Waves in Communication
Waves in communication refer to the transmission of information through the propagation of electromagnetic or mechanical waves. These waves carry signals that can be used for various forms of communication, such as radio, television, and mobile phones. Understanding the properties and behavior of waves is crucial for designing and optimizing communication systems.
6 Key excerpts on "Waves in Communication"
eBook - ePubWireless Sensors and Instruments
Networks, Design, and Applications
- Halit Eren(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...2 Wireless Communication ______________ Communication is the transfer of information from one device to another. Modern communication systems involve man-made signals that can be transmitted to different places. The communication signals that carry the information can be in the form of electrical energy, such as currents and voltages, electromagnetic energy, optical energy, or sonic energy. Signals are generated electronically and transmitted via cables and wired lines or wire-lessly through electromagnetic radiation in space in the form of radio waves or microwave energy. Signals can also be transmitted by optical or sonic methods. Communication between instruments takes place via transmission of electrical signals from a source to a sink. The originator of the information is called the source, and the receiving end is the sink. The source converts the original message (e.g., voice, text) into electrical signals that are transmitted to the sink. The source also produces electrical signals suitable for transmission in the selected media—wired, wireless, optical, and so on. The hardware and software that comprises the source is called the transmitter. The task of the transmitter is to process the communication signal into a suitable form for successful transmission along a selected channel. The communication channel is the medium that connects the transmitter to the receiver. The medium can be wires, coaxial cables, fiber-optic cables, or space that carries electromagnetic waves or light waves. On the sink side, a receiver extracts the signal coming from the communication channel and processes it such that the information can be interpreted and understood. The sink converts the electrical signal from the receiver back into the form of the original information, such as voice, text, or data. This chapter concentrates on the basic principles of wireless communication techniques using electromagnetic waves, particularly at radio frequencies...
- Navale Pandharinath(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...This was exactly Marconi achieved in his experiments. The traditional aerial is called a halfwave dipole shown in Fig. 14.1. The speed of propagation of electromagnetic wave is 3 × 10 8 m/s. The transmitted waves from a simple system with a single wire aerial travel in all directions around the antenna. Fig. 14.1 A half-wave dipole aerial The magnetic field propagates at right angle to the electric field. The wave is polarised in the direction of the electric field. The propagation of an alternating electromagnetic field in space constitutes electromagnetic waves. Electromagnetic waves are transverse waves because the electric and magnetic intensity vectors E → and H → of the wave fields are mutually perpendicular (shown in Fig 14.2) and lie in a plane perpendicular to the velocity vector v of wave propagation. The Vectors V →, E → and H → form a right handed system. Fig. 14.2 Radio wave polarisation According to classical electro dynamic theory electromagnetic waves originate by the accelerated electric charges. A frame or loop antenna is a closed AC circuit. Radio communication includes transmission of any type of information by means of radio waves, that is electromagnetic waves of frequency less than 3 × 10 5 MHz. Radio broadcasting in transmission of speach, music, telegraphic signals by means of radio. Television broadcsting in transmission of images by means of radio. Radio communications are the transmission of modulated electromagnetic waves by the radio transmitter and their demodulation in a radio receiver. The alteration or change of parameters of electromagnetic waves is called modulation. The wave which is modulated is called carrier wave and its frequency is called carrier frequency. Depending upon the parameter of carrier wave that is altered in modulation we have: Amplitude modulation see Fig. 14.3 (in which amplitude of the wave is changed). Fig...
eBook - ePubRF and Microwave Engineering
Fundamentals of Wireless Communications
- Frank Gustrau(Author)
- 2012(Publication Date)
- Wiley(Publisher)
...Chapter 8 Radio Wave Propagation Spherical electromagnetic waves that emanate from a transmitting antenna experience a reduction in field strength as the distance to the antenna increases. Furthermore, in terrestrial wireless communication links, EM waves interact with obstacles (buildings, walls, trees, hills, etc.) leading to absorption, diffraction and scattering of waves. Consequently, the field strength decreases even more quickly than in free space. In order to design and operate wireless communication systems it is essential to estimate the path loss from transmitter to receiver. For a given transmit power the path loss determines the received power and hence the coverage of the wireless system. In this chapter we start by illustrating physical aspects of electromagnetic wave propagation. Furthermore, fundamental mathematical models that predict path loss in simple environments are derived from basic theory. Finally, we present more complex models to predict path loss in real environments. 8.1 Propagation Mechanisms 8.1.1 Reflection and Refraction In free space plane waves and spherical waves may propagate. In Section 2.5.3 we looked at reflection and refraction of plane waves interacting with material interfaces. In the following we will summarize the basics and include further physical effects of wave propagation that are important when investigating path loss. Figure 8.1 a shows a plane wave (starting in medium 1) that impinges on a material interface under an angle of ϑ f (oblique incidence). There are two physical effects to be observed: Reflection: A plane wave that hits a material surface is partly reflected back into medium 1. The angle of reflection ϑ r equals the angle of incidence ϑ f. Refraction: A plane wave that hits a material surface is partly transmitted through the material interface into medium 2. Due to different phase velocities in the different media, the plane wave changes its direction of travel...
