FACULTY DEVELOPMENT PROGRAMME on EC6602 - ANTENNA AND WAVE PROPAGATION VALLIAMMAI ENGINEERING COLLEGE SRM Nagar, Kattankulathur - 603 203. DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING FACULTY DEVELOPMENT PROGRAMME on EC6602 - ANTENNA AND WAVE PROPAGATION UNIT – I FUNDAMENTALS OF RADIATION Presented By S. RAMESH Reference : Constantine.A.Balanis “Antenna Theory Analysis and Design”, Wiley Student Edition, 2006.

Matching – Baluns, Polarization mismatch, Antenna noise temperature. PRESENTATION OUTLINE INTRODUCTION Definition of antenna parameters : Gain, Directivity, Effective aperture, Radiation Resistance, Band width, Beam width, Efficiency,Input Impedance. Matching – Baluns, Polarization mismatch, Antenna noise temperature. Radiation from oscillating dipole, Half wave dipole. Folded dipole, Yagi array. CONCLUSIONS References FDP-EC6602-AWP-Unit I-Antenna Parameters

To give insight of the radiation phenomena. OBJECTIVES To give insight of the radiation phenomena. To give a thorough understanding of the radiation characteristics of different types of antennas. To create awareness about the different types of propagation of radio waves at different frequencies. FDP-EC6602-AWP-Unit I-Antenna Parameters

INTRODUCTION In the 1890s, few antennas in the world & primarily a part of experiments that demonstrated transmission of EM waves. By World War II, antennas are ubiquitous & usage had transformed the lives of the person via radio and television reception. Early 21st century, thanks in large part to mobile phones, the average person now carries one or more antennas on them wherever they go (cell phones can have multiple antennas). This significant rate of growth is not likely to slow, as wireless communication systems become a larger part of everyday life. In addition, the strong growth in RFID devices suggests that the number of antennas in use may increase to one antenna per object in the world. Hence, learning a little about antennas couldn't hurt, and will contribute to one's overall understanding of modern world. FDP-EC6602-AWP-Unit I-Antenna Parameters

ANTENNA THEORY HISTORY What is the origin of the antenna? Ben Franklin's kite experiment wasn't quite an antenna, as that captured lightning discharge, which is a direct current path where the energy is not transferred independent of the medium it travels. The human eye of course receives high frequency electromagnetic waves (light, to the layman). Technically the eye could be classified as an antenna; however it can't transmit waves, it is really a sensor. First experiments that involved the coupling of electricity and magnetism and showed a definitive relationship was that done by Faraday somewhere around the 1830s. He slid a magnetic around the coils of a wire attached to a galvanometer. In moving the magnet, he was in effect creating a time-varying magnetic field, which as a result (from Maxwell's Equations), must have had a time-varying electric field. The coil acted as a loop antenna and received the electromagnetic radiation, which was received (detected) by the galvanometer - the work of an antenna. FDP-EC6602-AWP-Unit I-Antenna Parameters

ANTENNA THEORY HISTORY Contributors Maxwell (1831-79) Fundamental equations. (Scottish) Hertz (1857-94) First aerial propagation. (German) Marconi (1874-1937) Transatlantic transmission.(Italian) DeForest (Triode tube 1920) Signal generators.(American) World War II (1939-45) Intense war-driven development. Heinrich Hertz (1886 )developed a wireless communication system in which he forced an electrical spark to occur in the gap of a dipole antenna. He used a loop antenna as a receiver, and observed a similar disturbance. Marconi(1901) was sending information across the Atlantic. For a transmit antenna, he used several vertical wires attached to the ground. Across the Atlantic Ocean, the receive antenna was a 200 meter wire held up by a kite. In 1906, Columbia University had an Experimental Wireless Station where they used a transmitting aerial cage. This was a cage made up of wires and suspended in the air. FDP-EC6602-AWP-Unit I-Antenna Parameters

