Radar Signal Processing Using Spano Code Sequences
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Solution Overview
Problem
Conventional radar apparatuses experience interference and degraded correlation characteristics in reception signals due to phase rotation caused by Doppler frequency variations, particularly when a reflection wave signal from one transmission cycle is received in a subsequent cycle.
Innovation Solution
The radar apparatus employs a Spano code sequence with 2N+1 codes, where the transmission signal is generated by multiplying one code from the sequence by a first and second interference suppression code, ensuring that the sum of inner products of codes over two times 2N+1 cycles equals zero, effectively canceling interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional radar transmission methods are used, then the radar system can transmit signals, but interference occurs in reception signals due to phase rotation from Doppler frequency variation
Solution Approach 1:
The patent changes the code parameters by using Spano codes with specific mathematical properties (sum of inner products equals zero) and alternates between different code sequences in adjacent transmission cycles. This parameter change in the transmission signal structure compensates for phase rotation effects caused by Doppler frequency variation, thereby suppressing interference in reception signals while maintaining reliable target detection
Solution Approach 2:
The patent implements periodic action by alternating between different Spano code sequences in adjacent transmission cycles. This periodic variation in code selection creates a transmission pattern that systematically counteracts the phase rotation effects, allowing the radar to suppress interference while maintaining continuous operation
2Measurement precision
If radar transmits signals in multiple cycles, then measurement accuracy can be improved, but interference from previous transmission cycles degrades correlation characteristics
Solution Approach 1:
The patent changes the code parameters across transmission cycles by using Spano codes with zero-sum inner product properties and alternating between different code sequences. This parameter variation ensures that correlation calculations across multiple cycles remain accurate despite the presence of reflection waves from previous cycles, preventing information loss while improving measurement precision through multi-cycle integration
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 suppresses interference and maintains correlation characteristic integrity even with phase rotation, ensuring accurate target detection across varying environmental conditions.
Implementation Method 1
radar apparatus which transmit a radio-frequency signal (e.g., microwave signal or millimeter wave signal)
Implementation Method 2
phase rotation occurs in a reception signal due to a Doppler frequency variation (e.g., in a case that a target moves during a measurement)
Data Source
AI summary
A transmission signal generating unit generates a transmission signal by multiplying one (selected in prescribed order) of 2N+1 (N: an integer of 1 or more) codes of a Spano code sequence by one code (selected in prescribed order), having a length 1, of one of a first code or a second code each having a code length 2N+1 in every transmission cycle. A transmission RF unit converts the transmission signal into a radio-frequency radar transmission signal and transmits it from a transmission antenna. As for codes used in adjacent two transmission cycles for two times 2N+1 transmission cycles, the sum total of inner products of codes having a length 1 of the first code, inner products of codes having a length 1 of the second code, and inner products of codes of the first code and the second code becomes equal to 0.