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mczfit

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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.

 

Supported Product: INTERCONNECT

 

Syntax

Description

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_1                gain_1_1        gain_1_2        …        gain_1_Nc

freq_2                gain_2_1        gain_2_2        …        gain_2_Nc

…                        …                …                …        …

freq_Ns                gain_Ns_1        gain_Ns_2        …        gain_Ns_Nc

 

where the parameters are defined in the table below:

Nc

The number of gain curves

Ns

The number of frequency samples

carrierdensity_j

The carrier density corresponding to the j-th gain curve

freq_i

The i-th frequency sample

gain_i_j

The gain value for the i-th frequency sample in the j-th curve

 

Notes:

1.The frequencies must be ordered in ascending order, such that frequency_1 is  the lowest and frequency_Ns is the highest

2.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:

fit_out

A struct with fields

frequency

A column vector of the frequency sample points

input

A matrix with the column vectors containing the input frequency response to be fit for each operating point

operatingPoint

A row vector containing the input operating points corresponding to the input frequency responses in the columns of the input matrix

operatingPointInterpolated

A row vector containing values of the linearly interpolated values of operating points between the input values of operating points

output

A matrix with the column vectors containing the fit frequency response for each input operating point

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

Measurements, mcfit

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