A 10GHz Dielectric Rod Antenna

Summary

Dielectric rod antennas provide significant performance advantages and are a low cost alternative to free space high-gain antennas at millimeter-wave frequencies and the higher end of the microwave band.

The fundamental working principles of this type of antenna are explained and guidelines are given for a maximum gain design. These were applied to an X-band antenna design which resulted in a maximum end-fire gain of 20.5dBi for an antenna length of 11.18λ_o. E- and H-plane radiation patterns were measured as well, revealing high sidelobe levels, especially in the E-plane. This is about the only fundamental disadvantage of the dielectric rod antenna. However, some end-fire gain and main beam sharpness could be sacrificed to reduce the level of the sidelobes.

The tapered dielectric in waveguide feed configuration proved to be well matched over an extremely wide band; over 3GHz. The pattern bandwidth depends on the intended application of the antenna, but is in general also quite large. Not knowing the surface wave excitation efficiency of the feed was the only difficulty encountered during the design process. As a result, the maximum end-fire gain was achieved at a frequency different from the design frequency. This problem would not have existed if a computer code was available to model the transition from feed to antenna.

Analogy with the Rods and Cones of the Eye's Retina

Anatomy of the eye

Anatomy of the retina

The retina acts as an edge-detecting signal compressor.

The retina is an array of rods and cones.

The rod and cone disc-structure acts like an artificial dielectric.