Fresnel zone antenna

An offset Fresnel zone plate can be flush mounted to the wall or roof of a building, printed on a window, or made conformal to the body of a vehicle.

If the radiation from alternate zones is suppressed or shifted in phase by π, an approximate focus is obtained and a feed can be placed there to collect the received energy effectively.

Despite its simplicity, the half-wave zone plate remained mainly as an optical device for a long time, primarily because its efficiency is too low (less than 20%) and the sidelobe level of its radiation pattern is too high to compete with conventional reflector antennas.

In 1948, Maddaus published the design and experimental work on stepped half-wave lens antennas operating at 23 GHz and sidelobe levels of around −17 dB were achieved.

A year later a phase reversal zone plate reflector operating at 94 GHz was reported by Huder and Menzel, and 25% efficiency and −19 dB sidelobe level were obtained.

Although a simple Fresnel lens antenna has low efficiency, it serves as a very attractive indoor candidate when a large window or an electrically transparent wall is available.

In the application of direct broadcasting services (DBS), for example, an offset Fresnel lens can be produced by simply painting a zonal pattern on a window glass or a blind with conducting material.

[10] Based on the focal field analysis, it is demonstrated that high efficiency zone plate reflectors can be obtained by employing the multilayer phase correcting technique, which is to use a number of dielectric slabs of low permittivity and print different metallic zonal patterns on the different interfaces.

The theory and design method of single layer printed flat reflectors incorporating conducting rings and experimental results on such an antenna operating in the X-band were given in.

With amplitude-only control, no bandwidth-limiting phase shifters are needed, saving complexity and alleviating bandwidth constraints at the cost of limited beamsteering capability.

[15] In order to increase the focusing, resolving and scanning properties and to create different shaped radiation patterns the Fresnel zone plate and antenna can be assembled conformable to a curvilinear natural or man-made formation and used as a diffractive antenna-Radome.