MIMO Radar Orthogonal Code Asymmetry for Doppler Interference
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Solution Overview
Problem
MIMO radar devices face interference issues between code multiplexed signals due to Doppler frequency shifts, leading to deteriorated positioning performance and increased likelihood of incorrect or failed target detection.
Innovation Solution
The radar device employs orthogonal code sequences with a predetermined code length, where the second half elements are arranged in reverse order of the first half elements, and these sequences are used to generate transmission code sequences by multiplying elements of a predetermined pulse sequence, reducing interference between code multiplexed signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If orthogonal code sequences are used for code multiplexing in MIMO radar, then the ability to detect multiple targets simultaneously is improved, but interference between code multiplexed signals increases due to Doppler frequency shifts
Solution Approach 1:
The patent applies asymmetry by designing orthogonal code sequences where the second half elements are arranged in reverse order of the first half elements. This asymmetric structure creates a specific correlation property that reduces interference between code multiplexed signals when Doppler frequency shifts occur, while maintaining the orthogonality needed for multi-target detection capability
Solution Approach 2:
The patent changes the structural parameter of the code sequences by imposing the constraint that the second half elements are reverse-ordered relative to the first half. This parameter modification alters the correlation characteristics of the codes, making them more robust against Doppler-induced interference while preserving their orthogonality for signal separation
2Measurement precision
If code length is increased to reduce peak sidelobe ratio, then range resolution is improved, but the required reception dynamic range becomes wider
Solution Approach 1:
The patent uses composite code structures by combining orthogonal code sequences with the specific constraint of reverse-ordered second half elements. This composite approach creates a code structure that achieves low peak sidelobe ratio without requiring excessively long code lengths, thereby balancing range resolution with manageable reception dynamic range requirements
Data Source
AI summary
A radar device includes: radar transmitting circuitry which, in operation, generates Nt radar signals by modulating Nt transmission code sequences and transmits the radar signals via Nt transmission antennas, Nt being more than 1; and radar receiving circuitry which, in operation, receives reflection wave signals via Nr reception antennas and performs Doppler frequency analysis, Nr being more than 1. The radar transmitting circuitry stores a predetermined pulse sequence and Nt or more orthogonal code sequences, second half elements of the Nt or more orthogonal code sequences are arranged in an order reverse to first half elements of the Nt or more orthogonal code sequences and generates each of the Nt transmission code sequences by multiplying elements of the predetermined pulse sequence by elements of the Nt or more orthogonal code sequences different from each other.