Electromagnetic radiation can cause disturbances in electronic systems. Considering the increased use of electronics in modern safety systems and the possible development of high-power microwave weapons (HPM), great concern is attached to Radiated Susceptibility (RS) testing and shielding of electronic equipment. In RS testing of electronic equipment for microwave frequencies, thousands of different angles of incidence/polarisations may be needed to find the angle of incidence that corresponds to the worst susceptibility. However, in practice, one can often only afford to perform a test with a few angles of incidence. In this Master of Science thesis, the results from low level coupling measurements, performed on three different objects, are used to investigate a method which could relieve the requirement of high angular resolution. The method uses only a few angles of incidence and polarisations, but a frequency interval consisting of frequencies that are adjacent to the frequency of interest. Statistical analysis of the electromagnetic coupling is performed as well. The frequency substitution method seems to work for all frequencies, except at the tested objects´ resonance frequencies. The X 2-distribution with one degree of freedom can be used as a rough estimate of the distribution function of the coupling data. This work was performed within the project High Power Microwave Protection Methods for Network Based Defence. The project was financially supported by the Swedish Armed Forces.