JPH06196950A - Microwave circuit - Google Patents

Abstract

PURPOSE:To provide a microwave circuit capable of adjusting a phase independently of the adjustment of reflection quantity and easily adjusting impedance. CONSTITUTION:The microwave circuit having an active element 12, I/O terminals 14, 20 for inputting/outputting signals to/from the element 12 and microstrip lines 16, 22 for connecting the I/O terminals 14, 20 to the element 12 is provided with matching capacitors 28, 40 connecting one ends to the lines 16, 22 and grounding the other ends and a line width adjusting means 50 for adjusting the line width of the lines 16, 22 connected between the element 12 and the capacitors 28, 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave circuit having a microstrip line, and more particularly to a microwave circuit such as an amplifier used in communication equipment having a frequency band of several GHz or less.

[0002]

2. Description of the Related Art In recent years, as a microwave transmission line, a microstrip line in which a thin metal line is formed on a dielectric substrate is small, lightweight, has a simple structure, and is suitable for mass production. It is widely used not only in passive circuits, but also in active element circuits such as oscillators and amplifiers.

The impedance of the transmission line formed by the microstrip line is determined by the width of the microstrip line, the thickness of the dielectric substrate, the dielectric constant, and the like. For this reason,
In the case of a microwave circuit having a relatively low frequency of several GHz or less, there is a problem that the microstrip line becomes large. In order to reduce the size of the microstrip line, which is becoming larger, a method is known in which the midpoint of the microstrip line is grounded via a capacitor.

A conventional microwave circuit using a microwave strip line is shown in FIG. A GaAs FET 12 which is an active element is provided in the center of the dielectric substrate 10.
A signal input terminal 14 for inputting a high frequency signal is provided at the left end of the dielectric substrate 10, and the signal input terminal 14 and the GaAs
A strip conductor film 16 for matching impedance is provided between the FETs 12. The gate terminal G of the GaAsFET 12 is connected to the strip conductor film 16, and the signal input terminal 14 and the strip conductor film 16 are connected via a capacitor 18.

A signal output terminal 20 for outputting a high frequency signal is provided at the right end of the dielectric substrate 10, and a signal output terminal 2 is provided.
A strip conductor film 22 for matching impedance is provided between 0 and the GaAs FET 12. The drain terminal D of the GaAsFET 12 is connected to the strip conductor film 22, and the signal output terminal 20 and the strip conductor film 22 are connected via a capacitor 24.

The source terminal S of the GaAsFET 12 is connected to a ground region (not shown) formed on the back surface of the dielectric substrate 10. A ground region 26 is provided on the dielectric substrate 10 above the strip conductor film 16 on the signal input side, and a matching capacitor 28 is provided between the strip conductor film 16 and the ground region 26.

The dielectric substrate 1 below the strip conductor film 16
A DC bias terminal 30 for applying a DC bias is provided on 0. A ground region 32 is provided on the left side of the DC bias terminal 30, and the DC bias terminal 3
0 and the ground region 32 are connected via a capacitor 34. The DC bias terminal 30 is connected to the strip conductor film 16 by a bias supply line 36 having a narrow width and meandering.

A ground region 38 is provided on the dielectric substrate 10 above the strip conductor film 22 on the signal output side, and a matching capacitor 40 is provided between the strip conductor film 22 and the ground region 38. A DC bias terminal 42 for applying a DC bias is provided on the dielectric substrate 10 below the strip conductor film 22. A ground region 44 is provided on the right side of the DC bias terminal 42, and the DC bias terminal 42 and the ground region 44 are connected via a capacitor 46. The DC bias terminal 42 is connected to the strip conductor film 22 by a bias supply line 48 having a narrow width and meandering.

In the microwave circuit, GaAsFE
Since variations in characteristics of T12 and variations in various conditions during assembly cannot be avoided, it is necessary to adjust impedance after assembly. In order to adjust the impedance as described above, in the conventional microwave circuit, as shown in FIG. 5, a matching capacitor 28 is provided between the strip conductor film 16 and the ground region 26 on the signal input side and a strip on the signal output side. A matching capacitor 40 is provided between the conductor film 22 and the ground region 38. The amount of reflection is adjusted by changing the constants of the matching capacitors 28 and 40.
The phase is adjusted by changing the distance from the ET 12 to the mounting position of the matching capacitors 28 and 40. Especially, the adjustment of the phase is very important in adjusting the frequency characteristic.

[0010]

However, as described above, the matching capacitor 2 is used to adjust the phase.
When the mounting positions of 8 and 40 are changed, the reflection amount also changes unless the characteristic impedance of the strip conductor films 16 and 22 is exactly 50Ω, and it is difficult to make an adjustment to optimize both the reflection amount and the phase. There was a problem. Further, the method of changing the mounting positions of the matching capacitors 28 and 40 has a problem that the phase adjustment range is limited.

