Phased Array Antenna Multipath Mitigation via Beam Bifurcation
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Solution Overview
Problem
Multipath signals interfere with direct path signals in communication and location determining operations, especially over water, causing destructive interference and attenuation, and existing mitigation techniques like beam tilt and large antenna arrays are imprecise or impractical for aircraft applications.
Innovation Solution
The solution involves electronically steering the main beam of a phased array antenna away from the signal transmitter and bifurcating it to create a null at its center, where the multipath signal can be placed, using phase tapering across antenna elements to attenuate the multipath signal relative to the direct path signal, while monitoring amplitude variations to optimize beam steering and phase control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a beam tilt technique is used to mitigate multipath signals, then multipath interference is reduced, but the technique is imprecise and difficult to implement under various flight conditions
Solution Approach 1:
The patent replaces mechanical beam tilting (altering aircraft attitude) with electronic beam steering using phase shifters and signal processing. The system electronically adjusts the phase of signals from different antenna elements to steer the beam away from the horizon without physically tilting the aircraft, thereby resolving the contradiction between multipath mitigation and ease of operation.
2Reliability
If a large array of antenna elements is used to create spatial independence, then fading issues are minimized, but the antenna size and weight increase
Solution Approach 1:
The patent changes the operational parameters of an existing antenna array by dynamically adjusting phase shifts and signal weights across elements rather than increasing physical array size. This allows the system to achieve fading resistance through electronic beam steering and signal processing, avoiding the weight penalty of larger physical arrays.
3Object-affected harmful factors
If the main beam is steered away from the signal source to place multipath signals in a null, then multipath signal strength is attenuated, but beam steering accuracy must be precisely controlled
Solution Approach 1:
The patent employs feedback mechanisms where the system monitors signal characteristics and dynamically adjusts beam steering angles and phase taper parameters. By continuously adapting the beam configuration based on received signal quality and multipath conditions, the system achieves precise multipath attenuation without requiring manual calibration or complex manual control.
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 approach effectively suppresses multipath signals by minimizing statistical deviation in the received signal amplitude, improving signal strength and facilitating signal source tracking, with significant attenuation of multipath signals compared to direct path signals, even in dynamic environments.
Implementation Method 1
Bifurcation of the main beam to produce a null at the beam's center can be achieved by tapering the phase of the received signal across groups of antenna elements
Implementation Method 2
the main beam is tilted by electronically steering that beam
Implementation Method 3
Because of the longer path traveled by the multipath signal as compared to the direct path signal, the multipath signal may be out of phase with the direct path signal. This can result in destructive interface and attenuation of the direct path signal
Data Source
AI summary
Mitigation of the effects of multipath signals is provided. Such mitigation can include electronically steering the main beam of a receive pattern associated with a phased array antenna away from a transmitting antenna. In addition, a phase taper is applied to groups of antenna elements to create a null in the main beam, bifurcating that beam. The multipath signal may be placed in or towards the null, while the direct path signal may be placed on one of the halves of the main beam adjacent the null, such that the signal strength of the multipath signal is attenuated as compared to the signal strength of the direct path signal.