Kota Bansal Pattern Chemistry Notes of periodic Table
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Descrição completa
transmission media and antenna system
Periodic TableDescripción completa
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Química..Tabla periódica
Química..Tabla periódica
Descripción: periodico 1968
antenna
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distributed antenna system for the enterprise
microstrip antenna for DTH application.
Antenna Andrew dscription
LOG PERIODIC ANTENNA
DESCRIPTION
A log periodic antenna is a multi_element and multidirectional, narrow beam antenna that operates over a wide range of frequencies. This type of antenna is defined as having it’s it’s structure structure prescribed by operating elements by opening angles. A particular form of log periodic dipole array is often used in television antennas that work in HF range. BASIC CONCEPT
The LPDA normally consists of a series of dipoles known as “elements” po sitioned along a support boom lying along the antenna axis. The elements are placed at intervals following a logarithmic function of frequency. The length of element corresponds to resonance frequencies within antenna overall bandwidth. This leads to a series ser ies of shorter dipole towards ‘front’ of antenna. The ever decreasing length makes LPDA look when viewed from top like a triangle sigma and tau are the key elements of LPDA APPLICATION
The log periodic antenna is used in number of applications where a wide bandwidth bandwidth is required along with the directivity and a modest level of gain . UHF TERRESTRIAL TV
The antenna is sometimes used in the form of UHF TV antenna. The TV spectrum extends over a wide bandwidth .Normally channels for a given area are located within a particular subset of UHF spectrum so that the channels are relatively close together .However there could be variation where UHF may be located over a wide portion of television spectrum.
HF COMMUNICATION
EMC measurements require scan over a wide band of frequencies .Log periodic antenna can be used in application to enable operation and scanning the signals over a large bandwidth needed .As such the log periodic antenna is key to operation of many EMC tests and tests environment. OTHER APPLICATION
There are many other applications where log periodic antenna can be used .Any application where directivity and wide bandwidth are needed are ideal applications of log periodic antenna TYPES OF LOG PERIODIC ANTENNA
There are several formats in which the log periodic antenna can be realized. The exact type that is most applicable for any given application will depend upon the requirements The main types of LOG PERIODIC antenna array include:
