Design and Development of Chaotic Cavity Coupled with Rotman Lens-based Multiplexer/Demultiplexer for DoA Estimation

Abstract

Along with increase in data rates, fast and accurate channel characterization at millimetre-wave (mmWave) frequencies is a critical requirement. The direction of arrival (DoA) is one of the basic parameters in channel characterization. At mmWave band, conventional DoA techniques face challenges of high cost and complexity, delayed and unreliable detection and high path loss and bandwidth. One of the novel approaches to estimate DoA is through frequency diverse imaging. This thesis presents a physical approach for estimating DoA using a large metallic chaotic cavity-backed meta-surface antenna integrated with rotman lens-based multiplexer/demultiplexer connected with diode detector estimator module at mm-Wave frequencies. The designed chaotic cavity at center frequency of 26GHz captures and compresses the channel information for the frequency band of 24 to 28GHz and compress the incoming plane wave radiation patterns into a single stream. Another cavity used in measurements is designed for 27 to 29 GHz with center at 28GHz. The compressed multimode signal obtained at the output of the cavity is split into equal four sub-bands through rotman lens (RL) based multiplexer which is designed using substrate integrated coaxial line (SICL) and micro-strip lines (MSL) technology. The sub bands are then processed through parallel estimator modules which will convert the incoming signal power into the detectable voltage levels. The binary output of the comparator after the diode detectors is further provided to the digital signal processing block at its output. The proposed approach uses the three distinct properties of mm-Wave communication hardware which are, frequency-diverse transfer function of a large voluminous metal made cavity to compress the channel, wideband signal demultiplexing using RL based demultiplexer and voltage detection using sensitive detector diodes. This paper demonstrates the design of individual modules and then simulation and experimental results of DoA estimation with simple hardware unlike of conventional methods, where DoA estimation is performed using large array of antennas. Results analysis including bandwidth constraints are also discussed which is an important factor in DoA estimation.