JP3357715B2 - Microwave phase shifter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave phase shifter for controlling the phase of an input signal such as a microwave signal.

[0002]

2. Description of the Related Art A microwave phase shifter outputs a desired phase of a high frequency input signal such as a microwave, and is used for a phased array antenna or the like.

A monolithic microwave integrated circuit uses a semi-insulating substrate such as gallium arsenide (GaAs), and has an active element such as a field effect transistor (hereinafter referred to as FET), a resistor, a capacitor, an inductor, etc. on the substrate. Is a microwave integrated circuit, and is a technology expected to reduce the size of a microwave phase shifter.

Here, a conventional microwave phase shifter will be described with reference to a circuit configuration diagram of FIG. 5, taking a monolithic microwave phase shifter using an FET as a switch element as an example.

[0005] IN is an input terminal.
51 and the FET 52 are connected. One FET 51
Is connected to a microstrip line 53 and an FET 54. Note that the FET 54 is connected to the output terminal OUT. A microstrip line 55 and an FET 56 are connected to the other FET 52. Also,
The FET 56 is connected to the output terminal OUT.

The FETs 51, 52, 54, 56 are
Each of them functions as a switching element, and the control terminal 5
7 and the control voltage applied from the control terminal 58 is turned on or off. In addition, each FET5
Reference numerals 1, 52, 54, and 56 denote a gate electrode by G, a drain electrode by D, and a source electrode by S, respectively. In addition,
The characteristic impedance of the microstrip lines 53 and 55 is usually set to 50Ω. The phase shift amount of the microwave signal input from the input terminal IN and output from the output terminal OUT is determined by the microstrip lines 53 and 55.

In the microwave phase shifter having the above-described configuration, a control voltage of, for example, 0 V is applied to the gate electrodes G of the FETs 51 and 54 from the control terminal 57.
A control voltage equal to or lower than the pinch-off voltage is applied to the gate electrodes 52 and 56 from the control terminal 58. In this case, F
The ETs 51 and 54 are turned on, while the FETs 52 and 54 are turned on.
56 is turned off.

At this time, when a microwave signal is input from the input terminal IN, the microwave signal is turned on.
It passes through the microstrip line 53 through the ET 51. Therefore, the microwave signal is output from the output terminal OUT with a phase shift amount passing through the FET 51, the microstrip line 53, and the FET 54.

A control voltage lower than the pinch-off voltage is applied to the gate electrodes G of the FETs 51 and 54,
When a control voltage of 0 V is applied to the gate electrodes G of 2, 56, the FETs 51 and 54 are turned off in this case,
The FETs 52 and 56 are turned on.

At this time, the microwave signal input from the input terminal IN passes through the microstrip line 55 through the FET 52 and the FET 56 side, and the output terminal O
Output from UT. Therefore, the microwave signal is
FET 52, microstrip line 55, FET 56
Is output with the amount of phase shift when passing through.

The phase shift is set to be different between when the microwave signal passes through one microstrip line 53 and when it passes through the other microstrip line 55.

[0012]

In the conventional microwave phase shifter described above, the FET 51, 54 or the FET 52,
By turning on one of the sets 56 and turning off the other set, the microstrip lines 53 and 55 for transmitting the microwave signal are switched, and the amount of phase shift given to the microwave signal is controlled.

However, the microstrip lines 53, 5
When the FETs 51, 52, 54, and 56 are used for switching the FET 5, when the FET is in the ON state, its drain
The VSWR between the sources cannot obtain good characteristics over a wide band. For this reason, if an FET is used, a microwave phase shifter having good characteristics over a wide band cannot be realized. In order to improve the VSWR characteristics between the drain and the source of the FET, it is conceivable to provide a matching circuit outside the microwave phase shifter. However, in this case, a matching circuit is provided, and accordingly, the size of the entire circuit is increased, and the microwave phase shifter cannot be downsized.

As described above, in the conventional microwave phase shifter, matching with an external circuit cannot be achieved due to the impedance when the FET is in the ON state, and the input and output VSWR characteristics deteriorate. Therefore, a microwave phase shifter having good characteristics over a wide band cannot be realized. Further, if a matching circuit is provided outside in order to widen the band width of the microwave phase shifter, the size of the entire circuit becomes large and it is impossible to reduce the size.

An object of the present invention is to solve the above-mentioned disadvantages and to provide a microwave phase shifter having good characteristics over a wide band.

