Multi-Channel Receiver AFC with Reference Demodulator Offset Tracking
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Solution Overview
Problem
Traditional automatic frequency control (AFC) methods for multi-channel receivers fail to accurately correct frequency offsets across different signals, leading to inefficiencies, increased costs, and user experience issues like audio muting due to the need for external tuner adjustments and complex calibration.
Innovation Solution
The proposed AFC system maintains separate frequency offset values for each signal, allowing individual demodulators to correct their respective frequencies independently, eliminating the need for tuner adjustments and using a reference signal's frequency drift to compensate for intermittently lost signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional AFC correction methods measure frequency offset from a single demodulator and adjust the tuner center frequency, then the frequency offset for that particular signal is corrected, but other signals with different offsets require additional corrections that traditional AFC fails to provide
Solution Approach 1:
The patent divides the frequency correction function into separate demodulator-specific operations. Each demodulator measures and corrects its own frequency offset independently, rather than using a single centralized correction for all signals. This segmentation allows each signal to receive tailored frequency correction appropriate to its specific offset, resolving the contradiction between precision for one signal and versatility across multiple signals.
Solution Approach 2:
The patent creates a universal frequency correction mechanism where the same correction algorithm and process are applied to multiple different signals simultaneously. Each demodulator executes the same frequency offset measurement and correction routine on its respective signal, providing universal adaptability across satellite, terrestrial, and other signal types without requiring signal-specific correction logic.
2Reliability
If the receiver switches reference frequency from a satellite signal to a terrestrial signal when the reference signal is lost, then the receiver can continue receiving broadcasts, but the frequency offset correction becomes inaccurate because offsets differ between signal types
Solution Approach 1:
Each demodulator performs self-service frequency correction by independently measuring its own frequency offset and applying correction to its own signal processing. When switching between satellite and terrestrial references, each demodulator continues to measure and correct its own offset autonomously, eliminating the need to transfer correction state between signal types and maintaining precision during transitions.
Solution Approach 2:
The system performs preliminary frequency offset measurement and correction for each signal type before switching occurs. By continuously measuring and correcting offsets for all active signals in advance, the system ensures that when a reference signal switch is needed, the new reference signal already has its offset corrected, preventing accuracy loss during the transition.
3Device complexity
If a single frequency tuner is used for multiple signals instead of separate tuners, then receiver cost and footprint are reduced, but frequency offset correction becomes more complex and less accurate
Solution Approach 1:
The patent segments the frequency correction function to operate at the demodulator level rather than the tuner level. Each demodulator independently measures and corrects frequency offset for its signal, eliminating the need for complex centralized tuner control mechanisms. This segmentation maintains high correction precision while keeping the tuner simple and universal, resolving the contradiction between hardware simplicity and correction accuracy.
Solution Approach 2:
The patent replaces the mechanical approach of using separate physical tuners for each signal with a digital/software-based frequency correction mechanism. The frequency offset measurement and correction are performed through digital signal processing in each demodulator, substituting physical hardware complexity with flexible software algorithms that maintain high precision without requiring multiple physical tuner components.
Data Source
AI summary
Systems and methods for performing automatic frequency control are provided. Instead of relying on individual frequency tuners for each channel of a multi-channel receiver system, the present subject matter uses a single frequency tuner for receiving each channel of the multi-channel receiver system. A locked demodulator may be designated as a reference demodulator and frequency offset values associated with the reference demodulator may be applied to other demodulators of the multi-channel receiver. These frequency offset values may be used by individual demodulators of each channel for correcting corresponding frequency offsets.