Abstract

Broadband antenna arrays are essential for applications such as radar, frequency-agile microwave communication and electronic counter-measures. Optical feeding of the individual elements of such arrays is promising for beam steering, remote positioning of the antenna with respect to the signal source or receiver, and for high-frequency operation where the inter-element spacing becomes too small for individual waveguide feeds. In this paper we describe the design, fabrication and evaluation of a compact broadband antenna on semi-insulating GaAs or similar material, which lends itself readily to array formation, and which is readily integrable with high-speed electronic and optoelectronic components for optical feeding and phase-shifting. Our design methodology has used the effective index method commonly used in optical waveguide analysis, in place of the more conventional but cumbersome method of moments. This simplification is justified by the strong confinement of the fields within the high-permittivity substrate. A slot-line antenna with a four-section Chebyshev quarter-wave impedance transformer and Marchand balun was designed and fabricated on Duroid 6010, a material chosen for its similar dielectric properties to semi-insulating GaAs. By measuring the SWR using a microwave network analyzer and sweep oscillator, and by using the antenna in receiving mode on an anechoic test range, we have demonstrated successful performance with at least 10 dB directional gain in the designed range 16-18 GHz. Possible applications of single- and multiple-element antennas of this type in hybrid optical/microwave systems will be discussed.

© 1990 Optical Society of America