Medical Equipment Immunity Assessment by Time Domain Analysis Application to GSM signals

This paper presents a measurement method to assess the immunity of medical equipment (bioelectrical signal recording systems) to short duration interferences, like that of a GSM signal during the call establishment and ringing phase. Frequency domain measurement methods do not allow the analysis of these signals due to their short duration and transient nature. To measure these interferences we use the intermediate frequency (IF) signal output of a spectrum analyzer working in "zero span" to obtain a signal in time domain, and we connect it to the input of a digital oscilloscope. Then, we demodulate the IF signal to obtain the interference in base band. The combination of the characteristics of both instruments, allow us to measure the interfering signal, and to assess the effect of these kinds of signals in medical systems that record low-level, low-frequency signals