Phased Array Antenna Pointing Error Estimation via Sub-Array Segmentation
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Solution Overview
Problem
Conventional methods for estimating pointing errors in antennas, such as the four-horn monopulse antenna, are impractical for moving platforms like Low Earth Orbit satellites or High Altitude Platform Systems, as they cannot maintain beam illumination on fixed cells on the ground, leading to reduced coverage and efficiency.
Innovation Solution
A receive planar phased array antenna is segmented into sub-arrays, allowing for simultaneous estimation of pointing errors in azimuth and elevation directions using combined signal weights, enabling optimal orientation and coverage without interfering with primary reception tasks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated four-horn monopulse antenna is used to estimate pointing error, then pointing error estimation accuracy is improved, but device complexity and weight increase
Solution Approach 1:
The phased array antenna is designed to perform dual functions: primary communication signal reception and pointing error estimation. By segmenting the antenna into sub-arrays and using signal combination techniques, the same hardware infrastructure serves both communication and orientation functions, eliminating the need for a separate dedicated monopulse antenna system
Solution Approach 2:
The invention merges the pointing error estimation function with the primary communication antenna system. The phased array antenna elements are grouped into sub-arrays that generate difference signals for pointing error measurement while simultaneously maintaining communication capabilities, combining multiple functions into a single integrated system
2Measurement precision
If a fixed monopulse antenna is used on a moving platform, then pointing error estimation is possible, but the system becomes impractical for moving platforms like LEO satellites
Solution Approach 1:
The system transitions from a fixed monopulse antenna configuration to a dynamic phased array system that can adapt to platform motion. The phased array electronically steers beams and dynamically adjusts sub-array combinations to track signals from ground transmitters despite satellite movement, making the system suitable for LEO and other moving platforms
Solution Approach 2:
The phased array antenna is divided into multiple sub-arrays that can be independently weighted and combined. This segmentation allows the system to form difference signals for pointing error estimation while maintaining the ability to track moving targets and adapt to changing platform positions, enabling operation on moving platforms
3Measurement precision
If the phased array antenna is used for pointing error estimation, then orientation accuracy is improved, but user data reception may be interfered with
Solution Approach 1:
The system performs pointing error estimation periodically or in alternating intervals with user data reception. By timing the estimation operations appropriately and using periodic signal processing, the system obtains orientation information without continuously interfering with communication signals, maintaining both functions with minimal mutual interference
Solution Approach 2:
The system uses only the necessary subset of antenna elements and signal processing operations for pointing error estimation, leaving the majority of the phased array capacity available for primary communication. This partial action approach ensures that estimation functions do not excessively consume resources needed for user data reception
Data Source
AI summary
A receive planar phased array antenna on a communications platform is used to estimate a pointing error of the antenna and to orient the antenna boresight towards the transmitter. A method for orienting the communications antenna includes: segmenting a receive phase array antenna into N sub-arrays with M-antenna elements in each sub-array; receiving, a known signal, by each of the M-antenna elements of at least four (4) of the N-sub-arrays; scanning in a direction of the known signal by applying a beam weight associated with each of the M elements in each of the at least 4-sub-arrays to obtain M-weighted signals for each of the at least 4-sub-arrays; combining the M-weighted signals for each of the at least 4-sub-arrays into signals A, B, C and D, respectively; generating an azimuth difference signal per a weighted sum of (A+B) and (C+D) and an elevation difference signal per a weighted sum of (A+C) and (B+D); computing the weights of the azimuth difference signal, such that the azimuth difference signals is driven to a zero signal; and computing the weights of the elevation difference signal, such that the elevation difference signal is driven to a zero signal.