Pattern Reconfigurable Resonance Based Reflector Antenna for Thorax Imaging

摘要

The design and analysis of a pattern reconfigurable resonance based reflector antenna is presented. The antenna is designed to meet the light weight, compact size, wide bandwidth and unidirectional radiation requirements of thorax imaging systems. It is comprised of a dipole antenna that is vertically positioned on top of a loop structure. The loop antenna operates both as a resonator and a reflector at the same time, thus creating a wide operating bandwidth and a unidirectional radiation. To reduce the lateral size of the antenna, a C-shaped structure is utilized to increase the electrical length of the dipole-antenna without physically altering its dimensions. To switch the radiation beam of the antenna at different directions without using mechanical rotation, the position of the dipole's arms are electronically altered. Consequently, this creates three virtual dipoles, which enable switching the radiation pattern at the direction of the active one. The proposed antenna achieves a compact size of 0.32λ× 0.32λ with respect to the wavelength at the lowest operating frequency of the antenna. It achieves a maximum fractional bandwidth of 41% at 0.8-1.21 GHz with a peak gain and front-to-back-ratio (FBR) values of 5.9 dBi and 15 dB, respectively, with a scanning range of ±27 degrees at the elevation plane.