Ambient Power Density and Electric Field From Broadband Wireless Emissions in a Reverberant Space

With broadband wireless communications networks currently being deployed in ships, aircraft, and other confined, reflective structures, it is necessary to assess the electromagnetic environment (EME) created by these radio-frequency emissions in a reverberant space. The resultant ambient power density and electric field may be identified as a cause of electromagnetic interference to co-located electronic equipment. In this study, we measure and characterize the EME created by emissions from a broadband IEEE 802.11n wireless local area network (WLAN) in a reverberation chamber mock-up of a shipboard below-deck space. The interaction between the wide-bandwidth power spectral density of the communications signal and the highly frequency-selective channel of the reverberant space leads to average ambient power density and average ambient electric field that exhibit very small spatial variation. This spatial uniformity in average field results from integration of the received signal power spectral density across the wide frequency bandwidth. The peak-to-average power ratio (PAPR) of the received wireless signal is derived from time-dependent power waveform statistics measured by a real-time spectrum analyzer. A maximum electric field is computed from the peak received power. Previously, the maximum electric field was assessed using continuous-wave (CW) signal transmission and mechanical mode stirring in the reverberant space. For a given total power radiated into the space, it is shown that maximum electric fields obtained from these two approaches are in good agreement.