# A report onAntenna (radio)

Antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver.

- Antenna (radio)

## Decibel

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Relative unit of measurement equal to one tenth of a bel (B).

Relative unit of measurement equal to one tenth of a bel (B).

dBd: dB(dipole) – the gain of an antenna compared with the gain a half-wave dipole antenna. 0 dBd = 2.15 dBi

## Line-of-sight propagation

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Characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver.

Characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver.

The radio horizon is the locus of points at which direct rays from an antenna are tangential to the surface of the Earth.

## Gain (antenna)

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Proportional to the gain. An antenna's effective length is proportional to the square root of the antenna's gain for a particular frequency and radiation resistance. Due to reciprocity, the gain of any antenna when receiving is equal to its gain when transmitting.

Proportional to the gain. An antenna's effective length is proportional to the square root of the antenna's gain for a particular frequency and radiation resistance. Due to reciprocity, the gain of any antenna when receiving is equal to its gain when transmitting.

Partial gain is calculated as power gain, but for a particular polarization.

## Circulator

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Passive, non-reciprocal three- or four-port device that only allows a microwave or radio-frequency signal to exit through the port directly after the one it entered.

Passive, non-reciprocal three- or four-port device that only allows a microwave or radio-frequency signal to exit through the port directly after the one it entered.

In radar, circulators are used as a type of duplexer, to route signals from the transmitter to the antenna and from the antenna to the receiver, without allowing signals to pass directly from transmitter to receiver.

## Bandwidth (signal processing)

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Difference between the upper and lower frequencies in a continuous band of frequencies.

Difference between the upper and lower frequencies in a continuous band of frequencies.

For instance, in the field of antennas the difficulty of constructing an antenna to meet a specified absolute bandwidth is easier at a higher frequency than at a lower frequency.

## Antenna boresight

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In telecommunications and radar engineering, antenna boresight is the axis of maximum gain (maximum radiated power) of a directional antenna.

## Sergei Alexander Schelkunoff

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Sergei Alexander Schelkunoff (Сергей Александрович Щелкунов; January 27, 1897 – May 2, 1992), who published as S. A. Schelkunoff, was a distinguished mathematician, engineer and electromagnetism theorist who made noted contributions to antenna theory.

## Gain (electronics)

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Measure of the ability of a two-port circuit to increase the power or amplitude of a signal from the input to the output port by adding energy converted from some power supply to the signal.

Measure of the ability of a two-port circuit to increase the power or amplitude of a signal from the input to the output port by adding energy converted from some power supply to the signal.

The term gain has a different meaning in antenna design; antenna gain is the ratio of radiation intensity from a directional antenna to (red) of an ideal linear amplifier with a voltage gain of 3 with an arbitrary input signal.

## Telegrapher's equations

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Electrical transmission line with distance and time.

Electrical transmission line with distance and time.

It can also be used to electrically model wire radio antennas as truncated single-conductor transmission lines.

## Friis transmission equation

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The Friis transmission formula is used in telecommunications engineering, equating the power at the terminals of a receive antenna as the product of power density of the incident wave and the effective aperture of the receiving antenna under idealized conditions given another antenna some distance away transmitting a known amount of power.