Reconfigurable Varactor-Based Microwave Components for Low-Cost Antenna Array Design: Phase Shifters, Attenuators and Diplexers
Date
2023
Authors
Yuan, Yuan
Editors
Advisors
Fumeaux, Christophe (The University of Queensland)
Chen, Shengjian Jammy (Flinders University)
Chen, Shengjian Jammy (Flinders University)
Journal Title
Journal ISSN
Volume Title
Type:
Thesis
Citation
Statement of Responsibility
Conference Name
Abstract
Phased array antennas are important for advanced wireless communications, providing high directivity and beam steering capabilities. However, conventional phased arrays are expensive, bulky, heavy and power-hungry due to their complex architecture and electronic controls. For systems demanding low cost, light weight, compact size, and low power consumption, reconfigurable antenna arrays can be a practical alternative to traditional phased arrays. Electronically controlled reconfigurable antennas offer the ability to adjust their operating frequency, radiation pattern, polarization, or any combinations of these aspects by using tunable electronic components such as PIN diodes, switches, varactors and/or microelectromechanical systems (MEMS). One way to realize reconfigurable antenna array is to start by designing a reconfigurable feeding network and then co-designing corresponding antenna elements, before combining these two structures to form the whole array based on the system requirements. However, when designing low-cost and compact reconfigurable antenna arrays, several critical aspects should be taken into consideration. Firstly, the reconfigurable feeding network may result in a large number of components and a complex structure, leading to a higher insertion loss and a possible degradation in antenna performance through reduced efficiency. Secondly, if the feeding network is not designed properly, integrating it into the system can lead to a high demand in space, consequently enlarging the overall size, manufacture complexity and cost. In this context, compact, seamlessly-integrable, low-power, low-cost and tunable microwave components are needed to build reconfigurable feeding networks. Through using these feeding networks, low-cost and compact reconfigurable antenna arrays can be realized as alternatives to conventional phased arrays. Varactor-based phase shifters to control the signal phase, reconfigurable attenuators to control the signal magnitude and reconfigurable diplexers to control the signal frequency are essential components to construct these so-called reconfigurable feeding networks. This is in line with the goal of this thesis, which comprises three coherent objectives. Firstly, the dissertation presents a concept of low-cost varactor-based phase shifters, which are operating in differential mode. A phase shifter pair based on this concept is able to supply full- 360◦ phase difference tuning range between its two output ports. The devices can be directly integrated with 50 Ω feed transmission lines, which results in a compact, lowcost and lightweight design of the feeding network and saves space which would be required by conventional phase shifter blocks. Based on such differential phase shifter pairs, a 1×4 linear dielectric resonator antenna array is designed, which is excited by a feeding network comprising 3 phase shifter pairs to control the array scanning sumpattern continuously from -45◦ to 45◦ and the null of a difference pattern from -30◦ to 30◦. A dedicated procedure for accurately calibrating these beam-steerable antennas is also proposed, aiming to provide a general approach to enhance the performance of the reconfigurable feeding network. Secondly, a tunable transmission-type attenuator with easily-extendable and tunable attenuation level, small initial insertion loss, and satisfactorily low reflection coefficient is presented, which is integrated onto a 50 Ω microstrip transmission lines with several side-loaded shorted-end varactorbased stubs. This arrangement allows a compact and low-loss structure, as well as seamless integration with planar transmission lines in microwave circuits, which also makes them suitable for applications with limited real estate. It is proven that a 3-stub attenuator can offer tunable attenuation from 1.0 to 13.5 dB with reflection coefficient lower than -11.4 dB, and that by cascading them a larger attenuation range can be obtained. Thirdly, a frequency-switchable varactor-based diplexer concept is proposed for a low-cost and compact pattern- and frequency-switchable microstrip antenna array. This diplexer concept, which represents an extension in functionality of the differential phase shifter pair, is able to supply different responses to different frequencies in a wide-band range, instead of utilizing the phase difference performance in a narrow operation band. Seamless integration with the feeding network enables a dual-band antenna pair to become a pattern- and frequency-switchable array with unique functionality. All the results presented in this thesis are derived fromvaractor-based microwave components that offer a range of benefits, including low cost, lightweight construction, low power consumption, and a seamless integration topology. All these proposed reconfigurable devices allow construction of reconfigurable feeding networks with phase and magnitude tuning abilities, as well as frequency reconfigurability. This means that antenna arrays fed by this type of feeding networks can achieve versatile and competitive reconfigurability in their radiation performance, while maintaining a compact size, low weight, low power consumption and affordability.
School/Discipline
School of Electrical and Mechanical Engineering
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Mechanical Engineering, 2023
Provenance
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals