Hertz changed the frequency of his radiated waves by altering the inductance or capacity of his radiating conductor or antenna, and reflected and focused the electromagnetic waves, thus demonstrating the correctness of Maxwell's electromagnetic theory of light.

This is similar to a radio antenna, but with the difference that, in theory, the relativistic speed will change the observed frequency due to the Doppler effect by the Lorentz factor,.

* Antennas, Antenna theory, List of antenna terms

Neri has worked at the Institute of Electrical Research, Mexico, in the Radiocommunications Group, doing research and system planning on antenna theory and design, satellite communications systems, and Earth station technology.

In horn and other directional antennas, the apparent phase center is used since radiation is only emitted at certain angles. In antenna design theory, the phase center is the point from which the electromagnetic radiation spreads spherically outward, with the phase of the signal being equal at any point on the sphere.

* 1986: Ronold W. P. King, Leader in the development of electromagnetic antenna theory

In electromagnetics and antenna theory, antenna aperture or effective area is a measure of how effective an antenna is at receiving the power of radio waves.

For example, articles about blocking and traffic theory used in trunked radio systems, base stations, AMPS, remote control consoles, or transmitter antenna combiners in two-way radio systems belong in the Wireless category.

In antenna theory, an isotropic antenna is a hypothetical antenna radiating the same intensity of radio waves in all directions.

In wireless communication, space-division multiplexing is achieved by multiple antenna elements forming a phased array antenna.

Simultaneous electrical scanning in both azimuth and elevation was first demonstrated in a phased array antenna at Hughes Aircraft Company, Culver City, CA, in 1957 ( see Joseph Spradley, “ A Volumetric Electrically Scanned Two-Dimensional Microwave Antenna Array ,” IRE National Convention Record, Part I-Antennas and Propagation ; Microwaves, New York: The Institute of Radio Engineers, 1958, 204-212 ).

More modest phased array longwire antenna systems may be employed by private radio enthusiasts to receive longwave, mediumwave ( AM ) and shortwave radio broadcasts from great distances.

An aspect of this radar is phased array antenna technology which is now common in defence applications.

The phased array antenna is in a fixed position and can be part of the building wall.

A phased array antenna, as with any other directional antenna, will receive signals from space only in the direction in which the beam is aimed.

The maximum practical deflection on either side of antenna center of the phased array beam is 60 degrees.

In most antenna designs, gain is realized primarily by concentrating power toward the horizontal plane and suppressing it at upward and downward angles, through the use of phased arrays of antenna elements.

The infrastructure used a phased array antenna K < sub > u </ sub > band antenna manufactured by either Boeing or Mitsubishi Electric Corporation on the aircraft, leased satellite transponders, and ground stations.

A technique closely related to SAR uses an array ( referred to as a " phased array ") of real antenna elements spatially distributed over either one or two dimensions across the range dimension.

The new antenna was a three-faced phased array antenna providing 360 degrees of coverage.

The highest Field of View ( FOV ) for a flat phased array antenna is currently 120 °, however this can be combined with mechanical steering as noted above.

Less space is required than a VOR because a VOR requires a large counterpoise and a fairly complex phased antenna system.

* MIMO channels ( i. e. phased array antenna )

Poker Flat's scope of activities is ever changing with the recent addition of SRI's PFISR ( Poker Flat Incoherent Scatter Radar ) phased array antenna and the recent purchase of several Insitu UAV / UAS ( Unmanned Aerial Vehicle / Unmanned Aerial System ).

It is technologically feasible today to build phased antenna arrays operable in the 1-to 3 GHz region with total collecting areas of 100 or more square kilometers.

This operation is equivalent to the generation of a large synthetic aperture phased array antenna formed by the coherent summation of the receiver outputs for varying target / antenna geometries.

In electrical engineering degrees of freedom is often used to describe the number of directions in which a phased array antenna can form either beams or nulls.