eBook - ePubSmart Grid Telecommunications
Fundamentals and Technologies in the 5G Era
- Alberto Sendin, Javier Matanza, Ramon Ferrús(Authors)
- 2021(Publication Date)
- Wiley-IEEE Press(Publisher)
...3 Telecommunication Fundamental Concepts 3.1 Introduction There are a number of elements that are key in the correct understanding of telecommunications systems and services, and specific relationships exist among them. The study of telecommunications involves the analysis of the transmission of information signals (both analog and digital) in an effective and reliable way. The evolution from analog to digital must be comprehended and specially the implications of the digital world in terms of adaptation of the telecommunication systems. The modulation of signals, together with the access to the medium, affects their capability to share physical media, and it needs to be explained. Some modulations may convey better throughput (data rate) while being more prone to errors as well. Finally, the main concepts and their trade‐offs (signal‐to‐noise ratio, bandwidth, propagation – reach, etc.) of the different telecommunication technologies must be highlighted. This chapter drills down into the framework provided by Chapter 2 and the previously defined concepts in a detailed manner, while not diving too deep into their mathematical derivation. It also covers the propagation characteristics of specific telecommunication technologies, i.e. optical fiber communications and radiocommunications (wireless). 3.2 Signals 3.2.1 Analog vs. Digital Chapter 2 has already introduced some general ideas about the different nature of analog and digital signals. This section deep dives into the essence of these two types of information sources, their relationships, and how one may be converted to the other, and vice versa. 3.2.1.1 Continuous vs. Discrete The very foundations of telecommunications are the transmission of signals from one point to another. A signal is a mathematical representation of the evolution of a physical quantity concerning some parameters (usually time or space). This physical quantity can be voltage, electrical intensity, pressure, light intensity, etc...
eBook - ePubModern Telecommunications
Basic Principles and Practices
- Martin J N Sibley(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...5 Transmission and Propagation of Electromagnetic Waves In this chapter, we will discuss transmission lines, which are used to carry signals, and the propagation of electromagnetic waves which encompasses antennae. Probably the most familiar example of a transmission line is the length of coaxial cable linking the TV antenna on the roof to the TV in the house. What is seldom realised is that a piece of wire is also a transmission line as is a printed circuit board (pcb) track. What is important is the relationship between the wavelength and the length of the line, and that is dealt with in this chapter. We must keep a sense of perspective when considering transmission lines. We will not have to worry about transmission line effects in a 10 m length of mains cable. The wavelength of 50 Hz in free space is 6 × 10 6 m and at 60 Hz it is 5 × 10 6 m; so, 10 m is a minute amount of wavelength. Conversely, if we take a 30 GHz signal and a 10 cm line, the line has 10 wavelengths on it and we would certainly need to use transmission line theory here. There are many types of transmission lines – pcb track over a ground plane; twin feed (parallel conductors); 75 Ω coaxial cable (coax); 50 Ω coax; unshielded twisted pair (UTP); to name a few. Note that the choice of 75 Ω or 50 Ω coax is historical. It might be thought that there is little difference between the two; however, early experimentation showed that the best power handling capability came from 30 Ω coax whereas the lowest attenuation came from 77 Ω coax. So, 50 Ω was used as a compromise and it is used wherever power needs to be carried (transmitters and also radio receivers). TV receiver systems use 75 Ω and we will see why in Section 5.4. 5.1 WAVES ON TRANSMISSION LINES Consider a transmitter connected to an antenna via a length of coaxial cable. When the transmitter is turned on, the signal travels down the cable to the antenna. This takes time – nothing happens instantaneously...
- Albert Sabban(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...3 Introduction to Basic Theory for Wireless Wearable Communication System Designers This chapter provides a short introduction to wireless wearable communication systems. Transmitting and receiving information in microwave frequencies is based on electromagnetic wave propagation. Wireless wearable communication systems operate in the vicinity of the human body. 3.1 WIRELESS WEARABLE COMMUNICATION SYSTEM FREQUENCY RANGE The electromagnetic spectrum of wireless wearable communication systems corresponds to electromagnetic waves from the meter range to the centimeter wave range to date. However, there are some new designs in the mm wave rage. The characteristic feature of this phenomena is the short wavelength involved. The wavelength is of the same order of magnitude as the circuit device used. The propagation time from one point of the circuit to another point of the circuit is comparable to the period of the oscillating voltages and currents in the circuit. Conventional low circuit analysis based on Kirchhoff’s and Ohm's laws can not analyze and describe the variation of fields, voltages, and currents along the length of the components. Components whose dimensions are lower than a tenth of a wavelength are called lumped elements. Components whose dimensions are higher than a tenth of a wavelength are called distributed elements. Kirchhoff’s and Ohm's laws may be applied to lumped elements. However, Kirchhoff’s and Ohm's laws cannot be applied to distributed elements. To prevent interference and to provide efficient use of the frequency spectrum, similar services are allocated in frequency bands, see [ 1 – 4 ]. Bands are divided at wavelengths of 10 n meters or frequencies of 3 × 10 n hertz...
