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# fdesign.isinchp

Inverse sinc highpass filter specification

## Syntax

`D = fdesign.isinchpD = 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 `'Fst,Fp,Ast,Ap'`.

`D = fdesign.isinchp(SPEC)` constructs object `D` and sets the `Specification` property to `SPEC`. Entries in the `SPEC` represent various filter response features, such as the filter order, that govern the filter design. Valid entries for `SPEC` are shown below. The entries 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 filter specifications 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 `'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:

`$H\left(\omega \right)=sinc{\left(C\left(1-\omega \right)\right)}^{-P}$`

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

collapse all

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,'SystemObject',true); ```

Shape the stopband to have a linear slope of 20 dB/rad/sample

``` Hd1 = design(d,'StopbandShape','linear','StopbandDecay',20,'SystemObject',... true); 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(?) = sinc(0.25*(1-?))^(-16) .

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