dfilt.dfsymfir

Discrete-time, direct-form symmetric FIR filter

Syntax

Hd = dfilt.dfsymfir(b)
Hd = dfilt.dfsymfir


Description

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

Hd = dfilt.dfsymfir returns a default, discrete-time, direct-form symmetric 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 symmetric. 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

$$\left[\begin{array}{c}z(1)\\ z(2)\\ z(3)\\ z(4)\end{array}\right]$$

Examples

Odd-Order Symmetric FIR Filter Structure

Create a Type-2 15th-order direct-form symmetric FIR filter structure for a dfilt object.

Num_coeffs = fir1(15,0.5);
Hd = dfilt.dfsymfir(Num_coeffs);

Display the impulse response of the filter.

impz(Hd)

Even-Order Symmetric FIR Filter Structure

Create a Type-1 16th-order direct-form symmetric FIR filter structure for a dfilt object.

Num_coeffs = fir1(16,0.5);
Hd = dfilt.dfsymfir(Num_coeffs);

Display the impulse response of the filter.

impz(Hd)

Version History

Introduced before R2006a