DOCSLIB.ORG

Antenna Glossary

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Antenna Glossary Antenna Glossary ADAPTIVE (SMART) ANTENNA BASE STATION An antenna system having circuit elements associ- In a cellular communication system, a base station ated with its radiating elements such that one or could be considered a central mode of transmis- more of the antenna properties are controlled by sion and reception for the network. This station the received signal. includes an omnidirectional antenna or several sec- torial antennas. ANTENNA A metallic device used in the transmission and BEAMWIDTH reception of electromagnetic waves. An antenna is The angle of signal coverage provided by an anten- a passive or an active device which permits trans- na. Beamwidth usually decreases as antenna gain mission. increases. ANTENNA DIVERSITY CABLE ASSEMBLY The use of two or more antennas to improve signal A cable that is ready for installation in specific quality. applications and usually terminated with connec- tors. ANTENNA POWER GAIN The ratio of the antenna’s maximum radiation CABLE LOSS intensity in a stated direction to the maximum A numeric value describing the amount of signal radiation intensity of a reference antenna (dipole, loss from one point on a length of cable to another. isotropic antenna) with identical power applied to This is measured in decibels (dB). both. CENTER CONDUCTOR ATTENUATION A solid or stranded electrical conductor generally The loss in power of electromagnetic signals composed of copper and located at the center of between transmission and reception points. the coaxial cable. AZIMUTH CENTER FED Horizontal direction expressed as the angular dis- Transmission line connection at the electrical cen- tance between the direction of a fixed point (as the ter of an antenna radiator. observer’s heading) and the direction of the object. COAXIAL CABLE BANDWIDTH Cable consisting of a single copper conductor in A range of consecutive frequencies comprised of a the center surrounded by a plastic layer for insula- band (i.e. the US cellular bandwidth is 72 MHz wide tion and a braided metal outer shield. Coax is used between the frequencies of 824 MHz - 890 MHz) to transfer radio frequency energy from the trans- over which an antenna shall perform without the mitter to the antenna. need of any adjustment. www.pulseelectronics.com/products/antennas 1-800-ANTENNA (268-3662) Antenna Glossary COLLINEAR ARRAY dBm A system of two or more antenna radiators A measure of power based upon the decibel scale, arranged in a line and connected end-to-end to but referenced to the milliWatt: i.e. 1 dBm = .001 generate a directed field pattern (serial linear Watt. dBm is often used to describe absolute topology). power level where the point of reference is 1 milli- Watt. In high power applications the dBW is often used with a CONDUCTOR reference of 1 Watt. A metal body such as tubing, rod or wire which permits current to travel continuously along its length. dBW The ratio of the power to 1 Watt expressed in deci- bels. COUPLER Referring to on-glass antennas, a coupler is the two-piece interface between the coaxial cable DC GROUND on the inside of the glass and the radiator on the An antenna which is a dead short to a DC current, outside of the vehicle. It is designed to efficiently and has a shunt-fed design. To RF it is not seen as couple RF energy through the glass. The formula- a short. tion of the glass and glass thickness normally have a substantial effect on coupler performance. DIPOLE An antenna - usually a half wavelength long - split CURRENT LOOP at the exact center for connection to a feed line. A point of current maxima (antinode) on an anten- Also called a “doublet”. na. DIRECTIONAL ANTENNA CURRENT NODE An antenna having the property of radiating or A point of current minima on an antenna. receiving electromagnetic waves more effectively in some directions than others. DECIBEL (dB) The standard unit used to express transmission DIRECTIVITY gain or loss and relative power levels. See Basic The theoretical characteristic of an antenna to Antenna Concepts. concentrate power in only one direction, whether transmitting or receiving. dBd Quantification of the gain for an antenna in com- DRIVEN ELEMENT parison with the gain of a dipole. A radiator element of an antenna system to which the transmission line is connected. dBi The dB power relative to an isotropic source. EFFICIENCY The ratio of useful output to input power, deter- mined in antenna systems by losses in the system including losses in nearby objects. www.pulseelectronics.com/products/antennas 1-800-ANTENNA (268-3662) Antenna Glossary ELECTRICALLY SMALL ANTENNA FIELD TUNABLE Some antennas (such as various low profile anten- Antennas identified as Field Tunable are shipped nas, some base loaded whips and often rubber with a cut chart the installer uses to select a duckie portable antennas) are physically consider- desired operating frequency by tuning the anten- ably smaller than either a 1/2 or 1/4 wavelength na to resonance. Cut charts should be used as antenna. The challenge with electrically small guidelines and are adequately accurate for many antennas is to maintain radiating efficiency. A applications. However, Larsen recommends using greater challenge is to design an antenna with ade- appropriate RF measurement devices whenever quate bandwidth. Careful design using high quality possible for more accurate tuning. materials often overcome these obstacles. FREQUENCY ELEVATED FEED The number of cycles per second of a sound wave Raises the radiating element above the vehicle roof level reducing obstruction. FRONT-TO-BACK RATIO The gain of an antenna, in a specified direction. ELEMENT, ELEMENTS Typically a subset or a more elementary part of a larger antenna system. For example, an element of GAIN a Yagi-Uda array is normally a dipole antenna that, The increase in signal strength that is produced together with other dipoles, forms the array. An by an amplifier. The ratio between the amount of 8-element Yagi antenna would then ordinarily have energy propagated from an antenna that is direc- 8 dipoles. tional compared to the energy from the same antenna that would be propagated if the antenna were not directional. The gain of an antenna is the EMBEDDED ANTENNAS same regardless of if the antenna is used to trans- Antennas directly integrated into a system such as mit or receive. an access point, a terminal or a handset. In most cases, this antenna is matched to the system and can not be used in other applications without mod- GIGAHERTZ (GHz) ification. One billion cycles per second. E-PLANE AND H-PLANE GPS Antenna measurements in general and radiation GPS (Global Positioning System) is a radio naviga- patterns in particular must be performed with tion system allowing land, sea and airborne users polarization in mind. Since polarization is defined to determine their exact location, velocity, and time as having the same orientation as an antenna’s 24 hours a day, in all weather conditions, anywhere electric field vector, it is common practice to refer in the world. to measurements aligned with either the electric vector ( E-plane) or magnetic vector (H-plane). GROUND PLANE A man-made system of conductors placed below FIELD STRENGTH an antenna to serve as an earth ground An absolute measure in one direction of the elec- tromagnetic wave field generated by an antenna at some distance away from the antenna. www.pulseelectronics.com/products/antennas 1-800-ANTENNA (268-3662) Antenna Glossary HALF-WAVE DIPOLE ANTENNA MOBILE ANTENNA A center-fed antenna whose electrical length is half Refers to any antenna mounted on a vehicle. the wavelength of the transmitter or received sig- Includes a radiating element and a mechanism to nal. An antenna consisting of two rods (1/4 wave- fix the antenna to the vehicle. length each) in a straight line, that radiates electro- magnetic energy. MONOPOLE Literally, one pole, such as a vertical radiator oper- HELICAL ANTENNA ated against the earth or a ground plane. A hand- An antenna with a spiral conductor wound around held rubber duck type of antenna will most likely a cross section. An antenna that has the form of a be a monopole. helix. MOUNT HERTZ (Hz) A mount is the device onto which a mobile antenna A unit of frequency equal to one cycle per second. attaches. It is the mechanical and electrical inter- face between an antenna and the vehicle. HOTSPOT Public area where wireless LAN Internet access is MULTI-PATH PROPAGATION apt to be used (for high-speed access to e-mail, The result of interference from reflections off web sites, etc.). Users are usually unproductive surfaces surrounding the antenna. This interfer- while waiting. Examples are convention centers, ence changes the target’s return signal strength. hotels, airports, train stations, bus stations, restau- Sometimes it is stronger and sometimes weaker rants, and coffee shops. than expected. The degree of multi-path propaga- tion depends on the type of reflective surface; flat metal, towers and buildings cause the strongest H-PLANE effects. Antenna measurements in general and radiation patterns in particular must be performed with polarization in mind. Since polarization is defined NMO as having the same orientation as an antenna’s Perhaps the most prolific of all mobile antenna electric field vector, it is common practice to refer mounts is the NMO. It enables one mount, inserted to measurements aligned with either the electric in a drilled hole in the vehicle body, to be used vector ( E-plane) or magnetic vector (H-plane). over the lifetime of the vehicle with many screw-on antennas. IMPEDANCE The Ohmic value of an antenna feed point, match- NOISE ing section or transmission line at a radio frequen- Any unwanted and unmodulated energy that is cy.
