TDM-MIMO Radar Multipath Ambiguity Resolution
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Solution Overview
Problem
Conventional TDM MIMO FMCW radars face challenges in discriminating target detections from first-order multipath detections, leading to false alarms and target-tracking confusion due to unwanted echoes from reflective surfaces, and existing methods require dynamic scene information or complex computations.
Innovation Solution
A computationally efficient method for resolving multipath ambiguity in TDM MIMO FMCW radars using a simple test based on phase differences in the angle spectrum, requiring only static information about the radar's geometry and signal waveform, to distinguish between direct reflections and first-order multipath artefacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TDM MIMO FMCW radar is used to monitor moving objects, then target detection capability is achieved, but multipath artefacts cause false alarms and tracking confusion
Solution Approach 1:
The patent applies phase conjugation (inversion) to the steering vector corresponding to the leading peak in the angle spectrum. By multiplying the virtual array signal by the conjugate of the steering vector, the method inverts the phase characteristics of the multipath artefact, causing it to align constructively and enable its identification and removal through threshold-based detection.
Solution Approach 2:
The patent extracts the multipath artefact component from the radar signal by identifying the leading peak in the angle spectrum, computing its steering vector, and using phase conjugation to isolate this component. The extracted artefact is then removed from the original signal, leaving only the clean target detection components.
2Measurement precision
If existing multipath mitigation methods are used, then multipath discrimination capability is improved, but dynamic scene information or complex computations are required
Solution Approach 1:
The method uses the signal's own angular spectrum characteristics to identify and remove multipath artefacts. By computing the angle spectrum from the virtual array signal and identifying the leading peak, the system uses inherent signal properties rather than external dynamic scene information, achieving self-contained multipath mitigation.
Solution Approach 2:
The patent transforms the signal processing approach by working in the angular spectrum domain rather than directly in the time or frequency domain. By computing the angle spectrum and operating on phase parameters of the steering vector, the method simplifies the detection and removal process compared to conventional approaches that require complex scene modeling.
Data Source
Figure 1A~2B
Figure 3A~4A
Figure 4B~5
AI summary
A TDM MIMO FMCW radar comprises at least one row of physical receivers with a first spacing (dr) in a first direction, and further comprises a plurality of physical transmitters arranged with a second spacing (dt) in said first direction. To determine whether a peak in an angle spectrum corresponds to a direct reflection or a first-order multipath artefact, an inverse phase-shift vector corresponding to a phase (ϕ̂1) of the peak is applied and a constant signal with the amplitude of the peak is subtracted. To the thus obtained intermediate signal (v), a further inverse phase-shift vector - now corresponding to an offset phase (Δϕ̂) of the two leading peaks of the angle spectrum - after which a constant signal is subtracted. It is then detected whether the thus obtained test signal (w) has any non-noise content. If yes, the peak corresponds to a multipath artefact, and otherwise to a direct reflection.