Prediction & modelling of EMI in communication systems due to non-linearities

The interference in radio receivers has been an issue of concern right from the days when radio communication was in its infancy. Many techniques like super-heterodyne principle were introduced to simplify radio receivers, which brought along with them more interference problems due to the image frequency & the local oscillator frequency and its harmonics. Interference is also caused due to the inherent non-linearities existing in the transmitter subsystem. Receiver subsystem or even joints and rusty bolts in the immediate vicinity of the antenna which give rise to effects like intermodulation and cross modulation. This paper attempts to give an approach to modelling of the interference in radio receivers concentrating mainly on the intermodulation problems to give an alternative to the tentative & inaccurate methods used to calculate their effects.