An object of the present invention is to provide a microwave circuit in which the phase can be adjusted independently of the reflection amount and the impedance can be easily adjusted.

[0012]

The above object is to provide an active element, an input / output terminal for inputting / outputting a signal to / from the active element, and a microstrip line for connecting the input / output terminal and the active element. In a microwave circuit having, one end is connected to the microstrip line,
And a line width adjusting means for adjusting a line width of the microstrip line between the active element and the matching capacitor. .

[0013]

According to the present invention, the grounding matching capacitor is connected to the microstrip line, and the line width adjusting means for adjusting the line width of the microstrip line between the active element and the matching capacitor is provided. The line width of the strip line can be changed to adjust the phase independently of the adjustment of the reflection amount.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A microwave circuit according to an embodiment of the present invention will be described with reference to FIGS. The same components as those of the conventional microwave circuit shown in FIG. 5 are designated by the same reference numerals. A GaAs FET 12 is provided as an active element in the center of a dielectric substrate 10 such as glass epoxy resin or Teflon.
A ground region (not shown) is formed on the entire back surface of the dielectric substrate 10.

At the center of the dielectric substrate 10 is an active element G
The aAsFET 12 is provided. A high frequency signal is input to the left end of the dielectric substrate 10, width 2 mm, length 60
mm signal input terminal 14 is provided.
A strip conductor film 16 having a width of 1 mm and a length of 60 mm is provided between the GaAs FET 12 and the GaAs FET 12. G for the strip conductor film 16
The gate terminal G of the aAsFET 12 is connected to the signal input terminal 14 and the GaAsF by the ground area (not shown) formed on the strip conductor film 16 and the back surface of the dielectric substrate 10.
A microstrip line that connects the ET 12 is configured. The signal input terminal 14 and the strip conductor film 16 are 10
It is connected through a 00 pF capacitor 18.

A signal output terminal 20 having a width of 2 mm and a length of 60 mm for outputting a high frequency signal is provided at the right end of the dielectric substrate 10, and a width for matching impedance between the signal output terminal 20 and the GaAs FET 12. A strip conductor film 22 having a length of 2 mm and a length of 60 mm is provided.
The drain terminal D of the GaAsFET 12 is connected to the strip conductor film 22, and the strip conductor film 22 and the ground region (not shown) formed on the back surface of the dielectric substrate 10
A microstrip line that connects the GaAs FET 12 and the signal output terminal 22 is configured. Signal output terminal 20
The strip conductor film 22 is a capacitor 2 of 1000 pF.
4 are connected.

The source terminal S of the GaAsFET 12 is connected to a ground region (not shown) formed on the back surface of the dielectric substrate 10. A ground region 26 is provided on the dielectric substrate 10 above the strip conductor film 16 on the signal input side, and a 5 pF matching capacitor 28 is provided between the strip conductor film 16 and the ground region 26.

The dielectric substrate 1 below the strip conductor film 16
A DC bias terminal 30 for applying a DC bias is provided on 0. A ground region 32 is provided on the left side of the DC bias terminal 30, and the DC bias terminal 3
0 and the ground region 32 are connected via a capacitor 34 of 1000 pF. DC bias terminal 30 has a width of 1 m
A meandering bias supply line 3 having a length of m and a length of 60 mm
6 is connected to the strip conductor film 16.

A ground region 38 is provided on the dielectric substrate 10 above the strip conductor film 22 on the signal output side, and an 8 pF matching capacitor 40 is provided between the strip conductor film 22 and the ground region 38. Strip conductor film 22
A DC bias terminal 42 for applying a DC bias is provided on the lower dielectric substrate 10. A ground region 44 is provided on the right side of the DC bias terminal 42,
The DC bias terminal 42 and the ground region 44 are connected via a capacitor 46 of 1000 pF. The DC bias terminal 42 is connected to the strip conductor film 22 by a meandering bias supply line 48 having a width of 1 mm and a length of 60 mm.

In order to adjust the impedance after assembly, a 5 pF matching capacitor 28 is provided between the strip conductor film 16 and the ground region 26 on the signal input side, and between the strip conductor film 22 and the ground region 38 on the signal output side. Is provided with a matching capacitor 40 of 8 pF. The microwave circuit of this embodiment is characterized in that an adjustment line 50 for adjusting the line width W of the strip conductor film 16 is provided on the GaAsFET 12 side from the connection point of the matching capacitor 28.

FIG. 2 shows a specific example of the adjusting line 50.
In this specific example, as shown in FIG.
0 is parallel to the strip conductor film 16 and is separated by seven thin lines 50a and 5 having a width of 0.5 mm and a length of 20 mm.
0b, ... Strip conductor film 16
2B, both ends of the lines 50a, 50b, ... Are connected to the strip conductor film 16 by the connection wires 52, as shown in FIG. 2B. The effective line width W of the strip conductor film 16 is adjusted by the number of lines 50a, 50b, ... Connected to the strip conductor film 16.

FIG. 3 shows another specific example of the adjusting line 50. In this specific example, as shown in FIG. 3A, the adjustment line 50 is connected in parallel to the strip conductor film 16.
7 thin lines 50a with a width of 0.5 mm and a length of 20 mm,
50b, ... Strip conductor film 1
In order to adjust the effective line width W of 6, the connecting portions of the lines 50a, 50b, ... Are cut off by a laser or the like as shown in FIG. 3 (b). Depending on the number of lines 50a, 50b, ... Connected to the strip conductor film 16,
The effective line width W of the strip conductor film 16 is adjusted.

Next, a method of adjusting the microwave circuit of this embodiment will be described with reference to FIG. FIG. 4 is a Smith chart of the microwave circuit of this embodiment. The Smith chart was devised to easily solve equations in microwave circuits and shows the mapping between the impedance plane and the reflection coefficient plane. The principle of the present invention is that the adjustment line 5
When the number of connections of 0 is changed to change the effective line width W of the strip conductor film 16, the phase can be changed while the reflection amount remains substantially constant, and the matching capacitor 2
The point is that the amount of reflection can be adjusted by changing the constant of 8 while keeping the phase substantially constant.

This point will be described with reference to the Smith chart of FIG. When the effective line width W of the strip conductor film 16 is changed by 1 mm from 1 mm to 10 mm, the impedance of the input matching circuit moves on the same impedance circle on the Smith chart as shown by □ in FIG. . On the other hand, if the constant of the matching capacitor 28 is changed,
The diameter of the same impedance circle on the Smith chart changes, but the phase does not change.

For example, the conjugate value of the input impedance of the GaAsFET 12 is 0.98 (c
In the case of os3π / 4 + jsin3π / 4) (point ■), first, the constant of the matching capacitor 28 is changed to 15 pF so that the reflection amount at the point ■ becomes, and then the phase at the point ■ becomes 1 mm wide. Width 0.5 mm on the strip conductor film 16
The two line 50a and 50b are connected to change the effective line width W of the strip conductor film 16 to 2 mm. As a result, the impedance of the input matching circuit is set to GaAs FET.
It can be matched to 12 input impedances.

As described above, when the adjustment line 50 is adjusted to the strip conductor film 16, the effective line width W of the strip conductor film 16 is equal to that of the adjustment line 50 connected to the line width of the strip conductor film 16. Since it becomes almost equal to the total value of the line width, the input impedance matching can be easily performed. The present invention is not limited to the above embodiment, and various modifications can be made.

For example, although the line width adjusting region shown in FIG. 3 or FIG. 4 is provided in the above embodiment, the wide line 26C of the strip conductor film 16 is previously formed wider than the optimum value.
The phase may be adjusted by thinning the line width as necessary by a method such as laser trimming. Further, although the present invention is applied to the microwave circuit in which the active element is mounted on the dielectric substrate in the above-described embodiment, the MMIC (Monolithic Microwave I) which simultaneously forms the required active element and passive element on the substrate is required.
The present invention can be applied to an integrated circuit).

[0028]

As described above, according to the present invention, the grounding matching capacitor is connected to the microstrip line, and the line width adjusting means for adjusting the line width of the microstrip line adjacent to the active element is provided. Therefore, the line width of the microstrip line can be changed to adjust the phase independently of the adjustment of the reflection amount.

[Brief description of drawings]

FIG. 1 is a plan view of a microwave circuit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a specific example of an adjustment line of the microwave circuit shown in FIG.

FIG. 3 is a diagram showing another specific example of the adjustment line of the microwave circuit shown in FIG.

FIG. 4 is a Smith chart of the microwave circuit shown in FIG.

FIG. 5 is a plan view of a conventional microwave circuit.

[Explanation of symbols]

 10: Dielectric substrate 12: GaAsFET 14: Signal input terminal 16: Strip conductor film 18: Capacitor 20: Signal output terminal 22: Strip conductor film 24: Capacitor 26: Ground area 28: Matching capacitor 30: DC bias terminal 32: Ground region 34: Capacitor 36: Bias supply line 38: Ground region 40: Matching capacitor 42: DC bias terminal 44: Ground region 46: Capacitor 48: Bias supply line 50: Adjustment line 50a, 50b, ...: Line 52: Connection wire

Claims (1)

[Claims] 1. A microwave circuit having an active element, an input / output terminal for inputting / outputting a signal to / from the active element, and a microstrip line connecting the input / output terminal and the active element, A matching capacitor having one end connected to the microstrip line and the other end grounded; and a line width adjusting means for adjusting the line width of the microstrip line between the active element and the matching capacitor. Characteristic microwave circuit.