JPH02246505A - Balanced modulating circuit - Google Patents

Abstract

PURPOSE:To output a modulated wave which is not affected by a noise generated when a carrier input signal is switched by providing a differential amplifier circuit and leading the modulated wave after noise removal out of the output terminal of the differential amplifier circuit. CONSTITUTION:The differential amplifier circuit 3 consists of transistors(TR) Q7 and Q8, constant current sources I3 and I4, a load Z3, and a resistance R6. The TR Q7 has its base connected to a connecting circuit 1, its collector connected to a source voltage Vcc, and its emitter grounded through the constant current source I3 and the TR Q8, on the other hand, has its base connected to a connecting circuit 2 and its collector connected to the source voltage Ccc through the resistance R5 and also connected to the output terminal OUT. Then the modulated wave after the noise removal is led out of the output terminal OUT of the differential amplifier circuit 3. Consequently, the switching noise which is generated when the carrier signal is switched is not superposed upon the modulated wave.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a balanced modulation circuit used for frequency conversion, etc., and in particular to a balanced modulation circuit that outputs a modulated wave that is not affected by noise generated when switching a carrier wave input signal. This relates to modulation circuits.

[Conventional technology]

FIG. 2 shows a conventional double-balanced type balanced modulator which is constructed by connecting two sets of balanced modulators so that their polarities are reversed on the output side. In the figure, A is a modulated wave input signal, B and C are carrier wave input signals, OUT is an output terminal for a modulated output signal, ■ is a power supply voltage, Q, Q3° CCI, Q4 are transistors forming a set of balanced modulators, Q,
Q and Q6 are transistors that constitute another set of balanced modulators, including transistors Q1 and Q, Q and Q, and Q.
and Q6 are connected to form a differential pair.

The base of the transistor Q1 is grounded through a resistor R and a constant voltage source V1, and the emitter is grounded through a constant current source 1. The transistor Q2 has a base connected to the resistor R and a constant current source v1, and an emitter connected to the ground through a constant current source 2. A resistor R3 is connected between the emitters of transistors Q 1 and Q 2 . A modulated wave input signal A is applied to the base of the transistor QI via a capacitor c1. The capacitor C1 is for removing the DC component of the modulated wave human input signal A. Resistance R, R2,
The constant voltage source V 1 is for applying a bias to a differential pair consisting of transistors Q 1 and Q 2 .

The transistor Q3 has a base supplied with the carrier wave input signal B, a collector connected to the power supply voltage cc, and an emitter connected to the collector of the transistor Ql. Transistor Q4 has a carrier wave input signal C applied to its base, a collector connected to the output terminal OUT, and an emitter connected to the transistor Q.
3 emitters, respectively. transistor Q
, Q are alternately set to 0N10FF according to the levels of the carrier wave signals B and C.

The transistor Q5 has a base supplied with the carrier wave input signal C, a collector connected to the collector of the transistor Q3, and an emitter connected to the collector of the transistor Q2. The transistor Q6 has a base supplied with the carrier wave input signal B, and a collector supplied with the power supply voltage V through a resistor R. 0 and is also connected to the output terminal OUT, and its emitter is connected to the emitter of the transistor Q5. The resistor R is used to determine the output level of the output terminal OUT by causing a voltage drop due to the current flowing through the transistors Q and Q6. The transistors Q5 and Q6 are alternately turned ON and OFF depending on the levels of the carrier wave signals B and C.

Next, the operation will be explained. By applying carrier wave input signals B and C as shown in FIG. 3 to the bases of transistors Q3 to QB, carrier wave input signal B is applied to two differential pairs consisting of transistors Q and Q and transistors Q and Q6.

Every half period of C, the set of transistors Q and Q6 and the set of transistors Q and Q5 are turned on alternately.

Repeat OFF. On the other hand, by applying the modulated wave input signal A to the base of the transistor Q, in the differential pair consisting of the transistors Q and Q2, the transistors Q and Q2 conduct in an inverse relationship (that is, the transistor Q1 becomes The transistor Q2 conducts in proportion to the signal level of the modulated wave input signal A, and the transistor Q2 conducts in inverse proportion to the signal level of the modulated wave input signal A. The output signal from the output terminal OUT is taken out from the collectors of transistors Q and QB, so transistors Q and Q
is ON (when carrier wave input signal C is “H”)
The output signal depends on the current flowing through the transistors Q and Q1, and when the transistors Q and QB are ON (when the carrier wave input signal B is "H"), the output signal depends on the current flowing through the transistors Q and Q2.

Therefore, the output signal from the output terminal OUT is obtained as a modulated wave obtained by inverting the modulated wave input signal A every half period of the carrier wave input signals B and C.

[Problem to be solved by the invention]

The conventional balanced modulation circuit is configured as described above, and performs modulation by alternately turning ON and OFF the set of transistors Q 1 and Q 2 and the set of transistors Q and Q 5 of transistor B . Therefore, the transistor Q,
Switching noise NB (see Figure 3) and transistors Q and Q that occur when the set of QB turns on and off
There is a problem in that the switching noise Nc (see FIG. 3) generated when the set No. 5 turns ON and OFF and the modulated wave are superimposed and output from the output terminal OUT.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a balanced modulation circuit in which switching noise generated when switching carrier signals is not superimposed on a modulated wave.

