The antenna is often the most visible element of a radio system. The sizes and shapes of the conductors that comprise the
antenna determine the directional characteristics of the electromagnetic (radio) waves it radiates. However, the antenna
cannot be considered independently. Additional elements, such as the transmission line, duplexers, matching networks, etc., must be considered as part of the antenna system.
The full description of the interaction of an antenna with its surrounding environment is based on very complex mathematics, but its function in a radio system is quite simple. The key elements of a radio communications system. When an antenna isused for transmitting, it converts electrical signals, delivered by a transmission line, from a transmitter into propagating electromagnetic waves. When an antenna is used for receiving, it converts electromagnetic waves back into electrical signals that are delivered by a transmission line to a receiver for processing. In fact, the same antenna (used for both transmitting and receiving) is often attached to a transmitter and a receiver using either a duplexer or a transmit/receive (XMT/RCV) switch. A duplexer allows one antenna to be used by both the transmitter and receiver at the same time (see sec. 6.3), and a transmit/receive switch connects the antenna to either the transmitter or receiver.
An antenna is a device that provides suitably localized and oriented paths for oscillating electric currents. The sizes and shapes of the
conductors that comprise the antenna determine the directional characteristics of the radio waves it radiates. A transmitting antenna converts electrical currents, delivered by the transmission line from a transmitter, into propagating radio waves, and a receiving antenna converts radio
waves back into electrical currents that are delivered by a transmission line to a receiver.
An antenna has two basic functions:
The primary function is to radiate, as radio waves, the RF signals from the transmitter, or to convert radio waves into RF signals for processing by a receiver. The other function is to direct the radiated energy in the desired direction or directions, or to be “sensitive” to reception from the desired direction or directions. Another, often overlooked, aspect of an antenna’s directional properties is the suppression of radiation in undesired directions, or the rejection of reception from undesired directions.
The directional characteristics of an antenna are fundamental to an understanding of the antenna and how it is used in a radio communications system. These interrelated characteristics include gain, directivity, radiation (antenna) pattern, and polarization. Other characteristics such as beamwidth, effective length, and effective aperture are derived from the four listed above. Terminal (input) impedance is one other characteristic that is of fundamental importance. It is necessary to know the impedance of an antenna in order to efficiently couple the transmitter’s output power into it, or to efficiently couple the power from it into the receiver. All of these antenna characteristics are a function of frequency.
The full description of the interaction of an antenna with its surrounding environment is based on very complex mathematics, but its function in a radio system is quite simple. The key elements of a radio communications system. When an antenna isused for transmitting, it converts electrical signals, delivered by a transmission line, from a transmitter into propagating electromagnetic waves. When an antenna is used for receiving, it converts electromagnetic waves back into electrical signals that are delivered by a transmission line to a receiver for processing. In fact, the same antenna (used for both transmitting and receiving) is often attached to a transmitter and a receiver using either a duplexer or a transmit/receive (XMT/RCV) switch. A duplexer allows one antenna to be used by both the transmitter and receiver at the same time (see sec. 6.3), and a transmit/receive switch connects the antenna to either the transmitter or receiver.
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| Elements radio system |
What Is an Antenna?
Characteristics of Antenna
In a radio communications system, How many function of antenna?
An antenna has two basic functions:
The primary function is to radiate, as radio waves, the RF signals from the transmitter, or to convert radio waves into RF signals for processing by a receiver. The other function is to direct the radiated energy in the desired direction or directions, or to be “sensitive” to reception from the desired direction or directions. Another, often overlooked, aspect of an antenna’s directional properties is the suppression of radiation in undesired directions, or the rejection of reception from undesired directions.
The directional characteristics of an antenna are fundamental to an understanding of the antenna and how it is used in a radio communications system. These interrelated characteristics include gain, directivity, radiation (antenna) pattern, and polarization. Other characteristics such as beamwidth, effective length, and effective aperture are derived from the four listed above. Terminal (input) impedance is one other characteristic that is of fundamental importance. It is necessary to know the impedance of an antenna in order to efficiently couple the transmitter’s output power into it, or to efficiently couple the power from it into the receiver. All of these antenna characteristics are a function of frequency.
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