Carrier Chrominance Signal Frequency Correction Circuit
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Solution Overview
Problem
Existing broadcasting receivers face challenges in accurately correcting distorted frequency characteristics of carrier chrominance signals, particularly in the high frequency band, which affects the reproduction of color signals during analog broadcasting.
Innovation Solution
An apparatus and method that utilize multi burst signals within the vertical blanking interval to detect and adaptively correct frequency characteristics of the carrier chrominance signal through a compensating circuit with gain adjustment, ensuring accurate correction by comparing and equalizing the amplitude differences between the 3.58 MHz and 4.2 MHz bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant fixed value is used to correct color signal distortion, then the correction process is simple, but the correction accuracy is insufficient for different degrees of distortion
Solution Approach 1:
The patent transforms the static fixed-value correction into a dynamic adaptive correction system. The correction value is no longer constant but varies according to the detected frequency characteristics of the received signal. The system dynamically adjusts the correction amount based on the measured distortion level, allowing optimal correction for different distortion scenarios while maintaining system simplicity through automated adaptation.
Solution Approach 2:
The patent implements a feedback mechanism where the frequency characteristics of the received signal are continuously detected and used to adjust the correction value. The detection unit measures the actual distortion, and this information feeds back to the correction unit, which then adjusts its correction amount accordingly. This closed-loop feedback system ensures accurate correction adapt to varying distortion conditions.
2Measurement precision
If the frequency characteristics are corrected adaptively based on detected distortion, then the correction accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent divides the correction system into distinct functional modules: a detection unit for measuring frequency characteristics, a processing unit for calculating correction values, and a correction unit for applying the correction. This segmentation allows each module to perform its specific function efficiently, reducing overall system complexity while maintaining high correction accuracy through specialized functional decomposition.
Solution Approach 2:
The patent introduces an intermediate processing stage between detection and correction. The detection unit first measures the frequency characteristics, then an intermediate calculation process determines the appropriate correction value before applying it. This intermediary step acts as a buffer that simplifies the relationship between detection and correction, making the overall system more manageable while preserving accuracy.
3Reliability
If high frequency band signals are transmitted, then the broadcasting quality is improved, but the signals are more susceptible to distortion during transmission
Solution Approach 1:
The patent applies preliminary anti-action by pre-compensating for the expected high-frequency distortion before transmission, or by detecting and correcting the distortion immediately upon reception. The system proactively counteracts the harmful distortion effects rather than merely reacting to them, maintaining high broadcasting quality despite the inherent susceptibility of high-frequency signals to distortion.
Solution Approach 2:
The patent converts the harmful distortion into a beneficial measurement signal. By detecting the frequency characteristics of the distorted signal, the system uses the distortion itself as information to calculate the appropriate correction value. The harmful distortion becomes the basis for adaptive correction, transforming the problem into a solution.
Data Source
AI summary
A method and an apparatus are provided for correcting the frequency characteristics of a carrier chrominance signal, which, by use of the correcting signal for the frequency characteristic involved in a vertical blanking interval, determine whether the frequency characteristics of the carrier chrominance signal are distorted and correct the frequency characteristics. A band pass filter is used which determines a degree of the frequency characteristic distortion of the carrier chrominance signal band from the correcting signal for the frequency characteristic, and has a gain in accordance with the determined result. If the frequency characteristic of the carrier chrominance signal involved in the input composite video signal is distorted by the frequency characteristics and so on of the analog broadcasting radio channel and the broadcasting receiver, the distortion is corrected whereby a stable reproduction of the color signal is possible irrespective of the broadcasting channels and the broadcasting receiver.