JPH0766659A - Microwave amplifier - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a variable bandwidth microwave amplifier with a simple configuration. [Structure] The filter group 40 is connected to the input side matching circuit 13, and the filter group 40 is composed of three stages of band-pass filters 41, 42, 43 connected in series. Filter 41
Comprises a capacitor 4 (capacitance C ₁ ) connected in series, an inductor 3 (inductance L ₀ ), a gold wire 2 (inductance Lg), and a gate-source capacitance C _gs of the FET 1. The variable capacitor 10 (capacitance C) is connected between the connection point between the inductor 3 and the gold wire 2 and the ground. The bandpass filters 42 and 43 also have similar configurations. [Effect] By controlling the capacitance of the capacitor connected to the shunt in the filter, the frequency band of the microwave amplifier can be made variable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for matching a microwave amplifier used for microwave communication.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional microwave amplifier 200.
3 is a circuit diagram showing an example of FIG. This circuit includes a phase adjustment circuit, for example, MMIC (Monolithic Microwave Integrate).
d Circuit: Microwave integrated circuit).
FIG. 10 is a perspective view showing the configuration of the microwave amplifier 200. The FET 25 is connected to the input side matching circuit 33 via the gate pad 29. Further, it is connected to the output side matching circuit 34 via the drain pad 30. Further, an air bridge 27, a source finger 28, and a source ground 26 are also provided. In order to adjust the input side matching circuit 33 and the output side matching circuit 34 independently, the FET 25 has a dual gate structure with good isolation.

The first gate of the FET 25 is a variable capacitance diode (varactor diode) connected in series with each other.
It is grounded via the input side frequency characteristic control unit 23 including the D1 and the short stub S1.

Further, the source of the FET 25 is also grounded via the output side frequency characteristic control section 24 composed of a varactor diode D2 and a short stub S2 connected in series.

An input side matching circuit 33 is connected to the first gate of the FET 25, and an output side matching circuit 34 is connected to the source of the FET 25. Further, while the predetermined potential Vg2 is applied to the second gate, the capacitor 3
Grounded via 5. Since the input side matching circuit 33, the output side matching circuit 34, and the capacitor 35 form a loaded type phase shifter, the pass phase of the microwave amplifier 200 has the admittance of the capacitor 35 as Y _O ,
Letting B be the susceptance of the input side matching circuit 33 and the output side matching circuit 34, Φ = tan ⁻¹ (B / 2 · Y _O ). Therefore, the passing phase can be changed by changing the junction capacitance of the varactor diodes D1 and D2, and the frequency characteristic of the microwave amplifier 200 can be made variable.

[0006]

Since the conventional microwave amplifier is constructed as described above, it is necessary to change the junction capacitance between the two diodes, and the potentials of both diodes must be controlled. However, there was a problem that two power supplies were required.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to use a single microwave power supply for the diode or to make the band variable with a simple structure in which no power supply is required. The purpose is to get an amplifier.

[0008]

A microwave amplifier according to the present invention has (a) an input terminal and an output terminal, and (b)
An output end connected to the output terminal, and an input end,
An amplifying element that amplifies the signal given to the input end and gives it to the output end; and (c) a first bandpass filter connected between the input end of the amplifying element and the input terminal. Prepare Here, the frequency band of the first bandpass filter is variable.

Preferably, the first bandpass filter has (c-1) a first potential point for providing a first potential, and (c-
2) a connection point, (c-3) a first capacitor and a first inductor connected in series between the input terminal and the connection point, and (c-4) the connection point and the amplification element. A second capacitor and a second capacitor connected in series with the input end;
An inductor and (c-5) a third capacitor connected between the connection point and the first potential point and having a variable capacitance.

Preferably, the third capacitor is (c-
5-1) A varactor diode, and (c-5-2) a power supply that applies a predetermined voltage to the varactor diode.

Alternatively, the third capacitor is (c-5
-3) an insulator, and (c-5-4) a first sandwiching the insulator.
And a second electrode, and (c-5-5) an auxiliary electrode formed on the same side as the first electrode with respect to the insulator. Here, the capacitance of the third capacitor is made variable by connecting the first electrode and the auxiliary electrode.

Preferably, the amplifying element is (b-
1) A second potential point for applying a second potential, (b-2) a control electrode connected to the input end of the amplification element, and the second
A transistor including a first current electrode connected to a potential point and a second current electrode connected to the output terminal of the amplification element, and further including the second capacitor in the first bandpass filter. Share with. The second capacitor substantially comprises a parasitic capacitance formed by the control electrode and the first current electrode of the transistor.

