Programmer Guide/Command Reference/EVAL/hcomb: Difference between revisions
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{{DISPLAYTITLE:{{SUBPAGENAME}}}} | {{DISPLAYTITLE:{{SUBPAGENAME}}}} | ||
This function implements a methods to detect harmonics in a spectrum and to create a harmonic comb filter. | This function implements a methods to detect harmonics in a spectrum and to create a harmonic comb filter. | ||
;Usage:<code>hcomb(<var>mflag</var>, <var>oflag</var>, <var>a</var>, <var>imin</var>, <var>imax</var>, <var>ot</var>, <var>ok</var>, <var>oo</var>, <var>nget</var>, <var>rrms</var>, <var>nrms</var>, <var>nset</var>)</code> | ;Usage:<code>hcomb(<var>mflag</var>, <var>oflag</var>, <var>a</var>, <var>imin</var>, <var>imax</var>, <var>ot</var>, <var>ok</var>, <var>oo</var>, <var>nget</var>, <var>rrms</var>, <var>nrms</var>, <var>nset</var>)</code> | ||
:;<var>mflag</var>:selects the method used to detect the test tone ''ft'' | :;<var>mflag</var>:selects the method used to detect the test tone ''ft'' | ||
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:;<var>oflag</var>:selects the format and content of the result (see '''Result'''); the values '''0''' and '''1''' are supported | :;<var>oflag</var>:selects the format and content of the result (see '''Result'''); the values '''0''' and '''1''' are supported | ||
:;<var>a</var>:a vector containing an amplitude spectrum (linear, with constant df); in the description below ''n'' is the length of ''a''. | :;<var>a</var>:a vector containing an amplitude spectrum (linear, with constant df); in the description below ''n'' is the length of ''a''. | ||
:;<var>imin, imax</var>:index range for test tone (''ft'') detection; 0 | :;<var>imin, imax</var>:index range for test tone (''ft'') detection; 0 ≤ ''imin'' < ''imax'' < ''n'' | ||
:;<var>ot</var>:test tone order (''f0'' = ''ft'' / ''ot''); 0 < ''ot'' | :;<var>ot</var>:test tone order (''f0'' = ''ft'' / ''ot''); 0 < ''ot'' | ||
:;<var>ok, oo</var>:order factor and offset for the components of the comp ''fc''[i]; | :;<var>ok, oo</var>:order factor and offset for the components of the comp ''fc''[i]; | ||
::<code>''fc''[i] = ''f0'' * (''oo'' + ''ok''*i); with: i=1,2,...</code> | ::<code>''fc''[i] = ''f0'' * (''oo'' + ''ok''*i); with: i=1,2,...</code> | ||
:;<var>nget</var>:the number of points (+/-) to detect the peak of a harmonic component ''fc''[i]; 3 | :;<var>nget</var>:the number of points (+/-) to detect the peak of a harmonic component ''fc''[i]; 3 ≤ ''nget'' | ||
:;<var>rrms</var>:defines the energy ratio threshold for harmonic components; 0 | :;<var>rrms</var>:defines the energy ratio threshold for harmonic components; 0 ≤ ''rrms'' < 1 | ||
:;<var>nrms</var>:defines the bandwidth (+/- ''nrms'' points) used to compute the energy ratio; 2 | :;<var>nrms</var>:defines the bandwidth (+/- ''nrms'' points) used to compute the energy ratio; 2 ≤ ''nrms'' | ||
:::(<code>component-rms / testband-rms | :::(<code>component-rms / testband-rms ≥ ''rrms''</code>) | ||
:;<var>nset</var>:defines the comb bandwidth (+/- ''nset'' points); if ''nset'' equals 0, a variable comb bandwidth is used to remove the detected components; this argument is only used if ''oflag'' equals '''1''' | :;<var>nset</var>:defines the comb bandwidth (+/- ''nset'' points); if ''nset'' equals 0, a variable comb bandwidth is used to remove the detected components; this argument is only used if ''oflag'' equals '''1''' | ||
;Description: | ;Description: | ||
Latest revision as of 19:21, 21 April 2011
This function implements a methods to detect harmonics in a spectrum and to create a harmonic comb filter.
- Usage
hcomb(mflag, oflag, a, imin, imax, ot, ok, oo, nget, rrms, nrms, nset)- mflag
- selects the method used to detect the test tone ft
mflag=0 peak picking mflag=1 harmonic grid
- oflag
- selects the format and content of the result (see Result); the values 0 and 1 are supported
- a
- a vector containing an amplitude spectrum (linear, with constant df); in the description below n is the length of a.
- imin, imax
- index range for test tone (ft) detection; 0 ≤ imin < imax < n
- ot
- test tone order (f0 = ft / ot); 0 < ot
- ok, oo
- order factor and offset for the components of the comp fc[i];
fc[i] = f0 * (oo + ok*i); with: i=1,2,...- nget
- the number of points (+/-) to detect the peak of a harmonic component fc[i]; 3 ≤ nget
- rrms
- defines the energy ratio threshold for harmonic components; 0 ≤ rrms < 1
- nrms
- defines the bandwidth (+/- nrms points) used to compute the energy ratio; 2 ≤ nrms
- (
component-rms / testband-rms ≥ rrms)
- (
- nset
- defines the comb bandwidth (+/- nset points); if nset equals 0, a variable comb bandwidth is used to remove the detected components; this argument is only used if oflag equals 1
- Description
- The function extracts the frequency ft of the test tone from the selected test frequency band (arguments: mflag, imin, imax and rr).
- The argument ot is used to compute the fundamental frequency f0 of the harmonic comb.
- For each frequency band of the harmonic comb is tested if there is a spectral component (peak) or not. The frequency, amplitude and order of the detected harmonic components are saved.
- Result
-
- oflag=0: The result r is a (M+1)x3 matrix, with M is the number of detected harmonics
r[0,0] fundamental frequency f0 (weighted average of component frequencies) r[0,1], r[0,2] always 0 r[i,0] frequency of component i (i=1..M) r[i,1] amplitude of component i (i=1..M) r[i,2] order of component i (i=1..M)
- oflag=1: The result r is a vector with n elements containing the amplitude spectrum of the comb filter. Inside each detected band the amplitudes are set to 1, outside the amplitudes are set to 0.
- Note: All frequencies computed and returned by this function are relative frequencies, computed for a frequency resolution df=1.
- See also
- optmm, cvphase, script application MulAc
