Calling all stations: antenna design

18 April 2017

Professor LUK Kwai-man (Croucher senior research fellowship 2000) is Chair Professor of Electronic Engineering and former Director of State Key Laboratory of Millimeter Waves at the City University of Hong Kong. Luk is an international authority on microwave antenna design and while he is distinguished for his significant contributions to the design and development of microwave wideband patch antennas he is also leading research in the field of millimeter wave and terahertz technology at the state key laboratory. He has just been awarded the prestigious John Kraus Antenna Award in 2017. 

“I measure the success of my research by its impact in the real world,” he says.

Significant advances in the development of millimeter-wave and terahertz (30-10 000 GHz) technologies have been made over recent years in response to the increasing interest in this electromagnetic spectrum. The nature of electromagnetic waves over this frequency range is well suited for the development of high-resolution imaging applications, molecular-sensitive spectroscopic devices, and ultra-broadband wireless communications.

“When the state key lab was set up in 2008 to look at millimeter wave technology, nobody really understood exactly what it was,” admits Luk but explains after initially focusing on applications related to 5G mobile communications, its key mission now includes antenna design, imaging techniques and RFID design. Millimeter wave RFID is used for applications such as luggage identification at airports, book archiving in libraries and stock management in supermarkets. A millimeter wave antenna can radiate a scanned beam with a narrow beam width of about 4 degrees, so at relatively short ranges items can not only be identified but also accurately located.

Luk has recently been awarded funding for the development of open ended substrate integrated waveguide fed electric dipole antennas, for millimeter wave communications. This is one of the designs for realising this hi-resolution scan beam technology for RFID, IoT or imaging applications.

“Terahertz (THz) is an even higher frequency at more than 300 GHz and we have a major project here to develop a terahertz imaging system,” he says. Terahertz wave is the electromagnetic spectrum between the conventional microwave and infrared regions with a wide range of applications including biomedical imaging, food safety, industrial materials inspection.

Terahertz imaging is very sensitive to water molecules and capable of distinguishing intrinsic contrast between normal and cancerous tissues. THz spectroscopy can also differentiate plant oils and animal fats because their refractive indices and absorption rates vary differently with increasing frequency and temperature. THz technologies have also been used in the detection of melamine in milk powder, antibiotics in food-matrices and pesticides in vegetables but researchers looking to exploit this promising frequency regime must overcome challenging entry barriers. The cost of testing equipment is high and there are availability problems for THz sources with sufficient power and suitable integrated circuits (ICs). As this little-known part of the electro-magnetic spectrum is explored further, Luk remains focused on his specialist field of expertise.

“Whether it’s communications or imaging, these new systems all need advanced antennas and I am the antenna guy,” says Luk with typical modesty. He is the author of three books, 10 research book chapters, over 350 journal papers and 250 conference papers but despite his impressive international reputation in research, Luk says he has never been over ambitious.

I am a person without high aims or great ambition. I usually look for incremental improvement

He admits that his first love at school was mathematics rather than electronics. It was only when his teacher at Kwun Tong Maryknoll College discouraged him from pursuing a career in mathematics “unless he was a genius” that Luk opted for engineering. He studied electrical engineering and after completing his PhD at the University of Hong Kong (HKU) accepted a post as lecturer at the newly established City Polytechnic.

“Teaching remains very important to me- you can’t just teach by the book- you need to be connected to research,” says Luk and when asked to list his most notable research achievements, he mentions two.

“I have invented important antenna designs that have been accepted by industry,” he says referring to the wideband patch antenna with an L-shaped probe feed, published in 1998, which has been the subject of more than 10 PRC and five US patents. Many mobile phone base stations on the roofs of many cities and still use his L-shape antenna design as do many Wi-Fi hotspots. There are also a number of radar applications.

Microstrip patch antennas have found many applications in wireless communication systems because of their properties as low profile, light weight, low cost, and easy fabrication but typically they also present a narrow bandwidth. Luk’s design enhanced their bandwidth substantially

“The bandwidth was enhanced by as much as 50%,” he says and lists a second and more recent achievement.

“Ten years ago, I invented the magneto-dielectric dipole antenna and many researchers have followed this lead since then,” he says.

Luk is a pioneer in the design of dielectric resonator antennas which are non-metallic antennas, often constructed of ceramic material and suitable for applications in wideband millimeter-wave communication systems. Radio waves are introduced into the inside of the resonator material and Luk explains this technology will be valuable in the future development in 5G technology. He clearly values the close relationship between his research and industry.

“I think it’s important that designs are tested by industry and their response motivates and pushes me to improve my designs and continue my research,” he says.

“I would say I am more an engineer than a scientist which means I need to understand the needs of the end user,” he adds and points to a water based micro-wave antenna he has developed for body worn applications.

“I think this lab is quite strong and well respected- if we are not the best we are at least one of the world leaders in this field,” he says.

Prof. Kwai-Man Luk was born and educated in Hong Kong. He received the B.Sc.(Eng.) and Ph.D. degrees in electrical engineering from The University of Hong Kong in 1981 and 1985, respectively.

He joined the Department of Electronic Engineering at City University of Hong Kong in 1985 as a Lecturer. Two years later, he moved to the Department of Electronic Engineering at The Chinese University of Hong Kong where he spent four years. Professor Luk returned to the City University of Hong Kong in 1992, and he is currently Chair Professor of Electronic Engineering. He served as Head of Department of Electronic Engineering from August 2004 to July 2010. His recent research interests include design of patch, planar and dielectric resonator antennas, microwave and antenna measurements, and computational electromagnetics. He is the author of three books, 10 research book chapters, over 350 journal papers and 250 conference papers. He was awarded five US and more than 10 PRC patents on the design of a wideband patch antenna with an L-shaped probe. He was the Technical Program Chairperson of the 1997 Progress in Electromagnetics Research Symposium (PIERS 1997) , and the General Vice-Chairperson of the 1997 and 2008 Asia-Pacific Microwave Conference, and the General Chairman of the 2006 IEEE Region Ten Conference. Professor Luk received the Japan Microwave Prize, at the 1994 Asia Pacific Microwave Conference held in China in December 1994. He received the Best Paper Award at the 2008 International Symposium on Antennas and Propagation held in Taipei in October 2008 and at the 2015 Asia-Pacific conference on Antennas and Propagation held in Bali in July 2015. He was awarded the very competitive 2000 Croucher Foundation Senior Research Fellowship in Hong Kong. In 2011 he received the State Technological Invention Award (2nd Honour) of China. Professor Luk is a Fellow of the Chinese Institute of Electronics, PRC, a Fellow of the Institution of Engineering and Technology, UK, a Fellow of the Institute of Electrical and Electronics Engineers, USA and a Fellow of the Electromagnetics Academy, USA. He has just been awarded the  John Kraus Antenna Award in 2017.

To view Prof Luk’s Croucher profile, please click here.