Load more

Recommended publications
  • Coplanar Stripline-Fed Wideband Yagi Dipole Antenna with Filtering-Radiating Performance
    electronics Article Coplanar Stripline-Fed Wideband Yagi Dipole Antenna with Filtering-Radiating Performance Yong Chen 1, Gege Lu 2, Shiyan Wang 2 and Jianpeng Wang 2,* 1 School of Physics and Electronic Electrical Engineering, Huaiyin Normal University, Huaian 223300, China; [email protected] 2 Ministerial Key Laboratory of JGMT, Nanjing University of Science and Technology, Nanjing 210094, China; [email protected] (G.L.); [email protected] (S.W.) * Correspondence: [email protected] Received: 6 July 2020; Accepted: 4 August 2020; Published: 6 August 2020 Abstract: In this article, a wideband filtering-radiating Yagi dipole antenna with the coplanar stripline (CPS) excitation form is investigated, designed, and fabricated. By introducing an open-circuited half-wavelength resonator between the CPS structure and dipole, the gain selectivity has been improved and the operating bandwidth is simultaneously enhanced. Then, the intrinsic filtering-radiating performance of Yagi antenna is studied. By implementing a reflector on initial structure, it is observed that two radiation nulls appear at both lower and upper gain passband edges, respectively. Moreover, in order to improve the selectivity in the upper stopband, a pair of U-shaped resonators are employed and coupled to CPS directly. As such, the antenna design is finally completed with expected characteristics. To verify the feasibility of the proposed scheme, a filtering Yagi antenna prototype with a wide bandwidth covering from 3.64 GHz to 4.38 GHz is designed, fabricated, and measured. Both simulated and measured results are found to be in good agreement, thus demonstrating that the presented antenna has the performances of high frequency selectivity and stable in-band gain.
    [Show full text]
  • Radiation Pattern of Yagi-Uda Antenna Using Usrp on Gnu Radio Platform
    IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 RADIATION PATTERN OF YAGI-UDA ANTENNA USING USRP ON GNU RADIO PLATFORM Sreethivya1 M, Dhanya.M.G2, Nimisha.C3, Gandhiraj.R4, Soman.K.P5 1M.Tech Student, Department of CEN, Amrita Vishwa Vidyapeetham, Tamilnadu, India 2M.Tech Student, Department of CEN, Amrita Vishwa Vidyapeetham, Tamilnadu, India 3M.Tech Student, Department of CEN, Amrita Vishwa Vidyapeetham, Tamilnadu, India 4Assistant Professor, Department of ECE, Amrita Vishwa Vidyapeetham, Tamilnadu, India 5Head of Department, Department of CEN, Amrita Vishwa Vidyapeetham, Tamilnadu, India Abstract In this paper we are planning to realize radiation pattern of a Unidirectional Yagi-Uda antenna using USRP2 which is connected with GNU Radio. Our basic approach is to get radiation pattern for H-plane structured Yagi-Uda antenna at different angles (0-360). The proposed method is of low cost and easy to implement with two USRP, two PC and a Yagi-Uda antenna. The platform which we have used for getting radiation pattern values is GNU Radio which is open source software.Yagi-Uda antenna is used for long distance communication since it has good directivity. It is designed with three pairs of oscillator, directors and active transducer. Oscillator is connected to the voltage feeder and active transducer incapacitates the wave from different sides of antenna. Keywords: Yagi-Uda antenna, GNU Radio, Radiation pattern, USRP2, Folded Dipole antenna. -----------------------------------------------------------------------***----------------------------------------------------------------------- 1. INTRODUCTION directors a yagi has, greater the forward gain. We have used a single director along with a reflector and a driven element. In this paper we present radiation pattern of a unidirectional Yagi [2] antenna.
