School of Physics and Astrophysics

Postgraduate research profiles

Contact

David Mouneyrac

Phone: (+61 8) 6488 3443


Supervisors

Start date

Jul 2008

Submission date

Nov 2011

David Mouneyrac

Thesis

Development of a novel ultra-stable very low-phase-noise oscillator and a study of the modification of intrinsic microwave properties of semi-insulating monocrystalline materials

Summary

This research is mainly divided in two important parts. The aim of the first is to develop two ultra-stable very low-phase-noise oscillators, operating at 77 K and using a double crystal sapphire and later, using a photonic band gap resonator I will build a room temperature oscillator. The second part is to study the modification of intrinsic microwave properties of semi-insulating materials. In both cases Whispering Gallery Modes (WGM), a type of resonant modes with very high quality factors at microwave frequencies. The aim of the first part of my research is to build a new kind of very-stable very low-phase-noise oscillators using for the first time two sapphire resonators in the same cryostat at 77 Kelvin and then later implement a photonic band gap resonator (PBGR) at room temperature. Ultra-stable oscillators can be used as a local flywheel for a GPS signal over a long period to get an accurate position even if the signal is very weak. This kind of system may also permit very secure military transmissions based on the hopping frequency technique. The operational frequency of cryogenic sapphire resonator oscillators will be near 11 GHz. These oscillators operating near 77 K have the potential to become the lowest-phase-noise oscillators in the world. The operational frequencies of the PBGR resonator oscillator will be around 75GHz and 110GHz. The second part of this research will study the modification of the intrinsic microwave properties of semi-insulating materials. The WGM method has been used to make the most accurate measurements of the complex permittivity of low-loss dielectric materials. The WGM technique has also been used to characterize the complex permittivity of semiconductors, including bulk monocrystalline Silicon, Gallium Arsenide (GaAs), and Gallium Phosphide (GaP), at microwave frequencies from cryogenic temperatures to room temperature. The properties of GaP and GaAs samples will be studied under light and dark conditions at cryogenic temperature. A model will be proposed to explain the change in dielectric properties.

Why my research is important

Today, the use of microwave devices using dielectric resonators is becoming very important especially in the telecommunication domain. The dielectric resonators have the advantages to be relatively small, temperature stable and have also a high unloaded quality factor. Because of the development of new low loss materials and also new kind of resonators, the performances of filters and oscillators are going to be improved significantly.

Funding

  • Ad Hoc scholarship from University of Western Australia


 

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