freqs

Compute analog filter frequency response values.

Syntax

h = freqs(b,a,w)

[h,w] = freqs(...)

Inputs

b
The numerator polynomial coefficients of the filter.
Type: double
Dimension: vector
a
The denominator polynomial coefficients of the filter.
Type: double
Dimension: vector
w
The frequencies (in radians/sec) at which the response is computed.
Type: double
Dimension: scalar | vector

Outputs

h
The frequency response values.
Type: complex
Dimension: scalar | vector
w
The frequencies (in radians/sec) at which the response is computed.
Type: double
Dimension: scalar | vector

Example

Verify the cutoff frequency of a fourth order Butterworth low pass analog filter with a 300 radians/sec cutoff frequency.
b = [0.0, 0.0, 0.0, 0.0, 8.10000e+09];
a = [1.0, 7.83938e+02, 3.07279e+05, 7.05544e+07, 8.10000e+09];
h = freqs(b,a,300);
abs(h)
ans = 0.70711