The code presented here concerns the frequency response measurement of a two-port circuit using the DAQ-system NI USB-6211. The measurement is based on the Discrete Fourier Transform (DFT) and Maximum Likelihood estimation (MLE) of the amplitude and phase of the input and output voltage of the two-port circuit, respectively. Then the frequency response modulus and phase is calculated. The excitation of the device under test is performed via single-tone sine-wave signal with stepwise increasing frequency. The measurement setup is given in the .zip file. The code provides:
1) a plot of the frequency response (gain and phase) of the two-port circuit;
2) FreqRespData.mat file with the measurement results (for post-processing purposes).
The code is based on the theory described in:
 H. Zhivomirov, I. Iliev. Impedance Frequency Response Measurement with Matlab Implementation. Journal of the Technical University of Gabrovo, ISSN: 1310-6686, Vol. 52, pp. 61-65, 2016. (http://epubl.tugab.bg/documents/cat_view/46-----/61--52-----)
 NI USB-621x Specifications.pdf. Austin, National Instruments, Corp., 2009.
Hristo Zhivomirov (2021). Frequency Response Measurement with Matlab (https://www.mathworks.com/matlabcentral/fileexchange/62722-frequency-response-measurement-with-matlab), MATLAB Central File Exchange. Retrieved .
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