Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-8, 2016 ISSN: 2454-1362, http://www.onlinejournal.in

A Review on Fundamental of

Rachna Devi1 & Naveen Rawat2 1PG Student, Department Of Electronics and Communication Engineering 2Assistant Professor, Department Of Electronics and Communication Engineering Prannath Parnami Institute, Chaudharywas, Hisar, Haryana 112413, India

Abstract— Antennas are useful for many applications elements or surfaces with no electrical connection to due to their broadband characteristics and relative the or receiver, such as parasitic simplicity. It has long been known that the antenna elements, parabolic reflectors or horns, which serve has broadband characteristics and good radiation to direct the waves into a beam or other efficiency. The design considerations in reducing the desired . size of top loaded conical antenna by using posts with [1.1] Fundamentals of Antenna : lumped resistive loading are presented. The antenna Different types of application requires antenna with designed is compact in size, Size reduction, different parameters. Like for cellular mobile bandwidth and gain enhancement. communication a circular polarized antenna is requires with high gain and for satellite Keywords— GPS , LMR , communication in downlink a high directive antenna is required. The selection and the performance of an I. INTRODUCTION antenna is characterize on the basis of some An antenna is an electrical device which parameters these are Bandwidth, , changes electric power into radio waves, and vice radiation, Pattern, Efficiency, Gain. These parameters versa. It is generally used with a radio are described in brief below: transmitter or radio receiver. In transmission, a radio  Radiation Patterns: transmitter supplies a high frequency alternating Also known as Antenna Pattern or Far-Field Pattern. electric current oscillating at radio frequency to the Radiation pattern of an antenna is graphical antenna's workstations, and the antenna radiates the representation of radiated power at as fix distance energy from the current as electromagnetic from the antenna as a function of azimuth and waves (radio waves). At reception, an antenna elevation angle. So the antenna pattern shows that captures some of the power of an electromagnetic how the power is distributed in the space. For wave in order to produce a small voltage at its simplicity the radiation pattern can be drawn in 2D terminals that is applied to a receiver to be amplified. plane for different azimuth and elevation angle Antennas are vigorous components of all equipment referred as azimuth plane pattern and elevation plane that uses radio. They are used in systems such pattern [22]. It is good to plot the radiation patterns in as radio broadcasting, broadcast television, two-way Cartesian (rectangular) coordinates, especially when radio, communications receivers, radar, cell phones, antenna radiation pattern consists of different side and satellite communications, as well as other lobes and where these side lobes levels plays an devices such as garage door openers, wireless important role. There are different types of antenna microphones, Bluetooth-enabled devices, wireless patterns described below: computer networks, baby monitors, and RFID tags on a. Omnidirectional Antennas: merchandise. can be referred as an Typically an antenna consists of an organization of antenna has radiation pattern uniform and equally metallic conductors, electrically connected to the distributed in one plane generally referred to receiver or transmitter. An oscillating current horizontal planes. Some applications like mobile, cell of electrons forced through the antenna by a phones, FM , walkie talkies, wireless computer transmitter will create an oscillating magnetic networks, cordless phones, GPS, many portable field around the antenna elements, while handheld devices and in base stations antenna the charge of the electrons also creates an required with the characteristics that can radiate oscillating electric field along the elements. These equally in a plane. Omnidirectional antenna has time-varying fields radiate away from the antenna radiation pattern like doughnut shaped. into space as a moving transverse electromagnetic and , , discone antenna, field wave. duck antenna are some good example of low gain Antennas can be designed to transmit and receive omnidirectional antenna. Omnidirectional antenna radio waves in all horizontal directions equally, or with high gain can also be design by narrowing the preferentially in a particular direction. In the latter beam width of the antenna in the vertical plane will case, an antenna may also include additional result in concentrating of energy in horizontal plane.

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Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-8, 2016 ISSN: 2454-1362, http://www.onlinejournal.in

Therefore a narrow beam width antenna has a high characteristics. Bandwidth can be described on the gain and different type of omnidirectional antenna basis of gain, axial ratio bandwidth, and Impedance with various gains can be design. A 0dBd gain or VSWR bandwidth .Impedance bandwidth related antenna radiates more efficiently in vertical plane. to Q factor can be described as b. Directional Antennas: As the name suggest directional antennas concentrate their radiation in a particular direction. They are also BW = known as Beam Antenna. They are useful in some point to point application like satellite communication, in base station antenna to transmitting energy in a particular sector. Yagi, horn, log-periodic antenna and panel antenna are some example that have directional radiation pattern. c. : An Isotropic antenna has the radiations distributed uniformly in all direction. An isotropic antenna radiates all the power given. It is an imaginary antenna does not exist practically. It is used as a reference to compared with the other antennas. Figure 1: Bandwidth The Fraunhofer distance is related to antenna’s larger dimension and can be calculated as: TYPES OF ANTENNA:

Antennas can be classified in several ways. One way is the frequency band of operation. Others include

Where physical structure and electrical/electromagnetic R= distance from antenna design. The antennas commonly used for LMR both D= larger dimension of antenna at base stations and mobile units represent only a λ= wavelength in free space very small portion of all the .  Directivity:  Dipoles and Monopoles : Directivity of an antenna shows that how much the The vertical dipole or its electromagnetic equivalent, antenna is able to radiate in a particular given the monopole could be considered one of the best direction. It is a major requirement when antenna is antennas for LMR applications. It is omnidirectional working as a receiver. Directivity in its simple form (in azimuth) and, if it is a half-wavelength long, has a can be described as the comparison of maximum gain of 1.64 (or G = 2.15 dBi) in the horizontal plane. radiation intensity to average radiation intensity As A center-fed, vertical dipole is illustrated in figure 2(a). Although this is a simple antenna, it can be Directivity = difficult to mount on a mast or vehicle. The ideal  Gain: vertical monopole is illustrated in figure 2(b). It is is also referred as Power gain or half a dipole placed in halfspace, with a perfectly simply Gain. This combines of antenna efficiency conducting, infinite surface at the boundary. and directivity. When it is calculated with efficiency Eantenna and directivity D it is referred as Power Gain. Power Gain = Eantenna . D When the directivity with a particular direction is given it is known as Directive Gain. Directive Gain (θ,π) = Eantenna. D (θ,π)  Antenna polarization: Polarization of an antenna is polarization of the electromagnetic waves radiated from the antenna. Polarization on a wave is the orientation or path traces by the electric field vector as a function of time. Polarization can be categorized in three parts : a. Linear polarization Figure 2. The vertical dipole and its electromagnetic equivalent, b. Circular polarization the vertical monopole c. Elliptical polarization A monopole over an infinite is  Antenna Bandwidth: theoretically the same (identical gain, pattern, etc., in Antenna bandwidth is another important parameter of the half-space above the ground plane) as the dipole antenna can be described as the range of frequencies in free space. In practice, a ground plane cannot be over which antenna justify some desired

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Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-8, 2016 ISSN: 2454-1362, http://www.onlinejournal.in infinite, but a ground plane with a radius (usually one or two) reflector elements and one or approximately the same as the length of the active more (usually two or more) director elements. Figure element, is an effective, practical solution. The flat 5 shows a Yagi antenna with one reflector, a folded- surface of a vehicle’s trunk or roof can act as an dipole active element, and seven directors, mounted adequate ground plane. for horizontal polarization.  Omnidirectional Base antenna: For base-station installations (where an omnidirectional pattern is desired), there are two Figure 5. The Yagi antenna — (a) three elements and (b) practical implementations of the vertical dipole. The multiple elements first type is the sleeve antenna, as illustrated in figure  3(a). The sleeve antenna is a vertical dipole with the Log-Periodic Antenna : feed (transmission line) entering from one end of a A somewhat novel, but very useful, design is the log- hollow element. The second type is a monopole over periodic antenna. This antenna is based on the dipole a ground plane, as illustrated in figure 3(b). The element. As shown in the illustration of figure 6, it is monopole in this illustration uses a set of four wire in fact comprised of a set of dipoles, all active, that elements to provide the ground plane. Figure 8 shows vary in size from smallest at the front to largest at the a typical pattern for a base-station monopole. rear. Usually, this antenna is constructed so the antenna terminals are located at the front (on the shortest dipole). The key features of this antenna are, first of all, its broadband nature, and second, its relatively high front-to-back gain ratio.

Figure 6. A log-periodic antenna Figure 3. Omnidirectional base-station antennas

 Arrays Antenna :  : An (or array antenna) is, much like it An antenna comprised of one or more dipole sounds, several elements interconnected and arranged elements in front of a corner reflector, called the in a regular structure to form an individual antenna. corner-reflector antenna. A photograph of a typical The purpose of an array is to produce radiation corner reflector is shown in figure 4. patterns that have certain desirable characteristics that a single element would not. A stacked dipole array, as shown in figure 7, is comprised of vertical dipole elements. This dipole array has an omnidirectional pattern like the element dipole does; but has higher gain and a narrower main lobe beamwidth in the vertical plane. Figure 7 shows how the vertical-plane gain of the dipole element can be “enhanced” by making an array of them.

