JPH04373206A - Phase modulation circuit - Google Patents

Abstract

PURPOSE:To keep the phase modulator in the best operating state at all times independently of a temperature change and a power supply fluctuation by making DC offset voltages of modulation wave balance inputs automatically equal to each other through a feedback loop. CONSTITUTION:A signal entering from a modulation wave unbalance input terminal 1 is converted into a balance signal at a differential amplifier 5, and the signal entering a noninverting modulation wave input terminal 11 of a phase modulator 6 is subject to phase conversion and the resulting signal is outputted from a modulation amplitude terminal 4. Then DC components of balance signals via two integration devices 7 connecting to a noninverting modulation wave input terminal 2 and an inverting modulation wave input terminal 3 are inputted to a differential voltage detection circuit 8. Then a bias voltage is outputted to one input of the differential amplifier 5 from a DC bias conversion circuit 9 so that the detected voltage difference is '0 '. Thus, the DC offset voltages of the modulation wave balance input signals are always made equal to each other.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The present invention is utilized in a receiving device for a communication device. The present invention relates to a phase modulator having means for automatically equalizing DC offset voltages of modulated wave balance inputs.

0002

2. Description of the Related Art A conventional phase modulation circuit includes a differential amplifier 5, a phase modulator 6, and a DC bias adjustment circuit 10, as shown in FIG. and-
Digital voltmeters were connected alternately to the side modulated wave input terminals 3, and the DC bias adjustment circuit 10 was adjusted so that they were equal.

0003

[Problems to be Solved by the Invention] In such conventional examples, the DC bias of one side of the differential amplifier is fixed, so temperature fluctuations and power supply fluctuations can cause the modulated wave unbalanced input signal and the internal circuit of the differential amplifier to change. If this changes, the DC offset voltage of the modulated wave balance input shifts, causing the internal balance of the phase modulator to collapse, increasing the amount of leakage of the modulated wave, and resulting in poor amplitude and phase characteristics of the modulated wave.

SUMMARY OF THE INVENTION The present invention aims to eliminate these drawbacks and provides a phase modulation circuit that always maintains the best operating condition of a phase modulator.

[0005]

[Means for Solving the Problems] The present invention includes a differential amplifier that converts an input modulated wave unbalanced signal into two balanced signals, and a phase modulator that inputs the balanced signal from the differential amplifier. In the phase modulation circuit, two integrators extract DC components from each of the balanced signals from the differential amplifier, and a differential voltage detection circuit detects a difference between the voltages output from the two integrators. The present invention is characterized by comprising a DC bias conversion circuit that changes the DC bias of one side of the differential amplifier according to the differential voltage detected by the differential voltage detection circuit.

[0006]

[Operation] A DC component is extracted from each of the two balanced signals output by the differential amplifier, and the DC bias of one of the differential amplifiers is changed in accordance with the voltage difference between the DC components. This automatically equalizes the DC offset voltage of the balance signal input to the phase modulator.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. As shown in FIG. 1, this embodiment includes a differential amplifier 5 that converts an input modulated wave unbalanced signal into two balanced signals, and a phase modulator 6 that inputs the balanced signal from the differential amplifier 5. Further, as a feature of the present invention, two integrators 7 extract DC components from each of the balanced signals from the differential amplifier 5, and a voltage difference between the voltages output from these two integrators 7 is provided. The differential voltage detection circuit 8 includes a differential voltage detection circuit 8 for detecting the voltage, and a DC bias conversion circuit 9 for changing the DC bias of one side of the differential amplifier 8 according to the differential voltage detected by the differential voltage detection circuit 8.

Next, the operation of this embodiment will be explained. The signal input from the modulated wave unbalanced input terminal 1 is converted into a balanced signal by the differential amplifier 5, and then input to the + side modulated wave input terminal 2 and the - side modulated wave input terminal 3 of the phase modulator 6, and is then input to the modulated wave input terminal. The signal input to the terminal 11 is phase-modulated and output from the modulation amplitude terminal 4. And + side modulated wave input terminal 2
and two integrators 7 connected to the - side modulated wave input terminal 3
Each DC component of the balanced signal is input to the differential voltage detection circuit 8 via the DC bias conversion circuit 9 to bias one input of the differential amplifier 5 so that the detected voltage difference becomes "0". Voltage is output. Therefore, the DC offset voltages of the modulated wave balanced input signals are always equal.

[0009]

Effects of the Invention As explained above, the present invention automatically equalizes the DC offset voltage of the modulated wave balance input using the feedback loop, so that the phase modulator can always be adjusted to the best possible state regardless of temperature fluctuations or power supply fluctuations. It has the effect of keeping it in working condition.

[Brief explanation of drawings]

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

FIG. 2 is a block configuration diagram showing the configuration of a conventional example.

[Explanation of symbols]

1 Modulated wave unbalanced input terminal 2 + side modulation wave input terminal 3 - side modulation wave input terminal 4 Modulation output terminal 5 Differential amplifier 6 Phase modulator 7 Integrator 8 Differential voltage detection circuit 9 DC bias conversion circuit 10 DC bias adjustment circuit 11 Modulated wave input terminal

Claims (1)

[Claims] 1. A phase modulation circuit comprising: a differential amplifier that converts an input modulated wave unbalanced signal into two balanced signals; and a phase modulator that inputs the balanced signal from the differential amplifier; two integrators extracting the DC component from each of the balanced signals from the dynamic amplifier;
A differential voltage detection circuit that detects the difference voltage between the voltages output by these two integrators, and a DC bias that changes the DC bias of one of the differential amplifiers according to the difference voltage detected by this differential voltage detection circuit. A phase modulation circuit comprising a conversion circuit.