JPH0646681B2 - Microwave power combiner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power combiner and a distributor such as a fixed amplifier related to microwaves.

(Prior Art) In recent years, advances in semiconductor technology have led to higher power consumption of solid-state amplifiers using FETs (field effect transistors), impact diodes, etc. even in the microwave region. However, there is a limit to the power that can be output from each semiconductor, so in general, a power combiner is used to operate multiple semiconductors, and the output of multiple solid-state amplifiers is combined in a circuit to increase power consumption. It is connected.

As shown in FIG. 2, the power combiner is a circuit for supplying power from N amplifiers having the same characteristics to one load resistor. The requirements for a power combiner with N terminals are: (i) The internal loss of the combiner is as small as possible. That is, the total power of each amplifier should be supplied to the load resistor as much as possible.

(ii) The impedance of the combiner viewed from any of the N terminals is a matching impedance regardless of the impedance connected to the other terminals. That is, eliminate mutual coupling between N terminals.

If the latter of the above two requirements is not satisfied, the outputs of the amplifiers interfere with each other and the output impedances of the amplifiers are mismatched, resulting in unstable operation of the amplifiers, and in some cases, solid-state amplifiers. Leading to the destruction of semiconductors.

FIG. 3 shows an outline of the configuration of the power combiner. Using the impedance matrix [Z] of the network (passive circuit) of the N terminal of this synthesizer, and expressing the relationship between voltage and current, its general formula is The power combiner is a reversible symmetrical circuit, and if each of the N terminals is made equal, Can be expressed as

The analysis of this circuit will be described using eigenvalues and eigenvectors. The eigenvector i _n of the N-terminal symmetric circuit is: i _n = (1, e ^jna , e ^j2na , ... e ^{j (N-1) na} ) (3) n = 0, 1, ... , (N-1), a = 2π / N, and eigenvalue λ _n , [Z] [i _n ] = λ _n [i _n ] (4) To satisfy the requirement (ii) of the power combiner, the second (2)
As can be seen from the formula, the Z matrix element Z ₁₂ is replaced by Z ₁₂ = 0.
Is required. This When filled equation (4) the relationship of Z ₁₁ [i _n] = lambda _n [i _n] Since the (6) lambda _{n =} Z ₁₁ (7) is obtained.

As can be seen, in order to realize an ideal power combiner, Z ₁₁ is made equal to the matching impedance, and eigenvalues λ _n (n = 0, 1, ...
・, (N-1)) value is the matching impedance Z ₁₁ (= R) of the circuit.
_It is necessary to consider the circuit configuration of the combiner so that it becomes equal to _o ).

FIG. 4 shows an example of the structure of a conventional synthesizer. Connect the amplifier to the coaxial connector 2. Output is coaxial line 7
Take out from. Here, the case where N = 4 is shown, but in order to eliminate mutual coupling between the terminals, a slit 8 is provided and an absorber is inserted inside the slit.

From the equation (3), the first eigenvector corresponds to the current at each terminal corresponding to the same amplitude and the same phase, and thus is the same as that in the normal power combining operation. Since the internal magnetic field of the cylindrical cavity 1 has only a circumferential component and no radial magnetic field component,
The power loss in the slit absorber 8 is zero, and the output power propagates through the coaxial line 7. Next, in the second eigenvector (similar to the third and fourth), the current phases of the terminals are not the same, so that a magnetic field in the radial direction is generated and power is consumed in the slit absorber 8.

(Problems to be Solved by the Invention) Problems with the above structure are as follows.

(i) Since the copper loss of the output coaxial line 7 increases as the frequency increases (about 10 GHz or more), the combined loss increases effectively.

(ii) In the conventional microwave combiner, since there is no adjustment part (specifically, a slit) to make the eigenvalues of all eigenvectors equal, it is difficult to eliminate the mutual coupling between the input line terminals. It was

(Means for Solving the Problem) An object of the present invention is to eliminate the above-mentioned conventional drawbacks and provide a microwave power combiner having a relatively simple structure and a small combined loss.

That is, the microwave power combiner of the present invention is a microwave power combiner configured to connect a plurality of input lines to a cylindrical cavity and take out an output signal from an output line provided at the center of the cylindrical cavity. , In the cylindrical cavity, T
It is configured to generate an M-mode signal wave, and
A signal wave of TM ₀₁ mode is propagated to the output line and TE ₁₁
A filter for blocking a mode signal wave is provided on the output line side.

(Operation) As described in the section of the prior art, in order to realize an ideal microwave power combiner with less loss, the internal loss of the combiner should be as small as possible, and the arbitrary loss of multiple input terminals should be minimized. This is to configure the combiner so that the impedance seen from the terminal to the combiner becomes a matching impedance regardless of the impedance connected to other terminals.

Hereinafter, the present invention will be described in detail with reference to the drawings in the embodiments.

(Embodiment) First, when the coaxial line 7 is used as a waveguide for extracting output power as shown in FIG. 4, power loss due to copper loss increases at a frequency of 10 GHz or higher. Therefore, it is not preferable to increase the line length of the coaxial line from the combiner to the load.

