Evaluation of Time Domain Propagation Measurements of UWB Systems Using Spread Spectrum Channel Sounding

Spread spectrum sounding experiments for indoor wireless channel over a frequency band spanning 2-12 GHz, which exceeds the full FCC UWB band, are reported. Experiments were carried out for directional spiral antennas in line-of-sight (LOS) and omnidirectional biconical antennas in nonline-of-sight (NLOS) environments, in the latter case with up to 15 m antenna separation. For biconical antennas, channel multipath dispersion is the main reason for the delay spreads, while for spirals, frequency-dependent delays of the antennas modify signals upon radiation and reception. A special emphasis of this work is to assess the accuracy of the measured impulse responses extracted from the received waveforms by deconvolution in a typical indoor environment. In one scheme to assess accuracy, impulse responses obtained using different spread spectrum waveforms are compared; independent measurements show excellent agreement, with correlation coefficients about 0.99. In a second assessment approach, accuracy is tested by performing time reversal experiments based on the measured channel impulse response. Correlation coefficients between experimental and theoretical time-reversal traces are on the order of 0.98, which further confirms highly accurate measurements.