Panoramic, ultrawideband, diagnostic imaging of test volumes

Abstract

The Time-Domain, Free-Field Metrology Project at the National Institute of Standards and Technology (NIST) is developing methodologies to assess the quality and range of use (in frequency, test volume size, and test type) of EMC test facilities. Previous efforts (Johnk, R. et al., 2000; 2001) have focused on transmission tests that represented typical antenna and test artifact configurations. These tests illuminated a facility and measured the reflections from scattering objects and residual RF ringing to determine modal and basic propagation characteristics. Joint time-frequency-domain (JTFA) analysis of the measurements allow for characterization of signals in various categories, such as broad- or narrow-band scatterers, leakage, or systematic facility ringing. These directional measurements allow isolation in space and time to allow for location of facility irregularities. The initial results that are presented show scatterers intentionally placed in the Time-Domain, Free-Field Metrology Laboratory. These artifacts were imaged and identified in time, space and frequency. This panoramic, ultrawideband, reflection measurement takes a full 360/spl deg/ sweep of the facility and uses JTFA analysis tools to identify specific scatterers and other irregularities in the facility. Combinations of horizontal and vertical polarization sweeps show improved signal-to-noise ratio (SNR) and can highlight polarization sensitive events. We hope this fast testing technique, can be used as a precompliance check and determination of the RF performance of an EMC facility.