| Prof. Leo P. Ligthart |
Biography:Leo P. Ligthart received an Engineer's degree (cum laude) and a Doctor of Technology degree from Delft University of Technology in 1969 and 1985, respectively. He is Fellow of IET and IEEE. He got awards from UK-IET, IEEE MIKON conference, EuMA, Netherlands electronic and radio society (NERG). He is Honorary Member of the Delft EE student society. He received Honorary Doctorates (Honoris Causa) at Moscow State Technical University of Civil Aviation in 1999, Tomsk State University of Control Systems and Radioelectronics in 2001 and Military Technical Academy, Romania in 2010. He is academician of the Russian Academy of Transport. Since 1988, he has held the chair on radar and from 1992 he has held the chair of Microwave Transmission, Radar and Remote Sensing in the Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, The Netherlands. In 1994, he founded the International Research Center for Telecommunications and Radar (IRCTR) at Delft University and has been the director of IRCTR for more than 16 year. He is founding member of the European Microwave Association, chaired the first European Microwave Week (EuMW) and initiated the European Radar Conference (EuRAD) in 2004. He was project manager of more than 30 multi disciplinary projects valued over k€ 40.000. He was advisor of more than 50 PhD candidates. Currently Prof. Ligthart is emeritus professor of Delft University, guest professor at University Indonesia, consultant at LIPI (science foundation Indonesia), Scientific advisor of IRCTR-I, Chairman of CONASENSE (a global initiative on communications, navigation, sensing services), Chairman of ICT Friesland, Netherlands, Board of governors CTIF, Denmark and Board of Governors IEEE-AESS. He has been invited to give courses on radar, microwave remote sensing, antenna systems, sparse arrays at various universities and institutes in China, India, Indonesia, Australia, South Africa, Italy, Turkey, etc. His principal areas of specialization include antennas and propagation, radar and remote sensing, but he has also been active in satellite, mobile and radio communications. He has published over 600 papers and various book chapters and 2 books.
Abstract: In modern radio and radar the antenna arrays play an important multi-function role with respect to angular pattern and frequency characteristics. Most literature exists on so called ‘dense’ arrays with mutual, equidistant spacing between the antenna elements in the order of half the wavelength. Mutual coupling between the elements and wide-angular scanning requirements give degradation in the dense array performance and cause many headache problems for generations of antenna engineers. In so called ‘sparse’ arrays the mutual spacing is larger. For wide-angular scanning, individual transmit-receive modules are needed meaning that high gain dense antenna arrays with many elements are costly. Sparse arrays are interesting because they use ‘array thinning’ and have therefore a potential lower cost. In order to maximize the array efficiency in sparse arrays, the transmit power per element should be equal with a threat of high side lobes near the main lobe and unwanted grating lobes. For avoiding grating lobes in sparse arrays the spacing between elements should be non-equidistant. The so obtained spatial distribution of elements leads to a spatial field distribution over the array. Special design of this spatial field distribution can benefit the lowering of side lobes near the main lobe. The design of sparse arrays is the central theme of this tutorial, showing sparse array advantages and disadvantages in comparison with dense arrays. Contents of the tutorial |
