frmag

magnitude of FIR and IIR filters

Calling Sequence

[xm,fr]=frmag(sys,npts)
[xm,fr]=frmag(num,den,npts)

Arguments

:sys a single input, single output discrete transfer function, or a

polynomial or the vector of polynomial coefficients, the filter.

: :num a polynomial or the vector of polynomial coefficients, the

numerator of the filter

: :den a polynomial or the vector of polynomial coefficients, the

denominator of the filter (the default value is 1).

: :npts integer, the number of points in frequency response. : :xm vector of magnitude of frequency response at the points fr. : :fr points in the normalized frequency domain where magnitude is

evaluated.

:

Description

calculates the magnitude of the frequency responses of FIR and IIR filters. The filter description can be one or two vectors of coefficients, one or two polynomials, or a single output discrete transfer function.

the frequency discretisation is given by fr=linspace(0,1/2,npts).

Examples

hz=`iir`_(3,'bp','cheb1',[.15 .25],[.08 .03]);
[hzm,fr]=frmag(hz,256);
`plot`_(fr,hzm)
hz=`iir`_(3,'bp','ellip',[.15 .25],[.08 .03]);
[hzm,fr]=frmag(hz,256);
`plot`_(fr,hzm,'r')

See Also

• iir iir digital filter
• eqfir minimax approximation of FIR filter
• repfreq frequency response
• calfrq frequency response discretization
• phasemag phase and magnitude computation