CPM Correlation Matrix Inversion for UHF Satellite Demodulation
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Solution Overview
Problem
Ultra high frequency (UHF) satellite communications cause significant distortion and inter-symbol interference, leading to increased bit error rates in continuous phase modulation (CPM) signals, which existing technologies, such as LMS equalizers, struggle to adequately address due to the difficulty in modeling satellite channels with both linear and non-linear impairments.
Innovation Solution
A wireless communications device with a demodulator that generates a temporary correlation matrix by inverting and duplicating the CPM correlation matrix, allowing for improved demodulation of CPM signals over noisy channels, specifically addressing inter-symbol interference and carrier frequency and phase offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LMS equalization is used to address inter-symbol interference, then bit error rate performance improves, but the inability to simultaneously address carrier frequency and phase offset causes irreducible error floor
Solution Approach 1:
The patent segments the correlation process into multiple correlation banks, each handling specific impulse response variations. This segmentation allows the system to address different channel impairments (ISI, frequency offset, phase offset) through dedicated correlation paths, resolving the contradiction by dividing the complex adaptation task into manageable specialized components.
Solution Approach 2:
The patent changes the correlation parameters dynamically by generating multiple correlation matrices with different impulse response parameters (frequency and phase variations). This allows the receiver to adapt to different channel conditions without requiring separate adaptive algorithms for each impairment type, achieving both improved BER and multi-impairment handling.
2Device complexity
If non-coherent decoding is used for CPM signals, then implementation complexity is reduced, but phase continuity requirements create quasi-coherent behavior
Solution Approach 1:
The patent creates multiple copies of the correlation matrix with different impulse response variations to represent different phase and frequency conditions. This copying approach allows non-coherent decoding to handle phase variations without requiring explicit phase tracking, maintaining implementation simplicity while achieving reliable demodulation under phase continuity constraints.
3Reliability
If correlation banks are used for non-coherent CPM decoding, then bit error rate performance improves, but computational intensity increases
Solution Approach 1:
The patent performs preliminary generation of multiple correlation matrices before the actual decoding process. By pre-computing the correlation banks with different impulse response variations, the system reduces the computational burden during real-time operation, achieving improved BER performance while managing computational energy consumption through advance preparation.
Data Source
AI summary
A wireless communications device may include a receiver configured to receive a continuous phase modulation (CPM) signal and a demodulator coupled downstream from the receiver. The demodulator may be configured to generate a CPM correlation matrix based upon an expected CPM signal, and generate a temporary correlation matrix. The temporary correlation matrix may include a first copy of the CPM correlation matrix inverted in time, and a second copy of the CPM correlation matrix.