Finite-difference time-domain simulations of the effects of air gaps in double-shell extended hemispherical lenses

• Published in: IET microwaves, antennas & propagation Vol. 4; no. 1; pp. 35 - 42
• Main Authors: NGUYEN, N. T, SAULEAU, R, MARTINEZ PEREZ, C. J, ETTORRE, M
• Format: Journal Article
• Language: English
• Published: Stevenage Institution of Engineering and Technology 01.01.2010; The Institution of Engineering & Technology
• Subjects: Air gaps; Antennas; Applied sciences; Circuit properties; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Finite difference method; Lenses; Mathematical analysis; Mathematical models; Microwave antennas; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Radiocommunications; Resonant frequencies; Silicon; Telecommunications; Telecommunications and information theory; Input impedance; Lateral lobe; Microwave; Finite difference time-domain analysis; Spacing; Lens antenna; Boundary condition; Coatings; Coated material; Directivity; Millimetric wave; Integrated antenna; Simulation; Resonance frequency; Air gap
• ISSN: 1751-8725; 1751-8733
• DOI: 10.1049/iet-map.2008.0255

The effects of parasitic air gaps on the input impedance and radiation characteristics of dense double-shell integrated lens antennas are studied numerically at millimetre waves using the finite-difference time-domain method. The lens core is made up of Macor or silicon, and is coated with a quarter wavelength matching layer. The two kinds of gaps are compared, they are located either between both shells of the lens or between the lens base and the feed substrate. The authors show that their impact is much more critical in the second case, and that it becomes dramatic for silicon lenses even with very thin gaps; the three major observed effects are the following: 1. strong shift of the resonant frequency, 2. beam broadening and directivity loss, and 3. increase of the side lobe level.