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fdesign.rsrc

Rational-factor sample-rate converter specification

Syntax

D = fdesign.rsrc(L,M)
D = fdesign.rsrc(L,M,RESPONSE)
D = fdesign.rsrc(L,M,CICRESPONSE,D)
D = fdesign.rsrc(L,M,RESPONSE,SPEC)
D = fdesign.rsrc(L,M,SPEC,specvalue1,specvalue2,...)
D = fdesign.rsrc(...,Fs)
D = fdesign.rsrc(...,MAGUNITS)

Description

D = fdesign.rsrc(L,M) constructs a rational-factor sample-rate filter specification object D with the InterpolationFactor property equal to the positive integer L, the DecimationFactor property equal to the positive integer M and the Response property set to 'Nyquist'. The default values for the transition width and stopband attenuation in the Nyquist design are 0.1π radians/sample and 80 dB. If L is unspecified, L defaults to 3. If M is unspecified, M defaults to 2.

D = fdesign.rsrc(L,M,RESPONSE) constructs an rational-factor sample-rate converter with the interpolation factor L, decimation factor M, and the response you specify in RESPONSE.

D = fdesign.rsrc(L,M,CICRESPONSE,D) constructs a CIC or CIC compensator rational-factor sample-rate convertor filter specification object with the 'RESPONSE' property equal to 'CIC' or 'CICCOMP'. D is the differential delay. The differential delay, D, must precede the filter specification.

Because you are designing multirate filters, the specification options available are not the same as the specification options for designing single-rate filters. The interpolation and decimation factors are not included in the specification. Different filter responses support different specifications. The following table lists the supported response types and specification options. These options are not case sensitive.

Design Method

Valid Specification Options

'Arbitrary Magnitude'

See fdesign.arbmag for a description of the specification entries.

  • 'N,F,A' (default option)

  • 'N,B,F,A'

'Arbitrary Magnitude and Phase'

See fdesign.arbmagnphase for a description of the specification entries.

  • 'N,F,H' (default option)

  • 'N,B,F,H'

'Bandpass'

See fdesign.bandpass for a description of the specification entries.

  • 'Fst1,Fp1,Fp2,Fst2,Ast1,Ap,Ast2' (default option)

  • 'N,Fc1,Fc2'

  • 'N,Fst1,Fp1,Fp2,Fst2'

'Bandstop'

See fdesign.bandstop for a description of the specification entries.

  • 'N,Fc1,Fc2'

  • 'N,Fp1,Fst1,Fst2,Fp2'

  • 'Fp1,Fst1,Fst2,Fp2,Ap1,Ast,Ap2' (default option)

'CIC'

'Fp,Fst,Ap,Ast' — Only valid specification. Fp is the passband frequency, Fst is the stopband frequency, Ap is the passband ripple, and Ast is the stopband attenuation in decibels.

To specify a CIC rational-factor sample-rate convertor, include the differential delay after 'CIC' and before the filter specification: 'Fp,Ast'. For example:
d = fdesign.rsrc(2,2,'cic',4);

'CIC Compensator'

See fdesign.ciccomp for a description of the specification entries.

  • 'Fp,Fst,Ap,Ast' (default option)

  • 'N,Fc,Ap,Ast'

  • 'N,Fp,Ap,Ast'

  • 'N,Fp,Fst'

  • 'N,Fst,Ap,Ast'

To specify a CIC compensator rational-factor sample-rate convertor, include the differential delay after 'CICCOMP' and before the filter specification. For example:
d = fdesign.rsrc(2,2,'ciccomp',4);

'Differentiator'

'N' — filter order

'Gaussian'

'Nsym,BTNsym is the filter order in symbols and BT is the bandwidth-symbol time product.

The filter specification must be preceded by an integer-valued SamplesPerSymbol.

'Halfband

See fdesign.halfband for a description of the specification entries.

  • 'TW,Ast' (default option)

  • 'N,TW'

  • ‘N'

  • 'N,Ast'

If you use the quasi-linear IIR design method, iirlinphase, with a halfband specification, the interpolation factor must be 2.

'Highpass'

See fdesign.highpass for a description of the specification entries.

