研究目的
To study the frequency estimation of linear frequency modulated (LFM) signal with the STFT in the filtering viewpoint, focusing on the influence of the filter impulse response length on the time-frequency distribution (TFD) concentration.
研究成果
The study demonstrates that the optimal impulse response length for STFT in the filtering viewpoint depends on the IF slope of the LFM signal, with higher slopes requiring shorter lengths. The proposed method provides better time-frequency concentration than traditional STFT under the same resolution, and it allows for selective frequency band computation to reduce costs.
研究不足
The method is primarily effective for linearly modulated signals; for signals with nonlinear frequency modulation, the advantage is less obvious and requires further study. The approach may not generalize well to all nonstationary signals.
1：Experimental Design and Method Selection:
The study uses the STFT from a filtering viewpoint, treating it as a filter bank with adjustable impulse response lengths. Simulations are conducted to analyze LFM signals with varying frequency modulation parameters.
2：Sample Selection and Data Sources:
Simulated LFM signals (e.g., z1(t), z2(t), z3(t), z4(t)) are generated with specific instantaneous frequency functions and durations.
3：List of Experimental Equipment and Materials:
No specific equipment mentioned; simulations are likely performed using computational tools.
4：Experimental Procedures and Operational Workflow:
For each signal, TFDs are computed using filter banks with different impulse response lengths (e.g., 40, 80, 100, 150 samples for z1(t)), and the concentration is measured.
5：Data Analysis Methods:
The time-frequency concentration M(l) is calculated based on TFD magnitude, and optimal filter length is determined using argmax function.
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