JPH0520002B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to power combining of traveling waveform FET amplifiers.

[Conventional technology]

Figure 6 shows, for example, JBBeyer, ef al, “MESFET
Distributed Amplifier Design Guidelines,”
JEEE Trans., vol.MTT−32, No.3, PP.268−
275, Mar. 1984, etc., is an equivalent circuit diagram of an example of a conventional power combining traveling wave FET amplifier that combines the outputs of two traveling wave FET amplifiers using a normal T-branch, where 1 is an input terminal and 2 is an input terminal. Output terminal, 3a, 3b
is FET, 4a, 5a, 6a are each FET3a
gate terminal, drain terminal, source terminal, 4
b, 5b, 6b are the gate terminal, drain terminal, source terminal of FET 3b, 7a, 7b,
8a, 8b are inductors, 9a, 9b, 10a,
10b is a terminator, and 11 and 12 are T branches.

Next, the operation will be explained. The microwave power applied to the input terminal 1 is divided into two by the T-branch 11, and one of the microwave power propagates through each inductor 7a in the direction of the terminator 9a.
A part of the microwave power is supplied to each FET 3a. The microwave power supplied to each FET 3a is amplified there, propagates through each inductor 8a, and reaches the T-branch 12. Further, the other microwave power divided by the T-branch 11 propagates through each inductor 7b in the direction of the terminator 9b, but on the way, a part of the microwave power is transmitted to each FET 3b.
is supplied to The microwave power supplied to each FET 3b is amplified there, propagates through each inductor 8b, and reaches the T-branch 12. The two microwave powers that have reached the T-branch 12 are combined there and reach the output terminal 2.

Next, for the following explanation, the operating principle of such a power combining traveling waveform FET amplifier will be described in more detail.

Here, to simplify the explanation, each FET3a,
3b all have the same shape, and the inductance of each inductor 7a, 7b is constant at Lg/2,
The inductance of each inductor 8a, 8b is
constant at Ld/2, and terminators 9a, 9b
It is assumed that the terminators 10a and 10b have the same performance.

The equivalent circuit of FET is usually given as shown in Figure 7. In FIG. 7, when microwave power is applied to the gate terminal 4, the microwave power amplified by the mutual conductance gm within the FET is generated at the drain terminal 5, resulting in an amplification effect.
In Fig. 7, the gate-drain capacitance cdg is generally very small, so if this is ignored approximately, the equivalent circuit in Fig. 6 is the gate-side equivalent circuit in Fig. 8a, and the drain-side equivalent circuit in Fig. 8b. Express it with an equivalent circuit. 2 with loss in both Fig. 8a and Fig. 8b
This is an equivalent circuit equivalent to an equivalent circuit composed of a real distributed constant line and a T-branch connecting it. Generally, the characteristic impedance of a distributed constant line does not change with frequency. From this, appropriate inductors 7a, 7b, 8a, 8b and terminators 9a, 9 are suitable for FETs 3a, 3b.
b, 10a, and 10b, it is possible to obtain an amplifier having good VSWR characteristics over a wide band and flat gain characteristics.

By the way, the above operation can be said when the FETs 3a and 3b have exactly the same performance and the phases and amplitudes of the two microwaves reaching the T-branch 12 are equal. In general, FET3a and 3b have slightly different performance due to variations, and as a result, T
The two microwaves reaching the branch 12 have different phases and amplitudes. When there is such an unbalance in the microwave power, the unbalanced microwave power is reflected at the T branch 12 and the FET
This may adversely affect the FET, resulting in a decrease in gain, output, or oscillation.

[Problem that the invention seeks to solve]

In this way, in conventional power synthesis traveling waveform FET amplifiers, if there is an imbalance in the microwaves that reach the T-branch 12 due to variations in the FETs, the unbalanced microwaves will be reflected back to the FET side and have an adverse effect on the FETs. and as a result gain,
There have been cases where problems have occurred, such as a drop in output or oscillation.

This invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a power combining traveling wave FET amplifier that can achieve isolation of two traveling wave FET amplifiers over a wide band.

[Means for solving problems]

The power combining distributed semiconductor circuit according to the present invention includes:
A reactance circuit having a T-branch for synthesizing the outputs of the two distributed semiconductor circuits and connecting the output electrodes of the semiconductor elements of the two distributed semiconductor circuits is connected to a predetermined or It is connected by a passive element containing a resistance component.

[Operation] In the power combining distributed semiconductor circuit according to the present invention, the passive element connecting predetermined points facing each other in the reactance circuit compensates for the unbalanced output power of the two distributed semiconductor circuits reaching the output side. It absorbs over a wide band and isolates between two distributed semiconductor circuits.

〔Example〕

An embodiment of the present invention will be described below.
In FIG. 1, 20 is a resistor having a predetermined resistance value.

The microwave power input from input terminal 1 is T
The microwave power is divided into two by the branch 11, and one of the microwave power propagates through each inductor 7a toward the terminator 9a, and a portion of the microwave power is supplied to each FET 3a along the way. The microwave power supplied to each FET 3a is amplified there, propagates through each inductor 8a, and reaches the T-branch 12. Further, the other microwave power divided by the T-branch 11 propagates through each inductor 7b in the direction of the terminator 9b, but on the way, a part of the microwave power is supplied to each FET 3b. . Each FET3b
The microwave power supplied to is amplified there,
It propagates through each inductor 8a and reaches the T-branch 12.
The two microwave powers that have reached the T-branch 12 are combined there and reach the output terminal 2. FET3a, 3
b Due to performance variations, etc., T-branch 12 was reached 2
When an unbalance occurs between the two microwaves, the unbalanced microwave power is absorbed by each resistor 20 according to the frequency as shown in the following explanation, and the iso power between the two traveling wave FET amplifiers is increased over a wide band. ration is obtained.