More preferably, the amplifying element is (b-
3) It further has a connection line connecting the control electrode and the input end of the amplification element, and further shares the second inductor with the first bandpass filter. The second inductor is substantially composed of a parasitic inductance formed by the connection line.

More preferably, the first potential and the second potential are equal to each other.

Alternatively, (d) there is further provided at least one second bandpass filter connected between the first bandpass filter and the input terminal.

Preferably, the first band-pass filter is (c-1) a first potential point for applying a first potential,
(C-2) a first connection point, (c-3) a first capacitor and a first inductor connected in series between the second bandpass filter and the first connection point, and (c-4) ) A second capacitor and a second inductor connected in series between the first connection point and the input end of the amplifying element;
-5) A third capacitor connected between the first connection point and the first potential point and having a variable capacitance.

More preferably, the second bandpass filter comprises (d-1) a second potential point for applying a second potential, and (d-1)
-2) a second connection point, (d-3) a fourth capacitor and a third inductor connected in series between the input terminal and the second connection point, and (d-4) the second connection A fifth capacitor and a fourth inductor connected in series between a point and the first bandpass filter, and (d-5) a fifth capacitor and a fourth inductor connected in series between the second connection point and the second potential point. And 6 capacitors.

Further preferably, the first and fifth capacitors are also used by the first and second band pass filters, and the first and fourth inductors are the first and second inductors.
Also used as a bandpass filter.

[0019]

Since the frequency band of the first bandpass filter is variable, the microwave amplifier according to the present invention can be easily matched to various frequencies.

[0020]

EXAMPLES A. Basic Structure: Before specifically moving to the description of each embodiment, the basic structure of the present invention will be described.

FIG. 1 is a circuit diagram showing the configuration of a microwave amplifier 100 according to the present invention. The source of the FET 1 formed as a chip is grounded, and the drain is connected to the output side matching circuit 14 via the gold wire 9. The gold wire 9 has an inductance Ld. The input matching circuit 13 and the output matching circuit 14 can be formed by patterns. The equivalent circuits are represented as shown by the input matching circuit 33 and the output matching circuit 34, respectively.

The gate is connected to the filter group 40 via the gold wire 2 having the inductance Lg, and the filter group 40 is connected to the input side matching circuit 13.

The filter group 40 is composed of three stages of band-pass filters 41, 42 and 43 connected in series.
Each of 1, 42, and 43 has a configuration having the connection relationship shown in FIG. That is, the filter 41 includes a capacitor 4 (capacitance C ₁ ) connected in series, an inductor 3 (inductance L ₀ ), a gold wire 2 (inductance Lg), and a gate-source capacitance C _gs of the FET 1. And variable capacitor 1
0 (capacitance C) is inductor 3 and gold wire 2
Connected between the connection point and ground.

Similarly, the filter 42 includes an inductor 3 (inductance L ₀ ), a capacitor 4 (capacitance C ₁ ), a capacitor 5 (capacitance C ₁ ), and an inductor 6 (inductance L ₀ ) connected in series. . The capacitor 11 (capacitance C ₀ ) is connected between the connection point of the capacitors 4 and 5 and the ground. That is, the inductor 3 and the capacitor 4 are shared by the filters 41 and 42.

Similarly, the filter 43 includes a capacitor 5 (capacitance C ₁ ), an inductor 6 (inductance L ₀ ), an inductor 7 (inductance L ₀ ), and a capacitor 8 (capacitance C ₁ ) connected in series. . The capacitor 12 (capacitance C ₀ ) is connected between the connection point of the inductors 6 and 7 and the ground. That is, the capacitor 5 and the inductor 6 are shared by the filters 42 and 43.

Now, consider the characteristics of the filter 41.
However, for the sake of simplicity, each parameter has a capacitor (capacitor 10) that enters a shunt as shown in FIG.
(Corresponding to)). In this case, the impedance Z _{41 of the} bandpass filter is

[0027]

[Equation 1]

It is represented by Here, the frequency band is (ω ₂
Since it is expressed by −ω ₁ ) / 2π, the frequency band can be controlled by controlling the capacitance C of the variable capacitor 10.

FIG. 3 is a graph of simulation results showing that the frequency band can be controlled, and FIG. 4 is shown in FIG.
6 is a circuit diagram showing a configuration of a microwave amplifier circuit used to obtain the simulation result shown in FIG. Figure 4
At C ₀ = 2.0 pF, C ₁ = 16.0 pF, L
₀ = 0.001 nH, Lg = 0.02 nH, C _gs = 20
It is pF. However, the inductance of the inductor connected to the gold wire 2 is set to 0.005 nH.

