Antenna array

description array antennas

1. Members: id 1) YONAS YIFTER 209/09 2) ZEBERHE hagos 210/09 submitted to ins. Yowhanes date; mit = 2011 E.C .

2. Transmission line,Antenna And propagation(TAP) ARRAY ANTENNAS Mit 2011 E.C

3. Antenna What is an antenna? General definition of antenna What is Array antenna? Why an Array Antenna? Array antenna types Discuss array antenna parameters? Discuss Array Antenna application?

4. ANTENNA DEFINITIONS An antenna is a passive structure that serves as a transducer between transmission line and air in order to receive and transmit electromagnetic waves….

5. What is Array Antenna​? An antenna array is group of antennas connected and arranged in a regular structure to form a single antenna that is able to produce radiation patterns not produced by individual antennas. Antenna arrays are groups of isotropic radiators of electromagnetic frequency and energy. They provide a solution to the problems caused by single antennas. HOW this? ……

6.   For instance : - the dipole antenna allows better control of direction than an isotropic antenna, but as length of the dipole increases, control direction may decrease. More control and flexibility can be easily regained for beam direction with a multiple radiator arrangement . VHF sector reflective-array

7. Why an Array Antenna? Single element is relatively wide and low gain (directivity ) - To have very high gain and long distance antenna, this can be accomplished by increasing the electrical size of the antenna Enlarge dimensions of the antenna without increasing the size of individual elements is to form an assembly of radiating elements in an electrical and geometrical configuration -This new antenna, formed by multi-elements, is referred to as an array In Most cases, the elements of an array are identical The total field is determined by the vector addition of the fields radiated by the individual elements

8. In general array antenna can be used to : increase the overall gain 2 . provide diversity reception 3. cancel out interference from a particular set of directions 4. "steer" the array so that it is most sensitive in a particular direction 5. determine the direction of arrival of the incoming signals 6. to maximize the Signal to Interference Plus Noise Ratio (SINR )

9. Array Antenna Types There are two (2) types of array antenna i.e. Parasitic and Driven array antenna 1,Parasitic Array Antenna : used for controlling radar and various other narrow beams such as the microwave communication system. 2 , Driven Array Antenna :-radiating elements are connected to an energy source and have less loss when compared to parasitic arrays, but still maintain the narrow beam characteristics , are used as search radar antennas where narrow beams are less critical when compared to low losses.

10. Array Antenna Characteristics array gain: -   means a power gain of transmitted signals that is achieved by using multiple-antennas at transmitter and/or receiver, with respect to  single-input single-output  case. It can be simply called  power gain . In a broadside array, the array gain is almost exactly proportional to the length of the array.   Beam-width: The beam width is the product of the individual antenna pattern and the "array factor" shape. -what is array factor?

11. Bandwidth of an array is affected by many factors, Including impedances with frequency, change of array spacing in wavelengths that may allow grating lobes, change in element beam width, and so on… When an array is scanned with fixed units of phase shift, provided by phasers , there is also a band width limitation as the position of the main beam will change with frequency…

12. Beam width formulae

13. Pattern:

14. DIRECTIVITY: In an  antenna array   ( a set of multiple identical   antennas  which work together as a single antenna), the directivity of the entire array is the multiplicative sum of the individual antenna's directivity function with a mathematical expression known as the  array factor   which typically depends on the location, the excitation and the  phase  of each antenna element. The overall directivity function is given by Darray ( β , Φ )=AF * D( β , Φ ) Where D( β , Φ ) is the directivity of a single element. This single element term is sometimes referred to as the  element pattern

15. Antenna Array Aplications -An array widely used as a base-station antenna for mobile communication. Yagi-Uda array is used to TV and radio application Log periodic antenna is used for TV with wider bandwidth Broadcasting, Beam forming, Naval usage, optical phased arrays - Radio-frequency identification (RFID) - Weather research usage - Missiles guidance - Fire radar aircraft…etc.. Are the areas in which array antennas are used for…

16. Thank you!!!! THE END!!!