Author: Qi Jiang

Publisher:

Published: 2014

Total Pages:

ISBN-13: 9781321362930

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Clean and inexhaustible energy has long been a dream for the human race, especially over the last few decades with the ever increasing energy consumption requirements and severe environmental problems associated with the use of traditional fossil fuels. Fusion energy stands out among the possible candidates for its self-sustainability and environmentally friendly nature. To realize that on our planet, the tokamak (toroidal chamber with magnetic coils), which is a magnetically confined "donut" shaped device, was invented in the 1950s by Soviet physicists Igor Yevgenyevich Tamm and Andrei Sakharov and has become the dominant approach of fusion energy research. However, the physics inside the tokamak is extremely complicated and it is difficult to make measurements inside due to the high temperature plasma. Therefore, millimeter wave imaging systems for remote measurements have been developed to make the physics visible to fusion scientists. Currently, there are two types of imaging systems under development and application by UC Davis: Electron Cyclotron Emission Imaging (ECEI) and Microwave Imaging Reflectometry (MIR), both of which have been successfully applied to various tokamaks. However, there are still more improvements and upgrades needed for the current systems. In this dissertation, the author will focus on two aspects of the system improvement: wider bandwidth design and higher frequency operation.In the first part, a Coplanar Stripline (CPS) to Microstrip balun and a Conductor Backed Coplanar Waveguide (CBCPW) to Microstrip transition has been designed to widen the IF bandwidth of the current ECEI system. Both the balun and the transition feature wide bandwidth, low loss, and compact size. With the help of these improvements, the IF bandwidth can be successfully extended to 2~26.5 GHz.In the second part, the author focused on the high frequency operation of the ECEI system. As the operation frequency increases with higher magnetic field, finding a high frequency, high power LO source is becoming a major stumbling block. Thus, a higher frequency receiver operating both harmonically and subharmonically is proposed, investigated, and designed to lower the required LO frequency to only half of the RF frequency. Three types of higher frequency receivers have been designed: Single ultra wideband antenna topology, cross-polarized antenna topology, and dual-plane antenna topology. Each of them will be discussed in detail. The major concepts and design efforts are summarized as: looking for higher frequency, wide bandwidth antennas, eliminating the interference between antennas, and optimization of mixer input/output networks. Different types of antennas have been designed and tested; two methods have been proposed to eliminate the antenna interference; and the mixer input/output networks have been designed carefully. The designed higher frequency receiver can successfully operate at RF frequency of 150--170 GHz with an LO source at 75 GHz.

Download or read book Design of Extended Bandwidth and Frequency Millimeter Wave Imaging Receiver Arrays for Fusion Plasma Diagnostics written by Qi Jiang and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Clean and inexhaustible energy has long been a dream for the human race, especially over the last few decades with the ever increasing energy consumption requirements and severe environmental problems associated with the use of traditional fossil fuels. Fusion energy stands out among the possible candidates for its self-sustainability and environmentally friendly nature. To realize that on our planet, the tokamak (toroidal chamber with magnetic coils), which is a magnetically confined "donut" shaped device, was invented in the 1950s by Soviet physicists Igor Yevgenyevich Tamm and Andrei Sakharov and has become the dominant approach of fusion energy research. However, the physics inside the tokamak is extremely complicated and it is difficult to make measurements inside due to the high temperature plasma. Therefore, millimeter wave imaging systems for remote measurements have been developed to make the physics visible to fusion scientists. Currently, there are two types of imaging systems under development and application by UC Davis: Electron Cyclotron Emission Imaging (ECEI) and Microwave Imaging Reflectometry (MIR), both of which have been successfully applied to various tokamaks. However, there are still more improvements and upgrades needed for the current systems. In this dissertation, the author will focus on two aspects of the system improvement: wider bandwidth design and higher frequency operation.In the first part, a Coplanar Stripline (CPS) to Microstrip balun and a Conductor Backed Coplanar Waveguide (CBCPW) to Microstrip transition has been designed to widen the IF bandwidth of the current ECEI system. Both the balun and the transition feature wide bandwidth, low loss, and compact size. With the help of these improvements, the IF bandwidth can be successfully extended to 2~26.5 GHz.In the second part, the author focused on the high frequency operation of the ECEI system. As the operation frequency increases with higher magnetic field, finding a high frequency, high power LO source is becoming a major stumbling block. Thus, a higher frequency receiver operating both harmonically and subharmonically is proposed, investigated, and designed to lower the required LO frequency to only half of the RF frequency. Three types of higher frequency receivers have been designed: Single ultra wideband antenna topology, cross-polarized antenna topology, and dual-plane antenna topology. Each of them will be discussed in detail. The major concepts and design efforts are summarized as: looking for higher frequency, wide bandwidth antennas, eliminating the interference between antennas, and optimization of mixer input/output networks. Different types of antennas have been designed and tested; two methods have been proposed to eliminate the antenna interference; and the mixer input/output networks have been designed carefully. The designed higher frequency receiver can successfully operate at RF frequency of 150--170 GHz with an LO source at 75 GHz.