UC Davis

Passive millimeter wave (PMMW) is becoming increasingly popular for signal detection. However, it suffers from the attenuation during the propagation. Among all frequency windows, D-band PMMW has lowest attenuation in propagation within oxygen, water, fog and drizzle. The purpose of this research is to design wideband antennas for D-band passive millimeter wave imaging system with good gain performance and wide impedance bandwidth.The thesis presents two planar antennas for passive imaging systems. Both antennas are designed in D-band (140GHz) and are excited by Coplanar Waveguide (CPW). Both antennas are constructed using a low permittivity material, quartz (?$ = 3.78). The first design is a planar monopole antenna, which can provide large impedance bandwidth (97- 226GHz) due to characteristics of the planar monopole antenna. However, the leakage of back radiation decreases the gain of planar monopole antenna. The second antenna, coplanar patch antenna, is introduced to increase the gain within desired frequency range. By incorporating a back ground plane, the proposed coplanar patch antenna achieves 49.15 GHz -10dB impedance bandwidth (115.56 to 164.71 GHz) with a minimum gain larger than 4.8 dBi. Parametric sweepings are done to optimize the antenna performance, and corresponding discussions about the influences by those parameters are included. Both antennas can cover the desired frequency window with good gain performance, making them suitable for PMMW imaging system.