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Title: Bulk micromachined trench-coupler based microwave circuits
Author: Huang, Xuguo
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Micromachining and low temperature co-fired ceramic (LTCC) technology have been widely used in modern radio-frequency (RF) and microwave systems. Both technologies provide the possibility to construct a three dimensional (3D) RF/Microwave circuits, which may have advantages in RF performance, size and power consumption when compared to conventional planar circuits. In this thesis, novel tightly-coupled microstrip and coplanar waveguide (CPW) transmission lines have been developed for LTCC bars and high-resistivity silicon (HRS) trenches fabrication processing technologies. The characteristics of the proposed 3D coupled lines have been analyzed by a quasi-static method and confirmed by electromagnetic (EM) simulation. Compared to existing tightly-coupled transmission line, they have a simple and compact layout but can also provide very tight coupling, good balance of even-odd mode phase velocities and high power handling capability. Using the proposed 3D coupled lines, an S-band quadrature hybrid coupler has been designed and fabricated. In the proof-of-concept device, the measured coupling coefficient is 3.61 dB and the insertion loss is 0.7 dB over a 60% fractional bandwidth. Utilizing the hybrid coupler, a single stage reflection-type phase shifter has been demonstrated. The phase shifter exhibited the true phase shifter frequency characteristics in the range of 2.5-3.5 GHz and the measured maximum relative phase shift is 120°. In addition, an ultra-wideband bandpass filter has been synthesized by the modified narrowband bandpass filter design equations and realized by the 3D coupled-lines. The measured fractional bandwidth is 130%, with only 0.7 dB mid-band insertion loss at 6.4 GHz and better than -20 dB return loss across the whole passband. The measured differential-phase differential-phase group delay is less than 200 ps from 2.6 to 10.1 GHz. Being a monolithic filter, it has a compact area of only 3.5 x 5.5 mm2.
Supervisor: Lucyszyn, Stepan Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available