Name: Mashhour jumah ID: Welcome

What is an antenna? An antenna is an electrical conductor or system of conductors used for transmission and reception of electromagnetic waves Transmission radiates electromagnetic energy into space Reception collects electromagnetic energy from space

Antenna Fundamentals 3 Radiation Patterns

Antenna Fundamentals Relationship between antenna gain and effective area G = antenna gain A e = effective area f = carrier frequency c = speed of light (» 3 ´ 10 8 m/s) = carrier wavelength Property of R Struzak4

Types of antenna Antenna types: actually there are many types of Antenna and there some of them: 1- A Yagi antenna, 1- A Yagi antenna, also known as a Yagi-Uda array or simply a Yagi, is a unidirectional antenna commonly used in communications when a frequency is above 10 MHz This type of antenna is popular among Amateur Radio and Citizens Band radio operators. It is used at some surface installations in satellite communications systems.

Yagi Antenna 6

Type of antenna 2 - isotropic antenna 2 - isotropic antenna Radiates power equally in all directions 3 - Dipole antennas 3 - Dipole antennas Half-wave dipole antenna (or Hertz antenna) Quarter-wave vertical antenna (or Marconi antenna): The term "Marconi antenna" usually refers to a two part antenna consisting of a vertical portion and a "reflective" or "ground" portion. 4 -Parabolic Reflective Antenna 4 -Parabolic Reflective Antenna 5-Slot antenna 5-Slot antenna

monopole antenna 6-monopole antenna 6-monopole antenna : is a radio antenna that is one half of a dipole antenna combined with a right-angle ground plane of considerable length in place of its other half.

horn antenna -7 horn antenna -7 horn antenna : is used for the transmission and reception of microwave signals. It derives its name from the characteristic flared appearance. The flared portion can be square, rectangular, or conical.

helical antenna - 8- helical antenna - 8- helical antenna is a specialized antenna that emits and responds to electromagnetic filed with rotating (circular)polarization. These antennas are commonly used at earth-based stations in satellite communications systems. This type of antenna is designed for use with an unbalanced feed line such as coaxial cable.

Antenna functions Transmission line Power transport medium - must avoid power reflections, otherwise use matching devices Radiator Must radiate efficiently – must be of a size comparable with the half-wavelength Resonator Unavoidable - for broadband applications resonances must be attenuated

Reflector antennas Reflectors are used to concentrate flux of EM energy radiated/ received, or to change its direction Usually, they are parabolic (paraboloical). The first parabolic (cylinder) reflector antenna was used by Heinrich Hertz in 1888.

Reflector antennas Large reflectors have high gain and directivity Are not easy to fabricate Are not mechanically robust Typical applications: radio telescopes, satellite telecommunications.

Planar reflectors Uda-Yagi, Log-periodic antennas 14 d 2d Intended reflector antenna allows maintaining radio link in non-LOS conditions (avoiding propagation obstacles) Unintended antennas create interference

15 The antenna with the transmission line is represented by an (The venin) equivalent generator The receiver is represented by its input impedance as seen from the antenna terminals (i.e. transformed by the transmission line) V A is the (induced by the incident wave) voltage at the antenna terminals determined when the antenna is open circuited Receiving antenna equivalent circuit Radio wave Transm.line Receiver Antenna RrRr jX A VAVA jX L RLRL RlRl Thevenin equivalent

Power transfer The maximum power is delivered to (or from) the antenna when the antenna impedance and the impedance of the equivalent generator (or load) are matched 16

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Exercise ? 18 Exercise

Property of R Struzak19

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