Figure 4. Corner-reflector antennas

 Yagi Another antenna : Design that uses passive elements is the Yagi antenna. This antenna, illustrated in figure 5, is inexpensive and effective. It can be constructed with one or more

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Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-8, 2016 ISSN: 2454-1362, http://www.onlinejournal.in

 Diversity Antennas : Diversity is a technique that improves reception of radio waves by taking advantage of the fact that signals that vary with time (e.g., fading) are not the same at separated locations. In other words, the Diversity Antennas Diversity is a technique that improves reception of radio waves by taking advantage of the fact that signals that vary with time (e.g., fading) are not the same at separated locations.

[1.2] Conical Antenna : A wide-band antenna in which the driven element is conical in shape. Also known as cone antenna. Figure 9 shows the conical antenna.

Figure 7. A typical vertical array using folded dipoles

 Unusual Antennas : There are many other antenna types. Most of these are beyond the scope of this report, but knowledge about some may be useful for LMR users. While not as commonplace as wire or rod antennas, aperture antennas are by no means unusual. These antennas are implemented as an opening in a relatively large, conductive (metal) surface.

 Active Antennas : An active antenna is one that contains some Figure 9: conical Antenna electronic circuitry that can amplify a received signal at the antenna and thus avoid interference that may enter the system at the transmission line. Figure 8 II. LITERATURE REVIEW shows this concept. The antenna “element” is connected to the input of an amplifier. The output Shi-Shan Qi et. all (2014) In this paper, a high gain terminals of the amplifier are the antenna terminals conical beam antenna with large beam-pointing angle for this active antenna. The antenna element and the has been investigated. Total prototype contains a amplifier are included in the “active antenna,” shown three section circular waveguide aperture antenna as a dashed box in the figure 8. which operates in TM03 mode in order to generate a primary conical beam and a new hemitorus lens- reflector as the secondary large aperture radiator. Through optimized design, the gain of 12 dB and a beam-pointing angle of 50° have been achieved at the central frequency of 35 GHz. Sachin Gupta et. al. (2014) This paper reports the design of a wide band planar fed, planar conical . Parametric studies have been carried out to arrive at the optimum antenna dimensions to have a wide impedance bandwidth (VSWR<2). Experimental results confirmed the wide impedance bandwidth. Increasing demand for compact and multi

Figure 8: The antenna element and the amplifier band wireless systems call for low profile, wideband and compact antennas. Though microstrip patch specific pattern feature is desired, but cannot be antennas offer compactness and easy integration, they achieved without causing the antenna to have an are limited by their narrow impedance bandwidth. unusual terminal impedance. An active antenna is Fractal geometries have been widely used to design nonreciprocal and cannot be used for transmitting. multi band antennas. This can be in non-planar or planar form. Authors proposed a

novel embedded PICA employing a planar feeding,

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Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-8, 2016 ISSN: 2454-1362, http://www.onlinejournal.in which resulted in compactness. Characteristics of microstrip open end. A operating at these monopole antennas do not depend much on the 14.9 GHz is designed, fabricated and tested. substrate material as opposed to the conventional Measurements show that the horn has a rejection microstrip antennas. In this paper, a wideband Planar coefficient of less than ¡10 dB, and a port isolation Conical Loop Antenna (PCLA) has been greater than 30 dB, over 14.6{ 15.2 GHz, and a gain investigated, which has a wide impedance match. of 12.34 dBi and 10-dB beam widths of 87± and 88± Section 2 explains the antenna design along with the at 14.9 GHz. parametric studies used for designing the optimized antenna. Experimental results of prototype antennas heave been presented to verify the simulations. CONCLUSION Priyanka Bhagwat et. all (2013) Horn antennas are very popular at UHF (300 MHz-3 GHz) and higher Conical antenna are currently used for various frequencies ( as high as 140 GHz). Horn antennas application such as in wide band and lower band often have a directional radiation pattern with a high frequency ranges which are used in satellites, Wi-Fi, antenna gain, which can range up to 25 dB in some Bluetooth and in mobile communication. Here we cases, with 10-20 dB being typical. Horn antennas follow fractal geometry to simulate the antenna and have a wide impedance bandwidth, implying that the to obtain a frequency range for lower frequency input impedance is slowly varying over a wide range which are used for Wi-Fi and Bluetooth frequency range. The bandwidth for practical horn application. antennas can be of the order of 20:1 (for instance, operating from 1 GHz-20 GHz), with a 10:1 bandwidth being common. 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Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-8, 2016 ISSN: 2454-1362, http://www.onlinejournal.in

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