Abstract : Imaging and wireless communication systems have become essential in this day and age. Current civilian and military applications need to present great immunity against electromagnetic aggressions. However, the electromagnetic susceptibility threshold of complex electronic circuits at the center of these systems is continuously decreasing due to the increase of their operating frequencies and to the decrease of their bias currents. In this context, the aim of this research work is to highlight the effects of electromagnetic aggressions on micro-wave systems. The method of the study consists on analyzing the electromagnetic susceptibility of each circuit which composes the system and then studying the susceptibility of the complete system by associating the circuits together. Electromagnetic studies are carried out with an electromagnetic characterization bench using near field probes. Probes are made from coaxial cables and are characterized. The behavior of a Schottky diode disturbed by an electromagnetic aggression is then studied. We highlight resonance phenomena on the track of the printed board. This was a preliminary approach for studying the electromagnetic susceptibility of a phase lock loop system. Following the method previously presented, we show the different effects of electromagnetic aggressions on analog and digital electronic circuits, including an OpAmp circuit, an oscillator circuit and a phase comparator circuit. Carrying out an analysis and classification of these effects has allowed us to determine the contribution of each circuit on the susceptibility of the phase lock loop system.