frequency is reduced, an output cannot be obtained over a wide band, the gain is reduced, and the output is not increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain a distributed amplifier capable of obtaining high output over a wide band.

[Means for solving the problem]

The distributed amplifier according to the present invention sequentially connects input terminals of a plurality of multi-stage amplifiers having a multi-stage field-effect transistor, an inter-stage matching circuit, and a phase adjustment line and an input-side terminating resistor circuit via distributed constant lines. The output terminals of the multi-stage amplifiers and the output-side terminating resistance circuit are sequentially connected via another distributed constant line.

(Operation)

A distributed amplifier according to the present invention includes an inductance component of a distributed constant line that sequentially connects input terminals of a plurality of multistage amplifiers and input-side termination resistors, and a first stage of each multistage amplifier.
The input-side coupling circuit of the distributed configuration consisting of the gate-source capacitance component of the FET performs matching over a wide band, and the gate width of the final-stage FET of each multistage amplifier is increased, so that the adjacent By increasing the number of FETs arranged or increasing the gate width of the FETs, high-output microwave power can be obtained without lowering the cutoff frequency.

(Example of the invention)

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 12 is a first stage FET of a plurality of stages, 13 is an interstage matching circuit, 14 is a last stage FET, 17 is a first stage FET 12, an interstage matching circuit 13, a last stage FET 14, and a phase adjusting line 10. A two-stage amplifier 15 is an input terminal of the two-stage amplifier 17, and 16 is an output terminal. A plurality of these two-stage amplifiers are connected to the input-side termination resistance circuit 7 and the output-side termination resistance circuit 8 via the distributed constant lines 9 and 11 described above. In this distributed amplifier, the above two-stage amplifiers
A pseudo distributed constant line having a characteristic impedance Zg is formed by the gate-source capacitance Cgs of the 17 first-stage FET 12 and the distributed constant line 9, and an input-side coupling circuit is formed by the input-side terminating resistor circuit 7. Is done.

Similarly, a pseudo-distributed constant line is formed by the drain-source capacitance Cds of the final-stage FET 14 of each of the two-stage amplifiers 17, the phase adjusting line 10, and the distributed constant line 11, and the output-side termination resistor is formed. The circuit 8 forms an output-side coupling circuit. The coupling circuit having such a configuration can generally perform broadband matching.

Next, the operation will be described. The microwave power input from the input terminal 1 propagates through each distributed constant line 9 in the direction of the input-side termination resistor circuit 7 and is sequentially distributed to each two-stage amplifier 17. Here, the characteristic impedance of each distributed constant line 9, the line length, and the resistance value of the input-side termination resistor circuit 7 are set in each initial stage.
By selecting an appropriate value according to the FET 12, broadband matching can be performed, and each of the two
The power distributed to the stage amplifier 17 can be made as equal as possible. On the other hand, the microwave power amplified by the first-stage FET 12 of each two-stage amplifier 17 is input to the last-stage FET 14 via the interstage matching circuit 13 provided in each of the two-stage amplifiers 17. Therefore, the signal is further amplified according to the gate width of the final-stage FET 14. As a result, by increasing the gate width of the final-stage FET 14, high-output microwave power can be obtained without increasing the number of FETs arranged adjacently as in the conventional case. No matter how much the gate width is increased, Cgs of the first stage FET 12 is hardly affected.
Since the cutoff frequency is not reduced, high output can be obtained in a wide band. As described above, the microwave power output from the final-stage FET 14 propagates through the phase adjustment line 10 and the distributed constant line 11 in the direction of the output terminal 2, is sequentially combined, and is output from the output terminal 2. That is, according to the present invention, the characteristic impedance and the line length of each output-side phase adjusting line 10, the characteristic impedance and the line length of each distributed constant line 11, and the resistance value of the output-side terminating resistor circuit 8 are set to 2 respectively. By selecting an appropriate value according to the final-stage FET 14 of the stage amplifier 17, the output power of each of the two-stage amplifiers 17 can be combined over a wide band, and microwave power of higher output can be obtained from the output terminal 2. .

FIG. 2 is a circuit diagram showing another embodiment of the present invention.
In this embodiment, a multi-stage amplifier 17A in which two final-stage FETs 14 are operated in parallel is arranged adjacently. 18 is the final stage FET
This is an output-side combining circuit for combining 14 outputs. According to this embodiment, by operating the final-stage FETs 14 in parallel and synthesizing them by the output-side synthesizing circuit 18, high-output microwave power can be obtained with a simple input and output coupling circuit.

FIG. 3 is a circuit diagram showing still another embodiment of the present invention. In this embodiment, the multi-stage amplifiers 17 arranged adjacent to each other are used.
The B final stage FETs 14 are operated in parallel, and their outputs are directly connected to the phase adjustment lines 10 without combining the outputs. Since the output of each final stage FET 14 propagates through the phase adjustment line 10 and the distributed constant line 11 and is sequentially synthesized, the output side synthesis circuit
High power microwave power can be obtained without using 18.

〔The invention's effect〕

As described above, according to the present invention, a plurality of adjacent multistage amplifiers and the input-side terminating resistor circuit are sequentially connected by the distributed constant line to form the input-side coupling circuit. , Provides power distribution and matching over a wide band, and is located adjacently as before
By increasing the gate width of the final stage FET without increasing the number of FETs or increasing the gate width of the above-mentioned FETs, it is possible to output high-power microwave power without lowering the cutoff frequency. There is an effect that can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a distributed amplifier according to one embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams of a distributed amplifier according to another embodiment of the present invention, and FIG. 4 is a conventional distributed amplifier. FIG. 2 is a circuit diagram showing a type amplifier. 7 is an input-side termination resistor circuit, 8 is an output-side termination resistor circuit, 9 and 11 are distributed constant lines, 10 is a phase adjustment line, and 12 is FE
T (first stage FET), 13 is interstage matching circuit, 14 is FET (final stage FE
T) and 15 are input terminals of a two-stage amplifier, 16 is an output terminal of a two-stage amplifier, 17, 17A and 17B are multi-stage amplifiers (two-stage amplifiers), P is an input side coupling circuit, and Q is an output side coupling circuit. . In the drawings, the same reference numerals indicate the same or corresponding parts.

Continuation of the front page (72) Inventor Shuji Urasaki 5-1-1, Ofuna, Kamakura City, Kanagawa Prefecture Inside the Information Electronics Research Laboratory, Mitsubishi Electric Corporation (56) References JP-A-63-120506 (JP, A) JP-A Sho 62-109411 (JP, A) JP-A-60-233912 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H03F 3/60 JOIS WPI

Claims (1)

(57) [Claims] A plurality of multi-stage amplifiers having adjacent multi-stage field-effect transistors, an inter-stage matching circuit interposed between these respective field-effect transistors, and a phase adjusting line; The input-side coupling circuit in which the input terminals and the input-side terminating resistor circuits of the multi-stage amplifier are sequentially connected via a distributed constant line, and the output terminal and the output-side terminating resistor circuit of each of the multi-stage amplifiers are other. And an output side coupling circuit sequentially connected by distributed constant lines.