Phase-Coded FMCW MIMO Radar for Cross-Correlation Residue Removal
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Solution Overview
Problem
Existing MIMO radar systems face challenges in scalability and dynamic range degradation due to the use of code division multiple access (CDMA) schemes, particularly when a large number of transmitters are active, leading to reduced orthogonality ratios and hidden targets.
Innovation Solution
Implementing phase-modulated frequency-modulated continuous wave (PM-FMCW) signals with CDMA phase-codes within individual chirps and applying two-dimensional iterative residue cancellation to align and remove cross-correlation residues, enhancing the dynamic range and target detection capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CDMA phase codes are used for MIMO radar multiplexing, then the number of simultaneously active transmitters can be increased without limiting unambiguous velocity, but the dynamic range and orthogonality ratio degrade proportionally to the number of active transmit elements
Solution Approach 1:
The patent extracts and removes the harmful cross-correlation residues from the received signal through iterative residue cancellation processing. By identifying and subtracting the cross-correlation components between different transmit elements' phase codes, the system eliminates the degradation effect while maintaining the benefits of multiple active transmitters
Solution Approach 2:
The patent implements iterative residue cancellation where the processed signal from one iteration feeds into the next iteration. The cross-correlation residues identified in each iteration are subtracted from the signal, and the process repeats with the cleaned signal, progressively improving dynamic range while maintaining scalability to multiple transmitters
2Measurement precision
If the code length is increased to improve orthogonality ratio, then the dynamic range improves, but the number of chirps required increases which conflicts with the requirement for adequate chirp length
Solution Approach 1:
The patent introduces an intermediate processing stage (residue cancellation) between the standard CDMA processing steps. This intermediary processing removes cross-correlation residues without requiring longer codes or more chirps, thus improving orthogonality performance while maintaining the original frame rate and chirp length requirements
3Reliability
If more transmitters are added to improve coverage and detection capability, then the system becomes more robust, but the cross-correlation residues from stronger targets mask weaker targets
Solution Approach 1:
The patent converts the harmful cross-correlation residues into a detectable and removable component. By explicitly calculating the cross-correlation between different transmit phase codes and subtracting these residues from the received signal, the system transforms the masking effect into a manageable interference that can be eliminated, thereby improving weak target detection while maintaining multiple transmitters for robust coverage
Data Source
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AI summary
Aspects of this disclosure are directed to systems and a method of operating a MIMO radar system for automotive applications, comprising, transmitting FMCW, signals from first and second transmitters; wherein the signals each comprise a plurality of chirps, and each signal comprises phase modulation of the FMCW signal within each chirp by a respective CDMA phase-code to produce a respective first and second PM-FMCW signal; receiving a composite signal comprising at least one reflection the first PM-FMCW signal and the second PM-FMCW signal; and processing, in the digital domain, a plurality of down-converted and pre-processed groups of samples of the composite signal by: applying a frequency-response-correction; applying a group delay filter; removing the CDMA phase-code; applying a 2D-FFT; and removing phase-code cross-correlation residue from the respective transformed demodulated groups of samples by calculating an estimated residue and subtracting the estimated residue from the respective transformed demodulated signal.