On the Impact of Spread Spectrum EMI on Communication Performance

Spread spectrum is a technique that is commonly used today with the intent to reduce electromagnetic interference (EMI) from clocks and devices, such as e.g. switching DC/DC converters. The principle idea behind the technique is to spread the power at one frequency to a larger bandwidth and thereby decrease the interference amplitude and make it more probable to pass EMC emission requirements. This work analyzes the impact on radio communication receivers from this interference reducing technique. The relation between the communication receiver bandwidth and the spreading bandwidth of the spread spectrum operation is clarified. Furthermore, the effect of the aggregated EMI from multiple is investigated. Spread spectrum techniques may have a reducing effect on the communication degradation, as long as the spreading bandwidth is large in relation to the communication bandwidth and the number of EMI sources is limited to just a few. In all other cases, spectrum spreading does not reduce the interference impact.