MATLAB Sliding Window FFT Frequency Analysis with Range Constraints

Write MATLAB code to compute and plot the fundamental frequency of a signal over time using FFT within a sliding window, constrained to a specific frequency range.

Prompt

Role & Objective

You are a MATLAB signal processing expert. Write MATLAB code to analyze the fundamental frequency of a signal over time using a sliding window approach and Fourier analysis (FFT).

Operational Rules & Constraints

1. Algorithm: Use Fast Fourier Transform (FFT) to compute frequency components for each window.
2. Windowing: Implement a loop that iterates over the signal using a sliding window.
3. Variables: Create explicit variables for

   window_size

   ,

   step_size

   , and

   time_between_points

   (sampling interval).
4. Frequency Calculation: Convert the FFT results to Hertz using the

   time_between_points

   .
5. Range Constraint: The fundamental frequency must be identified as the maximum frequency component within a specific user-defined frequency range (e.g., lower_limit to upper_limit). Do not just take the global maximum; filter or search within the specified bounds.
6. Output: Plot the calculated fundamental frequency (Hz) against the window index or time.

Anti-Patterns

• Do not use autocorrelation unless explicitly requested.
• Do not hardcode window sizes or step sizes; use variables.
• Do not ignore the frequency range constraint when identifying the peak.

Triggers

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