High Q inductors on ultra thin organic substrates
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One of the chief components in a RF/microwave circuit is the inductor. The performance of the inductor affects the performance of widely used circuits such as the voltage controlled oscillator (VCO), low noise amplifier, and filter in the RF front end. It is very important to design inductors for accurate values of inductances and sufficiently high quality factors for these microwave applications. A key challenge in achieving high unloaded Q for an inductor in a thin substrate is the ground separation. This thesis aims at addressing this issue and achieving high unloaded Q's in the range 150 - 200 for a ground separation of about 100 - 140 microns in the frequency range of 1 - 15 GHz. One port and inductors will be designed using Electromagnetic field solvers. Various topologies will be explored for 2D and 3D inductors with the aim of achieving the desired inductance density and Q parameters in a minimum area possible. In order to address the issue of ground separation, design modifications will include the use of patterned grounds to take advantage of the reduced parasitic capacitive coupling which enables a high Q factor. The objective of the thesis also includes demonstration of the usefulness of these high quality inductors in RF front ends. To this effect, proof of concept designs of LC band pass filters will be presented. To enable this design, capacitors will also be designed. An extensive library of the designed inductors will be presented as a part of the thesis. The designed components will be fabricated at the Packaging Research Center (PRC), Georgia Tech using organic substrate compatible processes. High frequency measurements will be made with the Vector Network Analyzer (VNA) along with suitable de - embedding to demonstrate the correlation between designed and fabricated results. Following this, circuit models will be built for the characterized inductors.