MIMO Radar Phase Scrambling for Doppler Spur Suppression
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Solution Overview
Problem
Radar systems with multiple input multiple output (MIMO) face issues with phase errors leading to spurious frequencies in the Doppler spectrum, which can be mistaken for true reflectors, degrading sensitivity and detection accuracy.
Innovation Solution
A MIMO radar system employs Doppler Division Multiplexing (DDM) and scrambling phase rotations applied to each output radar signal by phase rotators, spreading the energy of spurious frequencies over the Doppler spectrum, thereby reducing the likelihood of clear spurs developing above the noise floor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If DDM phase rotation is applied to each transmit path, then the radar signals can be multiplexed across Doppler frequencies, but phase errors cause spurious frequencies that degrade sensitivity and create false detections
Solution Approach 1:
The patent converts the harmful effect of phase errors that create concentrated spurious frequencies into a beneficial spreading effect across the Doppler spectrum. By applying scrambling phase rotations, the energy of spurious frequencies is dispersed throughout the spectrum rather than concentrated at specific frequencies, transforming the harm into a benefit where the spurious energy becomes indistinguishable from thermal noise.
Solution Approach 2:
The patent changes the phase parameter of the transmitted signals by applying scrambling phase rotations that vary across different transmit paths. This parameter change ensures that spurious frequencies are spread across the Doppler spectrum rather than concentrated, thereby improving detection accuracy while maintaining the multiplexing capability.
2Reliability
If multiple transmit paths use the same scrambling phase rotation, then spurious frequency energy is spread across the Doppler spectrum, but this increases the complexity of phase rotation control
Solution Approach 1:
The patent implements a universal phase rotation controller that manages the scrambling phase rotations for all transmit paths simultaneously. This single controller performs multiple functions including generating scrambling sequences, applying phase rotations to multiple paths, and coordinating the spreading of spurious frequency energy across the Doppler spectrum, thereby reducing overall system complexity.
3Measurement precision
If scrambling phase rotations are applied to spread spurious frequency energy, then false detections are reduced, but the signal processing complexity increases
Solution Approach 1:
The patent applies scrambling phase rotations to the transmitted signals before they are sent out, performing the spreading action in advance. This preliminary action ensures that when the signals are received and processed, the spurious frequency energy is already distributed across the Doppler spectrum, simplifying the receiving signal processing compared to attempting to spread the energy after reception.
Data Source
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AI summary
A MIMO radar system comprising: a plurality of transmit paths wherein each transmit path is configured to transmit a corresponding output radar signal, wherein each transmit path comprises: a transmit antenna; a phase rotator; and wherein the phase rotator is configured to, for each output radar signal, apply: a DDM phase rotation to each output radar signal prior to transmission by the transmit antenna, and, a scrambling phase rotation to each output radar signal prior to transmission by the transmit antenna, wherein: the DDM phase rotation applied by each phase rotator is according to a DDM phase schedule; and the scrambling phase rotation applied by each phase rotator is the same as the scrambling phase rotation applied by each other phase rotator; and wherein the MIMO system further comprises a plurality of receive paths configured to receive reflected versions of the output radar signals from a reflector.