JPH03119811A - Balanced modulation circuit - Google Patents

Abstract

PURPOSE:To reduce distortion and to eliminate an adjusting work after manufacturing by performing the differential amplification of the secondary side output of a transformer with a differential amplifier, and generating equilibrium signals with opposite phases with each other. CONSTITUTION:An output signal corresponding to a carrier signal can be obtained from the secondary side of the transformer 2. And the secondary side output of the transformer 2 is differentially amplified with a differential amplifier circuit consisting of transistors 3, 4 a constant current source 8, and resistors 6, 7. Consequently, the equilibrium signals with the opposite phases with each other are generated from the collectors of the transistors 3, 4 regardless of position relation between the secondary side coil and the primary side coil of the transformer 2. Thereby, it is possible to realize a balanced modulation circuit without generating a fear to generate modulation distortion, and also, requiring no adjustment after manufacturing.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a balanced modulation circuit used in RF modulators and the like.

"Prior Art" FIG. 2 is a circuit diagram showing the configuration of a conventional balanced modulation circuit. A carrier wave signal output from the carrier wave oscillator 1 is supplied to the primary coil 14a of the transformer 14. transformer 1
The middle point of the secondary coil 14b of No. 4 is grounded via the capacitor 15, and the carrier signal is converted into a balanced signal and output from the secondary coil 14b. FIG. 3 shows the actual configuration of the transformer 14, and parts corresponding to those in FIG. 2 are given the same reference numerals. As shown in FIG. 3, the primary side fill 14a is realized by a rod-shaped conductive path that propagates the carrier signal output from the carrier wave oscillator l, and the secondary side coil is formed by a pickup loop disposed opposite to this rod-shaped conductive path. 14b has been realized.

The secondary coil 14b has one end connected to the balanced modulation diode 9.
The other end is connected to the anode of the balanced modulation diode l.
Connected to the cathode of O.

and the cathode of diode 9 and diode 10
The anode of is a resistor 11 whose one end is connected to the input terminal 12.
It is connected to the output end 13 together with the other end. Here, a video circuit is connected to the input end 12. Note that the resistor 11 is a matching resistor provided to match the output impedance of the video circuit. According to this balanced modulation circuit,
The carrier signal output from 1 to carrier wave oscillation a is input to input terminal 1.
The signal is balanced modulated by the video signal input to the output terminal 13, and outputted from the output terminal 13.

"Problems to be Solved by the Invention" By the way, in the conventional balanced modulator described above, when the primary coil 14a and the secondary coil 14b are not fixed in an optimal positional relationship during manufacturing, or when the diode 9 and the diode If there are variations in characteristics between IO, or
If the circuit wiring pattern is asymmetrical, modulation is performed in an unbalanced state, resulting in distortion in the modulated wave signal. For this reason, conventionally, after manufacturing, the secondary coil 14
By changing the distance from the primary coil 14a at both ends of b, or by tilting the secondary coil 14b with respect to the primary fill 14a as shown by broken lines U and V in FIG. The secondary coil 14 is
Adjust the position of b, and when this position adjustment is completed,
The next coil 14b was fixed. By adjusting the degree of modulation to be maximum in this manner, distortion of the modulated wave signal can be minimized. however,
This adjustment work was extremely difficult and troublesome. Further, after adjustment, there is a problem in that the secondary coil 14b may be displaced from the adjusted position due to external vibrations or the like.

This invention was made in view of the above circumstances,
It is an object of the present invention to provide a balanced modulation circuit which has less distortion and does not require adjustment work after manufacturing.

[Means for Solving the Problems] The present invention includes a transformer that receives an output signal of a carrier wave oscillator on its primary side, and differentially amplifies the secondary side output of the transformer,
It is characterized in that it is equipped with a differential amplifier that outputs balanced signals having mutually opposite phases, and that the input signal is balanced-modulated in accordance with each of the balanced signals.

"Operation" According to the above configuration, a signal corresponding to the oscillation output of the carrier wave oscillator is output to the secondary side of the transformer. Then, the secondary side outputs of the transformers are differentially amplified by the differential amplifier to generate balanced signals having opposite phases to each other, and these balanced signals are modulated by the input signal and output.

"Example" Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of a balanced modulation circuit according to an embodiment of the present invention. In this balanced modulation circuit, a transformer 2 with fixed relative positions of the primary coil and secondary coil is used.
is used in place of the transformer 14 in FIG.

Both ends of the secondary coil of the transformer 2 are input to the bases of transistors 3 and 4, respectively. Transistor 3.
The collectors of transistors 3.4 and 4 are respectively connected to the power supply terminal 5 via current limiting resistors 6.7.
The emitters of are commonly connected to the other end of a constant current R8 whose one end is grounded. The collector of transistor 3 is connected to the anode of diode 9, and the collector of transistor 4 is connected to the cathode of diode 10.

Note that the other configurations are the same as those shown in FIG. 2 described above, so corresponding parts are given the same reference numerals and explanations will be omitted.

In this balanced modulation circuit, an output signal corresponding to the carrier signal is obtained from the secondary side of the transformer 2.

And the secondary side output of transformer 2 is transistor 3.4
, a constant current source 8, and resistors 6 and 7. As a result, regardless of the positional relationship of the secondary coil of the transformer with respect to the primary fill, balanced signals having mutually opposite phases are generated from the collectors of the transistors 3 and 4.

While the video signal input to the input terminal 12 is positive, the diode 9 is in an off state. During this period, when the secondary output of the transformer 2 has the polarity shown by the arrow and the collector of the transistor 4 goes to L level, the diode IO is turned on and the modulated wave signal goes to the clamp level. Then, when the polarity of the secondary output of the transformer 2 is reversed to the polarity shown by arrow B, the diode IO is turned off and the video signal is output as a modulated wave signal. Similarly, during the period when the video signal is negative, the diode 10 is turned off, and the polarity of the secondary output of the transformer 2 is switched to A/B, and the diode 9 is turned on/off. . In this way, the balanced signals having mutually opposite phases are modulated by the video signal and outputted to the output terminal 13.

``Effects of the Invention'' As explained hereafter, according to the present invention, it is possible to realize a balanced modulation circuit that does not cause distortion and does not require post-manufacturing adjustment. effective.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a balanced modulation circuit according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing the configuration of a conventional balanced modulation circuit, and FIG. 3 is a circuit diagram showing the configuration of a conventional balanced modulation circuit after manufacturing. It is a figure explaining adjustment work. 3.4...transistor, 8...constant current source, 2...transformer, 1...carrier wave oscillator. Figure 2 Figure 3

Claims (1)

[Claims] A transformer that receives the output signal of the carrier wave oscillator on its primary side, and a differential amplifier that differentially amplifies the secondary side output of the transformer and outputs balanced signals having opposite phases to each other, and inputs each of the balanced signals. A balanced modulation circuit characterized by modulating signals.