The unit gate width of the FET is 7.5 μm.
2 sets a combination of GaAs transistors with a total gate width of 10.5 mm. Here, "2 composition"
Means arranging two FETs in parallel to combine output power.

Input side matching circuit 13 and output side matching circuit 1
The elements constituting No. 4 are shown as rectangles, and the numerical value shown in each of them indicates the impedance (unit: ohm). However, the output side matching circuit 14 is also provided with capacitors and inductors, and the numerical values shown beside each of them indicate their respective capacitances and inductances.

In FIG. 3, the vertical axis arbitrarily represents the reference (0d
The gain obtained in B) is plotted on the horizontal axis. From this result, as the capacitance C decreases from 12 pF to 4 pF, the frequency band increases from 13 GHz to 17 GHz.
It is shown to change to. The graph indicated by MAG in the figure is the maximum power gain at that frequency.

For example, the dielectric constant of an alumina (Al ₂ O ₃ ) substrate is 9.9, and the dielectric constant of a high dielectric constant substrate such as barium titanate is about 38. The electrode area is 2 mm x 0.
Assuming that the thickness of the dielectric material is 6 mm and the thickness of the dielectric material is 0.1 mm, the obtained capacitance is ˜4 pF when the dielectric constant is 38.

Various techniques for varying the capacitance C will be described below.

B. Specific Structure of Capacitor: First Embodiment: FIG. 5 is a circuit diagram showing a structure of a microwave amplifier 101 according to a first embodiment of the present invention. The microwave amplifier 101 is one in which the configuration of the variable capacitor 10 in the microwave amplifier 100 shown in FIG. 1 is specifically specified.

The variable capacitor 10 includes a fixed capacitor 15 and a power source 16 and a varactor diode 17 connected in parallel.
It is configured by connecting in series with. Here, the fixed capacitor 15 is provided so that the potential given by the power supply 16 is not applied to the FET 1. In order to control the band of the microwave amplifier 101 configured as above, only a single power supply 16 needs to be provided, and the number of required power supplies is reduced as compared with the conventional microwave amplifier 102. You can

Second Embodiment: The variable capacitor 10 can control its capacitance by making the electrode area variable. FIG. 6 is a perspective view showing a configuration of a microwave amplifier including the FET 1, the input side matching circuit 13 and the output side matching circuit 14. However, filter group 4
0 is configured in the same chip 20 as the input side matching circuit 13 except for the portion corresponding to the variable capacitor 10.

Variable capacitor 10, chip 20, FET
1. The output side matching circuit 14 is commonly provided on the ground plane 50. Further, these are connected to each other by a gold wire 21 above each other. Variable capacitor 10
Has a dielectric 19 and an upper electrode 18, and although not shown, a lower electrode facing the upper electrode 18 is further connected to the ground plane 50 through the dielectric 19 and thereby connected to the FET 1 and the like. ing.

FIG. 7 is a perspective view showing the structure of the variable capacitor 10 according to the second embodiment of the present invention.
1, the chip 20, and the output side matching circuit 14 are also shown. In addition to the upper electrode 18, an auxiliary electrode 22 formed of, for example, gold is provided, and both are connected by a gold wire 21, whereby the electrode area can be substantially increased and its capacitance can be increased.

FIG. 8 is a more detailed perspective view of FIG. 7. FET1 is connected to the upper electrode 18 on the variable capacitor 10 via the gate pad 29. Further, it is connected to the output side matching circuit 14 via the drain pad 30. Further, an air bridge 27, a source finger 28, and a source ground 26 are also provided. As described above, the FET1 and the FET25 are similar in configuration, but the output can be increased by increasing the gate width to increase the output, for example, five times.

Other Modifications: In the above description, the case where only the capacitance of the capacitor connected to the shunt in the filter 41 closest to the FET1 among the filters constituting the filter group 40 was made variable. Even in the stage filter, the frequency band can be made variable in a manner similar to that shown in Formula 1, so that even if the capacitance of the capacitor connected to the shunt in the filters 42 and 43 is made variable, the effect of the present invention can be obtained. To be Further, the number of filter stages is not limited to the above three stages.

[0042]

As described above, according to the microwave amplifier of the present invention, even if the third capacitance is composed of a varactor diode, it is possible to supply a single power supply. Further, by using the variable capacitance element, the band can be made variable with a simple configuration that does not require a power supply.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic configuration of the present invention.

