Multifunction waveform generator for EM receiver testing

Abstract. In many electromagnetic (EM) methods, such as magnetotelluric, spectrum induced polarization, time domain induced polarization, and controlled source audio magnetotelluric methods, it is important to evaluate and test the EM receivers during their development stage. To assess the performance of the developed EM receivers, controlled synthetic data that simulates the observed signals in different modes is required. Based on our testing, the frequency range, frequency precision, and time synchronization of the currently available function waveform generators in the market are deficient. This paper presents a multifunction waveform generator with three waveforms: (1) a wide-band low-noise electromagnetic field signal to be used for magnetotelluric, audio-magnetotelluric, and long period magnetotelluric studies; (2) a repeating frequency sweep square waveform for controlled source audio magnetotelluric and spectrum induced polarization studies; and (3) a positive-zero-negative-zero signal that contains primary and secondary fields for time domain induced polarization studies. In this paper, we provide the principles of the above three waveforms along with a hardware design for the generator. Furthermore, testing of the EM receiver was conducted with the waveform generator, and the results of the experiment were compared with those calculated from the simulation and theory in the frequency band of interest.