Main Content

zpk

Zero-pole-gain conversion of discrete-time filter System object

Description

example

[z,p,k] = zpk(sysobj) returns the zeros, poles, and gain corresponding to the filter System object™ in vector z, vector p, and scalar k, respectively.

[z,p,k] = zpk(sysobj,'Arithmetic',arithType) analyzes the filter System object based on the arithmetic specified in arithType.

For more input options, see zpk in Signal Processing Toolbox™.

Examples

collapse all

Compute the zero-pole-gain form of the highpass filter using the zpk function.

Design a minimum order highpass FIR filter with a passband frequency of 75 kHz and passband ripple of 0.2 dB. Specify a sample rate of 200 kHz.

hFilt = dsp.HighpassFilter('PassbandFrequency',75e3,'PassbandRipple',0.2,'SampleRate',200e3)
hFilt = 
  dsp.HighpassFilter with properties:

               FilterType: 'FIR'
    DesignForMinimumOrder: true
        StopbandFrequency: 8000
        PassbandFrequency: 75000
      StopbandAttenuation: 80
           PassbandRipple: 0.2000
               SampleRate: 200000

  Show all properties

Find the zeros, poles, and the gain of the designed filter using the zpk function.

[z,p,k] = zpk(hFilt)
z = 8×1 complex

  17.2236 + 0.0000i
  -3.0709 + 0.0000i
   0.9732 + 0.2300i
   0.9732 - 0.2300i
   0.9954 + 0.0957i
   0.9954 - 0.0957i
  -0.3256 + 0.0000i
   0.0581 + 0.0000i

p = 8×1

     0
     0
     0
     0
     0
     0
     0
     0

k = -0.0023

Input Arguments

collapse all

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

collapse all

Zeros of the filter, returned as a column vector.

Data Types: double
Complex Number Support: Yes

Poles of the filter, returned as a column vector.

Data Types: double
Complex Number Support: Yes

Gain of the filter, returned as a real scalar.

Data Types: double

Introduced in R2011a