[0016]

According to the present invention, a signal input from an input terminal is connected to a first switch element, a first microstrip line, and a second switch element so as to be sequentially transmitted. 1 and a signal input from the input terminal is a third switch element and a second switch element.
A second transmission system connected in parallel to the microstrip line and the fourth switch element, and connected in parallel to the first transmission system; and connected to the second and fourth switch elements. Output terminal, a first control terminal for applying a control voltage for controlling the first and second switch elements to be turned on or off simultaneously, and the third and fourth switch elements being turned on or off simultaneously. A second control terminal for applying a control voltage for controlling the input terminal to the input terminal.
Impedance and impedance of the output terminal on the load side
The dance has the same value, the impedance of the input terminal side from the connection end of the first microstrip line with the first switch element, and the second switch element of the first microstrip line. The characteristic impedance of the first microstrip line is made to match the impedance seen from the connection end of the output terminal side to the output terminal side, and the input end of the second microstrip line from the connection end with the third switch element. impedance viewed terminal side, and the impedance seen by the output terminal side from the connection end of the fourth switch element of the second microstrip line, and to match the characteristic impedance of the second microstrip line .

Further, the first to fourth switch elements are constituted by field effect transistors.

[0018]

According to the above arrangement, the signal input to the input terminal is output through the first microstrip line by simultaneously turning on the first and second switch elements. Further, by simultaneously turning on the third and fourth switch elements, the signal input to the input terminal is output through the second microstrip line. Therefore, when the input signal passes through the first and second microstrip lines and has a predetermined phase shift amount, a microwave phase shifter can be configured.

Then, the characteristic impedance of the first microstrip line is determined by changing the impedance of the first microstrip line from the connection end of the first microstrip line with the first switch element to the input terminal side or the second microstrip line of the first microstrip line. And the characteristic impedance of the second microstrip line from the connection end of the second microstrip line to the input terminal from the connection end of the second microstrip line to the third switch element. The impedance of the second microstrip line is matched with the impedance of the output terminal side from the connection end of the second microstrip line with the fourth switch element.

Therefore, matching between the first and second microstrip lines and the external circuit is achieved, and the input / output VS
The WR characteristics are good over a wide band, and a wide-band microwave phase shifter can be realized.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to a circuit configuration diagram of FIG. 1 taking a monolithic microwave phase shifter using an FET as a switch element as an example.

IN is an input terminal, and the input terminal IN is FE
T11 and FET13 are connected. One FET1
1 is a microstrip line 21 and an FET 12
Are connected to form a first transmission system. Also, FE
T12 is connected to the output terminal OUT. A microstrip line 22 and an FET 14 are connected to the other FET 13 to form a second transmission system.
Note that the FET 14 is connected to the output terminal OUT.

The above-mentioned FETs 11, 12, 13, 14,
Function as switch elements, and are turned on or off by a control voltage applied from the control terminal S1 or the control terminal S2. In addition, each FET
11, 12, 13, and 14 respectively denote G as the gate electrode,
D indicates the drain electrode and S indicates the source electrode.

In the above configuration, for example, FET1
A control voltage of 0 V is applied to the first and second gate electrodes G from the control terminal S1. Then, a control voltage equal to or lower than the pinch-off voltage is applied to the gate electrodes G of the FETs 13 and 14 from the control terminal S2. At this time, the FETs 11 and 12 are turned on, and the FETs 13 and 14 are turned off.

When the FETs 11 and 12 are on, the equivalent circuit of the FETs 11 and 12 can be represented by the equivalent resistance between the drain and the source. In addition, FET1
When the transistors 3 and 14 are in the off state, the equivalent circuit can be represented by an equivalent capacitance formed between the drain and the source or by a depletion layer. Note that the gate width is several hundred μm.
In the case of ET, the equivalent resistance in the ON state is several Ω, and the equivalent capacitance in the OFF state is about several 100 fF.

Here, when the FETs 11 and 12 are on,
FIG. 2 shows a case where the FETs 13 and 14 are in an off state by an equivalent circuit. In FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals. Reference numeral 10 denotes a power supply, reference numeral 20 denotes a load, and impedances on the power supply 10 side and the load 20 side are indicated by Z1 and Z2.

When the input signal is in the microwave band of several GHz, the impedance of the equivalent capacitances 13 and 14 is about several thousand Ω. On the other hand, when the line length of the microstrip line 22 is sufficiently smaller than ４ of the propagation wavelength of the input signal, the impedance of the microstrip line 22 becomes smaller than the impedance of the equivalent capacitors 13 and 14. Therefore, the impedance when viewed from the connection end C1 toward the equivalent capacitance 13 can be regarded as substantially open. Similarly, the impedance viewed from the connection end C2 toward the equivalent capacitance 14 can be regarded as open. Therefore, the equivalent circuit of FIG. 2 can be equivalently represented as shown in FIG.
In FIG. 3, parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals.

In the case of FIG.
Is the sum of the power supply impedance Z1 (FIG. 2) connected to the input terminal IN and the equivalent resistance 11. The impedance of the output terminal is the sum of the load impedance Z2 (FIG. 2) connected to the output terminal OUT and the equivalent resistance 12. The impedances Z1 and Z2 of the power supply and the load are usually set to the same value. Therefore, if the characteristic impedance of the microstrip line 21 is set to an impedance obtained by adding the equivalent resistance 11 or the equivalent resistance 12 to the impedances Z1 and Z2 of the power supply or the load, the microstrip line 21 can be matched with the external line. At this time, good input / output VSWR characteristics are realized over a wide band.

In FIG. 1, the same applies to the case where the FETs 11 and 12 are in the OFF state and the FETs 13 and 14 are in the ON state.
From the impedance and output terminal OUT
Can be regarded as open. In this case, the input terminal of the microstrip line 22 has an impedance obtained by adding the equivalent resistance of the FET 13 to the impedance Z1 of the power supply, and the output terminal has an impedance obtained by adding the equivalent resistance of the FET 14 to the impedance Z2 of the load. become.

Therefore, the microstrip line 22
Is set to the impedance obtained by adding the equivalent resistance of the FET 13 or 14 to the impedance Z1 or Z2 of the input terminal or the output terminal, respectively, the matching between the microstrip line 22 and the external circuit can be obtained, and a favorable over a wide band. An input / output VSWR characteristic can be realized, and a broadband microwave phase shifter can be realized. Further, since no special matching circuit is required, the size of the entire circuit does not increase.

FIG. 4 shows an example of the characteristics of a monolithic microwave phase shifter using an FET as a switch element. In FIG. 4 , the vertical axis is the input / output VSWR characteristic,
The horizontal axis is frequency (GHz). The solid line A is the characteristic of the present invention. In this case, the equivalent resistance when the FET is on is about 3
Therefore, the characteristic impedance of the microstrip line is about 53Ω. A dotted line B is a conventional example, and a solid line A has a smaller value.
The R characteristic is improved over a wide band.

In the above embodiment, the source electrode of the FET is connected to the microstrip line, and the drain electrode is connected to the input terminal or the output terminal. However, a configuration in which the source electrode and the drain electrode are exchanged and connected may be adopted. Further, although the switch element is configured by an FET, the same applies to a case where the switch element is configured by using a diode or the like.

[0033]

According to the present invention, a microwave phase shifter having excellent characteristics over a wide band can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram illustrating one embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram illustrating one embodiment of the present invention.

FIG. 4 is a characteristic diagram illustrating the present invention.

FIG. 5 is a circuit configuration diagram showing a conventional example.

[Explanation of symbols]

 11 to 14 FET 21, 22 Microstrip line S1, S2 Control terminal IN Input terminal OUT Output terminal D Drain electrode S Source electrode G Gate electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01P 1/185 H01P 1/15 H03K 17/00

Claims (3)

(57) [Claims] A first transmission system connected so that a signal input from an input terminal is transmitted to a first switch element, a first microstrip line, and a second switch element in this order; A second switch connected in parallel with the first transmission system and connected to transmit a signal input from the terminal to the third switch element, the second microstrip line, and the fourth switch element in order; A transmission system, an output terminal connected to the second and fourth switch elements, and a first control terminal for applying a control voltage for controlling the first and second switch elements to be turned on or off simultaneously. A second control terminal for applying a control voltage for controlling the third and fourth switch elements to be turned on or off at the same time . Power source impedance and front
The impedance of the output terminal on the load side is the same value, the impedance of the first microstrip line when viewed from the connection end of the first microstrip line with the first switch element, and the impedance of the first microstrip line. The characteristic impedance of the first microstrip line is made to match the impedance seen from the connection terminal with the second switch element to the output terminal side, and the third switch element of the second microstrip line It viewed the input terminal side from the connection end of the impedance, and <br/> the impedance seen the output terminal side from the connection end of the fourth switch element of the second microstrip line, the second A microwave phase shifter wherein the characteristic impedances of a microstrip line are matched. 2. The first microstrip line of claim 1,
Impedance viewed from the input terminal side from the connection end with the switch element
The dance is the power supply impedance of the power supply connected to the input terminal.
The equivalent resistance of the first switch element in the ON state.
The size of the first microstrip
From the connection end of the loop line to the second switch element to the output terminal side
Is the impedance of the load connected to the output terminal.
When the second switch element is turned on in the load impedance,
It is the size plus the equivalent resistance, and the second
Is the connection end of the cross trip line with the third switch element?
Impedance from the input terminal side to the input terminal
A third switch is connected to the power supply impedance of the connected power supply.
Size der the pitch element plus the equivalent resistance of the on state
And a fourth switch of the second microstrip line.
Impedance from the connection end with the switch element
The load is connected to the load terminal of the load connected to the output terminal.
Equivalent resistance when the fourth switch element is on in the impedance
2. The microwave phase shifter according to claim 1 , wherein the size of the microwave phase shifter is plus . 3. The method according to claim 1, wherein the first to fourth switching elements are field effect.
Claims characterized by being constituted by a transistor
The microwave phase shifter according to claim 1 or claim 2.