  • 'Fst,Fp,Ast,Ap' (default option)

  • 'N,F3db'

  • 'N,Fc'

  • 'N,Fc,Ast,Ap'

  • 'N,Fp,Ast,Ap'

  • 'N,Fst,Ast,Ap'

  • 'N,Fst,Fp'

  • 'N,Fst,Ast,Ap'

  • 'N,Fst,Fp,Ast'

'Hilbert'

See fdesign.hilbert for a description of the specification entries.

  • 'N,TW' (default option)

  • 'TW,Ap'

'Inverse-sinc Lowpass'

See fdesign.isinclp for a description of the specification entries.

  • 'Fp,Fst,Ap,Ast' (default option)

  • 'N,Fc,Ap,Ast'

  • 'N,Fp,Fst'

  • 'N,Fst,Ap,Ast'

'Inverse-sinc Highpass'

See fdesign.isinchp for a description of the specification entries.

  • 'Fst,Fp,Ast,Ap' (default option)

  • 'N,Fc,Ast,Ap'

  • 'N,Fst,Fp'

  • 'N,Fst,Ast,Ap'

'Lowpass'

See fdesign.lowpass for a description of the specification entries.

  • 'Fp,Fst,Ap,Ast' (default option)

  • 'N,F3dB'

  • 'N,Fc'

  • 'N,Fc,Ap,Ast'

  • 'N,Fp,Ap,Ast'

  • 'N,Fp,Fst'

  • 'N,Fp,Fst,Ap'

  • 'N,Fp,Fst,Ast'

  • 'N,Fst,Ap,Ast'

'Nyquist'

See fdesign.nyquist for a description of the specification entries. For all Nyquist specifications, you must specify the Lth band. This typically corresponds to the interpolation factor so that the nonzero samples of the upsampler output are preserved.

  • 'TW,Ast' (default option)

  • 'N'

  • 'N,Ast'

  • 'N,Ast'

D = fdesign.rsrc(L,M,RESPONSE,SPEC) constructs object D and sets its Specification property to SPEC. Entries in the SPEC represent various filter response features, such as the filter order, that govern the filter design. Valid entries for SPEC depend on the design type of the specifications object.

When you add the SPEC input argument, you must also add the RESPONSE input argument.

D = fdesign.rsrc(L,M,SPEC,specvalue1,specvalue2,...) constructs an object D and sets its specifications at construction time.

D = fdesign.rsrc(...,Fs) provides the sampling frequency of the signal to be filtered. Fs must be specified as a scalar trailing the other numerical values provided. Fs is assumed to be in Hz as are all other frequency values provided.

D = fdesign.rsrc(...,MAGUNITS) specifies the units for any magnitude specification you provide in the input arguments. MAGUNITS can be one of

  • 'linear' — specify the magnitude in linear units.

  • 'dB' — specify the magnitude in dB (decibels).

  • 'squared' — specify the magnitude in power units.

When you omit the MAGUNITS argument, fdesign assumes that all magnitudes are in decibels. Note that fdesign stores all magnitude specifications in decibels (converting to decibels when necessary) regardless of how you specify the magnitudes.

Examples

Design a rational-factor sample-rate converter. Set the rational sample-rate change to 5/3. Use the default Nyquist design with a transition width of 0.05π radians/sample and stopband attenuation of 40 dB. The Lth band factor in the Nyquist design is equal to the interpolation factor.

d = fdesign.rsrc(5,3,'nyquist',5,.05,40);
hm = design(d,'kaiserwin'); %design with Kaiser window

Design a rational-factor sample-rate converter. Set the rational sample-rate change to 5/3. Use a Nyquist design with the filter specification set to 'N,TW'. Set the order equal to 12 and the transition width to 0.1π radians/sample. The Lth band factor in the Nyquist design is equal to the interpolation factor.

d = fdesign.rsrc(5,3,'nyquist',5,'N,TW',12,0.1);

Design a rational-factor sample-rate converter. Assume the data are sampled at 10 kHz. Set the rational sample-rate change to 3/2. Use a Nyquist design with the filter specification set to 'N,TW'. Set the order equal to 12 and the transition width to 100 Hz. The Lth band factor in the Nyquist design is equal to the interpolation factor.

d = fdesign.rsrc(3,2,'nyquist',3,'N,TW',12,100,1e4);
hd = design(d,'equiripple');

Introduced in R2011a

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