# fdesign.highpass

Highpass filter specification object

## Syntax

`D = fdesign.highpass`

D = fdesign.highpass(SPEC)

D = fdesign.highpass(SPEC,specvalue1,specvalue2,...)

D = fdesign.highpass(specvalue1,specvalue2,specvalue3,

specvalue4)

D = fdesign.highpass(...,Fs)

D = fdesign.highpass(...,MAGUNITS)

## Description

`D = fdesign.highpass`

constructs
a highpass filter specification object `D`

, applying
default values for the specification, `'Fst,Fp,Ast,Ap'`

.

`D = fdesign.highpass(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. These entries are not case sensitive.

**Note**

Specification entries marked with an asterisk require the DSP System Toolbox™ software.

`'Fst,Fp,Ast,Ap'`

(default`spec`

)`'N,F3db'`

`'N,F3db,Ap'`

*`'N,F3db,Ast'`

*`'N,F3db,Ast,Ap'`

*`'N,F3db,Fp`

*`'N,Fc'`

`'N,Fc,Ast,Ap'`

`'N,Fp,Ap'`

`'N,Fp,Ast,Ap'`

`'N,Fst,Ast'`

`'N,Fst,Ast,Ap'`

`'N,Fst,F3db'`

*`'N,Fst,Fp'`

`'N,Fst,Fp,Ap'`

*`'N,Fst,Fp,Ast'`

*`'Nb,Na,Fst,Fp'`

*

The filter specifications are defined as follows:

`Ap`

— amount of ripple allowed in the pass band in decibels (the default units). Also called Apass.`Ast`

— attenuation in the stop band in decibels (the default units). Also called Astop.`F3db`

— cutoff frequency for the point 3 dB point below the passband value. Specified in normalized frequency units.`Fc`

— cutoff frequency for the point 6 dB point below the passband value. Specified in normalized frequency units.`Fp`

— frequency at the start of the pass band. Specified in normalized frequency units. Also called Fpass.`Fst`

— frequency at the end of the stop band. Specified in normalized frequency units. Also called Fstop.`N`

— filter order.`Na`

and`Nb`

are the order of the denominator and numerator.

Graphically, the filter specifications look similar to those shown in the following figure.

Regions between specification values like `Fst`

and `Fp`

are
transition regions where the filter response is not explicitly defined.

The filter design methods that apply to a highpass filter specification
object change depending on the `Specification`

. Use `designmethods`

to determine which design
method applies to an object and its specification.

Use `designopts`

to determine
which design options are valid for a given design method. For detailed
information on design options for a given design method, `METHOD`

,
enter `help(D,METHOD)`

at the MATLAB^{®} command
line.

`D = fdesign.highpass(SPEC,specvalue1,specvalue2,...)`

constructs
an object `d`

and sets its specification values at
construction time.

`D = fdesign.highpass(specvalue1,specvalue2,specvalue3,`

constructs an object

specvalue4)`D`

with
the default `Specification`

property and the values
you enter for `specvalue1,specvalue2,...`

.

`D = fdesign.highpass(...,Fs)`

provides the sampling frequency for the filter specification object. `Fs`

is
in Hz and must be specified as a scalar trailing the other numerical
values provided. If you specify a sampling frequency, all other frequency
specifications are in Hz.

`D = fdesign.highpass(...,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.

## Examples

## Version History

**Introduced in R2009a**