Phased Array Calibration via Mutual Coupling
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Solution Overview
Problem
Phased arrays in satellite communications require frequent calibration due to temperature fluctuations in low-Earth orbit, which must be simultaneous with transmit/receive digital beam-forming processing, and must avoid degrading beam performance or causing interference, especially in frequency division duplex systems where transmit and receive frequencies differ.
Innovation Solution
The calibration method exploits mutual coupling between antenna elements, using self and mutual coupling measurements to determine phase and amplitude characteristics of transmit/receive front-end modules, allowing for simultaneous calibration during service beam operation without degrading performance or causing interference, and utilizes pseudo-random calibration signals to minimize interference with beam signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed frequently to compensate for temperature changes in low-Earth orbit, then accuracy of beamforming is improved, but calibration time and interference with service beams increase
Solution Approach 1:
The patent implements periodic calibration by inserting calibration sequences at regular intervals within the frame structure. Multiple calibration sequences are distributed across different time slots, allowing the system to perform calibration periodically without continuous interruption of service beams. This resolves the contradiction by providing sufficient calibration frequency to track temperature changes while limiting total calibration time through structured periodic sampling.
Solution Approach 2:
The patent performs preliminary calibration measurements by capturing signals from neighboring elements before they are needed for service beamforming. Calibration sequences are transmitted and measured in advance within the same frame structure, allowing the system to prepare calibration data proactively. This enables frequent calibration without last-minute interruptions to service operations, reducing calibration time while maintaining accuracy.
2Measurement precision
If calibration sequences are inserted into the signal stream, then calibration measurements can be performed, but beamforming performance degrades due to signal interruptions
Solution Approach 1:
The patent segments the calibration process into multiple distributed calibration sequences rather than one continuous calibration period. Each calibration sequence is a short, isolated measurement embedded within the frame structure. This segmentation allows calibration to occur in small increments throughout the frame duration, minimizing the impact on beamforming performance while still providing sufficient measurement opportunities to maintain calibration accuracy.
Solution Approach 2:
Calibration sequences are inserted periodically at specific time slots within the frame structure, creating a rhythmic pattern of calibration and service beam operation. This periodic insertion ensures that calibration measurements are taken at regular intervals without continuously interrupting service beams. The structured periodic placement allows the system to maintain both calibration capability and beamforming reliability by clearly separating calibration and service functions in time.
3Measurement precision
If calibration signals are transmitted at high power, then calibration measurements are more accurate, but interference with service beams increases
Solution Approach 1:
The patent uses partial action by transmitting calibration sequences at elevated power only during specific calibration time slots, rather than continuously at high power. The calibration signals are transmitted at sufficient power to achieve accurate measurements during their brief transmission windows, but are absent or at low power during service beam time slots. This partial high-power transmission provides measurement accuracy when needed while avoiding continuous interference with service beams.
Solution Approach 2:
High-power calibration signals are transmitted periodically only during designated calibration time slots within the frame structure, rather than continuously. This periodic high-power transmission ensures that calibration measurements receive sufficient signal strength for accuracy during their brief windows, while the majority of the time service beams operate without interference. The temporal separation through periodic action resolves the contradiction between measurement accuracy and interference avoidance.
4Productivity
If multiple calibration measurements are performed simultaneously, then calibration speed increases, but system complexity and interference management become more difficult
Solution Approach 1:
The patent segments the array into multiple groups or subsets, with each group performing calibration measurements independently during the same time frame. Instead of coordinating a single complex simultaneous measurement across the entire array, the system divides calibration into smaller, manageable segments that can proceed in parallel. This segmentation reduces the complexity of managing simultaneous measurements while still achieving fast overall calibration through parallel execution of multiple independent calibration processes.
Solution Approach 2:
The patent performs partial calibration by having different groups of elements perform calibration measurements simultaneously rather than requiring complete array calibration at once. Each group conducts its own calibration independently, performing only the necessary measurements for that subset. This partial simultaneous calibration achieves fast overall calibration speed through parallel processing while keeping individual measurement complexities manageable and independent of each other.
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 enables accurate and efficient calibration of phased arrays in low-Earth orbit satellites, ensuring consistent beam performance despite temperature changes and aging, while avoiding interference with service beams and reducing calibration duration.
Implementation Method 1
we exploit the mutual coupling between transmit and receive antenna elements of the phased array
Implementation Method 2
utilizes pseudo-random calibration signals to minimize interference with beam signals
Data Source
AI summary
An antenna array includes an antenna assembly. The antenna assembly includes a plurality of elements. The antenna assembly is configured to measure a reference combined parameter of a reference element of the plurality of elements, measure a first combined parameter of the reference element and a first neighbor element of the plurality of elements and being adjacent or diagonal with respect to the reference element, calculate a differential parameter according to the first combined parameter and the reference combined parameter, and adjust a parameter of the first neighbor element according to the differential parameter. The parameter of first neighbor element is a phase or a amplitude of first neighbor element. The first combined parameter includes a coupling contribution of the first neighbor element and the reference element, and contributions from a path of the first element and a path of the reference element.