The antenna is the part of the microwave link that transmits electromagnetic energy

Antenna

The antenna is the part of the microwave link that transmits electromagnetic energy from transmission lines into the air and receives transmitted electromagnetic energy from the air to be then sent on transmission lines. The antenna can be in one of many different shapes (for example, horn, parabolic, flat or planar, lens, yagi, or array) to achieve its specific objectives.

The main characteristics of the microwave antenna are the following:

• Directivity: In practical terms, directivity is defined as:

- The ability to send the transmitted power in only the desired direction

- The ability to reject undesired signals coming from other directions.

• Gain: The gain is the amount of power radiated in a given direction using only the RF power at the input terminals of the antenna.

• Front-to-Back Ratio (FBR): The FBR is the ratio of the power radiated in the desired direction to the power radiated in the opposite direction, typically between 35 and 50 dB. In general, the higher the gain of the antenna, the higher the FBR.

• Radiation pattern: The radiation pattern is a diagram showing the direction of the radiated power. The portion of the pattern where the maximum gain occurs is often referred to as the main lobe of the pattern

• Polarisation: Polarisation is the ability to transmit only one of the two electromagnetic vector components of the wave (either the horizontal component or the vertical component). Using polarisation enables the same radio frequency to be used by different radio systems in physical proximity to one another.

• Cross Polarisation Discrimination (XPD): The XPD is the ratio of power received in the desired polarisation to the power received in undesired polarisation. XPD is a design parameter that is maximized in the main lobe of the antenna pattern.