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ABSTRACT
Detection of polarisation of microwave signals using infrared thermography is described in this paper. A metal grating consisting of parallel, equally spaced metallic strips is placed in between a microwave source (antenna) and a microwave absorption screen for permitting the determination of direction of electric field vector (polarisation). Very low frequency modulation of the microwave source is added to permit lock-in thermography which enhances thermal resolution.
In case of linear polarisation when the metallic strips of the grating are parallel to the direction of electric field vector, the temperature rise on the screen as observed by an infrared camera, is minimum. On the other hand if the metallic strips are perpendicular to the electric field vector the temperature rise observed on the screen is maximum. The orientation of the grid is changed by rotating the grid about a central axis perpendicular to its plane. With each different orientation of the grid a change in temperature rise is observed on the screen.
In case of circular polarisation the temperature rise on the absorption screen is almost independent of the grid orientation i.e. there is negligible change in temperature rise with each different orientation of the grid, as the electric field strength perpendicular to grid strips is almost constant for all grid orientations, corresponding to an axial ratio of unity. While in case of elliptical polarisation the temperature change is appreciable depending on the axial ratio.
The proposed method is validated on linearly, circularly and elliptically polarised patch antennas radiating at 8 GHz. Simulation is carried out in CST MICROWAVE STUDIO (CST MWS2013) and a good agreement between simulated and experimental (thermographic) results is observed.
Disclosure statement
No potential conflict of interest was reported by the authors.
Additional information
Notes on contributors
Khalid Muzaffar
Khalid Muzaffar (born 15 May 1981) did BTech in electronics and communication and MTech in communication and IT from National Institute of Technology, Srinagar, India in 2004 and 2006, respectively. He worked in Ericsson India Pvt Ltd. from July 2006 to July 2007. He Joined IUST Awantipora as an assistant professor in July 2007. He joined the Centre for Applied Research in Electronics, IIT Delhi in 2012 (through quality improvement programme), where he is currently working towards his PhD degree in characterising microwave antennas using infrared thermography. His research interests are microwave antennas, infrared thermography, and signal processing.
E-mail: [email protected]
Suneet Tuli
Suneet Tuli received the BE (Hons) in electrical and electronic engineering from Birla Institute of Technology and Science, Pilani, India, in 1982, and the MTech and PhD degrees from the Indian Institute of Technology (IIT), Delhi, India. He is a professor in the Centre for Applied Research in Electronics (CARE), IIT Delhi. He joined CARE, IIT Delhi, as a faculty member in 1986 and was a major participant in setting up a nondestructive thermal-acoustic-optical laboratory. He was a visiting researcher at the University of P. et. M. Curie, Paris, France, working on the generation and detection of microacoustic waves in solids. His current research interests include modelling, simulation, and system development for thermal and optical nondestructive characterisation.
Dr. Tuli was the recipient of a French Fellowship in 1987. In 2003, he received the 10th The Institution of Electronics and Telecommunication Engineers Professor K. Sreenivasan Memorial Award in recognition of his outstanding teaching and is presently the Dean (Industrial R&D) at IIT Delhi.
E-mail: [email protected]
Shiban K. Koul
Shiban K. Koul is a professor in the Centre for Applied Research in electronics at the Indian Institute of Technology Delhi. He is the author/co-author of more than 100 research papers and 7 state-of-the art books. He is the chief editor of the Journal of the Institution of Electronics and Telecommunication Engineers (IETE) India (Electromagnetics Section). He is on the editorial boards of the Journal of IETE, International Journal of RF and Microwave Computer-Aided Engineering and the Microwave and Optical Technology Letters. Dr. Koul is a fellow of the Indian National Academy of Engineering (INAE), fellow of the Institution of Electronics and Telecommunication Engineers (India), and fellow of IEEE, USA. He is recipient of several prestigious awards/accolades. His current research includes microwave and millimeter wave circuit design using suspended strip-line and dielectric integrated guides and RF MEMS. He is presently the Deputy Director (strategy and planning) at IIT Delhi.
E-mail: [email protected]