TDM-MIMO Radar Spatial Phase Change Rate for Doppler Unambiguity
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Solution Overview
Problem
Existing TDM MIMO FMCW radar systems face challenges in resolving velocity-induced phase ambiguity, leading to frequency folding and limitations in detecting radial velocities beyond a certain threshold, which affects the accuracy of angle-of-arrival computations.
Innovation Solution
A method is proposed to resolve phase ambiguity by computing a spatial phase change rate and predicting spatial phase shifts between subarrays, allowing for the determination of residual phase shifts and subsequent inversion to eliminate velocity-induced and folding-induced phase shifts in the virtual array signal, thereby enhancing the accuracy of angle-of-arrival estimations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Doppler correction is applied using apparent Doppler frequency, then velocity-induced phase shifts are compensated, but phase ambiguity remains when velocity exceeds maximum unambiguously detectable speed
Solution Approach 1:
The patent transitions from one-dimensional Doppler frequency analysis to two-dimensional spatial phase analysis by computing spatial phase change rates across multiple subarrays. This dimensional expansion allows resolution of velocity ambiguity that cannot be resolved within the single-dimensional Doppler spectrum, as the spatial distribution of phase changes provides additional constraints for disambiguation.
Solution Approach 2:
The patent introduces spatial phase change rate as an intermediary parameter that mediates between the observed phase shifts and the true velocity. By computing how phase changes spatially across subarrays, this intermediary provides a bridge to resolve the ambiguity between apparent and true Doppler frequencies, enabling accurate velocity determination beyond the conventional unambiguous range.
2Measurement precision
If TDM MIMO radar uses multiple physical transmitters, then virtual array elements increase improving AoA resolution, but velocity-induced phase shifts between subarrays cause measurement errors
Solution Approach 1:
The patent segments the virtual array into multiple subarrays, each associated with a specific physical transmitter. By analyzing spatial phase change rates within and between these segmented subarrays, the system can identify and correct velocity-induced phase shifts that would otherwise corrupt the AoA measurements from the expanded virtual array.
Solution Approach 2:
The patent changes the parameter being analyzed from raw phase shifts to spatial phase change rates. This parameter transformation reveals the velocity-induced components that systematically vary across subarrays, allowing their separation from the AoA-dependent phase components and enabling reliable measurements despite the presence of multiple transmitters.
3Ease of operation
If conventional Doppler correction is used, then computation is simple, but detectable velocity range is limited to maximum unambiguously detectable speed
Solution Approach 1:
The patent performs preliminary computation of spatial phase change rates across subarrays before final velocity determination. This preliminary action extracts the velocity-dependent phase components in advance, allowing the system to handle higher velocities while maintaining computational efficiency through a structured two-stage process rather than brute-force methods.
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 computationally efficient phase ambiguity resolution, improving the accuracy of angle-of-arrival computations and extending the detectable velocity range beyond the maximum unambiguously detectable speed, making the system suitable for higher-speed objects.
Implementation Method 1
the subarrays of virtual antenna elements will be separated by relative velocity-induced phase shifts. With knowledge of the radial velocity of the moving object, it is possible to compensate the velocity-induced phase shifts (Doppler correction).
Implementation Method 2
a spatial phase change rate with respect to the first direction is computed based on elements of the compensated virtual array signal corresponding to one subarray at a time
Data Source
AI summary
A TDM MIMO FMCW radar comprises an array of physical receivers with a first spacing in a first direction and a plurality of physical transmitters arranged with a second spacing in said first direction. A virtual array signal of a range-Doppler bin relating to a scene with a moving object is processed by a phase compensation method, which introduces a phase ambiguity between the subarrays. A positive or negative spatial phase change rate with respect to the first direction is computed based on elements of the compensated virtual array signal corresponding to one subarray at a time. From this, based on the spacings, a spatial phase change between a pair of the subarrays is predicted. Next, a residual phase shift between said pair of subarrays is determined by comparing an actual phase shift of the compensated virtual array signal and the predicted spatial phase shift.