Accurate Channel Sounding with a Phase Stabilizing Scheme

Abstract

Coaxial cables are vital to a wide range of electronic systems. Phase accuracy in coaxial cables is sensitive to the inevitable cable bending in actual usage and temperature change in the environment. For phase-critical applications, e.g. multi-antenna channel sounding, phase accuracy is fundamental to obtain trustworthy measurement results. A technique to track and remove random phase change in coaxial cables due to cable effect is presented. The phasestabilizing technique provides a general phase stabilizing framework via introducing a bi-directional transmission on the cable. The principle of the phase stabilizing scheme is explained and its effectiveness is experimentally validated in a back-to-back measurement.

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

“…2) Phase compensation scheme: The phase compensation scheme aims to remote the Rx antenna and stabilize the system phase when the Rx antenna rotates. The main difference in the proposed sub-THz system and previous works [11], [13] is explained below. Previous phase compensation schemes for sub-6 GHz and mmWave bands are implemented directly on the cable connected to the VNA receiving port.…”

“…Thus, it is unable to conduct phasecoherent measurements by these kinds of channel sounders. Phase compensation schemes are applied to stabilize the phase of the VNA-based channel sounder at lower frequency bands [11], [13]. However, the phase compensation scheme in [13] is directly implemented using microwave circulators and radio frequency (RF) cables at sub-6 GHz bands, and using circulators and E/O and O/E conversion units for 30 GHz channel sounder [11], respectively.…”

“…Phase compensation schemes are applied to stabilize the phase of the VNA-based channel sounder at lower frequency bands [11], [13]. However, the phase compensation scheme in [13] is directly implemented using microwave circulators and radio frequency (RF) cables at sub-6 GHz bands, and using circulators and E/O and O/E conversion units for 30 GHz channel sounder [11], respectively. These approaches cannot be directly applied for sub-THz system, due to lack of suitable E/O and O/E units at these frequencies.…”

Design and Validation of a Multilink Phase- Compensated Long-Range Ultrawideband VNA-Based Channel Sounder

“…However, the phase of the signal in the fiber is inherently sensitive to the thermal change and mechanical stress of the fiber cables [34], [35], limiting its application for phase-coherent measurements, e.g., VAA-based channel measurements, which is widely used for spatial channel measurements at mmWave bands [15]. To enable phase-coherent ultrawideband channel measurements in the long-range scenarios, phase compensation strategies were presented in [19], [20], [36], [37]. The phase compensation scheme using the bidirectional strategy was applied in the VNA-based channel sounder using RoF techniques up to 30 GHz in [19] and extended to 50 GHz in [37].…”

On the Phase-Compensated Long-Range VNA-based Channel Sounder for sub-6 GHz, mmWave and sub-THz frequency bands

“…Phase compensation schemes can be applied to stabilize the phase of the VNA-based channel sounder at sub-6 GHz, mmWave and sub-Terahertz (sub-THz) bands [3], [10]- [12]. The phase compensation scheme in [10] is directly implemented using microwave circulators and radio frequency (RF) cables at sub-6 GHz bands, and using circulators and E/O and O/E conversion units for channel sounder at 1-30 GHz [3] and 1-50 GHz [11], respectively. In [12], the phase compensation scheme was further extended to sub-THz bands, i.e., 220 to 330 GHz.…”