Next, the effect of loading each resistor 20 will be explained in more detail.

FIG. 2 is an equivalent circuit diagram on the drain side of FIG. 1 corresponding to FIG. 8b. FIG. 2 shows an equivalent circuit similar to a circuit in which two lossy distributed constant lines are connected at opposing predetermined positions to each other through a resistor 20. In FIG. 2, if the impedance of the current source is infinite and the source-drain resistance Rds is sufficiently large so that the loss effect caused by this can be ignored, then FIG. 2 can be approximately represented by the equivalent circuit of FIG. 3. That is, two distributed constant lines 21a, 2 with characteristic impedance Z and propagation velocity V
1b, a T-branch 12, and a resistor connected to each other at predetermined opposing positions of the two distributed constant lines. Note that under the above approximation It is becoming.

In FIG. 3, the distances from the T-branch 12 to each resistor are designated as l ₁ , l ₂ , l ₃ , ... _lo , and these are f ₁ , f ₂ ,
Suppose that it has a frequency of f ₃ ,...f _o and a length of 1/4 wavelength.

In FIG. 3, two distributed constant lines 21a, 2
When the phases and amplitudes of the microwaves propagating through 1b are equal, no power is consumed by each resistor, and the power is combined at the T-branch 12 to reach the output 2.

Next, a case will be described in which there is an imbalance in the microwaves that have reached the T-branch 12. For microwaves with frequency fn, according to the operating principle of a normal WilKinson type distributor, the unbalanced power is consumed by resistor Rn,
Absorbed. In addition, for example, in the case of a microwave with a frequency f ₁ , the unbalanced power is transmitted through the resistors R ₁ , R ₂ ,
Most of the energy is consumed in R ₃ ,...Rn. By appropriately selecting the positions where the resistors are loaded and the resistance values R ₁ , R ₂ , R ₃ ,...Rn, the unbalanced power can be absorbed over a wide band, and as a result, the two distributed constant lines Isolation between 21a and 21b is obtained.

Furthermore, from the shape of Figure 3, this is an ideal
Since the structure is different from the WilKinson type distributor, it is not possible to obtain ideal isolation at each frequency. Power composite progressive waveform in Figure 1
In a FET amplifier, the two microwaves that reach the branch 12 originally have almost the same phase and amplitude characteristics, so even if ideal isolation cannot be obtained at each frequency, it is not a problem. It won't happen.

FIG. 4 is an equivalent circuit diagram of an embodiment other than this invention in which the position where the resistor 20 is loaded is changed. In this way, the position where the resistor 20 is loaded may be changed.

Although the case where an inductor of a lumped constant circuit element is used as a reactance circuit has been described above, the present invention is not limited to this, but can also be applied to a case where a microstrip line 22 is used as a reactance circuit as shown in FIG. It's good to be warm. In addition, a resistor 20 is used as an element to absorb the unbalanced power.
Although we have explained the case where the terminator 10 is used,
When the impedance consisting of a, 10b, etc. includes a reactance component, it may be a passive element containing a resistance component instead of a pure resistance.

〔Effect of the invention〕

As described above, according to the present invention, by connecting predetermined positions facing each other of the output side reactance circuits of the two distributed semiconductor circuits with a predetermined passive element, the output side reactance circuits of the two distributed semiconductor circuits can be A power synthesis distributed semiconductor that can reduce problems such as decreases in gain, output, and oscillation even if an imbalance occurs in the synthesized power due to variations in semiconductor elements, as it can obtain isolation over a wide band between There is an effect that the circuit can obtain.

[Brief explanation of drawings]

FIG. 1 is an equivalent circuit diagram of a power combining traveling waveform FET amplifier according to an embodiment of the present invention, and FIG.
3 is an approximate equivalent circuit diagram of FIG. 2, FIG. 4 is an equivalent circuit diagram of another embodiment of the present invention, and FIG. 5 is an equivalent circuit diagram of still another embodiment of the present invention. The equivalent circuit diagram of the example, Figure 6 is the equivalent circuit diagram of the conventional power synthesis traveling waveform FET amplifier, and Figure 7 is the equivalent circuit diagram of the conventional power synthesis traveling waveform FET amplifier.
The equivalent circuit diagrams of the FET, FIGS. 8a and 8b, are equivalent circuit diagrams of the gate side and drain side of FIG. 6, respectively. 3a, 3b are FETs, 4, 4a, 4b are gate terminals, 5, 5a, 5b are drain terminals, 7a, 7
b, 8a, and 8b are inductors, 11 and 12 are T-branches, 20 is a resistor, and 22 is a microstrip line. In the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. Two distributed semiconductor circuits in which control electrodes of adjacent semiconductor elements and output electrodes of the adjacent semiconductor elements are connected by a reactance circuit, and In a power combining distributed semiconductor circuit equipped with a T-branch for combining the outputs of two distributed semiconductor circuits, at mutually opposing points of reactance circuits connecting the output electrodes of the two distributed semiconductor circuits. , the number of signals to be processed that are separated from the T-branch by an amount corresponding to approximately 1/4 of the wavelength of the plurality of signals to be processed within the band to be processed in the distributed semiconductor circuit; A power combining distributed semiconductor circuit characterized in that points corresponding to the above are connected by passive elements including at least a resistance component that absorbs unbalanced components of the outputs of the two distributed semiconductor circuits. 2. The power combining distributed semiconductor circuit according to claim 1, characterized in that a FET is used as the semiconductor element. 3. The power combining distributed semiconductor circuit according to claim 1, wherein the distributed semiconductor circuit is a traveling wave amplifier circuit.