freqzd (MathScript RT Module Function)

LabVIEW 2012 MathScript RT模块帮助

版本日期:June 2012



Owning Class: filter design

Requires: MathScript RT Module



freqzd(b, a)

freqzd(b, a, w)

freqzd(b, a, w, fs)

freqzd(b, a, n)

freqzd(b, a, n, 'whole')

freqzd(b, a, n, fs)

freqzd(b, a, n, 'whole', fs)

h = freqzd(b, a, w)

h = freqzd(b, a, w, fs)

[h, f] = freqzd(b)

[h, f] = freqzd(b, a)

[h, f] = freqzd(b, a, n)

[h, f] = freqzd(b, a, n, 'whole')

[h, f] = freqzd(b, a, n, fs)

[h, f] = freqzd(b, a, n, 'whole', fs)

Legacy Name: freqz


Computes the complex frequency response vector and the frequency vector of a filter. If you do not request an output, this function plots the magnitude and unwrapped phase of the filter in the current plot window. freqzd(b) is equivalent to freqzd(b, [1], 512). freqzd(b, a) is equivalent to freqzd(b, a, 512).



Name Description
b Specifies the numerator coefficients of the filter. b is a real or complex vector.
a Specifies the denominator coefficients of the filter. a is a real or complex vector. The default is [1].
w Specifies the frequency points at which you want to evaluate the frequency response. If you do not specify w, LabVIEW evaluates the frequency response at n points equally spaced around the upper half of the unit circle. w is a vector.
fs Specifies the sampling frequency in Hz. fs is a scalar.
n Specifies the number of frequency points. n is a positive integer. The default is 512.
'whole' Directs LabVIEW to evaluate the frequency response at n points equally spaced around the unit circle.


Name Description
h Returns the frequency response vector of the filter. h is a complex vector.
f Returns the discrete frequency vector in radians/sample that corresponds to h. f is a vector.


The following table lists the support characteristics of this function.

Supported in the LabVIEW Run-Time Engine Yes (if you request output)
Supported on RT targets Yes (if you request output)
Suitable for bounded execution times on RT Not characterized


b = [1, 2];
a = [-1, 1, 1, 3];
n = 32;
[H, F] = freqzd(b, a, n)

b = [3, 4];
a = [1, -3, 2, 5];
n = 10;
fs = 12;
[H, F] = freqzd(b, a, n, 'whole', fs)

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