AbstractReconfigurability has become a desirable and essential feature of modern Radio-Frequency (RF) systems for wireless communications due to the unprecedented challenge to accommodate multiple bands in communication standards. Reconfigurable circuitry makes it possible to reduce the size and cost of the system by providing RF tuning instead of duplicating the same circuits for every desired band. Optical reconfiguration is distinguished by its elimination of an electrical bias system and ElectroMagnetic Interference (EMI), while potentially providing fast switching compared with other conventional RF tunable approaches.
This project is primarily interested in the new designs and characterisations of optically-tunable switches which remove the need of a diode junction and thus, inherently demonstrate high linearity and power-handling ability. In addition, the recent development of a semiconductor laser and Light Emitting Diode (LED)/Infra-Red Emitting Diode (IRED) techniques has enabled the achievement of high-intensity and spatial illumination in a pulsed tuning operation. These facts are the motivation for a new investigation of optically reconfigurable microwave and millimetre wave switches. Initial work focuses on generating an ElectroMagnetic (EM) simulation model and investigating the high insertion loss in the photoconductive switches presented in previous work. It then involves the use of improved designs for optically- controlled switches at microwave and millimetre wave frequencies. The RF characterisation of these proposed devices is performed in terms of insertion loss, isolation, nonlinearity, power- handling and switching speed.
A novel, high-power optically controlled microwave microstrip switch is presented with superstrate structure through a low-loss glass substrate which reduces insertion loss to 1.11푑퐵 and simultaneously maintains good isolation of 20푑퐵 at 2퐺퐻푧. 3rd-order Input-referenced Intercept Point (IIP3) is measured up to +78.5푑퐵푚 in a two-tone nonlinearity test with maximum power handled at over 60푊 , which is reported for the first time. An optically reconfigurable Grounded-CoPlanar Waveguide (GCPW) microwave and millimetre-wave (mmW) switch has been designed and measured with good results showing an insertion loss of less than 3푑퐵 and isolation over 30푑퐵 in millimetre wave frequencies.
|Date of Award||23 Jan 2019|
|Supervisor||Martin J Cryan (Supervisor)|