    [Show full text]
  • 25. Antennas II
    25. Antennas II Radiation patterns Beyond the Hertzian dipole - superposition Directivity and antenna gain More complicated antennas Impedance matching Reminder: Hertzian dipole The Hertzian dipole is a linear d << antenna which is much shorter than the free-space wavelength: V(t) Far field: jk0 r j t 00Id e ˆ Er,, t j sin 4 r Radiation resistance: 2 d 2 RZ rad 3 0 2 where Z 000 377 is the impedance of free space. R Radiation efficiency: rad (typically is small because d << ) RRrad Ohmic Radiation patterns Antennas do not radiate power equally in all directions. For a linear dipole, no power is radiated along the antenna’s axis ( = 0). 222 2 I 00Idsin 0 ˆ 330 30 Sr, 22 32 cr 0 300 60 We’ve seen this picture before… 270 90 Such polar plots of far-field power vs. angle 240 120 210 150 are known as ‘radiation patterns’. 180 Note that this picture is only a 2D slice of a 3D pattern. E-plane pattern: the 2D slice displaying the plane which contains the electric field vectors. H-plane pattern: the 2D slice displaying the plane which contains the magnetic field vectors. Radiation patterns – Hertzian dipole z y E-plane radiation pattern y x 3D cutaway view H-plane radiation pattern Beyond the Hertzian dipole: longer antennas All of the results we’ve derived so far apply only in the situation where the antenna is short, i.e., d << . That assumption allowed us to say that the current in the antenna was independent of position along the antenna, depending only on time: I(t) = I0 cos(t) no z dependence! For longer antennas, this is no longer true.
    [Show full text]
  • Design and Application of a New Planar Balun
    DESIGN AND APPLICATION OF A NEW PLANAR BALUN Younes Mohamed Thesis Prepared for the Degree of MASTER OF SCIENCE UNIVERSITY OF NORTH TEXAS May 2014 APPROVED: Shengli Fu, Major Professor and Interim Chair of the Department of Electrical Engineering Hualiang Zhang, Co-Major Professor Hyoung Soo Kim, Committee Member Costas Tsatsoulis, Dean of the College of Engineering Mark Wardell, Dean of the Toulouse Graduate School Mohamed, Younes. Design and Application of a New Planar Balun. Master of Science (Electrical Engineering), May 2014, 41 pp., 2 tables, 29 figures, references, 21 titles. The baluns are the key components in balanced circuits such balanced mixers, frequency multipliers, push–pull amplifiers, and antennas. Most of these applications have become more integrated which demands the baluns to be in compact size and low cost. In this thesis, a new approach about the design of planar balun is presented where the 4-port symmetrical network with one port terminated by open circuit is first analyzed by using even- and odd-mode excitations. With full design equations, the proposed balun presents perfect balanced output and good input matching and the measurement results make a good agreement with the simulations. Second, Yagi-Uda antenna is also introduced as an entry to fully understand the quasi-Yagi antenna. Both of the antennas have the same design requirements and present the radiation properties. The arrangement of the antenna’s elements and the end-fire radiation property of the antenna have been presented. Finally, the quasi-Yagi antenna is used as an application of the balun where the proposed balun is employed to feed a quasi-Yagi antenna.
