Development and Experimental Validation of an Ultra-wideband Channel Sounder

Vector network analyzer (VNA) has been extensively utilized for radio channel sounding purposes. Due to its slow channel sounding speed, it has been mainly used for channel measurements in static propagation scenarios. The main limitation with VNA based channel sounder is its small measurement range, due to signal attenuation in the coaxial cable setup. Employing radio over fiber (RoF) can effectively eliminate the cable loss and hence enables the VNA for long range channel sounding. However, optical cables are sensitive to phase changes in optical cables in practical usage scenarios. In this paper, two phase correction strategies, i.e. two-branch scheme and bi-directional scheme, are discussed and experimentally validated to remove the random phase change in the cable. The bi-directional scheme is shown to be highly effective in removing the phase change in the measurements. The virtual array VNA channel sounder employing RoF technique and phase correction scheme is highly attractive, since it supports channel sounding with arbitrary frequency carrier setting, ultra-wideband, large-scale (virtual) antenna settings with a large measurement range.