A report on Antenna (radio)

A stack of "fishbone" and Yagi–Uda television antennas
Animation of a half-wave dipole antenna radiating radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods connected to a radio transmitter (not shown). The transmitter applies an alternating electric current to the rods, which charges them alternately positive (+) and negative (−). Loops of electric field leave the antenna and travel away at the speed of light; these are the radio waves. In this animation the action is shown slowed down enormously.
Electronic symbol for an antenna
Antennas of the Atacama Large Millimeter/submillimeter Array.
An automobile's whip antenna, a common example of an omnidirectional antenna.
Half-wave dipole antenna
Diagram of the electric fields ( blue ) and magnetic fields ( red ) radiated by a dipole antenna ( black rods) during transmission.
Cell phone base station antennas
Standing waves on a half wave dipole driven at its resonant frequency. The waves are shown graphically by bars of color ( red for voltage, V and blue for current, I ) whose width is proportional to the amplitude of the quantity at that point on the antenna.
Typical center-loaded mobile CB antenna with loading coil
Polar plots of the horizontal cross sections of a (virtual) Yagi-Uda-antenna. Outline connects points with 3 dB field power compared to an ISO emitter.
The wave reflected by earth can be considered as emitted by the image antenna.
The currents in an antenna appear as an image in opposite phase when reflected at grazing angles. This causes a phase reversal for waves emitted by a horizontally polarized antenna (center) but not for a vertically polarized antenna (left).
frame

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)
A stack of "fishbone" and Yagi–Uda television antennas

66 related topics with Alpha

Overall

Examples of sound levels in decibels from various sound sources and activities, taken from the "How loud is too loud" screen of the NIOSH Sound Level Meter app

Decibel

4 links

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

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

Examples of sound levels in decibels from various sound sources and activities, taken from the "How loud is too loud" screen of the NIOSH Sound Level Meter app
A schematic showing the relationship between dBu (the voltage source) and dBm (the power dissipated as heat by the 600 Ω resistor)

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 to an antenna

Line-of-sight propagation

6 links

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.

Line of sight propagation to an antenna
Objects within the Fresnel zone can disturb line of sight propagation even if they don't block the geometric line between antennas.
Two stations not in line-of-sight may be able to communicate through an intermediate radio repeater station.
R is the radius of the Earth, h is the height of the transmitter (exaggerated), d is the line of sight distance

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)

2 links

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.

ANSI and IEC standard schematic symbol for a circulator (with each waveguide or transmission line port drawn as a single line, rather than as a pair of conductors)

Circulator

1 links

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.

ANSI and IEC standard schematic symbol for a circulator (with each waveguide or transmission line port drawn as a single line, rather than as a pair of conductors)
A waveguide circulator used as an isolator by placing a matched load on port 3. The label on the permanent magnet indicates the direction of circulation.
Microwave diode reflection amplifier using a circulator

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.

Baseband bandwidth. Here the bandwidth equals the upper frequency.

Bandwidth (signal processing)

1 links

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.

Baseband bandwidth. Here the bandwidth equals the upper frequency.
The magnitude response of a band-pass filter illustrating the concept of −3 dB bandwidth at a gain of approximately 0.707.

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

1 links

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

Sergei Alexander Schelkunoff

0 links

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)

1 links

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.

Schematic representation of the elementary components of a transmission line.

Telegrapher's equations

2 links

Electrical transmission line with distance and time.

Electrical transmission line with distance and time.

Schematic representation of the elementary components of a transmission line.
Schematic showing a wave flowing rightward down a lossless transmission line. Black dots represent electrons, and the arrows show the electric field.
In the presence of losses the solution of the telegrapher's equation has both damping and dispersion, as visible when compared with the solution of a lossless wave equation.
Changes of the signal level distribution along the single dimensional transmission medium. Depending on the parameters of the telegraph equation, this equation can reproduce all four patterns.

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

Friis' Free-space Radio Circuit.

Friis transmission equation

0 links

Friis' Free-space Radio Circuit.

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.