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Antenna Terminology

This page on Antenna terminology describes terms related to Antenna. It covers antenna gain, antenna beamwidth, antenna figure of merit or G/T, antenna radiation pattern, antenna bandwidth, antenna efficiency, antenna impedance, antenna polarization, antenna effective aperture, antenna wavelength, antenna directivity etc.

Antenna Terms Basic description RF Wireless World Reference
Antenna Gain In the simple terms antenna gain is the factor by which input power to the antenna will be multiplied to provide higher output power. It is this higher power output which will be transmitted over the air as EM waves. Antenna Gain
Antenna Beamwidth The difference between half power points (3dB points) on antenna radiation pattern is referred as antenna beamwidth. The unit is degrees.
Antenna G/T(figure of merit) Antenna Gain to Noise temperature ratio is referred as figure of merit of the antenna. Also known as antenna G/T.
Antenna radiation pattern Electro-magnetic waves emitted from the antenna is referred as antenna radiation pattern. It is made of a major lobe and more than one side lobes. The region near the antenna is referred as near field region and region far away is referred as far field region. It can be represented either in polar or in rectangular coordinates. Near Field vs Far Field
Antenna Bandwidth Range of frequencies over which antenna operates satisfactorily. The difference between highest and lowest frequency points is referred as antenna bandwidth.
Antenna Efficiency It is the ratio of power radiated or power dissipated in the antenna structure to the power input to the antenna. Higher antenna efficiency means good amount of power is radiated into the space and less is the power losses within antenna. εR=Pradiated/Pinput
Antenna Impedance In simple terms, it is the ratio of voltage to the current at the antenna input. If antenna impedance at input is 50 Ohm means sinusoidal voltage amplitude is 1volt and current amplitude is 1/50 Amps. Based on this and transmission line impedance, balun may or may not require. Balun is also referred as impedance transformer.
Antenna Polarization Polarization refers to polarization of electro magnetic wave transmitted or received by the antenna. It is the direction of the electric field vector embedded within the EM wave. Horizontal vs Vertical Polarization
Antenna effective aperture This parameter describes how much power can be captured by the antenna. Effective aperture or effective area of the antenna can be expressed as follows:
Ae = λ2 * G / 4* pi
Antenna Wavelength Size of antenna depends on wavelength. Wavelength is distance a radio frequency wave travels during one cycle period. Half wave dipole will have half wavelength long. λ = c/f, where c is speed of light i.e. 3x 108 m/s Wavelength vs Frequency
Antenna directivity It is the ability of the antenna to focus EM waves in particular direction for transmission and reception. It related to antenna gain and antenna efficiency as follows:
Gain = η * Directivity, where η is antenna efficiency

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