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lpdfilter

Low-pass derivative filter.

Syntax

function [b, delay] = lpdfilter(fs, stopFreq, varargin)

Description

B = LPDFILTER(FS, STOPFREQ) designs a low-pass derivative (LPD) linear-phase FIR filter with a specified sampling frequency FS and stop-band frequency STOPFREQ. using least-squares estimation.

B = LPDFILTER(..., Name, Value) allows specifying additional options using name-value pairs. - 'PassFreq' - Pass-band frequency in Hz (positive scalar). Must be less than STOPFREQ. If not specified, defaults to (STOPFREQ - 0.2) Hz. - 'Order' - Filter order (positive even integer). If not specified, automatically calculated based on transition band requirements.

[B, DELAY] = LPDFILTER(...) also returns the filter delay, which is half the filter order.

Source Code

View source code

Examples

% Design filter and visualize the frequency response
fs = 100;
[b, delay] = lpdfilter(fs, 10);

[h, w] = freqz(b, 1, 2^16);
figure;
plot(w*fs/(2*pi), abs(h)/max(abs(h)));
title('Normalized Frequency Response');
xlabel('Frequency (Hz)');
ylabel('Magnitude');
grid on;

% Apply filter to a signal and compensate delay
signalFiltered = filter(b, 1, signal);
signalFiltered = [signalFiltered(delay+1:end); zeros(delay, 1)];

See Also

Module: TOOLS | Last Updated: 2025-09-04