JPS60113544A - Am-pm conversion compensating circuit - Google Patents

Abstract

PURPOSE:To permit stable AM-PM conversion by giving Wilkinson's synthesizing to one output of a 3dB coupler which terminates an isolation terminal through an AM limiter and a variable resistance, and by giving Wilkinson's synthesizing to the other through a distribution constant circuit. CONSTITUTION:A television modulated wave from an input 10 is separated to signals whose 90 deg. phases are different each other by a 3dB coupler 11. The modulated wave from one exit is only carrier components through a limiter 13 which suppresses an AM modulated wave and a variable resistance attenuator 14, and the modulated wave from the other exit is executed by Wilkinson's synthesis 16 through a distribution constant line 15 which is equal to the sum of the electrical length of the limiter 13 and the resistance attenuator 14. The signal which passes through the limiter becomes constant by a vector OX, the AM modulated wave which passes through the distribution constant line 15 becomes a vector OA, and it is changed by the rotation of a side-band wave vector CX. A phase angle phi of the vector OA and the vector OX becomes tanphi=OX/OA, and the phi becomes larger by the white level with the small amplitude. Thus, the stable AM-PM conversion is executed simply by adjusting the resistor 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an AM-PM conversion compensation circuit in a television broadcaster and a television relay broadcaster.

Conventionally, this type of AM-PM conversion compensation circuit distributes a television modulated wave to a distributor 1 in an intermediate frequency band or six carrier frequency bands as shown in FIG. The output of the splitter 1 is multi-amplitude detected by the detector 2 to obtain a video signal, which is passed through the amplifier 3. Using this video signal, the other output of the divider 1 is sent to the television receiver via the delay line 4. AM/PM generated in a television broadcasting machine or a television relay broadcasting machine by applying phase modulation, which is the opposite of the phase modulation that produces a power amplifier, to the modulated wave in the modulator 5.
It compensated for the conversion. Note that 6 in the figure is a bias circuit.

However, such a circuit configuration uses many semiconductor elements such as transistors, making the circuit complicated, and has problems with temperature characteristics and long-term reliability, as well as being expensive.

An object of the present invention is to provide an inexpensive AM-PM conversion compensation circuit with a simple circuit configuration and excellent stability.

According to the present invention, three
a dB coupler, the 3 dB coupler, a limiter for suppressing an AM modulated wave connected to one output of the 3 dB coupler, and a fixed variable resistor attenuator connected to the limiter output. 3, a distributed constant line connected to the other output of the IB coupler, and a Wilkinson type combiner that combines the output of the resistive attenuator and the output of the distributed constant line; The conversion compensation circuit obtains r
do.

Next, the present invention will be described in detail with reference to the drawings of one embodiment of the present invention. Referring to FIG. 2, the first embodiment of the present invention includes an input terminal 10 for a television modulated wave, a 3 dB coupler 11 having a termination resistor 12 connected to its isolation terminal, and a A limiter 13 that suppresses the A and M converted waves connected to one output, a variable resistance attenuator 14, and a 90'' phase p of the 3 dB coupler 11 (connected to the output of the IE side). limiter 13
and a variable resistance attenuator 14, a Wilkinson engraving 5LJX16, and an output terminal 17.

According to FIG.
It is distributed into signals with different 0 phases.

The AM component of the modulated wave output from one output of the 3 dB coupler 11 is suppressed by the limiter 13, and only the carrier wave component is adjusted to the required level by the variable resistance attenuator 14, and Wilkinson type synthesis is performed. The input signal is input to the device 16. On the other hand, the modulated wave output from the other output of the 3 dB coupler 11 passes through a distributed constant line 15 equal to the sum of the electrical lengths of the limiter 13 and the variable resistance attenuator 4, and is input to the Wilkinson combiner 16. be done. That is, in the Wilkinson type synthesizer, as shown in the vector diagram of FIG. 3, the modulated wave and carrier wave components are synthesized with phases different by 90' from each other. According to FIG. 3, the signal passing through the limiter 13 and the variable resistance attenuator 14 is given as a vector, and the AM modulated wave passing through the distributed modulus line 15 is given as a vector 6. The amplitude of the vector OA changes due to the rotation of the sideband vector a. In FIG. 3, the composite vector of vector Ω and vector OX is represented by vector OB,
The phase angle ψ can be expressed as -+ OX ψ=ta ro -=-... (1) A. In equation (1), the vector is constant, and the vector (blue is proportional to the amplitude (jl,l), so its magnitude changes, so the phase angle ψ is as shown in Figure 5. is large for a small white level and small for a black level with a large amplitude.On the other hand, in television broadcasting equipment and television relay broadcasting equipment, since power amplifiers are used in class AB, As shown in the figure, the AM/PM conversion deteriorates at a white level with a small amplitude.In other words, in the example of the implementation of the X invention shown in Figure 2, the variable resistance attenuator 1
By adjusting the vector OX in FIG. 3 by A by 4, the phase deviation ψ is opposite to the AM/PM conversion of the white level in the output of the television broadcaster and the television relay broadcaster.
6.
As shown in the figure, it is possible to compensate for AM/PM conversion of a television broadcaster and a television relay broadcaster.

As explained above, the present invention has a simple circuit configuration and excellent stability, and has the effect of being able to compensate for A fvl - P M conversion in a cheap image.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the prior art, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. A vector diagram showing the principle; Fig. 4 is a graph of A,'M/PM conversion characteristics of a television broadcasting machine and a television relay broadcasting machine; Fig. 5 is a graph of A M / P M f conversion characteristics according to the present invention. The graph of FIG. 6 is a graph illustrating the effect of AM/PM conversion compensation combined with FIGS. 4 and 5 according to the present invention. In the figure, 1...Distributor, 2...Amplitude detector, 3...Amplifier, 4...Delay line, 5... Phase modulator, 6...bias circuit, 10...input terminal, 11...
・3dB coupler, 12...Terminator, 13...
...Limiter-114...Variable resistance attenuator,
15...Distributed constant line, 16...Wilkinson type synthesizer, 17...Output terminal 0 1'-1\, Cde7J /I direct diagram B

Claims (1)

[Claims] a 3 dB coupler that terminates an isolation terminal to which a television modulated wave is applied; a limiter that suppresses an AM modulated wave that is connected to one output of the 3 dB coupler; and a limiter that is connected to the limiter output. a resistive attenuator,
A M - characterized by comprising a distributed constant line connected to the other output of the 3 dB coupler, and a Wilkinson type combiner that combines the output of the resistive attenuator and the output of the distributed constant line. PM conversion compensation circuit.