Miniaturized Radio Repeater Design for Enhanced Ad-hoc Wireless Communication.

Abstract

In complex communication channel environments the radio-link coverage at microwave frequencies is mainly restricted by the exorbitant path-loss between communication nodes due to non-line-of-sight propagation and multi-path communication. Radio repeaters are commonly used to enhance the signal coverage, but the current systems are bulky and power hungry as the received signal is down-converted, amplified and retransmitted at a different frequency. This thesis deals with development of a low-power subwavelength radio repeater that can handle multiple channels simultaneously without requiring a specific communication protocol. First, a metamaterial-based electromagnetic band-gap isolator is introduced, which prohibits substrate mode propagation between two low-profile miniaturized antennas. This isolator achieves 24dB of isolation improvement between the transmit and receive antennas that are a quarter-wavelength apart and allows for 32dB of active amplifier gain between the antennas. Also using a novel near-field cancellation technique an electromagnetic null-plane between two antennas of a transmit array is created, which reduces the mutual coupling by -86dB. This radio repeater can achieve more than 50dB of active amplification. Lastly, a dual-channel radio repeater with a radar cross section of more than 26dBsm for both channels is developed.