Cross-Polarization Interference Compensation Using Complex FIR Filters
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Solution Overview
Problem
Wireless communication systems face significant challenges with cross-polarization interference due to non-idealities such as atmospheric effects and imperfect signal isolation, especially at higher frequencies and in wideband systems, leading to depolarization and noise, which complicates signal decoding and requires complex computational corrections.
Innovation Solution
The implementation of a cross-polarization interference compensation (XPIC) module using complex-valued finite impulse response (FIR) filters in both transmitter and receiver systems to generate correction factors for cancelling cross-polarization components in dual-polarized signals, allowing for real-time adaptation to changing interference conditions without altering normal system operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dual-polarized signals are transmitted simultaneously in the same frequency band to double capacity, then communication system capacity is improved, but cross-polarization interference occurs due to depolarization from atmospheric effects and imprecise antenna pointing
Solution Approach 1:
The patent measures the cross-polarization leakage from one polarization to the other and uses this harmful interference signal to generate a correction factor. This correction factor is then applied to cancel the interference, effectively converting the harmful depolarization effect into a useful cancellation mechanism that improves signal quality while maintaining dual-polarized transmission capacity
2Measurement precision
If complex computational corrections are applied to compensate for cross-polarization interference, then signal accuracy is improved, but computational complexity increases
Solution Approach 1:
The system uses the received signal itself to generate the correction factor needed for interference cancellation. By measuring the cross-polarization leakage present in the received dual-polarized signal and using this measurement to create the cancellation signal, the system achieves accurate compensation without requiring external reference signals or complex pre-computed correction tables
3Reliability
If depolarization compensation is implemented for moving nodes such as non-geostationary orbit satellites, then communication reliability is improved, but the system requires rapid adaptation to quickly changing interference conditions
Solution Approach 1:
The patent implements a feedback mechanism where the received signal is continuously monitored for cross-polarization leakage, and the measured leakage is used to dynamically adjust the correction factor. This continuous feedback loop enables the system to rapidly adapt to changing depolarization conditions caused by satellite motion, atmospheric variations, and pointing adjustments, maintaining reliable communication without requiring complex prediction algorithms
Data Source
AI summary
In an embodiment, a cross-polarization interference compensation module is included in a receiver of a wireless communication system. The module includes first and second input lines configured to receive respective first and second down-converted digital polarized signals based on receipt of a wireless transmission. The module further includes first and second output lines electrically coupled to at least one modem. The module further includes a first complex finite impulse response (FIR) filter configured to receive the second down-converted digital polarized signal and generate a correction factor that cancels cross-polarization components in the first down-converted digital polarized signal. The module further includes a first filter coefficient engine in communication with the first complex FIR filter and configured to adapt the first complex FIR filter over time based on the first and second down-converted digital polarized signals.