Microwave

Microwave

Microwave transmission is line of sight transmission. The Transmit station must be in visible contact with the receive station. This sets a limit on the distance between stations depending on the local geography. Typically the line of sight due to the Earth's curvature is only 50 km to the horizon. Repeater stations must be placed so the data signal can hop, skip and jump across the country. Electromagnetic waves having frequencies between 1 and 300 GHz are called microwaves. Microwaves are unidirectional; when an antenna transmits microwaves they can be narrowly focused. This means that the sending and receiving antennas need to be aligned. The unidirectional property has an obvious advantage. A pair of antennas can be aligned without interfering with another pair of aligned antennas. Microwaves propagation is line-of-sight. Since the towers with the mounted antennas needs to be in direct sight of each other, towers that are far apart need to be very tall, the curvature of the earth as well as other blocking obstacles do not allow two short towers to communicate using microwaves, Repeaters are often needed for long distance communication very high frequency microwaves cannot penetrate walls. Parabolic dish antenna and horn antenna are used for this means of transmission.
Microwaves operate at high operating frequencies of 3 to 10 GHz. This allows them to carry large quantities of data due to the large bandwidth.

Advantages of Microwave

» They require no right of way acquisition between towers.
» They can carry high quantities of information due to their high operating frequencies.
» Low cost land purchase: each tower occupies small area.
» High frequency/short wavelength signals require small antenna.

Disadvantages of Microwave

» Attenuation by solid objects: birds, rain, snow and fog.
» Reflected from flat surfaces like water and metal.
» Diffracted (split) around solid objects
» Refracted by atmosphere, thus causing beam to be projected away from receiver.