dfilt.dfasymfir (Signal Processing Toolbox)

Discrete-time, direct-form antisymmetric FIR filter

Syntax

Hd = dfilt.dfasymfir(b)
Hd = dfilt.dfasymfir

Description

Hd = dfilt.dfasymfir(b) returns a discrete-time, direct-form, antisymmetric FIR filter, Hd, with numerator coefficients b.

Hd = dfilt.dfasymfir returns a default, discrete-time, direct-form, antisymmetric FIR filter, Hd, with b=1. This filter passes the input through to the output unchanged.

Note Only the first half of vector b is used because the second half is assumed to be antisymmetric. In the figure below for an odd number of coefficients, b(3) = 0, b(4) = -b(2) and b(5) = -b(1), and in the next figure for an even number of coefficients, b(4) = -b(3), b(5) = -b(2), and b(6) = -b(1).

The resulting filter states column vector for the odd number of coefficients example above is

Examples

Odd Order

Create a Type 4 25^th order highpass direct-form antisymmetric FIR filter structure for a dfilt object, Hd, with the following code:

Hd = firpm(25,[0 .4 .5 1],[0 0 1 1],'h');

Even Order

Create a 44^th order lowpass direct-form antisymmetric FIR differentiator filter structure for a dfilt object, Hd, with the following code:

h=firpm(44,[0 .3 .4 1],[0 .2 0 0],'differentiator');

dfilt.df2tsos dfilt.dffir