Phase-Compensated Optical Fiber-Based Ultrawideband Channel Sounder

Abstract

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.

Uncertainty of Millimeter-Wave Channel Sounder due to Integration of Frequency Converters

“…One of the components that is sensitive to external disturbance is the optical fiber cable that can cause signal phase variations [7]. To understand the impact of these phase changes in fiber cable on H cs (f ), an equivalent signal block diagram of the sounder in B2B configuration is elaborated in Fig.…”

Design and Validation of the Phase-Compensated Long-Range Sub-THz VNA-Based Channel Sounder

“…Phase-coherent measurement is a prerequisite for multichannel signal processing, e.g. virtual array concept as widely adopted in millimeter-wave (mmWave) channel sounding campaigns [11]. Besides, many sub-THz applications e.g., phasesensitive detection, requires the system to be highly phase stable [12].…”

System development and experimental validation of a long‐range VNA‐based channel sounder

“…In addition, the measurement time when using the VNA scales up/down depending on the bandwidth selected for the frequency sweep, number of frequency points and the intermediate frequency bandwidth settings. Nonetheless, the VNA remains an attractive solution for channel measurements in indoor static scenarios and the distance limitation can be mitigated by the use of frequency up‐converters and down‐converters or optical fibre cables [26–29].…”

“…VNA channel sounders based on radio‐over‐fibre (RoF) techniques have the limitation that the phase of the signal propagating in the optical fibre is susceptible to variation stemming from temperature and strain gradients on the cable [37]. In [29], a phase correction bidirectional scheme for a RoF based VNA channel sounder using optical circulators is proposed and validated in back‐to‐back measurements, over the air channel measurements in an anechoic chamber and realistic propagation scenarios. The bidirectional scheme utilising optical circulators is shown to achieve premium performance in correction of the phase errors due to temperature and strain gradients on the optical cable.…”