ANTENNA THEORY HISTORY Some major antennas and discovery: Yagi-Uda Antenna, 1920s Horn antennas, 1939. -waveguides as "hollow metal pipes". Antenna Arrays, 1940s Parabolic Reflectors, late 1940s, early 1950s? Just a guess. Patch Antennas, 1970s. PIFA, 1980s. Current research on antennas involves metamaterials, making antennas smaller, particularly in communications for personal wireless communication devices. A lot of work is being performed on numerical modeling of antennas, so that their properties can be predicted before they are built and tested. References [1] Balanis, Constantine,"Antenna Theory: A Review", Proceedings of IEEE, vol. 80, Jan 1992. [2] http://www.w2aee.columbia.edu/history/antenna-history.html. FDP-EC6602-AWP-Unit I-Antenna Parameters

Converts Electrons to Photons of EM energy. What is an Antenna? An antenna is a way of converting the guided waves present in a waveguide, feeder cable or transmission line into radiating waves travelling in free space, or vice versa. An antenna is a passive structure that serves as transition between a transmission line and air used to transmit and/or receive electromagnetic waves. Converts Electrons to Photons of EM energy. It is a transducer which interfaces a circuit and free space. FDP-EC6602-AWP-Unit I-Antenna Parameters

Antenna as a Transition Device Only accelerated (or decelerated) charges radiate EM waves. A current with a time-harmonic variation (AC current) satisfies this requirement. FDP-EC6602-AWP-Unit I-Antenna Parameters

Transmission-line Thevenin equivalent of antenna in transmitting mode FDP-EC6602-AWP-Unit I-Antenna Parameters

Role of antennas? FDP-EC6602-AWP-Unit I-Antenna Parameters

Antenna types Helical antenna Horn antenna Parabolic reflector antenna FDP-EC6602-AWP-Unit I-Antenna Parameters Helical antenna Horn antenna Parabolic reflector antenna

Solid angle, WA and Radiation intensity, U Antenna parameters Solid angle, WA and Radiation intensity, U Radiation pattern, Pn, sidelobes, HPBW Far field zone, rff Directivity, D or Gain, G Antenna radiation impedance, Rrad Effective Area, Ae All of these parameters are expressed in terms of a transmission antenna, but are identically applicable to a receiving antenna. FDP-EC6602-AWP-Unit I-Antenna Parameters

Isotropic antenna FDP-EC6602-AWP-Unit I-Antenna Parameters

Isotropic antenna FDP-EC6602-AWP-Unit I-Antenna Parameters

FDP-EC6602-AWP-Unit I-Antenna Parameters

Field Regions Radian and Steradian - measure of a plane angle is a radian & measure of a solid angle is a steradian. FDP-EC6602-AWP-Unit I-Antenna Parameters

Radiation Intensity FDP-EC6602-AWP-Unit I-Antenna Parameters

Radiation Pattern FDP-EC6602-AWP-Unit I-Antenna Parameters

FDP-EC6602-AWP-Unit I-Antenna Parameters

Radiation Pattern Characteristics FDP-EC6602-AWP-Unit I-Antenna Parameters

Radiation Pattern Lobes Radiation lobes and beamwidths of an antenna pattern. FDP-EC6602-AWP-Unit I-Antenna Parameters

Radiation Pattern Lobes (b) Linear plot of power pattern and its associated lobes and beamwidths. FDP-EC6602-AWP-Unit I-Antenna Parameters

Directivity and Gain FDP-EC6602-AWP-Unit I-Antenna Parameters

Directivity and Gain of the Antenna FDP-EC6602-AWP-Unit I-Antenna Parameters

Directivity or Gain FDP-EC6602-AWP-Unit I-Antenna Parameters

Directivity and Gain FDP-EC6602-AWP-Unit I-Antenna Parameters

Gain or Directivity FDP-EC6602-AWP-Unit I-Antenna Parameters

Relation b/w Directivity, HPBW,ΩA FDP-EC6602-AWP-Unit I-Antenna Parameters

Effective Aperture FDP-EC6602-AWP-Unit I-Antenna Parameters

FDP-EC6602-AWP-Unit I-Antenna Parameters

Effective Aperture FDP-EC6602-AWP-Unit I-Antenna Parameters

ANTENNA EFFICIENCY total antenna efficiency (e0) is used to take into account losses at the input terminals and within the structure of the antenna. FDP-EC6602-AWP-Unit I-Antenna Parameters

used to judge the quality of transmitting and receiving antennas. BEAM EFFICIENCY used to judge the quality of transmitting and receiving antennas. FDP-EC6602-AWP-Unit I-Antenna Parameters

