Multi-Element Antenna Interference Cancellation for Co-Located Satellites
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Solution Overview
Problem
Satellite communication systems face interference issues when co-located, particularly due to high-power signals from one system overlapping with low-power signals of another system using similar or adjacent frequency bands, leading to signal degradation and reciprocal mixing, which existing mitigation techniques like beam steering and frequency domain filtering may not effectively address when power ratios are significantly high.
Innovation Solution
A wireless communication terminal is configured with a multi-element antenna array and an auxiliary antenna to sample and subtract interfering signals, using complex weights to mitigate interference by combining signals from paired antenna elements and applying phase shifts to steer the main beam away from interfering signals, allowing for effective interference cancellation even with high power ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If beam steering or frequency domain filtering is used to mitigate interference, then interference reduction is achieved, but the technique fails when power ratios between interfering and desired signals are significantly high
Solution Approach 1:
The antenna array is divided into multiple independently controllable antenna elements, each capable of receiving and processing signals separately. This segmentation allows the system to apply different complex weights to individual elements, enabling precise spatial filtering and interference cancellation even in high power ratio scenarios where conventional beam steering fails.
Solution Approach 2:
The system dynamically adjusts complex weights (amplitude and phase parameters) applied to signals from each antenna element based on the interference characteristics. By changing these parameters adaptively, the system can effectively cancel interfering signals across a wide range of power ratios, overcoming the limitations of fixed beam steering approaches.
2Productivity
If co-located satellite communication systems use overlapping frequency bands, then spectrum efficiency is improved, but signal degradation and reciprocal mixing occur
Solution Approach 1:
The system uses an auxiliary antenna as an intermediary to sample the interfering signal from the co-located system. This sampled interference signal is then processed and subtracted from the main received signal, enabling the simultaneous operation of overlapping frequency bands while maintaining signal quality and preventing reciprocal mixing.
Solution Approach 2:
The interfering signal component is extracted from the composite received signal through the auxiliary antenna sampling and signal processing. By separating and removing the interference component, the system enables reliable concurrent operation of co-located systems using overlapping frequency bands, thus improving spectrum efficiency without sacrificing signal quality.
3Reliability
If expensive local oscillators with good phase-noise performance are used, then signal quality is improved, but system cost increases
Solution Approach 1:
Instead of using expensive high-performance local oscillators to prevent interference, the system converts the interfering signal into a useful component by sampling it with the auxiliary antenna and using it for active cancellation. This approach achieves signal quality improvement without requiring costly phase-noise optimized oscillators, thereby reducing system cost while maintaining reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables reliable communication by significantly reducing interference, allowing satellite communication systems to operate concurrently even when closely co-located and using overlapping frequency bands, thereby improving signal quality and reducing the need for expensive local oscillators with good phase-noise performance.
Implementation Method 1
a plurality of m antenna elements arranged linearly and displaced from one another... receive signals with the antenna array
Implementation Method 2
phase shifters to apply complex weights to interference-mitigated signals to produce complex-weighted versions of the interference-mitigated signals and effectively steer a main beam of the antenna
Implementation Method 3
another signal combiner to combine the complex-weighted versions of the interference-mitigated signals to produce an interference-mitigated output signal
Data Source
AI summary
In one implementation, a wireless communications terminal includes a multi-element antenna. In addition, the terminal includes preliminary signal combiners to combine received signals output by corresponding pairs of antenna elements. For each preliminary signal combiner, the signal output by a first of the pair of elements provides a model of interference present in the received signal output by the second of the pair of elements. The preliminary signal combiner is configured to combine the signal output by the first element with the signal output by the second element to produce an initial interference-mitigated signal. The terminal also includes phase shifters to apply complex weights to interference-mitigated signals to produce complex-weighted versions of the interference-mitigated signals and effectively steer a main beam of the antenna to facilitate reception of a desired signal and another signal combiner to combine the complex-weighted versions of the interference-mitigated signals to produce an interference-mitigated output signal.