Contents

fdesign.isinchp

Inverse sinc highpass filter specification

Syntax

D = fdesign.isinchp
D = fdesign.isinchp(SPEC)
D = fdesign.isinchp(SPEC,specvalue1,specvalue2,...)
D = fdesign.isinchp(specvalue1,specvalue2,specvalue3,specvalue4)
D = fdesign.isinchp(...,Fs)
D = fdesign.isinchp(...,MAGUNITS)

Description

D = fdesign.isinchp constructs an inverse sinc highpass filter specification object D, applying default values for the default specification string 'Fst,Fp,Ast,Ap'.

D = fdesign.isinchp(SPEC) constructs object D and sets the Specification property to SPEC. Entries in the SPEC string represent various filter response features, such as the filter order, that govern the filter design. Valid entries for SPEC are shown below. The strings are not case sensitive.

  • 'Fst,Fp,Ast,Ap' (default spec)

  • 'N,Fc,Ast,Ap'

  • 'N,Fst,Fp'

  • 'N,Fp,Ast,Ap'

  • 'N,Fst,Ast,Ap'

The string entries are defined as follows:

  • Ast — attenuation in the stopband in decibels (the default units). Also called Astop.

  • Ap — amount of ripple allowed in the passband in decibels (the default units). Also called Apass.

  • Fp — frequency at the start of the passband. Specified in normalized frequency units. Also called Fpass.

  • Fst — frequency at the end of the stopband. Specified in normalized frequency units. Also called Fstop.

  • N — filter order.

The filter design methods that apply to an inverse sinc highpass filter specification object change depending on the value of the Specification property. Use designmethods to determine which design method applies to a specific Specification.

Use designopts to see the available design options for a specific design method. Enter help(D,METHOD) at the MATLAB® command line to obtain detailed information on the design options for a given design method, METHOD.

D = fdesign.isinchp(SPEC,specvalue1,specvalue2,...) constructs an object D and sets the specifications at construction time.

D = fdesign.isinchp(specvalue1,specvalue2,specvalue3,specvalue4) constructs an object D assuming the default Specification property string 'Fst,Fp,Ast,Ap', using the values you provide in specvalue1,specvalue2, specvalue3, and specvalue4.

D = fdesign.isinchp(...,Fs) adds the argument Fs, specified in Hz to define the sampling frequency to use. In this case, all frequencies in the specifications are in Hz as well.

D = fdesign.isinchp(...,MAGUNITS) specifies the units for any magnitude specification you provide in the input arguments. MAGUNITS can be one of

  • 'linear' — specify the magnitude in linear units

  • 'dB' — specify the magnitude in dB (decibels)

  • 'squared' — specify the magnitude in power units

When you omit the MAGUNITS argument, fdesign assumes that all magnitudes are in decibels. Note that fdesign stores all magnitude specifications in decibels (converting to decibels when necessary) regardless of how you specify the magnitudes.

The design method of fdesign.isinchp implements a filter with a passband magnitude response equal to:

H(ω)=sinc(C(1ω))P

You can control the values of the sinc frequency factor, C, and the sinc power, P, using the 'SincFrequencyFactor' and 'SincPower' options in the design method. 'SincFrequencyFactor' and 'SincPower' default to 0.5 and 1 respectively.

Examples

Design a minimum order inverse sinc highpass filter and shape the stopband to have a slope of 20 dB/radian/sample.

 d = fdesign.isinchp('Fst,Fp,Ast,Ap',.4,.5,40,0.01);
 Hd = design(d);
 % Shape the stopband to have a linear slope of 20 dB/rad/sample
 Hd1 = design(d,'StopbandShape','linear','StopbandDecay',20);
 fvtool(Hd,Hd1);

Design a 50th order inverse sinc highpass filter. Set the sinc frequency factor to 0.25, and the sinc power to 16 to achieve a magnitude response in the passband of the form H(ω) = sinc(0.25*(1-ω))^(-16) .

 d = fdesign.isinchp('N,Fst,Fp',50,.4,.5);
 Hd = design(d,'SincFrequencyFactor',0.25,'SincPower',16);
 fvtool(Hd);

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