A substrate lens antenna basically contains a lens shaped dielectric body placed on an IC or printed circuit board that contains a feed antenna structure. Such an antenna is described for example in an article by X. Wu, G. Eleftheriades, T. Emie van Deventer-Perkins, titled “Design and Characterization of Single and Multiple Beam MM-Wave Circularly Polarized Substrate Lens Antennas for Wireless Communications”, and published in IEEE Transactions on Microwave Theory and Techniques, Vol. 49, no. 3, March 2001, pages 431-441.
The feed antenna structure is at a focal point of the lens shaped dielectric body. As a result ray breaking at the surface of the lens shaped dielectric body redirects all rays from the focal point towards directions closer to the optical axis of the lens, so that the antenna pattern from the feed antenna is focussed (narrowed). An ellipsoidal body may be used as lens shaped dielectric body, with the feed structure at one focal point of the ellipsoid and the other focal point in the body above the feed structure, in a direction perpendicular to the plane of the feed antenna.
Ideally, the ellipsoidal body has an outline corresponding to a surface of revolution obtained by rotating an ellipse around the line connecting its focal points, cutting off the body in a plane through the lower focal point and perpendicular to this line and placing this plane on the feed antenna structure. Instead an approximation of such a structure may be used, with a half sphere on a cylinder. In this case the cylinder is used to approximate the part of the ellipsoid between the focal points. Although approximate ellipsoid has less focussing effect than the ideal ellipse, it still provides for focussing.
In known substrate lens antenna slot or dipole feed antennas are used at the focal point of dielectric lens. Typically, such feed antennas have a resonant length somewhere between a quarter wavelength and one wavelength, and the dielectric body of the lens has a diameter of many wavelengths. Thus, the feed structure approximates a point source in the focal point and the lens approximately provides for focussing behaviour according to geometrical optics. However, this selection of size of the feed antenna limits the bandwidth over which it can be used.
Transmission of pulses with extreme bandwidth using elliptical lens antennas has been described for example in an article titled “Subpicosecond Photoconducting Dipole Antennas”, by Peter R. Smith, David H. Auston, and Martin C. Nuss and published in the IEEE Journal of quantum electronics, VOL 24. NO 2. February 1988 pages 255-260. This article uses a very short dipole, with a length that is much shorter than the wavelengths involved. Thus, wide bandwidth behaviour is realized, but at the cost of low antenna efficiency.