tailieunhanh - Lecture Wireless and mobile computing – Chapter 17: Antennas and propagation review/recap
The following will be discussed in this chapter: Antenna functions, isotropic antenna, radiation pattern, parabolic reflective antenna, antenna gain, signal loss in satellite communication, noise types, refraction, fading, diffraction and scattering, fast and slow fading, flat and selective fading, diversity techniques. | Antennas and Propagation Review/Recap Lecture 17 Overview Antenna Functions Isotropic Antenna Radiation Pattern Parabolic Reflective Antenna Antenna Gain Signal Loss in Satellite Communication Noise Types Refraction Fading Diffraction and Scattering Fast and Slow Fading Flat and Selective Fading Diversity Techniques Review Question: Antenna Functionality Q:- What two functions are performed by an antenna? Antenna Definition An antenna is defined as usually a metallic device (as a rod or wire) for radiating or receiving radio waves. The IEEE Standard Definitions of Antenna defines the antenna or aerial as “a means for radiating or receiving radio waves.” In other words the antenna is the transitional structure between free-space and a guiding device, as shown in Figure Why Antennas of Different Shapes In addition to receiving or transmitting energy, an antenna in an advanced wireless system is usually required to optimize or accentuate the radiation energy in some directions and suppress it in others. Thus the antenna must also serve as a directional device in addition to a probing device. It must then take various forms to meet the particular need at hand, and it may be a piece of conducting wire, an aperture, a patch, an assembly of elements (array), a reflector, a lens, and so forth. For wireless communication systems, the antenna is one of the most critical components. A good design of the antenna can relax system requirements and improve overall system performance. The antenna serves to a communication system the same purpose that eyes and eyeglasses serve to a human Basic Antenna Functions As Antenna resides between cable/waveguide and the medium air, the main function of antenna is to match impedance of the medium with the cable/waveguide impedance. Hence antenna is impedance transforming device. The second and most important function of antenna is to radiate the energy in the desired direction and suppress in the unwanted direction. This . | Antennas and Propagation Review/Recap Lecture 17 Overview Antenna Functions Isotropic Antenna Radiation Pattern Parabolic Reflective Antenna Antenna Gain Signal Loss in Satellite Communication Noise Types Refraction Fading Diffraction and Scattering Fast and Slow Fading Flat and Selective Fading Diversity Techniques Review Question: Antenna Functionality Q:- What two functions are performed by an antenna? Antenna Definition An antenna is defined as usually a metallic device (as a rod or wire) for radiating or receiving radio waves. The IEEE Standard Definitions of Antenna defines the antenna or aerial as “a means for radiating or receiving radio waves.” In other words the antenna is the transitional structure between free-space and a guiding device, as shown in Figure Why Antennas of Different Shapes In addition to receiving or transmitting energy, an antenna in an advanced wireless system is usually required to optimize or accentuate the radiation energy in some .
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