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International Journal of Antennas and Propagation
Volume 2015, Article ID 565734, 9 pages
Review Article

Transponder Designs for Harmonic Radar Applications

Department of Radio Science and Engineering, Aalto University School of Electrical Engineering, P.O. Box 13000, 00076 Aalto, Finland

Received 15 May 2015; Accepted 26 August 2015

Academic Editor: Shih Yuan Chen

Copyright © 2015 Kimmo Rasilainen and Ville V. Viikari. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This work presents a review on the concept of harmonic or secondary radar, where a tag or transponder is used to respond at a harmonic multiple of the incoming interrogation signal. In harmonic radar, the tag is called a harmonic transponder and the necessary frequency multiplication is implemented using a nonlinear element, such as a Schottky diode. Different applications and operating frequencies of harmonic transponders are presented, along with various tag design aspects. The designer may have to deal with certain tradeoffs during the design with respect to a number of transponder properties, and the role of these tradeoffs is also considered. Additionally, techniques usable for characterization of harmonic transponders are discussed.