Array Antenna Calibration for Phase Continuity Across Sub-Bands
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Solution Overview
Problem
Existing calibration methods for multi-channel array antennas fail to maintain phase coherence across different frequency sub-bands, leading to degradation of radiation patterns and insufficient radar image quality when operating in broadband mode.
Innovation Solution
A calibration process that adjusts phase shift commands by accounting for transit time-induced phase shifts between frequency sub-bands, ensuring phase continuity and coherence across the entire frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase shift commands are adjusted using calibration sets defined for center frequency of each sub-band, then phase coherence within each sub-band is improved, but phase continuity across different sub-bands deteriorates due to transit time-induced phase shifts
Solution Approach 1:
The patent modifies the phase shift commands by introducing a compensation term that accounts for transit time variations across frequency sub-bands. The corrected phase shift command is given by: φ_corrected = φ_original - (2πf/c) × ΔL, where ΔL is the path length difference. This parameter adjustment eliminates phase jumps between sub-bands while preserving phase coherence within each sub-band.
Solution Approach 2:
The patent creates a reference phase profile from measurements taken in a first operating mode (e.g., narrowband) and applies this reference profile to correct phase shifts in a second operating mode (e.g., broadband). The reference phase characteristics are copied and adapted to compensate for mode-specific phase variations, ensuring consistent phase continuity across different operational conditions.
2Measurement precision
If antenna operates in broadband mode using multiple frequency sub-bands, then range resolution is improved, but radiation pattern quality deteriorates due to phase jumps between sub-bands
Solution Approach 1:
The patent adjusts the phase shift commands by subtracting the transit time-induced phase shift component: φ_adjusted = φ_measured - (2πf/c) × ΔL. This correction removes the frequency-dependent phase jumps that would otherwise degrade the radiation pattern, allowing the antenna to maintain reliable performance in broadband mode while achieving improved range resolution through multi-sub-band operation.
Solution Approach 2:
The patent converts the harmful effect of transit time-induced phase shifts into a beneficial correction mechanism. By measuring and characterizing these phase shifts in one operating mode, the system creates a compensation profile that, when applied in broadband mode, eliminates the harmful phase discontinuities and enables high-quality radiation patterns across the entire frequency range.
3Device complexity
If phase shift commands are kept constant across frequency sub-bands, then device complexity is reduced, but phase coherence across broadband deteriorates
Solution Approach 1:
The patent performs preliminary measurements of phase shifts in a reference operating mode and stores these characteristics for later use. This preliminary action creates a lookup table or calibration profile that can be quickly applied during broadband operation, avoiding the need for complex real-time phase calculations while maintaining phase coherence across all frequency sub-bands.
Solution Approach 2:
The patent copies the phase calibration characteristics from a reference operating mode and applies them to broadband operation. This copying approach allows the system to maintain phase coherence across frequency sub-bands without implementing complex adaptive phase control algorithms, thereby keeping device complexity low while achieving high phase coherence.
Data Source
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AI summary
A calibration method for an electronically scanned array antenna (A) comprising channels (Vi), each comprising a radiating element (Ei) and capable of operating in a set of contiguous sub-bands forming an overall frequency band, each sub-band comprising a center frequency, the calibration method comprising the following step: - Generating phase-shift commands intended to be applied to the respective channels, in operational phase in a transmit or receive mode, so that the antenna points in a predetermined pointing direction to a first frequency belonging to a first sub-band of the set of sub-bands, the phase-shift commands being defined, for each channel (Vi), by the difference between a theoretical insertion phase of the channel, in the operating mode,and an overall phase shift being the sum of a channel insertion phase in the operating mode at the center frequency of the first frequency sub-band, and a transit phase shift introduced by a transit time, between the center frequency of the first frequency sub-band and a reference center frequency, in the operating mode, when the reference center frequency does not belong to the first frequency sub-band.