Micro-Doppler Spectrogram Periodicity Detection
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Solution Overview
Problem
Current radar sensor systems face challenges in reliably identifying objects, particularly pedestrians and cyclists, due to varying speeds and the need for long observation times, as well as limitations in Fourier analysis for periodic motion detection.
Innovation Solution
A method involving the determination of periodicity quantities from Micro-Doppler spectrograms by fitting smoothed curves to periodic signal components, adapting to speed variations, and using recursive state estimators for accurate peak and valley identification, allowing for reliable object recognition even under adverse conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fourier analysis is used to determine repetition frequency of patterns in Micro-Doppler spectrogram, then measurement precision of periodicity quantity is improved, but observation time required increases significantly
Solution Approach 1:
The patent extracts only the essential periodic information from the Micro-Doppler spectrogram by identifying peak positions and calculating time differences between consecutive peaks, rather than performing a complete Fourier analysis. This extraction approach achieves sufficient periodicity measurement without requiring the full computational process and long observation time of Fourier methods.
Solution Approach 2:
The patent applies partial action by using a simplified method that performs only the necessary steps for periodicity detection (peak identification and time difference calculation) without executing the complete Fourier analysis procedure. This partial approach provides adequate measurement precision for the application while significantly reducing the required observation time.
2Measurement precision
If Fourier analysis is used for periodic motion detection, then measurement precision of periodicity is improved, but device complexity and computational requirements increase
Solution Approach 1:
The patent extracts only the critical elements needed for periodic motion detection - the peak positions in the Micro-Doppler spectrogram - and calculates periodicity directly from these extracted features. This avoids the complex mathematical transformations of Fourier analysis while maintaining sufficient detection accuracy for practical applications.
Solution Approach 2:
Instead of applying the conventional Fourier analysis approach that transforms time-domain signals to frequency-domain spectra, the patent inverts the approach by directly analyzing the time-domain characteristics of the Micro-Doppler spectrogram peaks to determine periodicity, thereby simplifying the computational process.
3Measurement precision
If Fourier analysis is used assuming constant speed, then measurement precision is improved for stationary objects, but reliability decreases for objects with varying speed
Solution Approach 1:
The patent implements a dynamic approach by continuously tracking the positions of peaks in the Micro-Doppler spectrogram over time and calculating periodicity based on actual observed peak intervals. This dynamic method adapts to changing object speeds without requiring the constant speed assumption that limits Fourier analysis, thereby maintaining reliability under varying motion conditions.
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
Enables reliable identification of periodic motion components with short observation times and varying speeds, improving object classification accuracy in real-world scenarios.
Implementation Method 1
Often, the known Doppler effect is used to gather information relating to moving objects. The Doppler effect or Doppler shift is a change in frequency observed when a wave source moves relative to the receiver.
Data Source
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AI summary
In a method for the recognition of an object by means of a radar sensor system, a primary radar signal is transmitted into an observation space, a secondary radar signal reflected by the object is received, a Micro-Doppler spectrogram of the secondary radar signal is generated, and at least one periodicity quantity relating to an at least essentially periodic motion of a part of the object is determined based on the Micro-Doppler spectrogram. The determining of the at least one periodicity quantity includes the following steps: (i) determining the course of at least one periodic signal component corresponding to an at least essentially periodic pattern of the Micro-Doppler spectrogram, (ii) fitting a smoothed curve to the periodic signal component, (iii) determining the positions of a plurality of peaks and/or valleys of the smoothed curve, and (iv) determining the periodicity quantity based on the determined positions of peaks and/or valleys.