tf
Convert discrete-time filter System object to transfer function
Description
Examples
Transfer Function of SOS Filter
Compute the transfer function of an SOS filter using the tf
function.
Create a fourth-order, lowpass SOS filter object with a normalized cutoff frequency of 0.4.
[z,p,k] = ellip(4,1,60,0.4); % Set up the filter [sosMatrix,scaleValues] = zp2sos(z,p,k); [num,den] = sos2ctf(sosMatrix); sosFilt = dsp.SOSFilter(Structure='Direct form I',... Numerator=num,Denominator=den,... ScaleValues=scaleValues)
sosFilt = dsp.SOSFilter with properties: Structure: 'Direct form I' CoefficientSource: 'Property' Numerator: [2x3 double] Denominator: [2x3 double] HasScaleValues: true ScaleValues: [0.0351 1 1] Use get to show all properties
Compute the transfer function of the designed SOS filter. The tf
function returns the numerator and the denominator coefficient vectors of the filter.
[numTF,denTF] = tf(sosFilt)
numTF = 1×5
0.0351 0.1038 0.1432 0.1038 0.0351
denTF = 1×5
1.0000 -1.5676 1.7412 -1.0104 0.3093
Input Arguments
sysobj
— Input filter
filter System object
arithType
— Arithmetic type
'double'
(default) | 'single'
| 'Fixed'
Arithmetic used in the filter analysis, specified as 'double'
,
'single'
, or 'Fixed'
. When the arithmetic
input is not specified and the filter System object is unlocked, the analysis tool assumes a double-precision filter. When the
arithmetic input is not specified and the System object is locked, the function performs the analysis based on the data type of
the locked input.
The 'Fixed'
value applies to filter System objects with fixed-point
properties only.
When the 'Arithmetic'
input argument is specified as
'Fixed'
and the filter object has the data type of the
coefficients set to 'Same word length as input'
, the arithmetic
analysis depends on whether the System object is unlocked or locked.
unlocked –– The analysis object function cannot determine the coefficients data type. The function assumes that the coefficients data type is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.
locked –– When the input data type is
'double'
or'single'
, the analysis object function cannot determine the coefficients data type. The function assumes that the data type of the coefficients is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.
To check if the System object is locked or unlocked, use the isLocked
function.
When the arithmetic input is specified as 'Fixed'
and the filter
object has the data type of the coefficients set to a custom numeric type, the object
function performs fixed-point analysis based on the custom numeric data type.
Output Arguments
num
— Numerator coefficients
row vector
Numerator coefficients of the filter, returned as a row vector.
Data Types: double
den
— Denominator coefficients
scalar | row vector
Denominator coefficients of the filter, returned as a row vector.
Data Types: double
Version History
Introduced in R2011aR2024b: Support for dsp.VariableFIRDecimator
and dsp.VariableFIRInterpolator
Objects
Starting in R2024b, the tf
analysis function supports the dsp.VariableFIRDecimator
and dsp.VariableFIRInterpolator
objects.
R2024b: dsp.BiquadFilter
object warns
The dsp.BiquadFilter
object issues a warning and will be removed in a
future release. Use the dsp.SOSFilter
object
instead. For more information on how to replace your existing code, see the
Compatibility Considerations section in the dsp.BiquadFilter
reference page.
R2024b: Support for dsp.DCBlocker
object
Starting in R2024b, this function supports the dsp.DCBlocker
object.
R2023b: Support for dsp.ParallelFilter
and dsp.Delay
Objects
Starting in R2023b, the tf
analysis function supports the dsp.ParallelFilter
and the dsp.Delay
objects.
R2023b: dsp.BiquadFilter
object will be removed
The dsp.BiquadFilter
object will be removed in a future release. Use
the dsp.SOSFilter
object
instead.
Comando MATLAB
Hai fatto clic su un collegamento che corrisponde a questo comando MATLAB:
Esegui il comando inserendolo nella finestra di comando MATLAB. I browser web non supportano i comandi MATLAB.
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .
You can also select a web site from the following list:
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
Europe
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)