Prof. Steven Gao
Chair of RF and Microwave Engineering
School of Engineering and Digital Arts
University of Kent
Canterbury CT2 7NZ, UK
Low-Cost Smart Antennas
Abstract
Smart antennas are the key technology for wireless communications and radars. They can adjust their radiation patterns adaptively, i.e., forming maximum radiation towards the desired users and nulls towards the interference sources. Thus, they can improve the capacity of wireless communication networks significantly, increase the spectrum efficiency and reduce the transmit power. Traditionally, smart antennas are, however, too complicated, bulky, heavy and expensive for civil applications. For commercial applications, it is very important to reduce the cost, size, mass and power consumption of smart antennas.
This lecture will first give an introduction to smart antennas and their types such as passive and active phased arrays, digital beamforming smart antennas, adaptive arrays, multi-beam antennas, beam-switching antennas, multiple inputs and multiple outputs (MIMO) antenna systems, etc. The basic principles of each type of smart antennas will be explained. The advantages and disadvantages of each type of smart antennas will be highlighted.
The lecture will then describe different types of low-cost smart antenna technologies, such as Electrically-Steerable Parasitic Array Radiator (ESPAR) antenna, compact MIMO antennas, beam-switching array antennas and low-cost phased arrays. Many practical examples of antenna configurations and designs will be shown, explained and their performance discussed. These will include folded-monopole ESPAR (FM-ESPAR) for wireless communications, high-gain ESPAR using small director array, small-size MIMO, beam-switching reflectarray antennas for satellite communications, low-cost phased array antennas, etc.
Space Antennas
Abstract
Due to the special environment of space and the launch vehicle dynamics to get there, spacecraft antenna requirements and designs are quite different from those of terrestrial antennas. Onboard a satellite, there are a number of different antennas and arrays for various functions, such as Telemetry, Tracking and Command (TT&C), high-speed data downlink, GPS navigation and positioning, remote sensing, inter-satellite links, deep-space communications, etc. Since the launching of 1st man-made satellite “Sputnik” in 1957, a large variety of antennas and arrays have been developed for space applications and the antennas employ different frequency bands including UHF/VHF, L, S, C, X, Ku, Ka and V band.
This lecture will first explain the satellites, orbits, the space environment and special requirements of space antennas. Different types of satellites and orbits will be explained. Space environments such as extreme thermal conditions, materials outgassing, radiation environment, multipaction effects, passive inter-modulation, corona phenomenon, electro-static charging, atomic oxygen, etc, will be discussed and their impact on the antenna designs will be explained. Other issues, e.g., the interactions amongst antennas, satellite bodies and solar panels, will also be described. Key challenges for space antenna designs will be illustrated.
The lecture will then provide an overview of space antennas developed for different applications. This part will show many examples of the real-world space antennas for different applications such as TTC, navigations, high-speed data downlink, GPS reflectometry remote sensing, inter-satellite links, deep-space communications, etc. The operating principles of each antenna will be explained and their performance will be discussed. Finally, an outlook to the future development of space antennas will be presented.
Multi-Band Antennas for Global Navigation Satellite Systems (GNSS) Receivers
Abstract
Global Navigation Satellite System (GNSS) is a satellite based radio navigation system that provides precise information about the spatial coordinates (longitude, latitude and altitude) of an object anywhere on the earth or in the air. Global Positioning System (GPS) is the single fully operational navigation system available for commercial and military users around the globe while Galileo, GLONASS and COMPASS (European, Russian and Chinese respectively) are in the development stage with GLONASS operating with partial capability. GNSS operates at different frequency bands including L1, L2, L5, E5, etc. The use of a compact multi-band antenna instead of multiple single-band antennas can reduce the size, mass and cost of GNSS receivers significantly. During recent years, a variety of multi-band antennas have been developed for GNSS receivers.
This lecture will give an introduction to the GNSS system and the antenna design requirements for GNSS receivers. Various issues such as multipath mitigation, phase center stability, compact size, multi-band operation, etc, will be discussed. Techniques of multipath mitigation such as choke rings, electromagnetic-band-gap (EBG) antennas, etc, will be presented and their principles will be explained.
The lecture will then give a review of compact multi-band antennas and arrays for GNSS receivers. Many examples of GNSS antenna designs will be shown, and the antenna configurations and design principles will be explained. These will include the dual-band multipath mitigating GNSS antenna using the cross plate reflector ground plane (CPRGP), multi-band QHA antennas, active multi-band antennas, small multi-band GNSS array antennas, high-gain beam-switching multi-band GNSS arrays, etc. The performance of each antenna will be described.
Antennas for Synthetic Aperture Radars
Abstract
Synthetic aperture radars (SAR) is an imaging radar which produces high resolution radar images of the earth’s surface by using microwave signals. Unlike optical sensors which are limited by day lights and weather conditions, SAR can be used day and night and can see through clouds. SAR has important wide-ranging applications for earth observations in remote sensing and mapping of the surfaces of both the Earth and other planets. SAR is used in various fields of research ranging from oceanography, geology, to archaeology. Antenna for SAR is usually very complicated and expensive. SAR antenna is often one of the most expensive components onboard the aircraft or spacecraft.
This lecture will first give an introduction to SAR systems and how SAR works. Key parameters of SAR systems such as range resolution, azimuth resolution, frequency bands, etc, will be explained. Different SAR modes such as stripmap, scanSAR, spotlight and interferometric SAR (InSAR) will be described. SAR system design considerations and key challenges for SAR antenna designs will also be presented.
The lecture will then provide a review of antennas for SAR. An overview of antenna development for space-borne SAR will be illustrated and some examples will be given. The design principles of each example antenna will be explained and their performance discussed. Finally the lecture will give a discussion of future development such as the digital beam-forming SAR for satellite constellations, etc.
Biography
Steven Shichang Gao received PhD in Microwave Engineering from Shanghai University, China, in 1999. From 1993 to 1996, he was with China Research Institute of Radiowave Propagation, China. He worked as a Post-Doctoral Research Fellow at National University of Singapore, Singapore (Oct. 1999 - May 2001), Research Fellow at Birmingham University, UK (May 2001 - May 2002), Senior Lecturer (May 2002 - July 2006) and then Reader (July 2006 - Sep. 2007) at Northumbria University, UK, Senior Lecturer and Head of Space Antennas and RF Systems Group at Surrey Space Center, University of Surrey, UK (Sep. 2007-Dec. 2012), and Professor at University of Kent, UK (Jan. 2013 - July 2022). He also served as the Head of Communications Research Group at the University of Kent (Jan. 2020 - July 2022) and is an Honorary Professor at the University of Kent since August 2022. Since Sep. 2022, he has been with the Chinese University of Hong Kong, Hong Kong, where he is a Professor.
Prof. Gao was a Visiting Scientist at Swiss Federal Institute of Technology (ETHZ), Zurich, Switzerland in 2003, a Visiting Scientist at University of California at Santa Barbara (UCSB), USA, in 2005, and JSPS Visiting Fellow at Chiba University, Japan, in 2005 and 2013.
Prof. Gao is an IEEE Fellow, and also a Fellow of IET (UK) and the Royal Aeronautical Society (UK). He is the Editor in Chief of IEEE Antennas and Wireless Propagation Letters (AWPL). He is a Senior Member of the International Union of Radio Science (URSI). He was UK’s representative in European Association of Antennas and Propagation (2020 - 2022) and a Distinguished Lecturer of IEEE (2014 - 2016). He co-authored over 600 papers (including over 250 papers in IEEE Journals), 3 books and over 20 patents.