Abstract-Electromagnetic Analysis of Horn Antennas in the Terahertz region

Bevan, Mairead

http://eprints.nuim.ie/4486/

This thesis is concerned with the application of electromagnetic modelling techniques to the analysis of horn antenna characteristics over the terahertz range, 0.1 THz to 5 THz. The mode matching technique based on a scattering matrix approach to describe beam propagation in both the forward and backward direction is applied to the analysis of conical and pyramidal horn antenna both single and multi-moded, in particular the multi-moded pyramidal horn antenna array of the SAFARI instrument - a far infrared imaging spectrometer to be launched onboard the future SPICA mission. A second electromagnetic method - the finite integration technique is applied to the analysis of simple waveguide structures and characteristics associated with them through commercially available package CST. Where appropriate a quasi-optical approach to the analysis is also applied for comparison and verification of the results, namely Gaussian beam mode analysis. The underlying theory behind these analytical techniques and their implementation is provided along with descriptions of software packages used in the analysis, these are μWave Wizard a commercially available software package based on the mode matching technique, CST Microwave studio commercially available software utilising the finite integration technique and SCATTER code developed at NUI Maynooth using the mode matching technique. Gaussian beam mode propagation using both Gauss-Laguerre and Gauss-Hermite mode sets is implemented by code written within the Mathmatica environment. The effectiveness of each method in its application to particular structures to obtain accurate and computationally feasible results is discussed. Particular effects inherent is quasi-optical systems, crosstalk and standing wave effects are analysed in addition in later chapters. These effects are analysed both experimentally using a vector network analyser and within appropriate computational models.

Outer space research could benefit inner space

http://www.lethbridgeherald.com/local-news/outer-space-researchcould-benefit-inner-space-112611.htmlCaroline Zentner
lethbridge herald
czentner@lethbridgeherald.com
The medical tricorder used by Bones in the Star Trek series is getting closer to reality as local scientists work to develop ultra-sensitive diagnostic technology.
That it came from the world of astronomy should be no surprise. David Naylor, a physics professor at the University of Lethbridge, said the terahertz imaging technology on the Herschel space observatory is built to look deep into space at wavelengths far beyond visible light.
That same kind of sensitivity can be useful in medicine. Blue Sky Spectroscopy, a privately owned company in Lethbridge started by Naylor in partnership with the University of Lethbridge and the University of Calgary, is working on a terahertz imaging detector to diagnose breast cancer.
"It's been proven by a group in Taiwan, a research team there that has links with a medical faculty, that you can actually measure breast cancer with 100 per cent accuracy, which is amazing, without using a pathologist," Naylor said.
Current diagnostic methods can result in false test results that can be dangerous for patients and expensive for the health-care system.
"In astronomy we have to have the most sensitive detectors because our galaxies are so far away. Of all disciplines astronomy has the most sensitive detectors of anybody," Naylor said. "If I can see something a billion light years away, of course I can see something under a microscope a few millimetres in front of me."
Such an imager could be used in the operating room to tell surgeons the exact size and location of the cancer. As it stands, no real-time measurement of the cancer is possible, Naylor said. Surgeons estimate how much tissue to excise, but a second surgery is sometimes required if the first surgery didn't get all of the cancer.
That's just one of the items Naylor shared with those at the Canadian Space Society conference in Calgary this past week. He was speaking on astronomy and technology, including SPICA, the space infrared telescope for cosmology and astrophysics. Naylor is the Canadian principal investigator for the project which is being led by the Japanese Space Agency. The project has not yet received formal acceptance.
"If it goes ahead, the U of L will be leading Canada's interest in it," he said. "We're the only university in which a group is leading Canada in two space missions."
SPICA is expected to provide superior sensitivity and high spatial resolution with its unique design and scientists hope it will help answer questions about how galaxies were formed and how they evolved.
On the ground, the sensitive terahertz imaging detectors could also have applications beyond medicine.
"Terahertz imaging can penetrate many materials," Naylor said.
The technology could be used in locating improvised explosive devices (IEDs), to find masterpieces hidden behind walls in Italian palaces, to identify drugs, explosives and contraband cargo, and as security body scanners at airports.
"We joke that you'll be able to go through the airport (and) with a terahertz scanner they'll clear you for carrying weapons and they'll tell you if you've got cancer," Naylor said.
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