Measurements of EMI signals on radio links based on commercial off-the-shelf wireless devices

Wireless communication systems are expected to operate reliably in the ISM-Bands (Industrial, Scientific, and Medical) even in presence of noise and EMI [1]. The receiver´s input circuit, being attached to an antenna is a point of vantage for EMI to couple into the system and to distort the wanted signal. Neither shielding nor filtering effectively protects the receiver from being overdriven by front door coupling interfering signals so other concepts have to be created to prevent the receiver from blocking. A setup for analyzing the sensitivity of a wireless data link to EMI is described in this paper. Since the wireless standard defines a client´s disassociation from the selected access point (AP) as a reaction to bad link quality, the disassociation has been used as the indicator for insufficient radio link quality. The setup has been used to fulfill distortion measurements with different types of distorting signals at different signal levels. The measurement results will be presented and discussed in detail.