A stack of "fishbone" and Yagi–Uda television antennas
Schematic of a wave moving rightward down a lossless two-wire transmission line. Black dots represent electrons, and the arrows show the electric field.
For a monopole antenna (a), the Earth acts as a ground plane to reflect radio waves directed downwards, making them seem to come from an image antenna (b).
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.
One of the most common types of transmission line, coaxial cable.
The large light areas on this printed circuit board are the ground plane
Electronic symbol for an antenna
Variations on the schematic electronic symbol for a transmission line.
Antennas of the Atacama Large Millimeter/submillimeter Array.
An automobile's whip antenna, a common example of an omnidirectional antenna.
A transmission line is drawn as two black wires. At a distance x into the line, there is current I(x) travelling through each wire, and there is a voltage difference V(x) between the wires. If the current and voltage come from a single wave (with no reflection), then V(x) / I(x) = Z0, where Z0 is the characteristic impedance of the line.
Half-wave dipole antenna
Standing waves on a transmission line with an open-circuit load (top), and a short-circuit load (bottom). Black dots represent electrons, and the arrows show the electric field.
Diagram of the electric fields ( blue ) and magnetic fields ( red ) radiated by a dipole antenna ( black rods) during transmission.
A type of transmission line called a cage line, used for high power, low frequency applications. It functions similarly to a large coaxial cable. This example is the antenna feed line for a longwave radio transmitter in Poland, which operates at a frequency of 225 kHz and a power of 1200 kW.
Cell phone base station antennas
A simple example of stepped transmission line consisting of three segments.
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).
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In antenna theory, a ground plane is a conducting surface large in comparison to the wavelength, such as the Earth, which is connected to the transmitter's ground wire and serves as a reflecting surface for radio waves.

- Ground plane

Transmission lines are used for purposes such as connecting radio transmitters and receivers with their antennas (they are then called feed lines or feeders), distributing cable television signals, trunklines routing calls between telephone switching centres, computer network connections and high speed computer data buses.

- Transmission line

When a ground plane layer is present underneath, it forms a transmission line with the trace.

- Ground plane

An antenna lead-in is the transmission line, or feed line, which connects the antenna to a transmitter or receiver.

- Antenna (radio)

An antenna counterpoise, or ground plane, is a structure of conductive material which improves or substitutes for the ground.

- Antenna (radio)

A microstrip circuit uses a thin flat conductor which is parallel to a ground plane.

- Transmission line
A stack of "fishbone" and Yagi–Uda television antennas

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