Dielectric antennae

Antennas can receive or radiate electro-magnetic waves. Familiar TV aerials are receiving antennas to convert wave energy to the motion of electrons that is transformed to a measureable voltage. The vanes on an aerial are spaced to match the wavelength of the wave. Sometimes they chirp to accommodate a range of wavelengths. For shorter wavelengths, as in a microwave antenna. metal becomes too lossy and dielectric materials are used such as polystyrene. The tapered polyrod is a typical example. Often there is a need to radiate in a specific pattern called the radiation lobe and various periodic patterns are used. 

Dielectric antennas

Keratin has optical and magnetic properties that are suitable for antennas. The refractive index is high (1.58) and can be easily raised by dopants and lowered by pores.

The examples below show potential radiating structures in the European mole and barbastelle bat based on 2nd order Bragg interference.