MIMO Radar Modulation With FS-CDM for Low-Residue Target Detection
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Solution Overview
Problem
MIMO radar systems face challenges with increased noise floor and reduced Doppler dynamic range due to higher correlation and cross-channel residue, which can obscure weaker targets, and existing modulation techniques like CDM, DDM, and hybrid CDM+DDM require excessive computational resources or longer processing times.
Innovation Solution
Implement frequency-shifting code-division multiplexing (FS-CDM) to orthogonalize transmit channels, reducing residue without costly REST processing, and alternate between FS-CDM and CDM signal processing modes based on target strength to generate an optimized data cube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional transmitter and receiver antennas are added to create MIMO radar systems, then detection resolution is improved, but noise floor increases due to higher correlation and cross-channel residue
Solution Approach 1:
The patent applies parameter changes by introducing frequency shifting as a new parameter in the modulation scheme. Each transmit channel is assigned a unique frequency offset, transforming the frequency-domain representation of the radar signals. This frequency differentiation parameter allows the system to distinguish between signals from different transmit channels, thereby reducing cross-channel residue and noise floor interference while maintaining the benefits of MIMO radar with multiple antennas.
2Object-affected harmful factors
If REST techniques are used to reduce residue, then cross-channel residue is reduced, but computational complexity and processing time increase
Solution Approach 1:
The patent replaces the computationally intensive REST (Residue Estimation and Subtraction) processing mechanism with a frequency-shifting-based signal separation approach. Instead of using complex computational methods to estimate and subtract residue, the system uses frequency-domain differentiation to naturally separate signals from different transmit channels. This substitution of the processing mechanism dramatically reduces computational complexity while achieving the same goal of reducing cross-channel residue.
3Productivity
If CDM modulation technique is used, then multiple data signals can be transmitted simultaneously, but Doppler domain dynamic range is restricted due to decoding residue
Solution Approach 1:
The patent introduces a frequency dimension as an additional separation parameter alongside the code dimension used in CDM. By combining frequency shifting with code-division multiplexing, the system creates a two-dimensional separation space (frequency × code) that allows for more effective signal differentiation. This dimensional expansion enables the system to maintain high signal transmission capacity while achieving superior Doppler domain dynamic range by utilizing both frequency and code characteristics for signal identification and separation.
Data Source
AI summary
Radar systems and methods are provided and include transmitting radar signals with multiple transmit channels using a modulation technique and a frequency shift amount such that radar signals are shifted in frequency from adjacent transmit channels. Received radar signals are processed using first and second signal processing modes. In the first signal processing mode, virtual channel demodulation is performed by matching received radar signals within a radar chirp to a first transmit channel and performing Doppler FFT and range shifting. In the second signal processing mode, virtual channel demodulation is performed by matching received radar signals to a corresponding transmit channel and performing Doppler FFT without range shifting. An optimized data cube is generated based on data cubes from the signal processing modes and based on a strength of a target represented in the data cubes.