DDM Radar Target Detection for Velocity Ambiguity Resolution
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Solution Overview
Problem
Existing DDM radar systems face challenges in resolving velocity ambiguities due to undersampling, leading to non-unambiguous range in the velocity dimension, especially when the number of transmission antennas is smaller than the number of slots, which conventional algorithms struggle to address effectively.
Innovation Solution
A method involving the conversion of the range-Doppler matrix into a three-dimensional range-Doppler ambiguity matrix through non-coherent cyclic discrete convolution with a DDM code, followed by cell-by-cell comparison with a threshold matrix, utilizing a kernel defined by the DDM code to resolve velocity ambiguities and achieve a non-coherent integration gain, thereby enhancing signal-to-noise ratio and enabling detection of multiple targets with the same ambiguous velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of transmission antennas is smaller than the number of slots in DDM radar, then device complexity is reduced, but velocity ambiguity resolution capability deteriorates
Solution Approach 1:
The patent transforms the velocity ambiguity resolution from a 2D problem (range-Doppler matrix) to a 3D problem by introducing the ambiguity dimension. The range-Doppler ambiguity matrix adds a third dimension that explicitly represents different velocity ambiguity zones, allowing the system to resolve ambiguities by analyzing signal distribution across this additional dimension rather than being constrained by the limited antenna count.
Solution Approach 2:
The patent segments the velocity measurement space into multiple ambiguity zones along the Doppler dimension. By dividing the velocity range into distinct zones and assigning each zone to specific slots, the system can identify which zone contains the true target velocity. This segmentation allows conventional algorithms to work effectively within each zone while the overall ambiguity is resolved through zone identification.
2Productivity
If conventional algorithms are used for velocity ambiguity resolution, then computational simplicity is maintained, but resolution accuracy deteriorates
Solution Approach 1:
The patent introduces an intermediary processing step that converts the range-Doppler matrix into a range-Doppler ambiguity matrix using non-coherent cyclic discrete convolution with the DDM code. This intermediary transformation prepares the data in a format that makes velocity ambiguity resolution more effective, bridging the gap between simple conventional algorithms and the need for accurate ambiguity resolution.
3Measurement precision
If high-resolution velocity measurement is achieved through DDM modulation, then measurement precision is improved, but device complexity increases due to phase shifters for each antenna
Solution Approach 1:
The patent makes the DDM code and phase shifters configurable and adaptable to different operational requirements. The system can adjust the DDM code assignment and phase shifter settings based on the number of available antennas and the desired velocity measurement range, allowing the same hardware to achieve high-resolution velocity measurement under different conditions without requiring dedicated phase shifters for every possible slot configuration.
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
The method achieves improved resolution of velocity ambiguities with a non-coherent integration gain of approximately 7 log10 NTX dB, allowing for higher signal-to-noise ratio and the detection of multiple targets with the same ambiguous velocity, while reducing storage requirements and computational effort.
Implementation Method 1
The DDM phase modulator comprises a phase shifter for each of the simultaneously active transmission antennas, which rotates the phase of the signal forwarded to the antenna so that the phase of the signal transmitted in the current chirp is rotated by a certain angle compared to the phase of the previous chirp
Implementation Method 2
This phase progression from chirp to chirp has the same effect on the received signal as the Doppler shift caused by the radar target's own movement. In this way, each transmission antenna is characterized by a characteristic 'virtual' Doppler shift
Implementation Method 3
Distance information about the localized radar targets can then be obtained by mixing the received radar echo with a portion of the transmission signal, so that by beating a lower frequency signal is obtained, the frequency of which corresponds to the frequency difference between the transmitted and received signal
Implementation Method 4
The plurality of transmission antennas of the radar sensor are spatially offset from one another, thus making angularly resolved localization of radar targets possible
Data Source
AI summary
A method for target detection in a DDM radar sensor having a number NTX of transmission antennas Tx and a number NSlots>NTX of DDM slots, the assignment of which to transmission antennas is determined by a DDM code. The method includes: calculating a range-Doppler matrix, which is divided in the Doppler dimension into NSlots ambiguity zones; converting the range-Doppler matrix into a three-dimensional range-Doppler ambiguity matrix by converting the range-Doppler matrix into a three-dimensional range-Doppler ambiguity matrix by non-coherent cyclic discrete convolution with the DDM code; and target detection by cell-by-cell comparison of the range-Doppler ambiguity matrix (34) with a threshold matrix.