Wide Bandwidth Signals for Joint Time–Frequency Characterization of Nonlinear and Time-Varying Circuits

In this work, we generate and use a total of six different wideband signals for joint time–frequency characterization of nonlinear time-invariant [N-shaped differential resistor (NDR)] and linear time-varying (thermistor) circuits. A data acquisition board is used for applying the signals in the form of a voltage excitation and reading the induced current. The input signals have flat power spectra, thus avoiding the need for iterative calibration loops required to obtain signals with low crest factor. Such iterative loops are unavoidable when using random, pseudorandom, or chaotic signals all of which have a wideband spectrum but not necessarily a flat one. Flat spectra help in controlling the maximum voltage within the generated signal, thus eliminating large spikes in the obtained signal. The accuracy of the measurements is compared with the measurements acquired on a Biologic VSP-300 electrochemical station. An average relative error margin of 3% at most is obtained.