# fdesign.isinclp

Inverse sinc lowpass filter specification

## Syntax

```d = fdesign.isinclp d = fdesign.isinclp(spec) d = fdesign.isinclp(spec,specvalue1,specvalue2,...) d = fdesign.isinclp(specvalue1,specvalue2,specvalue3,specvalue4) d = fdesign.isinclp(...,Fs) d = fdesign.isinclp(...,MAGUNITS) ```

## Description

`d = fdesign.isinclp` constructs an inverse sinc lowpass filter specification object `d`, applying default values for the default specification, `'Fp,Fst,Ap,Ast'`.

`d = fdesign.isinclp(spec)` constructs object `d` and sets its '`Specification`' 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 options are not case sensitive.

• `'Fp,Fst,Ap,Ast'` (default option)

• `'N,Fc,Ap,Ast'`

• `'N,Fp,Ap,Ast'`

• `'N,Fp,Fst'`

• `'N,Fst,Ap,Ast'`

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 lowpass filter specification object change depending on the `Specification`. Use `designmethods` to determine which design method applies to an object and its specification.

`d = fdesign.isinclp(spec,specvalue1,specvalue2,...)` constructs an object `d` and sets its specifications at construction time.

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

`d = fdesign.isinclp(...,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.isinclp(...,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.isinclp` implements a filter with a passband magnitude response equal to:

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

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

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Pass the specifications for the default specification - 'Fp,Fst,Ap,Ast', as input arguments to the specifications object.

```d = fdesign.isinclp(.4,.5,.01,40); hd = design(d,'equiripple','SystemObject',true); fvtool(hd);```

Design a 50th order inverse sinc lowpass 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(w) = sinc(0.25*w)^(-16) .

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

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