JPH0810992Y2 - Non-linearity correction circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a non-linearity correction circuit used in a television transmitter using a klystron.

[Conventional technology]

Generally, the klystron is used for amplification and oscillation of microwaves. Television transmitters may use this to amplify high frequency signals. In a television transmitter using such a klystron, a picture signal is transmitted by using the klystron in the vicinity of the saturation region of the klystron in order to efficiently amplify the signal.

[Problems to be solved by the device]

For this reason, the amplitude characteristic of the output of the klystron is significantly deteriorated, and the linearity of luminance (luminance) and chrominance (color difference) do not match, and if linearity of luminance is corrected, the linearity of chrominance is excessively corrected. There was a problem.

Therefore, an object of the present invention is to provide a non-linearity correction circuit capable of adjusting only the amplitude characteristic of chrominance independently of the amplitude characteristic of luminance.

[Means for solving the problem]

In the non-linearity correction circuit of the present invention, (i) a distributor for distributing a high frequency signal after amplitude-modulating a video signal, and (ii)
It consists of a nonlinear amplifier that inputs one high frequency signal distributed by this distributor and amplifies this high frequency signal according to the chrominance correction curve, a synchronous detector that extracts the quadrature component, and a color subcarrier pass filter. A series circuit, (iii) a delay circuit for inputting the other high-frequency signal distributed by the distributor, and correcting the delay time of the synchronous detector and the color subcarrier pass filter, and (iv) the delay circuit A nonlinearity correction circuit is provided with a modulator that modulates a high-frequency signal with a color subcarrier that has passed through a color subcarrier pass filter to correct the amplitude characteristic of chrominance.

That is, the present invention achieves the above-mentioned object by correcting chrominance independently of luminance with a non-linear amplifier.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to embodiments.

FIG. 1 shows an outline of the circuit configuration of a non-linearity correction circuit according to an embodiment of the present invention. This non-linearity correction circuit distributes an input signal 11 as a high frequency signal after amplitude modulation of a video signal by a distributor 12, supplies one to a non-linear amplifier 13 and supplies the other to a delay circuit 14. There is. The nonlinear amplifier 13 is adjusted according to the chrominance correction curve at the klystron output.
The output of the nonlinear amplifier 13 is input to the synchronous detector 15, where the quadrature component converted into the baseband component is extracted. This quadrature component is input to the color subcarrier pass filter 16, where the color subcarrier is extracted. The color subcarrier is input to the modulator 17 arranged in the subsequent stage of the delay circuit 14,
The high frequency signal delayed by the delay circuit 14 is modulated to obtain the output signal 18. Here, the delay circuit 14 is a circuit that delays the color subcarrier output from the color subcarrier pass filter 16 and the color subcarrier in the high frequency signal so that they are in phase.

In this way, only the chrominance amplitude correction is performed.

[Effect of device]

As described above, according to the present invention, when the deterioration of the amplitude characteristics of the luminance and chrominance caused by the klystron is corrected, the chrominance is corrected independently of the luminance, so that the efficiency of the klystron is not reduced and high quality is achieved. The picture signal can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a non-linearity correction circuit according to an embodiment of the present invention. 11 ... Input signal, 12 ... Distributor, 13 ... Non-linear amplifier, 14 ... Delay circuit, 15 ... Synchronous detector, 16 ... Color subcarrier pass filter, 17 ... Modulator, 18 ... … Output signal.

Claims (1)

[Scope of utility model registration request] 1. A distributor for distributing a high-frequency signal after amplitude-modulating a video signal, and one of the high-frequency signals distributed by this distributor are input, and this high-frequency signal is amplified in accordance with a chrominance correction curve. A non-linear amplifier, a synchronous detector for extracting a quadrature component, a series circuit including a color subcarrier passing filter, and the other high-frequency signal distributed by the distributor are input, and the synchronous detector and the color subcarrier are passed. A delay circuit for correcting the delay time of the filter, and a modulator for correcting the amplitude characteristic of chrominance by modulating the high frequency signal passing through the delay circuit with the color subcarrier that has passed through the color subcarrier passing filter. A non-linearity correction circuit characterized by: