noisepsdopts

Create an options object for output noise PSD computation

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Syntax

opts = noisepsdopts(sysobj)

Description

opts = noisepsdopts(sysobj) uses the current settings in the filter System object™ to create an options object that contains specified options for computing the output noise power spectral density. You can pass the opts object as an input argument to the noisepsd function.

example

Examples

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Open Live Script

Use the noisepsdopts function to set options to compute the output noise PSD. filt1 and filt2 are lowpass filters that use different design methods. The opts object makes it easier to set the same conditions for the noise PSD computation in the noisepsd function.

d = fdesign.lowpass
d = 
  lowpass with properties:

               Response: 'Lowpass'
          Specification: 'Fp,Fst,Ap,Ast'
            Description: {4×1 cell}
    NormalizedFrequency: 1
                  Fpass: 0.4500
                  Fstop: 0.5500
                  Apass: 1
                  Astop: 60


filt1 = design(d,'butter','Systemobject',true)
filt1 = 
  dsp.SOSFilter with properties:

            Structure: 'Direct form II'
    CoefficientSource: 'Property'
            Numerator: [13×3 double]
          Denominator: [13×3 double]
       HasScaleValues: true
          ScaleValues: [0.4151 0.3718 0.3374 0.3099 0.2878 0.2701 0.2558 0.2445 0.2358 0.2293 0.2248 0.2221 0.4704 1]

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filt2 = design(d,'cheby2','Systemobject',true)
filt2 = 
  dsp.SOSFilter with properties:

            Structure: 'Direct form II'
    CoefficientSource: 'Property'
            Numerator: [5×3 double]
          Denominator: [5×3 double]
       HasScaleValues: true
          ScaleValues: [0.7003 0.5771 0.4734 0.3925 0.3466 1]

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opts = noisepsdopts(filt1)
opts = 
  struct with fields:

             FreqPoints: 'All'
                   NFFT: 512
    NormalizedFrequency: true
                     Fs: 'Normalized'
           SpectrumType: 'Onesided'
               CenterDC: false
              ConfLevel: 'Not Specified'
           ConfInterval: []


opts.NFFT = 256; % Same as set(opts,'nfft',256).
opts.NormalizedFrequency = false;
opts.Fs = 1.5e3;
opts.CenterDC = true
opts = 
  struct with fields:

             FreqPoints: 'All'
                   NFFT: 256
    NormalizedFrequency: false
                     Fs: 1500
           SpectrumType: 'Twosided'
               CenterDC: true
              ConfLevel: 'Not Specified'
           ConfInterval: []

With opts configured as needed, use it as an input argument for the noisepsd function.

npsd = noisepsd(filt1,20,opts);
plot(npsd)
title("Round-off Noise Power Spectrum")

Figure contains an axes object. The axes object with title Round-off Noise Power Spectrum, xlabel Frequency (Hz), ylabel Power/frequency (dB/Hz) contains an object of type line.

npsd = noisepsd(filt2,20,opts);
plot(npsd)
title("Round-off Noise Power Spectrum")

Figure contains an axes object. The axes object with title Round-off Noise Power Spectrum, xlabel Frequency (Hz), ylabel Power/frequency (dB/Hz) contains an object of type line.

Input Arguments

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Output Arguments

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Options object which contains the options for computing the output noise PSD, returned as a spectrum object. You pass the opts object as an input argument to the noisepsd function to specify values for the input parameters.

Using opts, you can set the following properties for noisepsd:

Property Name

Default Value

Description and Valid Entries

NFFT

512

Specify the number of FFT points to use to calculate the PSD.

NormalizedFrequency

true

Determine whether to use normalized frequency. Enter a logical value of the logical true or false. Because this property is a logical value, do not enclose with single quotation marks.

Fs

'Normalized'

Specify the sampling frequency to use when you set NormalizedFrequency to false. Use any integer value greater than 1. Enter the value in Hz.

SpectrumType

'Onesided'

Specify how noisepsd should generate the PSD. Options are 'Onesided' or 'Twosided'. If you choose a two-sided computation, you can also choose CenterDC = true. Otherwise, CenterDC must be false.

  • 'Onesided' converts the type to a spectrum that is calculated over half the Nyquist interval. All properties affected by the new frequency range are adjusted automatically.

  • 'Twosided' converts the type to a spectrum that is calculated over the whole Nyquist interval. All properties affected by the new frequency range are adjusted automatically.

CenterDC

false

Shift the zero-frequency component to the center of a two-sided spectrum.

  • When you set SpectrumType to 'Onesided', it is changed to 'Twosided' and the data is converted to a two-sided spectrum.

  • Setting CenterDC to false shifts the data and the frequency values in the object so that DC is in the left edge of the spectrum. This operation does not effect the SpectrumType property setting.

ArithmeticarithTypeAnalyze the filter System object, based on the arithmetic specified in the arithType input. arithType can be set to 'double', 'single', or 'fixed'. The analysis tool assumes a double-precision filter when the arithmetic input is not specified and the filter System object is in an unlocked state.

Version History

Introduced in R2011a

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See Also

Functions