Antenna Array Interference Cancellation for Co-located Satellite Systems
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Solution Overview
Problem
Co-located satellite communication systems often experience interference due to the use of similar, adjacent, or overlapping frequencies, leading to signal degradation, especially when the power of one system's transmission significantly exceeds the other's reception power, making it difficult to effectively mitigate interference using existing beam steering or frequency domain filtering techniques.
Innovation Solution
A wireless communication terminal is configured with a primary antenna array and an auxiliary antenna array, where the primary array steers its main beam to receive desired signals while the auxiliary array samples and subtracts interfering signals from co-located systems, using complex weights to optimize cancellation, even when the interfering signal is stronger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beam steering or frequency domain filtering techniques are used to mitigate interference, then interference mitigation is attempted, but they are ineffective when the interfering signal power significantly exceeds the desired signal reception power
Solution Approach 1:
The antenna system is segmented into multiple independent antenna elements that can be individually controlled with separate complex weights. This segmentation allows the system to create multiple independent beam patterns simultaneously, enabling the main beam to receive desired signals while null beams specifically target and reject interfering signals from co-located systems, even when those interferers are much stronger than the desired signals.
Solution Approach 2:
Different spatial regions are assigned different quality characteristics through localized beamforming. The main beam direction is optimized for maximum signal reception with high gain, while specific directions containing interferers are assigned null characteristics with minimum gain. This local quality differentiation allows the system to simultaneously enhance desired signals in one direction while suppressing interfering signals from other directions, resolving the contradiction when interferer power exceeds desired signal power.
2Adaptability or versatility
If co-located satellite communication systems use similar, adjacent, or overlapping frequencies, then frequency utilization is improved, but signal degradation occurs due to mutual interference
Solution Approach 1:
The system transitions from frequency-domain separation to spatial-domain separation for interference mitigation. Instead of relying solely on frequency differentiation which causes interference when frequencies overlap or are adjacent, the patent introduces a spatial dimension through multiple antenna elements and beamforming. This allows co-located systems to use the same or adjacent frequencies simultaneously by directing beams in different spatial directions, thereby maintaining high frequency utilization while preventing signal degradation through spatial isolation.
3Reliability
If a primary antenna array steers its main beam to receive desired signals, then desired signal reception is improved, but interfering signals from co-located systems received in side lobes cause degradation
Solution Approach 1:
The interfering signal component received in the side lobes is extracted and separately processed using the auxiliary antenna array. By isolating the side lobe interference path from the main beam reception path, the system can apply specific cancellation techniques targeted at the extracted interferer without affecting the main beam's desired signal reception. This extraction approach allows independent optimization of both main beam reception and side lobe interference rejection.
Solution Approach 2:
An auxiliary antenna array serves as an intermediary between the primary antenna array and the interference cancellation process. The auxiliary array specifically samples the interfering signals in the side lobes, and this sampled interference information is used to generate cancellation signals that are subtracted from the main beam output. This intermediary structure enables precise interference measurement and cancellation while preserving the integrity of the main beam's desired signal reception.
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 configuration effectively mitigates interference by combining and subtracting the interfering signal from the primary signal, allowing for reliable communication between co-located satellite systems using similar frequencies, even in close proximity, thereby enhancing the performance of satellite communication systems.
Implementation Method 1
The first controller is configured to steer a main beam of the primary antenna array in a desired direction to receive a desired signal from a satellite orbiting the earth
Implementation Method 2
The auxiliary antenna array includes a second number of auxiliary antenna elements and individual ones of the auxiliary antenna elements are configured to receive variants of a second signal
Implementation Method 3
Complex weights to be applied by individual antenna elements of the auxiliary antenna array to the corresponding variants of the secondary signal received by the individual antenna elements are set based on a direction of a main beam of the primary antenna array. The complex weights are applied to the corresponding variants of the secondary signal received by the individual antenna elements to shift (e.g., in amplitude and/or phase) the variants of the secondary signal
Implementation Method 4
The at least one signal combiner is configured to combine variants of the second signal received from auxiliary antenna elements into an interfering signal that models interference from a co-located wireless communication terminal and subtract the interfering signal from variants of the first signal received from antenna elements of the principal antenna array to produce an interference mitigated signal
Data Source
AI summary
In one implementation, a wireless communication terminal includes a primary antenna array and a first controller configured to steer a main beam of the primary antenna array in a desired direction. The wireless communication terminal also includes an auxiliary antenna array and a second controller configured to control complex weights to be applied by at least some antenna elements of the auxiliary antenna array to corresponding variants of a second signal received by the at least some auxiliary antenna elements. Furthermore, the wireless communication terminal includes at least one signal combiner configured to combine variants of the second signal received from auxiliary antenna elements into an interfering signal that models interference from a co-located wireless communication terminal and subtract the interfering signal from variants of the first signal received from antenna elements of the principal antenna array to produce an interference mitigated signal.