Phase array antennas are composed of evenly spaced similar antenna elements, such as aerials or rows of slotted waveguide.

Each antenna element or group of antenna elements incorporates a discreet phase shift that produces a phase gradient across the array.

Phase array antenna can be built to conform to specific shapes, like missiles, infantry support vehicles, ships, and aircraft.

In telecommunications, a collinear ( or co-linear ) antenna array is an array of dipole antennas mounted in such a manner that the corresponding elements of each antenna are parallel and collinear, that is they are located along a common line or axis.

Many antenna types, such as reflective array antennas, use flat surfaces of metal or metal screen to reflect radio waves from the antenna elements, and these can be analyzed using image antennas.

In telecommunication, a log-periodic antenna ( LP, also known as a log-periodic array or log periodic beam antenna / aerial ) is a broadband, multi-element, directional, narrow-beam antenna that has impedance and radiation characteristics that are regularly repetitive as a logarithmic function of the excitation frequency.

An antenna array is a group of multiple active antennas coupled to a common source or load to produce a directive radiation pattern.

Usually, the spatial relationship of the individual antennas also contributes to the directivity of the antenna array.

Phasing the array such that the lower elements are slightly delayed ( by making the distance to them longer ) causes a downward beam tilt, which is very useful if the antenna is quite high on a radio tower.

In telecommunications and radar, a planar array is an antenna in which all of the elements, both active and parasitic, are in one plane.

Reflective array ' billboard ' antenna of the AN-270 radar, an early radar system used in 1941 at Pearl Harbor.

As shown in Fig. 4, an external antenna is placed over or around the patient and excited 3000 times a second with short 400-kc. bursts.

The transducer itself moves the beam in a sector scan, just like a radar antenna, while the entire transducer structure is moved over a 90-degree arc in front of the eye to `` look into '' all corners.

The ratio of the measured antenna temperature change during a drift scan across the moon to the average brightness temperature of the moon over the antenna beam ( assuming that the brightness temperature of the sky is negligible ) was found, by graphical integration of the antenna directivity diagram, to be 0.85.

The measured brightness temperature is a good approximation to the brightness temperature at the center of the lunar disk because of the narrow antenna beam and because the temperature distribution over the central portion of the moon's disk is nearly uniform.

The radio station's antenna is atop an apartment building owned by Montefiore Medical Center.

Transmission is primary by terrestrial broadcast antenna.

This contrasts with traditional broadcast television ( terrestrial television ) in which the television signal is transmitted over the air by radio waves and received by a television antenna attached to the television.

Cable television in Canada began in 1952 with community antenna connections in Vancouver and London, Ontario ; which city is first is not clear.

One of the oldest means of receiving DTV ( and TV in general ) is using an antenna ( known as an aerial in some countries ).

In electromagnetic radiation ( such as microwaves from an antenna, shown here ) the term applies only to the parts of the electromagnetic field that radiate into infinite space and decrease in intensity by an inverse-square law of power, so that the total radiation energy that crosses through an imaginary spherical surface is the same, no matter how far away from the antenna the spherical surface is drawn.

When any wire ( or other conducting object such as an antenna ) conducts alternating current, electromagnetic radiation is propagated at the same frequency as the electric current.

Macro cells can be regarded as cells where the base station antenna is installed on a mast or a building above average roof top level.

Micro cells are cells whose antenna height is under average roof top level ; they are typically used in urban areas.

Indoor coverage is also supported by GSM and may be achieved by using an indoor picocell base station, or an indoor repeater with distributed indoor antennas fed through power splitters, to deliver the radio signals from an antenna outdoors to the separate indoor distributed antenna system.

An isotropic antenna is an idealized " radiating element " used as a reference ; an antenna that broadcasts power equally ( calculated by the Poynting vector ) in all directions.

The gain of an arbitrary antenna is usually reported in decibels relative to an isotropic antenna, and is expressed as dBi or dB ( i ).