    [Show full text]
  • Nested Loop Antennas This Low-Cost Five Band Loop Array Blends Into the Background
    Nested Loop Antennas This low-cost five band loop array blends into the background. G. Scott Davis, N3FJP This multi-band nested loop antenna array replaces my tribander Yagi, which is only up 20 feet. Inspired by suggestions from Bill Wisel, K3KEI, I first tried a full wave 20 meter band square loop antenna. On the air comparisons with my low Yagi confirmed instantly that this design was a hands-down winner for working both local and distant stations. I replaced that mono-band loop with a nested loop array for the 20, 17, 15, 12, and 10 meter bands. The antenna blends into the surroundings, so I needed the morning sun shining directly on it to snap the lead photo. This became a nice father-son project with my son Brad, KB3MNE. Here’s how we built the antenna. Construction We constructed the square loops shown in Figure 1 according to the dimensions in Table 1. The loops hang from a tree limb in the vertical plane. Because I feed them This stealthy nested loop is almost invisible among the trees. from the bottom corners, the loops radiate horizontal polarization. Calculate the perimeter size, P, of each holes through the pipe for the loop wire. screws into the PVC to hang the dipole loop by dividing the frequency in MHz After you run the wire through the holes, connectors seen in Figure 2. wrap a bit of electrical tape on each side of into 1005 feet. Table 1 shows the loop Matching and Feeding dimensions. Start with the 20 meter loop, the wire next to the pipe to keep the wire from sliding and to give the pipe additional Each loop antenna feed point impedance is the largest loop.
    [Show full text]
  • Performance Analysis of Helical Antenna for Different Physical Structure
    International Journal of Innovative Research in Electronics and Communications (IJIREC) Volume 5, Issue 4, 2018, PP 21-25 ISSN 2349-4050 (Online) & ISSN 2349-4042 (Print) DOI: http://dx.doi.org/10.20431/2349-4050.0504004 www.arcjournals.org Performance Analysis of Helical Antenna for Different Physical Structure Rahul koshti1, Simran Yadav2, Shikha Sharma3 MPSTME, NMIMS, Shirpur *Corresponding Author: Rahul koshti, MPSTME, NMIMS, Shirpur Abstract: Wireless technology is such of the potent areas of scan in the presence of communication systems today and a design of communication systems is incomplete without a perspective of the activity and fabricatio n of antennas. Helical antenna is used as easily done and shrewd radiators completely the get by few decades, this antenna can be utilized as an encourage for an explanatory dish for higher additions.. So in this we have varied various parameters of helical antenna. Manipulations for this helical antenna antenna have been done with the assist of Matlab softwar Keywords: helical antennas, Antenna gain, Directivity. 1. INTRODUCTION In 1946 Kraus invented the helix form of antenna that is helical antenna. For longer period of time this helical antenna gets famous. [1] Helical antennas are further called as unfiled helix. By the all of diameter D in large helical antenna is revitalizing by a coaxial line along the little ground plane. In communication system helical antenna have a very large approach, so there is a foist of broadband circular polarized antennas [2].This antenna is most significantly used nowadays in point communications, telephone, and television and Information communication. The normal mode helical antenna is particularly attractive for mobile communication and adaptable equipment [3].The shape of helix antenna is a cross breed of two straightforward emanating essentials, the dipole and circle reception apparatuses.
    [Show full text]
  • Class C Pool of Questions
    Class C Pool of Questions T2 1. What is the most common repeater frequency offset in the 2 meter band? T2 2. What is the national calling frequency for FM simplex operations in the 70 cm band? T2 3. What is a common repeater frequency offset in the 70 cm band? T2 4. What is an appropriate way to call another station on a repeater if you know the other station's call sign? T2 5. How should you respond to a station calling CQ? T2 6. What must an amateur operator do when making on-air transmissions to test equipment or antennas? T2 7. Which of the following is true when making a test transmission? T2 8. What is the meaning of the procedural signal “CQ”? T2 9. What brief statement is often transmitted in place of “CQ” to indicate that you are listening on a repeater? T2 10. What is a band plan, beyond the privileges established by the SMA? T2 11. Which of the following is an SMA rule regarding power levels used in the amateur bands, under normal, non-distress circumstances? T2 12. Which of the following is a guideline to use when choosing an operating frequency for calling CQ? T2B – VHF/UHF operating practices: SSB phone; FM repeater; simplex; splits and shifts; CTCSS; DTMF; tone squelch; carrier squelch; phonetics; operational problem resolution; Q signals T2 1. What is the term used to describe an amateur station that is transmitting and receiving on the same frequency? T2 2. What is the term used to describe the use of a sub-audible tone transmitted with normal voice audio to open the squelch of a receiver? T2 3.
