JPH0128554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflective phase modulator in the microwave band, and particularly to a reflective phase modulator using an FET that has a simple configuration and operates at high speed.

As a conventional microwave band reflective phase modulator,
Elements such as PIN diodes or shot barrier diodes are used. In the former case, the forward and reverse directions of the diode are switched by a modulated pulse signal, so when switching from the forward direction to the reverse direction, the minority carriers accumulated in the I layer limit the operation of the high-speed modulator and at the same time switch the diode in the forward direction. The latter has the disadvantage that it requires a large amount of power as a modulated pulse amplifier in order to pass a large amount of current through it, and the latter has the disadvantage that it cannot modulate large amounts of power in the microwave band. Furthermore, since both are diodes, a circuit is required to separate the microwave band input signal and the modulated signal.

The present invention aims to eliminate these drawbacks of the conventional technology, and has a structure in which the modulating signal and the modulated signal are isolated using an FET as a modulating element, and is capable of being driven in the microwave band with low power. The purpose of this invention is to provide a reflective phase modulator.

To achieve this purpose, in the microwave band reflective phase modulator of the present invention, one of the drain and source of the FET is connected to the terminal other than the input/output terminal of the input/output separation circuit, and the other is grounded. It is characterized in that a modulated pulse signal is applied from the gate, the pulse signal phase-modulates the high frequency signal applied from the input terminal of the separation circuit, and the modulated high frequency signal is taken out from the output terminal.

In other words, the present invention utilizes the characteristic that the impedance between the drain and source changes depending on the gate applied voltage, and applies a pulse signal (modulated signal) to the gate without applying a DC bias voltage between the drain and source of the FET. It phase modulates the microwave band signal.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a configuration diagram for explaining the principle of the present invention, in which an FET is connected between one end of the transmission line 4 and the ground conductor
Connect the drain D and source S of 1, respectively, and do not apply a DC bias between the drain and source.
Further, a DC voltage 2 is applied to the gate G so as to provide a reverse bias. Further, 3 is a voltage divider for bias adjustment. If we change the gate voltage Vg and plot the reflection coefficient of the FET on an impedance chart using the gate voltage Vg as a parameter, we will see the characteristics shown in Figure 2. In other words, the gate voltage -
The reflected wave is at its minimum between 1.5 and 1.6V, and when the gate voltage is increased or decreased, the phase of the reflected wave becomes almost the same.
Exhibits a phase difference of 180°.

FIG. 3 is a block diagram of an embodiment according to the present invention, and shows the case of a two-phase phase modulator.

In the figure, 1 is a FET, 2 is a gate bias power supply, 3 is a voltage divider for bias adjustment, 12 is a pulse amplifier, 5 is a modulated pulse input terminal, 6 is a gate bias and pulse signal superimposer, and 7 is a microwave 8 is a circulator for input/output separation; 9 is a high frequency signal input terminal; 10 is a high frequency modulation signal output terminal; 11 is a matching circuit for correcting the modulation phase.

The high frequency signal input from the high frequency signal input terminal 9 is passed through the circulator 8 and the matching circuit 11.
Input to drain D of FET1. On the other hand, a pulse signal inputted from the modulated pulse input terminal 5 is applied to the gate G of the FET 1 via the pulse amplifier 12 and the superimposed device 6. In this case, the pulse signal is
The bias has been changed by . Therefore, as explained above (explanation regarding Fig. 1), FET1
The high frequency signal inputted to the drain D of the circulator 8 is phase-shifted into two phases by a gate signal (pulse signal), and a modulated signal whose phase is shifted into two phases is taken out at the output terminal 10 of the circulator 8.

Furthermore, since the drain D and gate G of the FET 1 are electrically insulated, the circuit for separating the high frequency signal and the modulated signal described in the conventional example is unnecessary.

FIG. 4 is a block diagram when a hybrid circuit 13 is used in place of the circulator 8 shown in FIG.

FIG. 5 is an example in which the present invention is implemented in a four-phase phase modulator. 16 branches the high frequency signal and modulator 1
4 and a modulator 15, respectively, in phase. The modulated signal is a hybrid of 17
They are synthesized with a phase difference of 90°. In other words, the combined output is 0°, due to the input pulses of CH1 and CH2.
The signal is phase modulated at 90°, 180°, and 270°.

As described in detail above, since the phase modulator according to the present invention uses FET, it operates with less power and also eliminates the need for a circuit for separating the high frequency signal and the modulated signal, which has great advantages.

Note that since the drain and source of the FET have electrical symmetry, the object of the present invention can be achieved in the same way even if the drain and source are interchanged.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram for explaining the principle of the present invention, Fig. 2 is a characteristic diagram of Fig. 1, Fig. 3 is one embodiment of the present invention, and Figs. 4 and 5 are other embodiments. shows. 1...FET, 8...Input/output separation circuit, 9...
Input terminal, 10...Output terminal, D...Drain,
S...source, G...gate.

Claims (1)

[Claims] 1 Connect one of the drain and source of the FET to the terminal of the terminal other than the input/output terminal of the input/output separation circuit, ground the other, apply a modulated pulse signal from the gate, and apply the modulated pulse signal from the input terminal of the separation circuit with the pulse signal. A reflective phase modulator characterized in that it phase-modulates a high-frequency signal that is generated and extracts the modulated high-frequency signal from an output terminal.