measure
Measure frequency response characteristics of filterSystem object
Syntax
Description
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 constructsysobj
usingfdesign
anddesign
with the name-value pair argument'SystemObject', true
. You can optionally specify additional options by one or moreName,Value
pair arguments.
analyzes the filter System object,M
= measure(sysobj
,'Arithmetic',arithType
)sysobj
, based on the arithmetic specified in thearithType
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 toM
= 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
Examples
Input Arguments
Output Arguments
Tips
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 tomeasure
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, but
f = fdesign.lowpass('N,F3dB,Ast',8,0.5,80); H = design(f,'cheby2','SystemObject',true); measure(H,'Fpass',0.4)
Version History
Introduced in R2011a