Phase-Compensated Optical Fiber-Based Ultrawideband Channel Sounder

In this article, a novel vector network analyzer (VNA)-based ultrawideband (UWB) channel sounder using radio-over-fiber (RoF) techniques is presented. Benefiting from the usage of optical fiber cable, the measurement range and the dynamic range are significantly increased compared with the conventional coaxial-based VNA system. Specifically, using RoF increases the dynamic range to a maximum of 112 dB at 30 GHz for the back-to-back connection with an optical fiber cable of length 300 m. Moreover, a state-of-the-art phase compensation scheme using optical circulators is proposed for the first time. The novel scheme renders the channel sounder immune to stochastic phase changes in the optical fiber cable due to thermal changes and mechanical stress, thus permitting the remoting of virtual antenna arrays. The proposed channel sounder is experimentally validated in back-to-back measurements, an anechoic chamber, and practical indoor scenarios. The indoor channel measurements are conducted using a virtual uniform rectangular array (URA) at the millimeter-wave (mm-wave) band from 26.5 to 30 GHz. The measured results demonstrate the developed channel sounder's capability to perform UWB large-scale antenna array measurements with a long measurement range.