FM Receiver Antenna Diversity for Multipath Distortion
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Solution Overview
Problem
Existing FM receiver technologies face challenges in reducing multipath distortion, particularly in mobile environments where long and short delay multipath interference coexist, leading to frequency selective fading and broadband fading, and current antenna diversity systems like CMA and MRC have limitations in adapting to varying signal conditions, especially for weak signals.
Innovation Solution
A dual-algorithm approach is implemented, where a constant modulus algorithm (CMA) is used for strong signals and a maximum ratio combiner (MRC) algorithm for weak signals, with adaptation step sizes controlled to transition between the two based on received signal strength, ensuring optimal weight updates and improved antenna combining techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single antenna diversity system (CMA or MRC) is used, then the system structure is simple, but it cannot adapt optimally to both strong and weak signal conditions
Solution Approach 1:
The patent implements dynamic switching between CMA and MRC algorithms based on real-time signal strength detection. The system transitions from a static single-algorithm approach to a dynamic multi-algorithm system that adapts its combining strategy according to whether signals are strong or weak, thereby improving adaptability while managing complexity through conditional execution
Solution Approach 2:
The system changes the operating parameters by selecting different algorithms (CMA vs MRC) based on signal strength thresholds. This parameter change approach allows the system to optimize performance for different signal conditions without requiring a completely different system architecture, thus improving versatility while controlling device complexity
2Reliability
If CMA algorithm is used for strong signals, then multipath distortion is reduced effectively, but performance degrades for weak signals
Solution Approach 1:
The patent makes the algorithm selection dynamic by monitoring signal strength and switching between CMA (for strong signals) and MRC (for weak signals). This dynamic adaptation ensures that the system maintains high reliability for multipath distortion reduction in strong signal conditions while also performing adequately in weak signal conditions, thus improving overall adaptability
Solution Approach 2:
The system uses MRC as a backup or alternative implementation that copies the basic functionality of CMA but optimized for different signal conditions. This copying approach allows the system to maintain functional equivalence across different signal strengths while improving overall adaptability
3Adaptability or versatility
If MRC algorithm is used for weak signals, then signal quality is maintained, but multipath distortion reduction is less effective compared to CMA
Solution Approach 1:
The patent implements dynamic algorithm selection where MRC is activated specifically for weak signal conditions while CMA handles strong signals. This dynamic routing ensures that the system achieves optimal multipath distortion reduction when signals are strong (using CMA) while maintaining signal quality when weak (using MRC), thus balancing reliability and adaptability across different conditions
4Adaptability or versatility
If multiple algorithms are implemented, then adaptability to signal conditions improves, but computational complexity increases
Solution Approach 1:
The patent reduces the effective complexity by implementing dynamic switching that activates only the necessary algorithm for current signal conditions. Rather than running both CMA and MRC simultaneously, the system executes only one algorithm at a time based on signal strength, thereby improving adaptability while controlling computational complexity through conditional execution
Solution Approach 2:
The system implements partial action by using signal strength thresholds to determine algorithm selection, avoiding the excessive action of always running both algorithms. This partial execution approach allows the system to achieve full adaptability when needed while reducing computational overhead during normal operation, thus managing the trade-off between versatility and complexity
Data Source
AI summary
A technique for reducing multipath distortion in a mobile FM receiver with a plurality of antennas is accomplished through a number of steps. Initially, a first antenna signal and a second antenna signal are received. The first antenna signal is weighted with a variable first weight and the second antenna signal is weighted with a variable second weight. The weighted first antenna signal and the weighted second antenna signal are then combined to provide a combined received signal having a combined signal level. The variable first and second weights are determined by an adaptation strategy that is substantially controlled by a first algorithm, when the combined signal level is greater than a predetermined signal level. When the combined signal level is less than the predetermined signal level, the variable first and second weights are determined by an adaptation strategy substantially controlled by a second algorithm.