Linear, Circular, and Elliptical Polarizations defined as “the polarization of the wave transmitted (radiated) by the antenna. Polarization of a radiated wave is defined as “that property of an electromagnetic wave describing the time-varying direction and relative magnitude of the electric-field vector; specifically, the figure traced as a function of time by the extremity of the vector at a fixed location in space, and the sense in which it is traced, as observed along the direction of propagation.” Linear, Circular, and Elliptical Polarizations FDP-EC6602-AWP-Unit I-Antenna Parameters

Antenna Impedance FDP-EC6602-AWP-Unit I-Antenna Parameters

Antenna Impedance FDP-EC6602-AWP-Unit I-Antenna Parameters

Radiation Resistance FDP-EC6602-AWP-Unit I-Antenna Parameters

Radiation Resistance FDP-EC6602-AWP-Unit I-Antenna Parameters

Radiation Resistance FDP-EC6602-AWP-Unit I-Antenna Parameters

So , Antenna Input Impedance is FDP-EC6602-AWP-Unit I-Antenna Parameters

Antenna Bandwidth FDP-EC6602-AWP-Unit I-Antenna Parameters

Antenna Bandwidth FDP-EC6602-AWP-Unit I-Antenna Parameters

Antenna Bandwidth • For broadband antennas, the bandwidth is usually expressed as the ratio of the upper-to-lower frequencies of acceptable operation. For example, a 10:1 bandwidth indicates that the upper frequency is 10 times greater than the lower. • For narrowband antennas, the bandwidth is expressed as a percentage of the frequency difference (upper minus lower) over the center frequency of the bandwidth. For example, a 5% bandwidth indicates that the frequency difference of acceptable operation is 5% of the center frequency of the bandwidth. FDP-EC6602-AWP-Unit I-Antenna Parameters

Antenna Temperature Antenna Temperature is a property of an antenna and the environment it operates in. It is a measure of the noise received by the antenna due to thermal (or temperature) effects. Every object with a physical temperature above absolute zero (K = −273◦C) radiates energy. The amount of energy radiated is usually represented by an equivalent temperature TB, better known as brightness temperature, and it is defined as, FDP-EC6602-AWP-Unit I-Antenna Parameters

Baluns FDP-EC6602-AWP-Unit I-Antenna Parameters

Baluns A balun is a type of transformer Used at RF Impedance-transformer baluns having a 1:4 ratio are used between systems with impedances of 50 or 75 ohms (unbalanced) and 200 or 300 ohms (balanced). Most television and FM broadcast receivers are designed for 300-ohm balanced systems, while coaxial cables have characteristic impedances of 50 or 75 ohms. Impedance-transformer baluns with larger ratios are used to match high-impedance balanced antennas to low- impedance unbalanced wireless receivers, transmitters, or transceivers. Usually band-limited Improve matching and prevent unwanted currents on coaxial cable shields As in differential signaling, the rejection of common mode current is the most important metric for an antenna feed balun, although performance also requires proper impedance ratios and matching to the antenna. FDP-EC6602-AWP-Unit I-Antenna Parameters

Baluns Balun for connecting a center-fed dipole to a coaxial cable Transition from a 50 Ω coaxial cable to a 300 Ω half-wave folded dipole through a four-to- one impedance transformation balun FDP-EC6602-AWP-Unit I-Antenna Parameters

some basic sources of radiation. Single Wire Two-Wires RADIATION MECHANISM “how is radiation accomplished?” (or) how are the electromagnetic fields generated by the source, contained and guided within the transmission line and antenna, and finally “detached” from the antenna to form a free-space wave? some basic sources of radiation. Single Wire Two-Wires Radiation from oscillating dipole, Half wave dipole. Folded dipole, Yagi array. FDP-EC6602-AWP-Unit I-Antenna Parameters

RADIATION MECHANISM - Single Wire Conducting wires are material whose prominent characteristic is the motion of electric charges and the creation of current flow. Charge uniformly distributed in a circular cross section cylinder wire. to create radiation, there must be a time-varying current or an acceleration (or deceleration) of charge. FDP-EC6602-AWP-Unit I-Antenna Parameters

