RF-susceptibility analysis of complex integrated analog circuits

Large scale RF-immunity investigation of ICs with complex analog integrated circuits may be very complicated. The coupling path of the RF-interference to the susceptible analog circuit may be hard to understand. Moreover due to its complexity and the lack of possibilities to measure on the die, it will not be easy to identify that particular sub-circuit (e.g. op-amp, multiplier, reference source, current mirror etc) that is suffering from this RF-disturbance. Due to the nonlinear properties of the transistors, LF-interference is generated. Thorough investigation of the frequency spectrum of this LF-interference in combination with an appropriate understanding of the concerning analog sub-circuits will be useful to find the affected transistor(s). Then a model can be defined and subsequently an effective solution can be defined. Based on their behavior several kinds of sub-circuits can be investigated more effectively if a two-tone signal instead of an AM-modulated signal is applied as RF-disturbance.