Beat Frequency Spectrogram Matching for FMCW Drift Compensation
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Solution Overview
Problem
Nonlinearity in frequency modulated signals in FMCW radar systems causes energy diffusion and frequency drift, affecting the accuracy of speed and distance estimation of target objects, and conventional iterative correction methods fail due to external interference.
Innovation Solution
Determine a 2D time frequency spectrogram of the beat frequency signal, perform matching with theoretical spectrograms to identify a target spectrogram with a preset threshold, and use flight time and Doppler frequency offset to accurately estimate distance and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional iterative correction methods are used to correct nonlinearity of frequency modulated signals, then the output frequency can be adjusted based on previous measurements, but the correction becomes invalid when external factors like temperature and vibration cause frequency drift between measurements
Solution Approach 1:
The patent pre-calculates and stores a comprehensive correction lookup table containing correction values for multiple possible frequency differences before actual measurement occurs. This preliminary preparation ensures that when external factors cause frequency drift, the system can immediately find the appropriate correction value in the pre-built table without relying on previous measurements, thus maintaining correction validity under varying environmental conditions.
2Measurement precision
If frequency modulated signal generation is performed, then speed and distance of target objects can be measured, but nonlinearity in the frequency modulated signal causes energy diffusion and frequency drift that reduce estimation accuracy
Solution Approach 1:
The system pre-calculates the relationship between frequency differences and correction values, storing this correction map in a lookup table before actual radar measurement. When frequency drift occurs due to nonlinearity, the system quickly retrieves the appropriate correction from the pre-prepared table based on the detected frequency difference, thereby compensating for energy diffusion and frequency drift effects without real-time complex calculations.
Solution Approach 2:
The patent implements a feedback mechanism where the actual frequency of the frequency modulated signal is detected and compared with the ideal frequency. The frequency difference is used to index into the correction lookup table to obtain a correction value, which is then applied to adjust subsequent frequency modulated signal generation. This closed-loop feedback continuously compensates for nonlinearity-induced energy diffusion and frequency drift.
3Adaptability or versatility
If drive current is adjusted based on frequency difference from previous measurement, then output frequency can be corrected iteratively, but the correction fails when frequency does not match expected value due to external interference
Solution Approach 1:
Instead of relying on iterative correction from previous measurements, the patent pre-calculates correction values for a wide range of possible frequency differences and stores them in a lookup table. This preliminary preparation allows the system to directly find the appropriate correction for the actual frequency difference without iterative adjustments, making the system adaptable to various frequency drift conditions caused by external interference while maintaining high frequency matching accuracy.
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
Accurately estimates speed and distance of target objects despite nonlinear frequency modulated signals, unaffected by external factors like temperature and vibration, improving estimation accuracy.
Implementation Method 1
The frequency mixer performs frequency mixing on the echo signal and the local-frequency signal to generate a beat frequency signal
Implementation Method 2
Finally, the ADC converts the beat frequency signal from an analog signal to a digital signal to obtain a sampled sequence of the beat frequency signal
Implementation Method 3
Fast Fourier transform (FFT) may be performed on the sampled sequence of the beat frequency signal to obtain a frequency of the beat frequency signal
Implementation Method 4
The frequency modulated signal generation module generates a frequency modulated radio frequency or laser signal (frequency modulated signal for short)
Implementation Method 5
The splitter splits the frequency modulated signal into two signals, where one signal serves as a local-frequency signal, and the other signal is transmitted to a target object under measurement
Implementation Method 6
the other signal is transmitted to a target object under measurement and reflected by a surface of the target object to form an echo signal
Data Source
AI summary
A beat frequency signal processing method includes determining a two-dimensional (2D) time frequency spectrogram of a beat frequency signal based on a sampled sequence of the beat frequency signal, where the 2D time frequency spectrogram indicates a relationship between a frequency and a time of the beat frequency signal; performing matching between the 2D time frequency spectrogram of the beat frequency signal and a plurality of theoretical 2D time frequency spectrograms to determine, as a target 2D time frequency spectrogram, a theoretical 2D time frequency spectrogram whose matching degree is greater than or equal to a preset threshold. The plurality of theoretical 2D time frequency spectrograms are 2D time frequency spectrograms of the beat frequency signal, under combinations of a plurality of flight times and a plurality of Doppler frequency offsets, that are calculated based on a frequency sweep curve of the frequency modulated signal.