    [Show full text]
  • Loudspeaker Parameters
    Loudspeaker Parameters D. G. Meyer School of Electrical & Computer Engineering Outline • Review of How Loudspeakers Work • Small Signal Loudspeaker Parameters • Effect of Loudspeaker Cable • Sample Loudspeaker • Electrical Power Needed • Sealed Box Design Example How Loudspeakers Work How Loudspeakers Are Made Fundamental Small Signal Mechanical Parameters 2 • Sd – projected area of driver diaphragm (m ) • Mms – mass of diaphragm (kg) • Cms – compliance of driver’s suspension (m/N) • Rms – mechanical resistance of driver’s suspension (N•s/m) • Le – voice coil inductance (mH) • Re – DC resistance of voice coil ( Ω) • Bl – product of magnetic field strength in voice coil gap and length of wire in magnetic field (T•m) Small Signal Parameters These values can be determined by measuring the input impedance of the driver, near the resonance frequency, at small input levels for which the mechanical behavior of the driver is effectively linear. • Fs – (free air) resonance frequency of driver (Hz) – frequency at which the combination of the energy stored in the moving mass and suspension compliance is maximum, which results in maximum cone velocity – usually it is less efficient to produce output frequencies below F s – input signals significantly below F s can result in large excursions – typical factory tolerance for F s spec is ±15% Measurement of Loudspeaker Free-Air Resonance Small Signal Parameters These values can be determined by measuring the input impedance of the driver, near the resonance frequency, at small input levels for which the
    [Show full text]
  • Broadband Antenna 1
    Broadband Antenna Broadband Antenna Chapter 4 1 Broadband Antenna Learning Outcome • At the end of this chapter student should able to: – To design and evaluate various antenna to meet application requirements for • Loops antenna • Helix antenna • Yagi Uda antenna 2 Broadband Antenna What is broadband antenna? • The advent of broadband system in wireless communication area has demanded the design of antennas that must operate effectively over a wide range of frequencies. • An antenna with wide bandwidth is referred to as a broadband antenna. • But the question is, wide bandwidth mean how much bandwidth? The term "broadband" is a relative measure of bandwidth and varies with the circumstances. 3 Broadband Antenna Bandwidth Bandwidth is computed in two ways: • (1) (4.1) where fu and fl are the upper and lower frequencies of operation for which satisfactory performance is obtained. fc is the center frequency. • (2) (4.2) Note: The bandwidth of narrow band antenna is usually expressed as a percentage using equation (4.1), whereas wideband antenna are quoted as a ratio using equation (4.2). 4 Broadband Antenna Broadband Antenna • The definition of a broadband antenna is somewhat arbitrary and depends on the particular antenna. • If the impendence and pattern of an antenna do not change significantly over about an octave ( fu / fl =2) or more, it will classified as a broadband antenna". • In this chapter we will focus on – Loops antenna – Helix antenna – Yagi uda antenna – Log periodic antenna* 5 Broadband Antenna LOOP ANTENNA 6 Broadband Antenna Loops Antenna • Another simple, inexpensive, and very versatile antenna type is the loop antenna.