RADIATION MECHANISM - Single Wire To create charge acceleration (or deceleration) the wire must be curved, bent, discontinuous, or terminated. 1. If a charge is not moving, current is not created and there is no radiation. 2. If charge is moving with a uniform velocity: a. There is no radiation if the wire is straight, and infinite in extent. b. There is radiation if the wire is curved, bent, discontinuous, terminated, or truncated. 3. If charge is oscillating in a time-motion, it radiates even if the wire is straight. FDP-EC6602-AWP-Unit I-Antenna Parameters

RADIATION MECHANISM - Single Wire Wire configurations for radiation FDP-EC6602-AWP-Unit I-Antenna Parameters

RADIATION MECHANISM - Two-Wires Source, transmission line, antenna, and detachment of electric field lines. FDP-EC6602-AWP-Unit I-Antenna Parameters

Current Distribution Current distribution on a lossless two-wire transmission line, flared transmission line, and linear dipole. FDP-EC6602-AWP-Unit I-Antenna Parameters

(Short )Dipole Antenna simplest of all antennas. It is simply an open-circuited wire, fed at its center. The dipole antenna is similar to the short dipole except it is not required to be small compared to the wavelength "short" or "small" - "relative to a wavelength". So size of dipole antenna does not matter, only the size of wire relative to wavelength of the frequency of operation. Typically, a dipole is short if its length is less than a tenth of a wavelength. Formation and detachment of electric field lines for short dipole. FDP-EC6602-AWP-Unit I-Antenna Parameters

Half-Wave Dipole Antenna half-wave dipole antenna is a special case of the dipole antenna. length of this dipole antenna is equal to a half-wavelength at the frequency of operation. input impedance of the half-wavelength dipole antenna is given by Zin = 73 + j42.5 Ohms. directivity of a half-wave dipole antenna is 1.64 (2.15 dB). The HPBW is 78 degrees. reducing the length slightly the antenna can become resonant. If the dipole's length is reduced to 0.48 wavelength, the input impedance of the antenna becomes Zin = 70 Ohms, with no reactive component. This is a desirable property, and hence is often done in practice. FDP-EC6602-AWP-Unit I-Antenna Parameters

Yagi-Uda Antenna Yagi antenna was invented in Japan, with results first published in 1926. most brilliant antenna designs. It is simple to construct and has a high gain, typically greater than 10 dB. Yagi-Uda antennas typically operate in the HF to UHF bands (about 3 MHz to 3 GHz), although their bandwidth is typically small, on the order of a few percent of the center frequency. FDP-EC6602-AWP-Unit I-Antenna Parameters

Geometry of Yagi Antenna consists of a single 'feed' or 'driven' element, typically a dipole or a folded dipole antenna. feed antenna is often altered in size to make it resonant in the presence of the parasitic elements (typically, 0.45-0.48 wavelengths long for a dipole antenna). adding more reflectors improves performance very slightly. This element is important in determining the front-to-back ratio of the antenna. reflector slightly longer than resonant & impedance of the reflector will be inductive. directional antenna. FDP-EC6602-AWP-Unit I-Antenna Parameters

CONCLUSIONS To describe the performance of an antenna, definitions of various parameters are necessary. Some of the parameters are interrelated and not all of them need be specified for complete description of the antenna performance. Many of those in quotation marks are from the IEEE Standard Definitions of Terms for Antennas (IEEE Std 145-1983). (Revision of the IEEE Std 145-1973). FDP-EC6602-AWP-Unit I-Antenna Parameters

REFERENCES Constantine.A.Balanis “Antenna Theory Analysis and Design”, Wiley Student Edition, 2006. John D Kraus,” Antennas for all Applications”, 3rd Edition, Mc Graw Hill, 2005. R.E.Collin,”Antennas and Radiowave Propagation”, Mc Graw Hill 1985. H.Sizun “Radio Wave Propagation for Telecommunication Applications”, First Indian Reprint, Springer Publications, 2007. www.antenna-theory.com http://slideplayer.com/slide/download/ FDP-EC6602-AWP-Unit I-Antenna Parameters

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