Beamforming System Resolving Phase Ambiguity
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Solution Overview
Problem
Conventional beamforming methods face challenges when sensor spacing exceeds half the wavelength, leading to ambiguous phase differences and difficulties in utilizing high frequency energy due to environmental noise interference, particularly in acoustic localization systems.
Innovation Solution
A beamforming system that includes an input module, phase-difference module, delay distribution module, and delay estimation module to calculate phase differences across multiple frequency bins, derive candidate delays by adding/subtracting multiples of 2π, and apply a spread function to form a delay distribution function, enabling accurate delay estimation and alignment of signals from sensors spaced greater than half the wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor spacing is increased beyond half wavelength to get sufficiently different signals, then signal differentiation is improved, but phase difference ambiguity occurs making delay estimation unreliable
Solution Approach 1:
The patent segments the delay estimation process into multiple discrete delay candidates based on phase difference measurements. Instead of directly estimating a single delay value, the system divides the possible delay range into multiple segments (delay candidates) and evaluates the likelihood of each segment, thereby resolving the ambiguity caused by large sensor spacing.
Solution Approach 2:
The patent transforms the one-dimensional phase difference measurement into a multi-dimensional delay distribution by considering multiple delay candidates simultaneously. This dimensional expansion allows the system to capture the full range of possible delays and select the most probable one, overcoming the limitations of direct phase-based delay estimation.
2Reliability
If low frequency bins are used for delay estimation, then phase difference reliability is improved, but signal of interest may be lost when it lacks low frequency energy
Solution Approach 1:
The patent creates a universal delay distribution model that can effectively utilize phase difference information from both low and high frequency bins. By processing all frequency bins through the same multi-candidate delay estimation framework, the system achieves consistent and reliable delay estimation across the entire frequency spectrum, preventing loss of high frequency signal content.
3Measurement precision
If low frequency bins are used for delay estimation, then measurement consistency is improved, but environmental noise with strong low frequency energy destroys the low frequency phase difference
Solution Approach 1:
The patent implements a dynamic approach where the delay distribution is computed across multiple frequency bins and then aggregated. This dynamic aggregation process allows the system to adapt to varying noise conditions by weighting and combining information from different frequency ranges, thereby reducing the impact of low frequency environmental noise on the final delay estimation.
Data Source
AI summary
A beamforming system comprises an input module, a phase-difference module, a delay distribution module, and a delay estimation module configured to make a final delay estimation based on the delay distribution. The final delay estimation is applied to align one of two selected channels and combine the two channels to obtain a signal of interest. The phase-difference module calculates phase differences for a range of frequency bins. The delay estimation module considers all possible delays derived from the phase differences, including multiples of ±2π to overcome the ambiguity in high frequency bins when the spacing between two acoustic sensors is longer than the half of the wavelengths.