EMI analysis of a generic power line communication OFDM data link

In recent years Orthogonal Frequency Division Multiplexing (OFDM) techniques have increasingly been used in low-cost communication systems. Associated with new frequency and bandwidth characteristics there appear new challenges in regard to electromagnetic susceptibility that have to be solved. By the example of an OFDM data link with bandwidth 32 kHz and center frequency 900 kHz this paper gives a detailed view on the effects of out-of-band interferences and their harmonics, the effect of impulsive noise, the influence of analog discrete filters followed by digital filters in the digital domain, and the number of bits in the analog to digital converter (ADC). These aspects are discussed both in frequency and in time domain and various aspects are discussed using the symbol error rate (SER). To exclude influences of imperfect frequency synchronization multipath propagation and synchronization techniques will not be considered and the state of synchronization will be regarded as ideal. With these prerequisites this paper shows the need for a discrete analog filter to protect the ADC. Furthermore, it turns out that the number of bits of the ADC is of minor importance.