FIG. 2 is a circuit diagram illustrating the operation of the basic configuration of the present invention.

FIG. 3 is a graph illustrating the operation of the basic configuration of the present invention.

FIG. 4 is a circuit diagram illustrating the operation of the basic configuration of the present invention.

FIG. 5 is a circuit diagram showing a first embodiment of the present invention.

FIG. 6 is a perspective view showing a second embodiment of the present invention.

FIG. 7 is a perspective view showing a second embodiment of the present invention.

FIG. 8 is a perspective view showing a second embodiment of the present invention.

FIG. 9 is a circuit diagram showing a conventional technique.

FIG. 10 is a perspective view showing a conventional technique.

[Explanation of symbols]

 1 FET 2 Gold wire 3,6,7 Inductor 4,5,8,11,12 Capacitor 10 Variable capacitor 16 Power supply 17 Varactor diode 18 Upper electrode 19 Dielectric 22 Auxiliary electrodes 41-43 Bandpass filter

Claims (11)

[Claims] 1. An output terminal, comprising: (a) an input terminal and an output terminal; (b) an output terminal connected to the output terminal; and an input terminal, and amplifies a signal applied to the input terminal to output the output. An amplification element provided to an end, and (c) a first bandpass filter connected between the input terminal and the input terminal of the amplification element, wherein the frequency band of the first bandpass filter is variable. Is a microwave amplifier. 2. The first bandpass filter comprises: (c-1) a first potential point for applying a first potential; (c-2) a connection point; (c-3) the input terminal and the connection point. A first capacitor and a first inductor that are connected in series between and, and (c-4) a second capacitor and a second inductor that are connected in series between the connection point and the input end of the amplification element. The microwave amplifier according to claim 1, further comprising: (c-5) a third capacitor connected between the connection point and the first potential point and having a variable capacitance. 3. The microcapacitor according to claim 2, wherein the third capacitor includes (c-5-1) a varactor diode, and (c-5-2) a power supply that applies a predetermined voltage to the varactor diode. Wave amplifier. 4. The (c-5-3) insulator, (c-5-4) first and second electrodes sandwiching the insulator, (c-5-5), The auxiliary electrode formed on the same side as the first electrode with respect to an insulator, and the capacitance of the third capacitor is variable by connecting the first electrode and the auxiliary electrode. The described microwave amplifier. 5. The amplification element comprises: (b-1) a second potential point for applying a second potential; (b-2) a control electrode connected to the input end of the amplification element; and the second potential. A first current electrode connected to the point,
A transistor including a second current electrode connected to the output terminal of the amplification element, and further, sharing the second capacitor with the first bandpass filter, wherein the second capacitor is substantially The microwave amplifier according to claim 2, further comprising a parasitic capacitance formed by the control electrode and the first current electrode of the transistor. 6. The amplification element further comprises: (b-3) a connection line connecting the control electrode and the input end of the amplification element, and the second inductor is the first bandpass filter. The microwave amplifier according to claim 5, wherein, in common, the second inductor is formed of a parasitic inductance that is substantially formed by the connection line. 7. The microwave amplifier according to claim 6, wherein the first potential and the second potential are equal to each other. 8. The microwave amplifier according to claim 1, further comprising: (d) at least one second bandpass filter connected between the first bandpass filter and the input terminal. 9. The first bandpass filter comprises: (c-1) a first potential point for applying a first potential; (c-2) a first connection point; and (c-3) the second bandpass. A first capacitor and a first inductor connected in series between a filter and the first connection point, and (c-4) connected in series between the first connection point and the input end of the amplification element. 9. A second capacitor and a second inductor formed as described above, and (c-5) a third capacitor connected between the first connection point and the first potential point and having a variable capacitance. The described microwave amplifier. 10. The second bandpass filter comprises: (d-1) a second potential point for applying a second potential; (d-2) a second connection point; (d-3) the input terminal and the A fourth capacitor and a third inductor connected in series with a second connection point, and (d-4) a fifth capacitor connected in series with the second connection point and the first bandpass filter. The microwave amplifier according to claim 9, further comprising: a capacitor and a fourth inductor; and (d-5) a sixth capacitor connected between the second connection point and the second potential point. 11. The first and fifth capacitors are also used by the first and second bandpass filters, and the first and fourth inductors are also used by the first and second bandpass filters. 10. The microwave amplifier according to 10.