Miniaturized Radio Repeater Design for Enhanced Ad-hoc Wireless Communication

: 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 low-power subwavelength radio repeater that can handle multiple channels simultaneously without requiring a specific communication protocol. First, metamaterial based electromagnetic band-gap isolator which prohibits the substrate mode propagation between two low-profile miniaturized antennas is introduced. This isolator achieves 24dB of isolation improvement between the transmit and receive antennas that are 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 20dBsm for both channels is developed.