aerial, antenna

aerial, antenna

An aerial work platform (AWP), also known as an aerial device, elevating work platform (EWP), bucket truck or mobile elevating work platform (MEWP) is a mechanical device used to provide temporary access for people or equipment to inaccessible areas, usually at height. There are distinct types of mechanized access platforms and the individual types may also be known as a "cherry picker" or "scissor lift [剪式升降机]." A forklift truck or a forklift is a small vehicle with two movable parts on the front that are used to lift heavy loads. An escalator is a set of moving stairs that take people to different levels in a building.

Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other flying object.

The aerial bombing of cities in warfare is an optional element of strategic bombing which became widespread during World War I.

In radio engineering, an antenna or aerial is the interface between radio waves propagating [传播] through space and electric currents moving in metal conductors [导体], used with a transmitter or receiver.

In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified. Antennas are essential components of all radio equipment.

An antenna is an array [阵列] of conductors (elements), electrically connected to the receiver or transmitter. Antennas can be designed to transmit and receive radio waves in all horizontal directions equally (omnidirectional antennas), or preferentially [偏好地] in a particular direction (directional, or high-gain [高增益], or “beam” antennas).

The first antennas were built in 1888 by German physicist Heinrich Hertz in his pioneering experiments to prove the existence of waves predicted by the electromagnetic theory of James Clerk Maxwell.

In biology, an antenna is one of one or more pairs of appendages [附属物] used for sensing in arthropods. An arthropod /ˈɑːrθrəpɒd/ is an invertebrate animal [无脊椎动物] having an exoskeleton, a segmented body, and paired jointed appendages.

These are cell phone base station antennas: