Sparse Array Radar DoA Estimation Through Phase Unwrapping
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Solution Overview
Problem
Radar systems with sparse antenna arrays face challenges in determining unambiguous direction of arrival (DoA) angles due to antenna element spacings greater than λ/2, leading to ambiguous phase differences and suboptimal signal-to-noise ratio (SNR) when combining individual estimates.
Innovation Solution
A method for sparse antenna arrays that involves unwrapping ambiguous phase differences by splitting the phase domain into hypothesis regions, calculating phasors, and combining them with weighted averaging to determine the most likely DoA angle, using a radar controller processor to handle the signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If antenna elements are spaced larger than λ/2 to reduce array complexity, then device complexity is reduced, but measurement precision of DoA angle becomes ambiguous
Solution Approach 1:
The phase domain is segmented into multiple hypothesis regions, each corresponding to a possible unambiguous DoA angle range. By dividing the ambiguous phase measurements into distinct hypothesis regions, the system can resolve the ambiguity caused by sparse array spacing while maintaining the computational efficiency of the segmented approach
Solution Approach 2:
The invention changes the parameter representation by transforming ambiguous phase differences into unambiguous DoA angle estimates through hypothesis testing. By parameterizing the solution space into discrete hypothesis regions and selecting the optimal hypothesis based on phase consistency, the system achieves precise DoA estimation despite large antenna spacing
2Reliability
If all possible pairs of antenna elements are selected to maximize SNR, then signal-to-noise ratio is improved, but device complexity increases due to non-independent estimates
Solution Approach 1:
The invention extracts only the essential phase difference information from antenna element pairs that provide independent DoA estimates. By selecting a minimal subset of antenna pairs whose phase measurements are mutually independent, the system achieves optimal SNR without the computational burden of processing all possible pairs
Solution Approach 2:
Rather than processing all possible antenna element pairs (excessive action), the invention processes only the necessary subset of pairs that provide independent estimates (partial action). This selective approach achieves the required SNR performance while significantly reducing the computational complexity of combining multiple estimates
Data Source
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AI summary
A mechanism is provided for determining an unambiguous direction of arrival (DoA) for radio frequency (RF) signals received by a sparse array. A DoA angle domain is split into hypothesis regions. The hypothesis regions are derived from the phase differences of the antenna element pairs used for the DoA angle estimate. In each hypothesis region, the ambiguous phase of antenna element pairs is unwrapped according to expected wrap-around. After unwrapping the phase, for each hypothesis region, a phasor is calculated by combining the individual antenna element pair phasors. The hypothesis region that obtains the phasor with a largest amplitude is selected as the most likely DoA region and the phase of the winning phasor is used as an unambiguous estimate for the DoA angle.