TYPES OF ANTENNA :
BABINET’S PRINCIPLES OF COMPLEMENTARY ANTENNA :
The complementary impedance can be found by using Babinet’s Principles . It states when a screen has a opening that is added to complementary structure and a field lies behind it , then the additional value equals to a field where screen is absent . The main problem with this equation is that the screen must be thin to wavelength given . Or modes begin from fields fringing and are no longer negligible if the screen is not thin in the type of antenna .
HORN ANTENNA :
In this type of antenna consists of a flaring metal like a horn to help the radio waves to travel in a beam . In this type the horns are used as antennas and they mostly behave like feed horns for larger structures like for example parabolic antenna . The main advantage is that they can operate over a wide range because of absence of no resonant elements . It is mostly used because of its simple construction .
Figure of horn antenna
PARABOLIC REFLECTOR ANTENNA :
It is a type of antenna a parabolic reflector and a curved surface of sectional shape to direct radio waves . The most common form is shaped similar to a dish antenna or parabolic disc . Its operation is similar to flash light reflector and helps in direct radiation in narrow beam . The main advantage is that they can create narrowest bandwidths . It is mostly used in radar antennas .
Figure Parabolic Reflector antenna
SLOT ANTENNA :
The main advantage of slot antenna is its design , robust nature , its size and simple to use . It uses PC board technology . It has a metal surface usually like a flat plate with a slot or hole . Radio magnetic waves are radiated in similar way like dipole antenna . This type of antennas are mostly used in UHF and Microwave .They are also preffered in radar antennas .
Figure of slot antenna
FOLDED DIPOLE ANTENNA :
In radio telecommunication , it is the most simple and very widely used antenna class . It consists of the metal wires and rods which are conductive . Either the transmitter or the receiver is connected to each side of feedline .It follows the monopole antenna and the Rabbit Ears is a good example of this type of antenna . It is the simplest type of antenna from theory point of view.
YAGI UDA ARRAY :
It is also called as Yagi Antenna . The Yagi Antenna is a directional antenna mostly consisting of a dipole ana a folded dipole . This is mostly reffered to as beam antenna which have very high gains . This type of antenna uses narrow bandwidth , very useful for various communication bands . The operation depends on electromagnetic interaction between parasitic elements .
Figure Yagi uda antena
LENS ANTENNA :
The Lens antenna are mostly used in metering and radar equipments and it works in centimeter wavelength range consisting of a proper lens and a feed . There are two types of lens antenna
- ACCELERATING LENS : it is made up of shaped metal sheets .
- DECELERATING LENS : low quality homogenous dielectrics are used in its construction .
The surface of the lens is zoned , and hence the weight and dimension reduces .
TURNSTILE ANTENNA :
It is a set of two dipole antennas . It looks very similar to a turnstile when placed horizontally and the antenna acts directionaly in right angle to its plane when placed vertically . This same principle is followed by Yagi and Long periodic .
V – ANTENNA :
In this type of antenna the conductors are arranged in V – shape along with a balanced line at top . It is also called as Vee Antenna . The v-shape antenna the two side of a dipole are perpendicular to each other . It is mostly used in areas which have very limited space and this less space does not really have any effect on its performance . Amateur Radio stations mostly use Inverted vee antennas .
MICROSTRIP ANTENNA :
It has two dimensional physical geometry and hence it is easy to design and inexpensive to manufacture . They are mostly used in UHF . The microstrip antennas has high polarization diversity and can be used for multiple feed points .
figure of microstrip antenna
RHOMBIC ANTENNA :
A broadly directional antenna having high frequency is termed as Rhombic antenna . The main advantages is that it has stable input impedance and pattern of radiation . It is a simple to use and effective transmitting antenna .
BEVERAGE ANTENNA :
This antenna is mostly used in high frequencies because it has long wire receiving antenna . It is also used by amateur radio . A large amount of space is required because these antennas provide excellent directivity .
QUESTIONS AND ANSWERS :
QUE > WHAT IS FOLDED DIPOLE ANTENNA ?
ANS > In radio telecommunication the most simple and widely used antenna class . It consists of the metal wires and rods which are conductive in nature . The transmitter or the receiver is connected to each side of feedline .It follows the monopole antenna and the Rabbit Ears is a good example of this type of antenna . It is the simplest type of antenna from theory point of view.
QUE > WRITE SHORT NOTE ON RHOMBIC ARRAY ?
ANS > It is a broadly directional antenna having high frequency is termed as Rhombic antenna . The main advantages is that it has stable input impedance and pattern of radiation . It is a simple to use and very effective transmitting antenna.