Investigating EMI-characteristics of navigation receivers

Typically, the investigations of electromagnetic interference (EMI) refer to single limit values that may not be exceeded at a receiver's input stage. In that manner the actual quality of a navigation signal is not assessed at all, neither related to individual disturbance levels that are not continuous wave. This contribution discusses test setups and configurations of how to measure the navigation signal quality including the dynamic and non-linear behaviour of navigation receivers. Measurement results are presented for the instrument landing system (ILS) and the VHF omnidirectional radio range (VOR). In particular, the focus is on time-variant interferences that can occur either due to multipath propagation with rotating wind turbines or transient signals, such as noise.