Radar Code Multiplexing With Longer Sequences for Doppler Clarity
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Solution Overview
Problem
Existing radar systems, particularly MIMO radar, face challenges in accurately detecting targets due to Doppler aliasing, which limits the Doppler frequency range and causes ambiguity in determining Doppler components, thereby reducing target detection accuracy.
Innovation Solution
A radar apparatus employing code multiplexing transmission using orthogonal codes with longer code lengths and additional unused codes for Doppler frequency aliasing determination, expanding the Doppler frequency range detectable without ambiguity and improving target detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If code multiplexing transmission is used with shorter code lengths, then the device complexity is reduced, but Doppler aliasing occurs and target detection accuracy deteriorates
Solution Approach 1:
The patent changes the code length parameter from short to long (specifically code length ≥ 8) to eliminate Doppler aliasing and improve target detection accuracy. This parameter change resolves the contradiction by accepting increased code sequence complexity as necessary for achieving accurate target detection without aliasing effects.
Solution Approach 2:
The patent performs preliminary code sequence generation with predetermined lengths (≥8) before transmission to prevent Doppler aliasing from occurring in the first place. By preparing long code sequences in advance, the system proactively eliminates the need for complex aliasing correction during target detection, thereby improving accuracy while managing complexity through pre-computation.
2Adaptability or versatility
If the Doppler frequency range is expanded, then target detection capability is improved, but inter-code interference increases
Solution Approach 1:
The patent converts the potentially harmful inter-code interference into a beneficial effect by using long code sequences (≥8) that provide sufficient orthogonality. The extended code length creates a natural barrier against interference, allowing the system to expand the Doppler frequency range without suffering from degraded performance due to inter-code interference.
Solution Approach 2:
The long code sequences act as an intermediary mechanism that mediates between the desire for expanded Doppler frequency range and the harmful inter-code interference. The code sequences with length ≥8 serve as a buffer that maintains signal distinguishability even when the Doppler range is extended, thereby enabling wider detection capability without proportional increase in interference.
3Measurement precision
If code length is increased to eliminate Doppler aliasing, then target detection accuracy is improved, but signal processing time increases
Solution Approach 1:
The patent performs preliminary computation of long code sequences (≥8) before the actual signal transmission and processing. By pre-generating and storing these code sequences, the system eliminates the need for time-consuming real-time computation during target detection, thereby reducing the effective processing time while maintaining high Doppler frequency measurement accuracy.
Solution Approach 2:
The patent uses a moderate code length (≥8) that provides sufficient accuracy to eliminate Doppler aliasing without excessive length that would cause significant processing time increase. This partial action approach finds the optimal balance point where code length is long enough to resolve aliasing but not so long as to cause unacceptable processing delays.
Data Source
AI summary
This radar device comprises a signal generation circuit for generating a baseband signal, a code generation circuit for generating a plurality of code sequences, a phase rotation circuit for applying phase rotation based on one of the code sequences from among the plurality of code sequences to the baseband signal and generating a plurality of code multiplexed transmission signals, and a plurality of transmission antennas for transmitting the plurality of transmission signals. The code length of the plurality of code sequences is greater than the code multiplexing number of the plurality of transmission signals.