Antennas are inductive.Microwave antennas are horn antenna, Parabolic antenna, slot antenna, dipole antenna, dielectric antenna, printed antenna, phase array antenna, Micro strip patch antenna, Plasma antenna, MIMO antenna. Horn antenna is the most widely used microwave antenna. As frequency increases gain of horn antenna also increases. Horn antenna is a fixed size antenna. Horn antenna has low noise, so its directivity is almost equal to gain. Parabolic antenna has high gain and low cross polarisation. Gain of half dipole antenna over isotropic is 2.15db. In half wave dipole antenna current nodes are at end
Cassegrain feed is a small reflector to beam waves to the larger parabolic reflector. Half-wave dipole is refered as hertz antenna. Gain of the Hertzian dipole over isotropic antenna is 1.75db. Horizontal antenna is horizontally polarized. For broadcasting both vertical and horizontal antennas are used. Marconi antenna radiates an omnidirectional pattern in the horizontal plane with vertical polarization. Parabolic dish antenna has very high gain and very narrow beam width
Notch antenna is an open-ended slot antenna. Dipole antenna is bidirectional. Coupling unit of antenna is diplexer. Vertical polarization is employed in AM broadcasting. Horizontal polarization is employed in FM broadcasting. At microwave frequencies the size of the antenna becomes very Small
Microwave antenna aperture efficiency depends on antenna Aperture. Radiation resistance of a dipole antenna is 73 ohm. Radiation resistance of n dipoles in parallel is equal to (n^2 )* 73 ohm. Super heterodyne receiver is used in microwave communication, its IF is from 30 to 60 MHz