Signal Processing Flashcards

What does `ifft(X)` compute in MATLAB?

Answer: The inverse discrete Fourier Transform of X

`ifft(X)` computes the inverse discrete Fourier Transform, converting frequency-domain data back to the time domain.

Which MATLAB function designs a Butterworth IIR filter given order n and normalized cutoff frequency Wn?

Answer: butter(n, Wn)

`butter(n, Wn)` returns the transfer function coefficients [b, a] of an nth-order Butterworth lowpass filter with cutoff Wn.

What does the MATLAB `spectrogram(x, window, noverlap, nfft, fs)` function display?

Answer: A time-frequency representation showing how spectral content changes over time

`spectrogram` computes and displays the short-time Fourier transform, showing how the frequency content of a signal varies with time.

Which MATLAB function estimates the power spectral density of a signal using Welch's averaged periodogram method?

Answer: pwelch(x)

`pwelch(x)` estimates the PSD by dividing the signal into overlapping segments, windowing each, computing FFTs, and averaging.

What is the primary purpose of the MATLAB `resample(x, p, q)` function?

Answer: To change the effective sampling rate of signal x by ratio p/q

`resample(x, p, q)` resamples signal x at p/q times the original sample rate using a polyphase filter.

Which MATLAB function finds local maxima (peaks) in a data vector and returns their values and locations?

Answer: findpeaks(x)

`findpeaks(x)` returns the values and indices of local maxima in vector x, with optional threshold and prominence filtering.

The MATLAB `xcorr(x, y)` function computes:

Answer: The cross-correlation sequence of signals x and y

`xcorr(x, y)` returns the cross-correlation sequence estimating the similarity between x and y as a function of lag.