DTV Channel Equalizer Using Known Sequences for Ghost and Noise Compensation
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Solution Overview
Problem
Digital television receiving systems face challenges in transmitting supplemental data due to signal degradation caused by noise and ghost effects, particularly in indoor environments with blockages, which requires a system highly resistant to noise and compatible with conventional video/audio data transmission systems.
Innovation Solution
A channel equalizer for DTV receiving systems that uses a transformer, estimator, calculator, and compensator to convert and compensate broadcast signals in the frequency domain, employing known data sequences for channel impulse response estimation and equalization, ensuring robust transmission of supplemental data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If supplemental data is transmitted through the same channel as video/audio data using time-division method, then data broadcasting capability is enhanced, but receiving performance deteriorates in poor channel environments due to ghost effects and noise
Solution Approach 1:
The patent applies preliminary action by inserting known data sequences (training sequences) before the actual supplemental data transmission. These known sequences allow the receiver to pre-estimate channel impulse responses and equalization coefficients before the actual data arrives, enabling the system to prepare compensation parameters in advance. This preliminary estimation and preparation of equalization coefficients based on known training sequences resolves the contradiction by establishing reliable channel characteristics before actual data transmission, ensuring both data broadcasting capability and receiving performance even in poor channel environments
2Adaptability or versatility
If conventional receiving systems are supplied that receive only video/audio data, then market compatibility is maintained, but supplemental data transmission cannot be supported
Solution Approach 1:
The patent applies universality by designing a receiving system that can handle both conventional video/audio data and supplemental data through the same channel using time-division multiplexing. The channel equalizer is designed to process different data types uniformly by estimating channel characteristics during known data periods and applying the same equalization process to both video/audio and supplemental data. This multi-functional approach enables supplemental data transmission while maintaining compatibility with existing receiving systems without requiring separate dedicated channels or fundamentally different receiver architectures
3Reliability
If channel equalization is performed using estimated channel impulse responses, then noise resistance is improved, but calculation complexity increases
Solution Approach 1:
The patent applies self-service by using known data sequences that are already available in the transmission stream to automatically estimate channel impulse responses and calculate equalization coefficients. The system uses the transmitted known sequences themselves as training data, eliminating the need for external calibration equipment or manual channel characterization. The receiver autonomously performs channel estimation and equalization coefficient calculation by processing the known training sequences that are periodically inserted in the transmission, achieving noise resistance through self-contained channel adaptation without requiring additional complex external systems
Data Source
AI summary
A channel equalizer includes a first transformer, an estimator, an average calculator, a second transformer, a coefficient calculator, a compensator, and a third transformer. The first transformer converts normal data into frequency domain data, where a known data sequence is periodically repeated in the normal data. The estimator estimates channel impulse responses (CIR) during known data intervals adjacent to each normal data block. The average calculator calculates an average value of the CIRs. The second transformer converts the average value into frequency domain data. The coefficient calculator calculates equalization coefficients using the average value, and the compensator compensates channel distortion of each normal data block using the coefficients. The third transformer converts the compensated data block into time domain data.