In the first embodiment of the present invention, in principle, a circular waveguide is used as the output line instead of the coaxial line, which tends to cause a large loss.

FIG. 1 shows a first embodiment of the present invention, in which the height of the cylindrical cavity 1 constituting the combiner is set to be smaller than λ / 2. Where λ is the wavelength of free space with respect to the operating frequency.

Next, let the diameter of the circular waveguide 3 propagate in the TM ₀₁ mode and TE
₂₁ Select so that the mode is in the cutoff area. In this case, the TM mode is dominant in the electromagnetic field in the cylindrical cavity 1, and the TE ₁₁ mode and the TM ₀₁ mode are the propagation modes of the circular waveguide 3.

As described above, the magnetic field in the cylindrical cavity 1 has a vector component in the circumferential direction and does not have a vector component in the radial direction for the first eigenvector of the equation (3). The electromagnetic field in the body 1 is dominated by TM _0n0 (n ≧ 1) mode,
The TM ₀₁ mode is coupled to the circular waveguide 3 coupled to this and propagates as an output. TE ₁₁ mode is present as a mode capable of propagating in the circular waveguide 3 in addition to TM ₀₁ mode, but TE ₁₁ mode does not exist for the first eigenvector. When the mode in the cylindrical cavity is called TM _rnm mode, r is the number of waves in the circumferential direction (φ), n is the number of waves in the radial direction (ρ), and m is the height. It represents the number of waves in the direction (Z).

Next, if excitation is performed with the 2nd, 3rd, ..., (N-1) th eigenvectors, an electromagnetic field having a vector component in the radial direction is generated in the cylindrical cavity 1 and a circular waveguide is generated. The TE ₁₁ mode propagates to the tube 3. Since the load connected to the circular waveguide 3 is for the TM ₀₁ mode, it is not preferable that the TE ₁₁ mode propagates to the output side. Therefore, in the present embodiment, the first
The provided slit 4 as shown in FIG, connexion by the condition (through TM ₀₁ mode is lossless, TE ₁₁ mode attenuates) TM for mode filter of inserting the resistor has to absorb TE ₁₁ mode by. Note that the cylindrical cavity 1 is provided with a slit 8 as shown in FIG. 4, and a resistor made of ferrite or the like is inserted depending on conditions, and the second, third, ..., (N-1 ) Absorbs the power to the eigenvector. Further, the coupling hole 5 shown in FIG. 1 is provided for matching the cylindrical cavity 1 and the circular waveguide 3.

The following examples, a structure obtained by adding a TE ₁₁ mode rejection filter 9 as in the fifth diagram for completely blocking the TE ₁₁ mode in the structure of FIG. 1 (the case of N = 8).

Here, the slit 4 is provided in the section A of the circular waveguide 3 as in FIG. 1, and the height B of the filter 9 is set to B <λ / 2.

Furthermore, as shown in FIG. 6, a cylindrical cavity 10 may be separately provided between the cylindrical cavity 1 and the circular waveguide 3 to provide an impedance matching adjusting mechanism. Here, as shown in FIG. 6 (b), the cylindrical cavity 10 is provided with a mode filter slit 4 for absorbing the TE mode and passing the TM ₀₁ mode.

As described above, in the present invention, the circular waveguide 3 is used as the output waveguide of the power combiner as shown in FIGS. 1, 5 and 6, and the inside of the circular waveguide 3 is TM _01. Mode propagates and TE ₂₁
A frit 4 for a TM ₀₁ mode mode filter is provided near the junction between the cylindrical cavity 1 and the circular waveguide 3 so that the mode does not reach the output load. The structure in which a TE ₁₁ mode rejection filter 9 to further strongly damping effect of the TE ₁₁ mode (Figure 5) also shows as another method.

The above is the case where the circular waveguide is used as the output director.

As a next example, an example will be described in which when a coaxial line is used as an output waveguide, an adjusting mechanism is provided to bring the eigenvalue closer to the junction impedance for the operating state of each eigenvector.

The first one is to use the conventional cylindrical cavity shown in Fig. 4 as it is, and to devise the output coaxial line. This is shown in FIG. The devised part is that the coaxial line joined to the cylindrical cavity 1 has different diameters such as 11 and 12. That is, the diameter of the coaxial line 12 is set to propagate the coaxial TE ₁₁ mode,
The coaxial line 11 is dimensioned so as to block all higher-order modes other than the TEM mode.

A slit 14 is provided on the coaxial line 12, and a resistor is inserted to absorb the TE mode depending on conditions. By doing so, the TE ₁₁ mode generated in the coaxial line 12 due to the excitation of the second, third, ... (N-1) eigenvectors is absorbed, so that the length C of the coaxial line 12 and the absorption resistance are It can be adjusted to bring each eigenvalue to the desired value.

