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Skew (antenna)
Skew is a term used in antenna engineering. It is a technique to improve the horizontal radiation pattern of a high power transmitter station. In a high power VHF or UHF station, usually the antenna system is constructed to broadcast to four directions each separated 90° from each other. So the directivity of the antenna system resembles a four leaf clover. While settlements within the main lobe receive enough energy, the energy received by the settlements between the main lobes may be 6 dB less. One popular method to solve the problem is to skew the antenna panels symmetrically around the central axis of the mast.R.Busi: ''High altitude VHF and UHF Broadcasting stations'', EBU technical center, Brussels, 1967 p 25 Usually a skew of λ/4 gives the desired almost-uniform horizontal radiation pattern. But in cases where more than one RF signal is applied to antenna system (via combiner Power dividers (also power splitters and, when used in reverse, power combiners) and dire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna (radio)
In radio-frequency engineering, an antenna (American English) or aerial (British English) is an electronic device that converts an alternating current, alternating electric current into radio waves (transmitting), or radio waves into an electric current (receiving). It is the interface between radio waves Radio propagation, propagating through space and electric currents moving in metal Electrical conductor, conductors, used with a transmitter or receiver (radio), receiver. In transmission (telecommunications), transmission, a radio transmitter supplies an electric current to the antenna's Terminal (electronics), terminals, and the antenna radiates the energy from the current as electromagnetic radiation, electromagnetic waves (radio waves). In receiver (radio), 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 amplifier, amplified. Antennas are essential components ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiation Pattern
In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: "Antenna Theory, Analysis and Design", John Wiley & Sons, Inc., 2nd ed. 1982 David K Cheng: "Field and Wave Electromagnetics", Addison-Wesley Publishing Company Inc., Edition 2, 1998. Edward C. Jordan & Keith G. Balmain; "Electromagnetic Waves and Radiating Systems" (2nd ed. 1968) Prentice-Hall. Particularly in the fields of fiber optics, lasers, and integrated optics, the term radiation pattern may also be used as a synonym for the near-field pattern or Fresnel pattern.Institute of Electrical and Electronics Engineers, "The IEEE standard dictionary of electrical and electronics terms"; 6th ed. New York, N.Y., Institute of Electrical and Electronics Engineers, c1997. IEEE Std 100-1996. d. Standards Coordinating Committee 10, Terms and D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmitter Station
A transmitter station or transmission facility is an installation used for transmitting radio frequency signals for wireless communication, broadcasting, microwave link, mobile telephone or other purposes. Choice of location The location may be chosen to fit the coverage area and for VHF-UHF-applications Line-of-sight propagation, line of sight considerations. For lower frequencies a location with good ground conductivity is required. In case of microwave link chains, stations should be in observable ranges of each other. (see Earth bulge) Computer programmes for the terrain profile and abacs are used in addition to on site observations. Avoidance of industrial noise is also taken into consideration. Another parameter may be the government regulations concerning public health requiring a minimum distance to human habitation. The distance depends on the Effective radiated power, power and the frequency of the transmitting signal. Low power stations may be in cities; higher pow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Four Leaf Clover
The four-leaf clover is a rare mutation of the common three-leaf clover that has four leaflets instead of three. According to traditional sayings, such clovers bring good luck, a belief that dates back to at least the 17th century. The term ''four-leaf'' is botanically a misnomer, as cloverplants have multiple leaves (multiple clovers), each consisting of a varying number of leaflets, typically three. Occurrence A 2017 survey of approximately 5.7 million clovers in six European countries found the frequency of 4-leaf clovers to be around 5000 to 1 (one 4-leaf clover for every 5076 normal 3-leaf clovers), almost twice the commonly stated probability of 10,000 to 1. According to this survey, the frequency of a 5-leaf clover is 24,390 to 1, and that of a 6-leaf clover is 312,500 to 1. According to Guinness World Records, the clover with the most leaflets ever found had 63 of them, and was discovered by Yoshiharu Watanabe of Nasushiobara city, Tochigi prefecture, Japan, on 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Main Lobe
In a antenna (electronics), radio antennas, the main lobe or main beam is the region of the radiation pattern containing the highest Power (physics), power or exhibiting the greatest field strength. The radiation pattern of most antennas shows a pattern of "'':wikt:lobes, lobes''" at various directions, where the radiated signal strength reaches a local maximum, separated by "''null (radio), nulls''", at which the radiation falls to zero. In a directional antenna in which the objective is to emit the radio waves in one direction, the lobe in that direction is designed to have higher field strength than the others, so on a graph of the radiation pattern it appears biggest; this is the main lobe. The other lobes are called "''sidelobes''", and usually represent unwanted radiation in undesired directions. The sidelobe in the opposite direction from the main lobe is called the "''backlobe''". The radiation pattern referred to above is usually the horizontal radiation pattern, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Frequency
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upper limit of audio frequencies that humans can hear (though these are not electromagnetic) and the lower limit of infrared frequencies, and also encompasses the microwave range. These are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves, so they are used in radio technology, among other uses. Different sources specify different upper and lower bounds for the frequency range. Electric current Electric currents that oscillate at radio frequencies (RF currents) have special properties not shared by direct current or lower audio frequency alternating current, such as the 50 or 60 Hz current used in electrical power distribution. * Energy from RF currents in conduct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Combiner
Power dividers (also power splitters and, when used in reverse, power combiners) and directional couplers are Passivity (engineering), passive devices used mostly in the field of radio technology. They couple a defined amount of the electromagnetic power in a transmission line to a Port (circuit theory), port enabling the signal to be used in another circuit. An essential feature of directional couplers is that they only couple power flowing in one direction. Power entering the output port is coupled to the isolated port but not to the coupled port. A directional coupler designed to split power equally between two ports is called a hybrid coupler. Directional couplers are most frequently constructed from two coupled transmission lines set close enough together such that energy passing through one is coupled to the other. This technique is favoured at the microwave frequencies where transmission line designs are commonly used to implement many circuit elements. However, lumpe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antennas (radio)
In radio-frequency engineering, an antenna (American English) or aerial (British English) is an electronic device that converts an alternating electric current into radio waves (transmitting), or radio waves into an electric current (receiving). It is the interface between radio waves propagating through space and electric currents moving in metal conductors, 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 of conductor segments ( elements), electrically connected to the receiver or transmitter. Antennas can be designed to transmit and receive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
