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Measure frequency response characteristics of filter System object

`measure(sysobj)`

M = measure(sysobj)

M = measure(sysobj,'Arithmetic',ARITH,...)

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.

`M = measure(`

returns
the measurements, `sysobj`

)*M*, such that the measurements
can be queried programmatically. For example, to query the 3 dB point,
type `M.F3dB`

. Type `get(M)`

to
see the full list of properties that can be queried. Note that different
filter responses generate different measurements.

`M = measure(`

analyzes
the filter System
object, `sysobj`

,'Arithmetic',ARITH,...)`sysobj`

, based on
the arithmetic specified in the `ARITH`

input. `ARITH`

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.

`M = measure(`

passes the frequency value as an input
to `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

When `sysobj`

is a generic discrete-time filter,
for example, a single-rate lowpass filter, `measure(sysobj)`

returns
the following filter specifications.

Lowpass Filter Specification | Description |
---|---|

| Filter sampling frequency. |

| Location of the edge of the passband as it enters transition. |

| Location of the –3 dB point on the response curve. |

| Location of the –6 dB point on the response curve. |

| Location of the edge of the transition band as it enters the stopband. |

| Ripple in the passband. |

| Attenuation in the stopband. |

| Width of the transition between the passband and stopband,
in normalized frequency or absolute frequency. Measured between |

When `sysobj`

is a bandstop filter, `measure(sysobj)`

returns
these specifications for the resulting bandstop filter.

Bandstop Filter Specification | Description |
---|---|

| Filter sampling frequency. |

| Location of the edge of the first passband. |

| Location of the edge of the –3 dB point in the first transition band. |

| Location of the edge of the –6 dB point in the first transition band. |

| Location of the start of the stopband. |

| Location of the end of the stopband. |

| Location of the edge of the –6 dB point in the second transition band. |

| Location of the edge of the –3 dB point in the second transition band. |

| Location of the start of the second passband. |

| Ripple in the first passband. |

| Attenuation in the stopband. |

| Ripple in the second passband. |

| Width of the first transition region. Measured between the –3 and –6 dB points. |

| Width of the second transition region. Measured between the –6 and –3 dB points. |

When `sysobj`

is an interpolator, decimator,
or a rate converter, `measure(sysobj)`

returns these
specifications for the resulting filter.

Interpolator Filter Specification | Description |
---|---|

| Filter sampling frequency. |

| Location of the edge of the passband as it enters transition. |

| Location of the –3 dB point on the response curve. |

| Location of the –6 dB point on the response curve. |

| Location of the edge of the transition band as it enters the stopband. |

| Ripple in the passband. |

| Attenuation in the stopband. |

| Width of the transition between the passband and stopband,
in normalized frequency or absolute frequency. Measured between |

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)

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