Slow-Time Modulation of Multiple Radar Channels for Angular Resolution
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Solution Overview
Problem
MIMO radar systems face challenges in increasing the quantity of channels while maintaining high angular resolution, signal-to-noise ratio (SNR), and Doppler dynamic range, which can lead to missed detections of smaller objects like pedestrians next to larger ones.
Innovation Solution
A slow-time modulation process combining code-division multiplexing (CDM) and frequency-division multiplexing (FDM) is applied to modulate multiple radar channels, reducing signal residue and maintaining Doppler dynamic range, allowing for a greater number of channels without degrading performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the quantity of transmit and receive channels is increased to improve angular resolution, then angular resolution is improved, but signal-to-noise ratio deteriorates
Solution Approach 1:
The patent segments the channels into two distinct sets: a first set of transmit channels modulated with code sequences only, and a second set of transmit channels modulated with both code sequences and frequency phase shifts. This segmentation allows different modulation strategies to be applied to different channel groups, optimizing both angular resolution through multiple channels and signal-to-noise ratio through differentiated modulation that reduces interference and signal residue across the channel sets.
2Measurement precision
If the quantity of transmit and receive channels is increased to improve angular resolution, then angular resolution is improved, but Doppler dynamic range deteriorates
Solution Approach 1:
The patent applies dynamic modulation strategies where the second set of transmit channels uses frequency phase shifts that vary over time, creating time-varying modulation patterns. This dynamic approach allows the system to maintain Doppler dynamic range by introducing temporal variations that prevent signal residue accumulation, while still utilizing multiple channels for high angular resolution through the code sequence modulation component.
3Measurement precision
If the quantity of simultaneous-transmit channels is increased, then angular resolution is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal modulation framework where code sequences serve multiple functions: they provide channel identification, enable signal separation, and contribute to angular resolution enhancement. The same code sequences are applied across both sets of transmit channels, with the addition of frequency phase shifts for the second set. This multi-functionality reduces device complexity by reusing the same modulation components rather than requiring entirely separate modulation schemes for different channel sets.
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 enhances angular resolution and maintains SNR, enabling effective detection of both large and small objects even when close together, improving safety in automotive applications.
Implementation Method 1
A set of transmit channels are modulated using code sequences to phase-modulate transmission signals
Implementation Method 2
A second set of transmit channels are modulated using the same codes for phase modulation as well as using a frequency phase shift
Implementation Method 3
Demodulation is achieved by multiplying received signals by the code sequences
Implementation Method 4
Fast Fourier transforms (FFT) are applied to the received signals to generate a range-Doppler map for each receive channel
Implementation Method 5
A non-coherent integration is performed on the range-Doppler maps to form a range-Doppler average map
Data Source
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AI summary
This document describes techniques and systems directed at slow-time modulation for multiple radar channels. A set of transmit channels are modulated using code sequences to phase-modulate transmission signals. A second set of transmit channels are modulated using the same codes for phase modulation as well as using a frequency phase shift. Demodulation is achieved by multiplying received signals by the code sequences. Fast Fourier transforms (FFT) are applied to the received signals to generate a range-Doppler map for each receive channel. A non-coherent integration is performed on the range-Doppler maps to form a range-Doppler average map. The range-Doppler average map is shifted by the frequency phase shift, and the minimal of the range-Doppler average map and the shifted range-Doppler average map is retained. These techniques may reduce the impact of signal residue and increase angular resolution by enabling multiple transmit channels to be utilized.