Fits a variable gain filter to a family of gain curve data, where each curve in the family corresponds to a value of carrier density, producing a file of gain filter coefficients to be used by the TWLM element.
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Syntax |
Description |
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out=mczfit(inputfilename, outputfilebase, centrefrequency, samplerate, maxnumcoef, tol, maxiter, rectangular, rolloff); |
Fits a variable gain filter to a family of gain curve data, where each curve in the family corresponds to a value of carrier density, producing a file of gain filter coefficients to be used by the TWLM element. " inputfilename " is a string containing the name of the input data file (including the suffix). The format of the input data is specified below. " outputfilename " is a string containing the name (excluding the suffix) of the file containing the gain filter coefficients. " centrefrequency " is the center frequency of the frequency band for which the gain fitting is to be performed. " samplerate " is the bandwidth of the frequency band for which the gain fitting is to be performed. " maxnumcoef " is the maximum number of filter coefficients to be used to fit to the data. " tol " is the tolerance " rectangular " is a bool value, it defines the data format. "true" represents 'real' and 'imaginary' format; "false" represents polar coordinate format with 'amplitude' and 'phase' " maxiter " is the maximum number of iterations used in fitting to the data. " rolloff " is the fraction of the bandwidth over which the input frequency data is rolled off to the average of the two values at the band edges. |
Implementation detail
The format of the data file is as follows:
(1, Nc) carrierdensity_1, carrierdenisty_2, …, carrierdensity_Nc (Ns, Nc+1) freq_1gain_1_1gain_1_2…gain_1_Nc freq_2gain_2_1gain_2_2…gain_2_Nc …………… freq_Nsgain_Ns_1gain_Ns_2…gain_Ns_Nc
where the parameters are defined in the table below:
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Nc |
The number of gain curvers |
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Ns |
The number of frequency samples |
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carrierdensity_j |
The carrier density corresponding to the j-th gain curve |
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freq_i |
The i-th frequency sample |
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gain_i_j |
The gain value for the i-th frequency sample in the j-th curve |
Notes:
- The frequencies must be ordered in ascending order, such that frequency_1 is the lowest and frequency_Ns is the highest
- The gain curves and carrier densities must be ordered in descending order of carrier density. That is, carrierdensity_1 is the largest carrier density and carrierdensity_Nc is the lowest carrier density, and gain_i_1 is the gain for the largest carrier density and i-th frequency sample and gain_i_Nc is the gain for the lowest carriest density and i-th frequency sample.
The return values are listed in the table below:
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fit_out |
A struct with fields |
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frequency |
A column vector of the frequency sample points |
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input |
A matrix with the column vectors containing the input frequency response to be fit for each operating point |
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operatingPoint |
A row vector containing the input operating points corresponding to the input frequency responses in the columns of the input matrix |
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operatingPointInterpolated |
A row vector containing values of the linearly interpolated values of operating points between the input values of operating points |
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output |
A matrix with the column vectors containing the fit frequency response for each input operating point |
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outputInterpolated |
A matrix with the column vectors containing the fit frequency response for each linearly interpolated operating point contained in row vector ‘operatingPointInterpolated’. |
Note:
This script function also produces a gain filter coefficients to be used by the TWLM element. The name of the file will be outputfilename.mcfdb.
Example
Please refer to the application example page Gain Fitting for the detailed usage of this command.
See Also