    [Show full text]
  • Characteristic Impedance of Lines on Printed Boards by TDR 03/04
    Number 2.5.5.7 ASSOCIATION CONNECTING Subject ELECTRONICS INDUSTRIES ® Characteristic Impedance of Lines on Printed 2215 Sanders Road Boards by TDR Northbrook, IL 60062-6135 Date Revision 03/04 A IPC-TM-650 Originating Task Group TEST METHODS MANUAL TDR Test Method Task Group (D-24a) 1 Scope This document describes time domain reflectom- b. The value of characteristic impedance obtained from TDR etry (TDR) methods for measuring and calculating the charac- measurements is traceable to a national metrology insti- teristic impedance, Z0, of a transmission line on a printed cir- tute, such as the National Institute of Standards and Tech- cuit board (PCB). In TDR, a signal, usually a step pulse, is nology (NIST), through coaxial air line standards. The char- injected onto a transmission line and the Z0 of the transmis- acteristic impedance of these transmission line standards sion line is determined from the amplitude of the pulse is calculated from their measured dimensional and material reflected at the TDR/transmission line interface. The incident parameters. step and the time delayed reflected step are superimposed at the point of measurement to produce a voltage versus time c. A variety of methods for TDR measurements each have waveform. This waveform is the TDR waveform and contains different accuracies and repeatabilities. information on the Z0 of the transmission line connected to the d. If the nominal impedance of the line(s) being measured is TDR unit. significantly different from the nominal impedance of the Note: The signals used in the TDR system are actually rect- measurement system (typically 50 Ω), the accuracy and angular pulses but, because the duration of the TDR wave- repeatability of the measured numerical valued will be form is much less than pulse duration, the TDR pulse appears degraded.
    [Show full text]
  • Helical Feed Manipulation for Parabolic Reflector Antenna Gain Control
    International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-4 Issue-2, December 2014 Helical Feed Manipulation for Parabolic Reflector Antenna Gain Control Zohair Mohammed Elhassan Hussein, Abdelrasoul jabar kizar alzubaidi Abstract Helical antennas have long been popular in A sketch of a typical helical antenna is shown in Figure (1). applications from VHF to microwaves requiring circular The radiating element is a helix of wire, driven at one end polarization, since they have the unique property of naturally and radiating along the axis of the helix. A ground plane at providing circularly polarized radiation. One area that takes the driven end makes the radiation unidirectional from the advantage of this property is satellite communications. Where far (open) end. There are also configurations that radiate more gain is required than can be provided by a helical antenna alone, a helical antenna can also be used as a feed for perpendicular to the axis, with an unidirectional pattern. a parabolic dish for higher gains. The helical antenna can be W e shall only consider the axial-mode configuration. an excellent feed for a dish, with the advantage of circular Typical helix dimensions for an axial-mode helical antenna polarization. One limitation is that the usefulness of the have a helix circumference of one wavelength at the center circular polarization is limited since it cannot be easily frequency, with a helix pitch of 12 to 14 degrees. Kraus reversed to the other sense, left- handed to right-handed or defines the pitch angle α as: vice-versa. This paper deals with applying an electronic technique to control the helical feed of the parabolic reflector = ………………..(1) feed.
    [Show full text]
  • G9C01 (A) Which of the Following Would Increase the Bandwidth of a Yagi Antenna? A
    Section 5.2 G9C01 (A) Which of the following would increase the bandwidth of a Yagi antenna? A. Larger-diameter elements B. Closer element spacing C. Loading coils in series with the element D. Tapered-diameter elements ~~ G9C02 (B) What is the approximate length of the driven element of a Yagi antenna? A. 1/4 wavelength B. 1/2 wavelength C. 3/4 wavelength D. 1 wavelength ~~ G9C03 (A) How do the lengths of a three-element Yagi reflector and director compare to that of the driven element? A. The reflector is longer, and the director is shorter B. The reflector is shorter, and the director is longer C. They are all the same length D. Relative length depends on the frequency of operation ~~ G9C05 (A) How does increasing boom length and adding directors affect a Yagi antenna? A. Gain increases B. Beamwidth increases C. Front-to-back ratio decreases D. Front-to-side ratio decreases ~~ G9C06 (D) What configuration of the loops of a two-element quad antenna must be used for the antenna to operate as a beam antenna, assuming one of the elements is used as a reflector? A. The driven element must be fed with a balun transformer B. There must be an open circuit in the driven element at the point opposite the feed point C. The reflector element must be approximately 5 percent shorter than the driven element D. The reflector element must be approximately 5 percent longer than the driven element ~~ G9C07 (C) What does “front-to-back ratio” mean in reference to a Yagi antenna? A.
    [Show full text]