FIG. 8 shows the next embodiment. This is provided with a special circular waveguide 16 on the side facing the coaxial line 15 for taking out the output. The diameter of this special circular waveguide 16 allows the TE ₁₁ mode to propagate, while the TM ₀₁ mode is the cutoff region. The end face of this circular waveguide 16 is short-circuited, and a resistor 18 that absorbs microwave power is inserted into the waveguide. In this way, the second, third, ..., the electromagnetic field for the eigenvectors of the (N-1) is to excite the TE ₁₁ mode in the circular waveguide 16, the TE ₁₁ mode The electromagnetic wave is absorbed by the resistor 18. Therefore, the coupling hole 1 is set so that each eigenvalue becomes a desired value.
The conductivity of 7 and the resistor 18, the length of the circular waveguide, etc. may be adjusted.

Next, FIG. 9 shows an arrangement in which an adjusting cavity 19 is added to the portion of the circular waveguide 16 in FIG. 8 and an adjusting mechanism is provided so that each eigenvalue becomes a desired value.

FIGS. 10 and 11 show application examples of the combiner or the distributor to which the idea can be applied, and FIG. 10 shows a combination of a cylindrical cavity and a circular waveguide. FIG. 11 shows a combination of a cylindrical cavity and a coaxial line.
The blocking filter 23 shown in FIG. 10 has the same function as the blocking filter 9 shown in FIG. These are related to solid-state amplifiers using FETs, and if they are connected in series as described above, a multi-stage solid-state amplifier can be efficiently realized in a small size and easily.

(Effect of the invention) In the embodiment in which the circular waveguide is used as the output waveguide, by using the circular waveguide, when the line from the combiner to the load is long, the transmission loss is smaller than that of the coaxial line. Therefore, it helps to reduce the power synthesis loss.

In addition, a mode filter for the TM mode is provided near the junction of the circular waveguide and the cylindrical cavity, and there is also an adjustment mechanism, which makes it easy to adjust the impedance for each eigenvector to satisfy the requirements of the power combiner. Power combiner can be realized.

Furthermore, in the embodiment in which the coaxial line is used as the output waveguide, in the joint portion of the cylindrical cavity and the output coaxial line or in the portion of the special circular waveguide provided in the portion facing the coaxial line,
Since an absorber that absorbs the TE mode is provided and an adjustment mechanism is also provided, impedance adjustment for each eigenvector is facilitated and an ideal power combiner can be realized.

The multi-stage solid-state amplifiers of FIGS. 10 and 11 to which the present invention is applied are small and simple and have high efficiency, and are particularly effective when small and light weight is required such as a power amplifier for satellites.

[Brief description of drawings]

1 (a) and 1 (b) are a side sectional view and a side view of the structure of the microwave power combiner showing the first embodiment of the present invention, and FIG. 2 shows the power combining of N power amplifiers. Fig. 3, Fig. 3 is a diagram showing a basic configuration of a power combiner, and Figs. 4 (a) and 4 (b) are side sectional views showing the structure of a conventional power combiner and a plan view seen from above, Fig. 5 (a), (b) is a sectional view of the side surface of the structure of the combiner showing the second embodiment of the present invention and a plan view seen from above (the blocking filter 9 is omitted), FIG. 6 (a), (b) is a sectional side view and a side view of the structure of the synthesizer showing the third embodiment of the present invention, and FIGS. 7 (a) and 7 (b) are the structures of the synthesizer showing the fourth embodiment of the present invention. And FIG. 9 is a side sectional view of the structure of the synthesizer showing the fifth and sixth embodiments of the present invention, and FIG. 10, FIG. Multi-stage type solid showing the first and second application examples It is a cross-sectional view of the amplifier.

Claims (7)

[Claims] 1. A microwave power combiner configured to connect a plurality of input lines to a cylindrical cavity and take out an output signal from an output line provided at the center of the cylindrical cavity. In the above paragraph, a filter is provided on the output line side, which is configured to generate a TM mode signal wave and propagates the TM ₀₁ mode signal wave to the output line and blocks the TE ₁₁ mode signal wave. Characteristic microwave power combiner. 2. The microwave power combiner according to claim 1, wherein the input line is a coaxial line, and the output line is a circular waveguide or a coaxial line. 3. The filter according to claim 2, wherein the filter for blocking the signal wave of the TE ₁₁ mode is provided with a slit in the lengthwise direction of the circular waveguide forming the output line. Microwave power combiner. 4. A circular waveguide forming the output line is provided with a cavity as a filter for blocking the TE ₁₁ mode signal wave. The microwave power combiner according to. 5. As a filter for blocking the TE ₁₁ mode signal wave, a cavity having a slit parallel to the TE ₁₁ mode magnetic field direction is provided between the cylindrical cavity and the output line. The microwave power combiner according to claim 2, wherein 6. A coaxial line to the output line, a portion connected to the cylindrical cavity, the TE ₁₁ mode signal wave is configured in such a thickness can be transmitted, further signal wave of the TE ₁₁ mode 3. The microwave power combiner according to claim 2, wherein a slit parallel to the magnetic field direction of is provided. 7. A filter for blocking the TE ₁₁ mode, wherein a cavity for absorbing only the TE ₁₁ mode is provided on the side of the cylindrical cavity facing the output line. The microwave power combiner according to the item.