[Means to solve the problem]

The balanced modulation circuit according to the present invention is constructed by connecting two sets of balanced modulation circuits such that their polarities are reversed on the output side, and having a first output terminal and a second output terminal that output modulated waves having mutually opposite phases. In a double-balanced balanced modulation circuit with - universal power is the first
A differential amplifier circuit is provided at each output terminal of the differential amplifier circuit, and the other terminal is connected to a second output terminal, and the modulated wave from which noise has been removed is derived from the output terminal of the differential amplifier circuit.

[Effect]

The differential amplifier circuit in this invention is the first one of the balanced modulation circuit.
．． Since the differential amplification operation is performed by receiving the modulated waves outputted from the second output terminal and having mutually opposite phases, the first. When in-phase noise is superimposed on the modulated wave from the second output terminal, the noise is canceled out by the common-mode removal effect of the differential amplifier circuit.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of a balanced modulation circuit according to the present invention. In the figure, the difference from the conventional circuit shown in FIG. 2 is that a connection circuit 1, 2 consisting of loads Z, Z2, an emitter follower and a level shift circuit, and a differential amplifier circuit 3 are newly provided. . The load Z1 is the collector of the transistor Q3 and the power supply voltage V. 0
connected between. Connection circuit 1 is transistor Q3
connected to the collector. The load Z corresponds to the resistor R4 in the conventional circuit, and is connected to the transistor Q6 and the power supply voltage V. 0. Connection circuit 2 is connected to the collector of transistor Q6. The load zl is for determining the input level to the connection circuit 1 by causing a voltage drop due to the current flowing through the transistors Q and Q5, and the load z2 is for determining the input level to the connection circuit 1 by causing a voltage drop due to the current flowing through the transistors Q4 and Q6. This is for determining the input level to the circuit 2.

The differential amplifier circuit 3 includes transistors Q, Q8, and a constant current source I.
, I, load 2 and resistor R5. The transistor Q7 has a base connected to the connection circuit 1, a collector connected to the power supply voltage Vcc, and an emitter connected to the ground via the constant current source I3. The transistor Q8 has a base connected to the connection circuit 2, and a collector connected to the power supply voltage V through a resistor R.
. 0 and is also connected to the output terminal OUT. The resistor R is used to determine the output level of the output terminal OUT by causing a voltage drop due to the current flowing through the transistor Q8. Further, the emitter of the transistor Q is connected to the emitter of the transistor Q7 via a load Z3, and is also grounded via a constant current source 4. The other configurations are the same as the conventional circuit.

Next, the operation will be explained. When carrier wave human input signals B and C similar to those shown in FIG. , Q repeats ON and OFF alternately. On the other hand, by applying the modulated wave input signal A to the base of the transistor Q1, the transistors Q and Q2 become conductive in an inverse relationship as in the conventional case. The signal applied to the base of transistor Q7 depends on the current flowing through transistors Q and Q2 when transistors Q4 and Q5 are ON (when carrier wave input signal C is "H"), and when transistors Q and Q are ON. When (carrier input signal B is “
When transistors Q and Q5 are ON, the signal applied to the base of transistor Q8 depends on the current flowing through transistors Q and Q1. , transistor Q
, Q are ON, transistors Q , Q
Depends on the current flowing through. As described above, the signals applied to the bases of transistors Q 1 and Q 2 have opposite phases to each other, so the difference between the signals applied to the bases of transistors Q and Q8 is amplified and output. That is, the output signal from the output terminal OUT is obtained as a modulated wave obtained by inverting the modulated wave input signal A every half period of the carrier wave input signals B and C as shown in the figure.

On the other hand, the set of transistors Q and Q5 and the transistors Q and Q
Switching noise N generated when switching between sets of 6
, N are applied in the same phase to the bases of the transistors Q7°C and Q8, so the switching noises N and No are canceled by the common mode removal effect of the differential amplifier circuit 3 and are not output to the output terminal OUT. the result,
The switching noises N and N are not superimposed on the modulated wave output to the output terminal OUT.

〔Effect of the invention〕

As described above, according to the present invention, the first
．． Since a differential amplifier circuit is provided which performs a differential amplification operation upon receiving modulated waves having mutually opposite phases outputted from the second output terminal, the first. When in-phase noise is superimposed on the modulated wave from the second output terminal, that noise is canceled out by the common-mode removal effect of the differential amplifier circuit, and the switching noise that occurs when switching the balanced modulation circuit is superimposed on the modulated wave. The effect is that there is no problem.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the balanced modulation circuit according to the present invention, Fig. 2 is a circuit diagram showing a conventional balanced modulation circuit, and Fig. 3 explains the operation of the circuit shown in Fig. 2. This is a diagram for In the figure, A is a modulated wave manual signal, B and C are carrier wave input signals, OUT is an output terminal, and 3 is a differential amplifier circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A double-balanced type consisting of two sets of balanced modulation circuits connected so that the polarities are reversed on the output side, and having first and second output terminals that output modulated waves with opposite phases to each other. In the balanced modulation circuit, one input is connected to the first output terminal, and the other input is connected to the second output terminal.
A balanced modulation circuit characterized in that a differential amplifier circuit is provided, each connected to an output terminal of the differential amplifier circuit, and a modulated wave from which noise has been removed is derived from the output terminal of the differential amplifier circuit.