Integrated microwave antennas and passive filters using 3D microfabrication and metamaterial architectures

Implementation of integrated microwave antennas and passive filters using advanced surface micromachining technologies and metamaterial architectures is presented. The main objective of this research is to demonstrate new device concepts and improve the performance of the antennas and passive filters for high efficiency, high gain, low loss, broad bandwidth and high integrability and manufacturability. These are achieved with two main technologies, three dimensional (3D) advanced microfabrication and metamaterial architecture. From the fabrication point of view, polymer-core conductor, multi-directional UV lithography, and surface tension assisted thermal reflow process are utilized as advanced surface micromaching processes together with conventional fabrication techniques such as electroplating, etching, sputtering and so on. From the design point of view, metamaterial architectures are adapted for beam focusing with zero-refractive index materials and for size reduction with metamaterial particles. Two metamaterial architectures having zero or near zero refractive indices have been demonstrated for antenna gain enhancement. While both show the improvement of the antenna gain, one that consists of a circular grid and a fan-shape patch converts linear polarization to circular polarization and the other that consists of a four-leaf clover shape metamaterial unit cell sustains the same circular polarization of the source patch antenna. Alternatively, gain of a patch antenna is improved using a micromachined dielectric lens made of photopatternable epoxy, SU8, which is supported by polydimethylsiloxane (PDMS). The dielectric lens fabricated using micromolding, polymer reflow, and ultraviolet (UV) lithography is integrated on top of a conductor-backed coplanar waveguide (CBCPW) fed coplanar patch antenna. The designed dielectric lens antenna (DLA) has a broad bandwidth of 6% and a high gain of 7.54 dBi at 77 GHz, which can be used for an anti-car collision radar system. An integrable sphere shape monopole antenna is demonstrated, where its bandwidth is enhanced using tapered transition between the main radiator and the feeding line. A super wideband (SWB) antenna with a bandwidth from 3 GHz up to 35.8 GHz is implemented. The sphere SWB monopole antennas is fabricated using multi-directional UV lithography and photopatternable polyurethane, D50. Also, planar-type SWB antennas fabricated on a exible liquid crystal polymer substrate are demonstrated, which will find applications in wearable electronics. Compact bandpass and bandstop filters are demonstrated using a metamaterial particle, split-ring resonator (SRR). A bandpass filter is designed with a combination of a half mode substrate integrated waveguide (HMSIW) for high integrability and broad bandwidth, and complementary SRR structures for size reduction. Since the CSRR-loaded HMSIW bandpass filter is built on a glass substrate with through glass vias (TGVs), it has a low insertion loss of 1.3 dB which is not achievable with a silicon substrate based technology. Also, a dual-functional glass interposer technology has been demonstrated: one is for an original glass interposer function such as interconnection and the other is a substrate for RF component integration. The glass interposer technology is expected to be more prosperous in high speed electronics in the future as parasitic and loss suppression in high frequency operation becomes a more important issue. Two highly compact tunable stopband filters using microstrip transmission lines coupled with split ring resonators (SRRs) and varactor diodes are presented. Frequency or bandwidth tuning capability of each device is demonstrated. The frequency tunable filter, realized by a single stage, shows a wide tuning range of 19.8% with a maximum bandwidth of 5% and an insertion loss of approximately 20 dB at 4 GHz. The bandwidth tunable filter, realized by double stages, shows a 10-dB bandwidth of 19 ↑ 3 % with a biasing voltage of 0 ↑ 10 V. The implemented frequency tuning and bandwidth tuning devices show a significant area reduction of 60.1% and 53.5%, respectively, Last, various air-lifted 3D periodic structures in pillar, bowtie and horn shapes are designed and fabricated for THz frequency notch filter applications. Dielectric loss, which is one of the most critical factors for THz performance, is greatly suppressed with the air-lifted architecture, and the bandwidth of the notch filter is broadened with bowtie and horn structures. In addition, the bowtie and horn structure can be utilized for a polarization and frequency selective surface (PFSS). The geometrical parameter effects of the air-lifted structures are studied. The 3D arrays are batch fabricated using multi-directional UV lithography and the polymer-core conductor techniques. Fabricated pillar structures are characterized in the THz range of 1-5 THz using a Bruker 113v Fourier Transform Infrared Spectrometer (FTIR) system. Device analysis and characterization of the fabricated structures are detailed. 21.