(A) study on the millimeter-wave propagation measurement for multipath environment at 28GHz band

Abstract

This work presents the design of the FMCW radar at 28GHz band and investigation of millimeter-wave propagation for multipath environment. The design of FMCW Radar is presented at 28GHz band, and which is applied to channel sounder for ra-dio propagation measurement. The proposed FMCW radar is based on phase locked loops and a direct digital synthesizer for linear frequency modulation, suitable for wideband performance. Also, it contains pre-scalers in the baseband to prevent spurious noise from up-converting with enhanced noise characteristics. The estimated range of the proposed FMCW radar system is measured in anechoic chamber for confirm the performance of overall FMCW radar system. The propagation measurement of mm-wave at 28GHz is conducted in a reverberation chamber which emulates multipath fading phenomena. The propagation of mm-wave at 28GHz band should be characterized for designing 5G mobile systems and predicting the wireless channel. An intermediate frequency signal of FMCW radar can be utilized in terms of both time and frequency domain signals due to a unique property of linear frequency modulation. Four different scenarios are examined by changing the boundary conditions of reverberation chamber with/without flat microwave absorbers. This investigation leads to obtained normalized propagation delay profiles, scattered plots, mean excess delay, root-mean-square delay spread and envelope distribution of Rayleigh fading channel at about 28 GHz band. The outdoor propagation measurement for cellular networks at 28GHz band is presented. The modified FMCW radar sweeps 400MHz bandwidth for high range resolution As the sweep signal at the low frequency is transmitted from baseband to RF system with low loss of transmission line, it is possible to separate TX and RX system with a long distance for high isolation performance. In order to radio characteristic according to antenna polarization, the 1st, 2nd reflected and penetrated signals are investigated under co- and cross-polarization condition.