Note: This page has been translated by MathWorks. Click here to see

To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

Measure frequency response characteristics of filter System object

`measure(sysobj)`

`M = measure(sysobj)`

`M = measure(sysobj,'Arithmetic',arithType)`

```
M = measure(sysobj,'freqspec',
freqspecvalue)
```

`measure(`

displays
measurements of various quantities from the frequency response of the filter System
object™, `sysobj`

)`sysobj`

. Measurements include the actual passband ripple, the
minimum stopband attenuation, the frequency point at which the filter's gain is 3 dB below the
nominal passband gain, etc. You must construct `sysobj`

using
`fdesign`

and `design`

with the name-value pair argument
`'SystemObject', true`

. You can optionally specify additional options by one
or more `Name,Value`

pair arguments.

analyzes the filter System
object, `M`

= measure(`sysobj`

,'Arithmetic',`arithType`

)`sysobj`

, based on the arithmetic specified in the
`arithType`

input. `arithType`

can be set to one of
`'double'`

, `'single'`

, or `'fixed'`

.
When the arithmetic input is not specified and the filter System
object is in an unlocked state, the analysis tool assumes a double precision
filter.

passes the frequency value as an input to `M`

= measure(`sysobj`

,'freqspec',
`freqspecvalue`

)`measure`

in order to determine the
corresponding magnitude measurements. For designs that do not specify some of the frequency
constraints, you can determine the corresponding magnitude measurements using this
option.

In the following example, the passband edge, passband ripple, and the transition width of the IIR filter are unknown.

designLowpass = fdesign.lowpass('N,F3dB,Ast',8,0.5,80); chebFilter = design(designLowpass,'cheby2'); measure(chebFilter)

Sample Rate : N/A (normalized frequency) Passband Edge : Unknown 3-dB Point : 0.5 6-dB Point : 0.51823 Stopband Edge : 0.68727 Passband Ripple : Unknown Stopband Atten. : 79.9994 dB Transition Width : Unknown

`0.4`

, and measure the passband ripple and the
transition width of this
filter.` measure(chebFilter,'Fpass',0.4)`

Sample Rate : N/A (normalized frequency) Passband Edge : 0.4 3-dB Point : 0.5 6-dB Point : 0.51823 Stopband Edge : 0.68727 Passband Ripple : 0.013644 dB Stopband Atten. : 79.9994 dB Transition Width : 0.28727

For designs that do not specify some of the frequency constraints, the function may not be
able to determine corresponding magnitude measurements. In these cases, a constraint can be
passed in to `measure`

to determine such measurements. For example:

f = fdesign.lowpass('N,F3dB,Ast',8,0.5,80); H = design(f,'cheby2','SystemObject',true); measure(H)

`Unknown`

for the passband edge, passband ripple, and transition width
measurements, butf = fdesign.lowpass('N,F3dB,Ast',8,0.5,80); H = design(f,'cheby2','SystemObject',true); measure(H,'Fpass',0.4)