Different type of antennas documented by Pooja (B.Tech student)

Antennas:- Types of antennas.

1.      Dipole antenna

2.      loop antennas

3.      yagi uda antennas

4.      reflectors antennas

5.      Microstrip antennas

6.      Fractal antennas

Dipole antenna:- 

A dipole antenna is a radio antenna that can be made of a simple wire, with a center-fed driven element. It consists of two metal conductors of rod or wire, oriented parallel and collinear with each other (in line with each other), with a small space between them. The radio frequency voltage is applied to the antenna at the center, between the two conductors. These antennas are the simplest practical antennas from a theoretical point of view. They are used alone as antennas, notably in traditional "rabbit ears" television antennas, and as the driven element in many other types of antennas, such as the Yagi. 

 the dipole antenna is the simplest antenna, despite of not being used Practically in applications, it is also known as reference antenna (becoz it is used to test antenna labs) a dipole antenna consists of 2 wires (lambda /4 for its length).

Loop antenna:-

as the diploe is the conventional electric field antenna, loopa are reference maganetic field antenna. Loop antennas can take different shapes like square, circle, triangle, ellipse or any other closed shape. In dipoles current moves till discontinuity occurs and then radiates (electric field).and in loop antenna when current circulates in the loop its obvious that a magnetic field is produced.

The single-turn loop antenna is a metallic conductor bent into the shape of a closed curve, such as a circle or a square, with a gap in the conductor to form the terminals. A multiturn  loop or coil is a series connection of overlaying turns. The loop is one of the primary antenna structures; its use as a receiving antenna dates back to the early experiments of

 Hertz on the propagation of electromagnetic waves.

Types of loop antenna:-

Electrically small loops

Electrically large loops

Shielded- loop antenna

Pulse-excited circular-loop antenna

Yagi Uda antenna:-

A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional antenna consisting of a driven element (typically a dipole or folded dipole) and additional parasitic elements(usually a so-called reflector and one or more directors). The name stems from it's inventors, as the Yagi-Uda array was invented in 1926 by Shintaro Uda of Tohoku Imperial University, Japan, with a lesser role played by his colleague Hidetsugu Yagi. However the "Yagi" name has become more familiar with the name of Uda often omitted. The reflector element is slightly longer (typically 5% longer) than the driven dipole, whereas the so-called directors are a little bit shorter. This design achieves a very substantial increase in the antenna's directionality and gain compared to a simple dipole.

Reflector antenna:-

Reflector:-while using aperture antennas we always need to increase the aperture area to increase its directivity, but as this is not practical , instead of using large apertures we place a reflecting surface face to face with the aperture , the reflecting surface collimates radiation to the small aperture and thus we satisfied high directivity with a small aperture, and overcome space limitations.

Microstrip antenna:-

Microstrip or patch antennas are becoming increasingly useful because they can be printed directly onto a circuit board. Microstrip antennas are becoming very widespread within the mobile phone market. Patch antennas are low cost, have a low profile and easily fabricated