JPS6181057A - 0-pi phase modulator - Google Patents

Abstract

PURPOSE:To obtain a microwave modulated signal having less phase deviation and amplitude deviation by inserting transmission lines having the about 1/4 wavelength of an input microwave and standing wave ratio improving resistances in series to the outputs of respective microwave switch circuits in the first and the second paths. CONSTITUTION: Transmission lines 14 and 15 having the about 1/4 wavelength of the input microwave are connected in series to output sides of diodes 2 and 3, and standing wave ratio improving resistances 16 and 17 are connected in series to these transmission lines 14 and 15. In this constitution, a high frequency equivalent circuit is as shown in the lower figure when the diode 2 is turned on and the diode 3 is turned off. In this figure, resistances 16 and 17 have the same value, and the normalized impedance normalized by the characteristic impedance of transmission lines is expressed with R. This equivalent circuit clarifies that the resistance 17 is connected to the 1/4 wavelength transmission line 15 whose front end is opened and the impedance of the diode side viewed from the connection point of the resistance 17 is short-circuited.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a microwave 0-π phase modulator.

[Technical background of the invention]

The phase of the microwave is modulated by a control signal, and the phase is 180
As a 0-π phase modulator for obtaining microwave modulated signals of different degrees, the one shown in FIG. 3 has been proposed.

That is, the microwave input from the microwave input terminal 1 is turned on and off depending on the bias state, and guided to two diodes 2.3 connected so that the polarities are different from each other, and by the control voltage applied to the bias supply terminal 4, The two diodes 2.3 are biased in different directions via choke coils 9.10. Then, when one diode is on, the other is off, and the microwave applied from the microwave input terminal 1 is output to the output terminal of one of the diodes 2 and 3. Therefore, a hybrid coupling circuit 6 with a coupling degree of 3 dB and a coupling direction of 90 degrees passes the device chromatic wave consisting of the output terminal of the diode 2 through a DC removal capacitor 11 and a phase shifter 5 with a phase shift delay of about 90 degrees. The input end is input to 1,000 people.

On the other hand, the microwave sent out from the output terminal of the diode 3 is input to the other input terminal B of the high breadth coupling circuit 6 via the DC removal capacitor 12.

Here, the diodes 2 and 3 are assumed to be ideal switching elements, and the microwave incident wave at the microwave input terminal 1 is set to V,
Assuming that the line length between input terminals 1 and 8 is ignored, what are the waveforms at points A and B when diode 2.3 is in the on state? a,? b becomes -Jωl. however? == V 4 where ■ is the amplitude of the incident wave, ω is its angular frequency, and l is the time. Also,
1 It is well known that the waveform output to the output terminal 7 of the hybrid coupling circuit 6 is expressed as follows.

Therefore, when equation (1) is substituted into equation (2), the output waveforms of the microwave signals that pass through the diode 3 and are output to the output terminal 7 are different in phase by 180 degrees. Therefore, if you apply the 1 control signal to the bias supply terminal 4 of the diodes 2 and 3 to switch the diodes on and off, you can obtain phase wave modulation (1. In addition, in Figure 3, 8
is a choke coil, and 13 is a terminating resistor.

[Problems with background technology]

However, in the circuit described above, the microwave switch circuit using a diode is connected to the input terminal of the hybrid coupling circuit 6 via the phase shifter 5 with a phase shift delay of about 90 degrees, and the microwave switch circuit using the diode is connected directly to the input terminal B. It is connected. For this reason, A
ZA is the normalized impedance when looking at the diode side from point and point B, respectively.

Assuming ZB, when the diode 2 is off, the impedance viewed from the 0 point to the diode side is open, and the impedance ZAK at the point A via the phase shifter 5 is short-circuited.

On the other hand, when the diode 3 is off, the impedance seen from point D to the diode side is open, and if the line length between B and D is ignored, the impedance ZB at point B is open.

This means that the termination conditions of the isolation terminal on the input side of the hybrid coupling circuit 6 vary greatly depending on whether the diode 2.3 is on or off.

The hybrid coupling circuit 6 requires matching between each input/output connector and the external circuit in order to obtain a desired degree of coupling. However, as described above, if one input terminal of the hybrid coupling circuit 6 is open or short-circuited, the degree of coupling between the input and output terminals in the hybrid coupling circuit 6 does not reach the desired value, and the equation (2) , and by extension, the relational expression (3) cannot be satisfied, and 2
There is a problem in that the passing phase difference of the microwaves in the two paths becomes different from each other by more than 180 degrees, and the amplitudes of the signals outputted through the two paths also have different values. [Objective of the Invention] The present invention eliminates the above drawbacks and provides a microwave phase modulated signal with small phase deviation and amplitude deviation.
The present invention aims to provide a −π phase modulator.

[Summary of the invention]

The present invention achieves the above object by inserting in series a transmission line of approximately 1/4 wavelength of the input microwave and a resistor for improving the standing wave ratio to the output of the microwave switch circuit.

[Embodiments of the invention]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and the same parts as in FIG. 3 are represented by the same symbols. In Figure 1,
What is different from the conventional circuit shown in Fig. 3 is that a transmission line 14 with approximately 1/4 wavelength of the input microwave is installed on the output side of the diode 2.3.
．． 11 - connected in series and further this transmission line 14 , 1
5 and resistors 16 and 17 for improving the standing wave ratio are connected in series.

According to this configuration, the high frequency equivalent circuit when diode 2 is on and diode 3 is off is as shown in FIG. However, in FIG. 2, resistors 16 and 17
are of equal value, and the normalized impedance when normalized by the characteristic impedance of the transmission line is expressed as R.

As is clear from these circuits, the resistor 17 is connected to the 1/4 wavelength transmission line 15 with an open end, and the impedance seen from the connection point of the resistor 17 to the diode side is short-circuited. Therefore, it can be done from point B.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, approximately 17% of the input microwave is applied to the output of the microwave switch circuit.
By inserting a four-wavelength transmission line and a resistor for improving the standing wave ratio in series, the reflection coefficient of one isolation terminal on the input side of the hybrid coupling circuit is improved, and the influence of the matching state of the other isolation terminal is reduced. Therefore, it is possible to obtain a microwave modulated signal with small phase deviation and width deviation.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
The high frequency equivalent circuit shown in FIG. 3 is a circuit diagram showing a conventional 0-π phase modulator. 1... Microwave input terminal, 2, 3... Diode, 4... Bias supply terminal, 5... Phase shifter, 6...
・Hybrid coupling circuit, 7...Microwave output terminal, 13...Terminal resistor, 14, 15...Transmission line,
16, 17...resistance.

Claims (1)

[Claims] The input microwave is branched into two paths, and the first path includes a first microwave switch circuit, a transmission line of approximately 1/4 wavelength of the input microwave, a resistor for improving the standing wave ratio,
Phase shifters having a phase delay of about 90 degrees or about 180 degrees are connected in series, and the second path includes a second microwave switch circuit that operates reciprocally with the first microwave switch circuit, and an input microwave. A transmission line of approximately 1/4 wavelength of the wave and a resistor for improving the standing wave ratio are connected in series, and the microwaves output from these first and second paths have a phase difference of 180 degrees.
1. A 0-π phase modulator, characterized in that a microwave phase modulated signal is synthesized by a hybrid coupling circuit so as to have a phase difference of 180 degrees, and the hybrid coupling circuit outputs a microwave phase modulated signal having a phase difference of 180 degrees.