RFAntenna Terminology Explained
antenna
rf
gain
beamwidth
polarization
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This page describes various terms related to antennas, including antenna gain, antenna beamwidth, antenna figure of merit (G/T), antenna radiation pattern, antenna bandwidth, antenna efficiency, antenna impedance, antenna polarization, antenna effective aperture, antenna wavelength, and antenna directivity.
| Antenna Terms | Basic description | RF Wireless World Reference |
|---|---|---|
| Antenna Gain | In simple terms, antenna gain is the factor by which input power to the antenna will be multiplied to provide a 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 the antenna radiation pattern is referred to as antenna beamwidth. The unit is degrees. | |
| Antenna G/T (Figure of Merit) | Antenna Gain to Noise temperature ratio is referred to as the figure of merit of the antenna. Also known as antenna G/T. | |
| Antenna Radiation Pattern | Electromagnetic waves emitted from the antenna are referred to as the antenna radiation pattern. It is made of a major lobe and more than one side lobe. The region near the antenna is referred to as the near-field region, and the region far away is referred to as the far-field region. It can be represented either in polar or rectangular coordinates. | Near Field vs Far Field |
| Antenna Bandwidth | Range of frequencies over which the antenna operates satisfactorily. The difference between the highest and lowest frequency points is referred to 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 a good amount of power is radiated into space, and less power is lost within the antenna. ε R = P radiated / P input | |
| 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, it means the sinusoidal voltage amplitude is 1 volt, and the current amplitude is 1/50 Amps. Based on this and the transmission line impedance, a balun may or may not be required. A balun is also referred to as an impedance transformer. | Balun |
| Antenna Polarization | Polarization refers to the polarization of the electromagnetic 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. The effective aperture or effective area of the antenna can be expressed as follows: A e = λ 2 *G / 4*pi | |
| Antenna Wavelength | The size of the antenna depends on the wavelength. Wavelength is the distance a radio frequency wave travels during one cycle period. A half-wave dipole will have half a wavelength long. λ = c/f, where c is the speed of light, i.e., 3 x 10^8 m/s | Wavelength vs Frequency |
| Antenna Directivity | It is the ability of the antenna to focus EM waves in a particular direction for transmission and reception. It is related to antenna gain and antenna efficiency as follows: Gain = η * Directivity, where η is antenna efficiency |
