ATSC Interference Detection Circuit Using PN63 Correlation
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Solution Overview
Problem
Existing interference detection methods in digital TV systems, such as those using ATSC standards, fail to accurately identify interference from NTSC signals due to signal distortion, leading to incorrect activation of interference rejection filtering and compromised picture quality.
Innovation Solution
An interference detecting circuit that utilizes a buffering module to delay PN63 synchronization format data, a correlation arithmetic circuit to compare synchronized data, and a determining circuit to selectively perform interference rejection based on similarity analysis of PN63 synchronization format data within fields, ensuring accurate identification and filtering of interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the prior art interference detecting method compares the received Field SYNC with a known Field SYNC, then the interference detection can identify interference, but the detection becomes unreliable when the received Field SYNC is distorted due to noise or transmission path variation
Solution Approach 1:
The Field SYNC is segmented into multiple identical PN63 synchronization format data blocks. Instead of comparing a single received Field SYNC with a known pattern, the circuit divides the Field SYNC into multiple segments (PN63 blocks) and performs correlation comparison among these segments. This segmentation allows the system to average out noise and distortion effects across multiple identical patterns, improving both detection accuracy and reliability when the received signal is distorted
Solution Approach 2:
The patent performs correlation comparison on only a portion of the Field SYNC structure - specifically the multiple identical PN63 synchronization format data blocks - rather than processing the entire Field SYNC. By focusing the comparison on these specific partial segments that are guaranteed to be identical in the transmitted signal, the system achieves reliable interference detection even when other parts of the signal are distorted by noise or transmission variations
2Object-affected harmful factors
If interference rejection filtering is activated based on distorted Field SYNC comparison, then interference may be rejected, but unnecessary filtering occurs leading to deteriorated picture quality
Solution Approach 1:
The interference detecting circuit uses feedback from the correlation comparison result to control the interference rejection filter. By continuously monitoring the similarity between multiple PN63 synchronization format data blocks and adjusting the filter activation accordingly, the system provides feedback-based control that prevents unnecessary filtering. When the correlation indicates no significant interference (similar patterns), the filter remains inactive, preserving picture quality. When interference is detected (divergent patterns), the filter is activated to reject the harmful NTSC signal
3Device complexity
If the digital TV receiver uses a single Field SYNC pattern for interference detection, then the detection process is simple, but the receiver cannot reliably identify Field SYNC when distortion occurs
Solution Approach 1:
The patent merges multiple identical PN63 synchronization format data blocks within the Field SYNC structure to create a robust identification mechanism. By combining the information from multiple identical blocks through correlation comparison, the system achieves reliable Field SYNC identification even when individual blocks are distorted. This merging approach maintains relatively simple circuit complexity while dramatically improving identification accuracy under distorted conditions
Data Source
AI summary
An interference detecting circuit for use in an ATSC system and for detecting interference of an ATSC signal includes: a buffering module for delaying to output a first PN63 synchronization format data when receiving the first PN63 synchronization format data; a correlation arithmetic circuit coupled to the buffering module for receiving the ATSC signal and performing a correlation operation on a second PN63 synchronization format data and the delayed first PN63 synchronization format data to output a detection signal when receiving the second PN63 synchronization format data; and a determining circuit for determining whether performing interference rejection on the ATSC signal or not according to the result of the above-mentioned correlation operation.