DOCSLIB.ORG

Antenna Gain Validation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Antenna Gain Validation Validation of antenna performance Usually a switched calibration signal is injected into the signal path of a receiver for estimating the total power available at the terminals of the antenna (the antenna temperature) and the noise power due to the receiver system (the receiver temperature). Normally, the antenna output is fed to a balun for converting their balanced output to unbalanced output. The electrical connection between the antenna output terminals and the balun input is established through pressure contact alone, using a bolt and nut arrangement as shown in the Fig 1. Unless the bolt holds the antenna terminal firmly against the balun input, the antenna signal is bound to undergo a finite amount of transmission loss at the connection. Thus the receiver produces less than what is expected when the antenna gain is maximum. It often becomes difficult to know that there is a loss of signal owing to improper connection at the feeding point of the antenna, since the sky signal also keeps varying as a function of time. In order to avoid this problem, a calibration setup was made to measure the absolute transmission loss in the signal path. A CW signal is radiated from a known distance towards the antennas and the receiver response is compared with the expectation as a check on the quality of the electrical/mechanical contact at the feeding point. The prediction of the received CW power at the antenna terminals can be easily made using the Frii’s transmission equation. Bolt head Pcb for balun Balun EoR antenna Balun Bolt and Nut for holding the antenna terminals Fig. 1. Bolt and nut arrangement for making electrical connections of the antenna Fig. 2 shows the experimental setup used for monitoring the gain of the EoR antenna. It consists of a standard calibrated half-wave dipole of ETS Lindgren (Model No. 3121 D) that is placed at equal distances from each of EoR antennas and with the same polarization as that of the antennas; the dipole is mounted 3 m above the ground. A standard signal generator from Agilent Technologies (Model No.8257D) is connected to the calibrated antenna through a balun for transmitting CW signals at various frequencies. The two EoR antenna outputs are connected to receiver systems for estimating the signal received at their terminals. If a continuous wave (CW) is transmitted through the calibrated half wave dipole, then the net signal power available at the EoR antenna terminals situated at a distance of ‘R’ from the radiating dipole is calculated using the Friis equation for transmission as given by Calibrated half wave dipole antenna EoR Ant - 2 Transmitter B a l u n EoR Ant - 1 R=5m Ant – 1 Output Ant – 2 Output 30 dB Signal Generator Front End 1 Front End 2 Digital Receiver Spectrum output Fig. 2. Experimental setup used for monitoring the gain of the EoR antenna λ Pr = Pt GtGr ( ----------- ) (4*3.14*R)2 where Pr is the power available at the EoR antenna Pt is the power fed to the transmitter Gt is the gain of the transmitting antenna Gr is the gain of the receiving antenna λ is thewavelength of the transmitted signal R is the distance between the transmitting and receiving antennas If baluns used in both transmitter and receiver have finite amount of insertion loss ( Lt & Lr), then the above equation gets modified to λ Pr = Pt GtGr ( ----------- ) LtLr (4*3.14*R)2 The power available Pr can be expressed in terms of temperature using the relationship Pr = kTrB where k is the Boltzmann constant = 1.38e-23 m2kg s-2 K-1 Tr is the temperature of the blackbody producing same power as Pr B is the bandwidth over which measurement is made = 85.4 KHz Thus the equivalent temperature Tr corresponding to Pr is given by Tr = Pr/(kB) K Signals of various frequencies having a constant power level of -100 dBm were transmitted through the calibrated antenna. The signal generator was set to provide a power level of -70 dBm and a 30 dB attenuator was used between the signal generator and dipole; this was done in order to have a stable power from the signal generator. The power available at each of the EoR antennas is calculated using the relationships shown above. The equivalent antenna temperatures corresponding to the received CW powers at each of the EoR antennas were estimated using the calibration signal available in the receivers. Table 1 lists the available power in terms of temperature along with their expectation values; this is done at a set of frequencies. The measurements made match closely the expected values with a maximum error of about 10%, indicating good electrical contact between the antenna terminals and the balun input and good understanding of the system performance and calibration. This in turn validates the expectations for gain and transmission losses for the antennas. It is assumed that the gain of the EoR antennas is constant throughout the frequency range of operation since their beamwidth and beam pattern is identical at all those frequencies. While predicting the value of power available at the antenna input, only balun loss is considered in case of antenna 2, whereas for the antenna 1, both the balun and phase switch losses have been considered. Sl. Frequenc Loss of Loss of Loss of Gain of Gain Expected Measured N y- MHz Balun of Balun of Phase Tx. of antenna temp. antenna o. Tx Rx switch – Antenna Rx. at the Rx. –K Temperature - K antenna- antenna – dB - dBi Ant. - Lt -dB Lr - dB dBi FE – 1 FE - 2 FE – 1 FE - 2 1. 131.25 -1.15 -0.83 -0.8 1.6 2.15 140.86 169.7 115.5 159.0 2. 116.1254 883 -1.53 -0.83 -0.8 0.9 2.15 140.32 169.06 140.0 178.0 3. 146.2036 13 -0.5 -0.83 -0.8 1.3 2.15 123.05 148.25 118.5 150.0 4. 161.2426 758 -0.22 -0.83 -0.8 1.8 2.15 121.06 145.86 121.5 152.0 Table 1..
Load more

Recommended publications
  • Radiometry and the Friis Transmission Equation Joseph A
    Radiometry and the Friis transmission equation Joseph A. Shaw Citation: Am. J. Phys. 81, 33 (2013); doi: 10.1119/1.4755780 View online: http://dx.doi.org/10.1119/1.4755780 View Table of Contents: http://ajp.aapt.org/resource/1/AJPIAS/v81/i1 Published by the American Association of Physics Teachers Related Articles The reciprocal relation of mutual inductance in a coupled circuit system Am. J. Phys. 80, 840 (2012) Teaching solar cell I-V characteristics using SPICE Am. J. Phys. 79, 1232 (2011) A digital oscilloscope setup for the measurement of a transistor’s characteristic curves Am. J. Phys. 78, 1425 (2010) A low cost, modular, and physiologically inspired electronic neuron Am. J. Phys. 78, 1297 (2010) Spreadsheet lock-in amplifier Am. J. Phys. 78, 1227 (2010) Additional information on Am. J. Phys. Journal Homepage: http://ajp.aapt.org/ Journal Information: http://ajp.aapt.org/about/about_the_journal Top downloads: http://ajp.aapt.org/most_downloaded Information for Authors: http://ajp.dickinson.edu/Contributors/contGenInfo.html Downloaded 07 Jan 2013 to 153.90.120.11. Redistribution subject to AAPT license or copyright; see http://ajp.aapt.org/authors/copyright_permission Radiometry and the Friis transmission equation Joseph A. Shaw Department of Electrical & Computer Engineering, Montana State University, Bozeman, Montana 59717 (Received 1 July 2011; accepted 13 September 2012) To more effectively tailor courses involving antennas, wireless communications, optics, and applied electromagnetics to a mixed audience of engineering and physics students, the Friis transmission equation—which quantifies the power received in a free-space communication link—is developed from principles of optical radiometry and scalar diffraction.
    [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]
  • ANTENNA INTRODUCTION / BASICS Rules of Thumb
    ANTENNA INTRODUCTION / BASICS Rules of Thumb: 1. The Gain of an antenna with losses is given by: Where BW are the elev & az another is: 2 and N 4B0A 0 ' Efficiency beamwidths in degrees. G • Where For approximating an antenna pattern with: 2 A ' Physical aperture area ' X 0 8 G (1) A rectangle; X'41253,0 '0.7 ' BW BW typical 8 wavelength N 2 ' ' (2) An ellipsoid; X 52525,0typical 0.55 2. Gain of rectangular X-Band Aperture G = 1.4 LW Where: Length (L) and Width (W) are in cm 3. Gain of Circular X-Band Aperture 3 dB Beamwidth G = d20 Where: d = antenna diameter in cm 0 = aperture efficiency .5 power 4. Gain of an isotropic antenna radiating in a uniform spherical pattern is one (0 dB). .707 voltage 5. Antenna with a 20 degree beamwidth has a 20 dB gain. 6. 3 dB beamwidth is approximately equal to the angle from the peak of the power to Peak power Antenna the first null (see figure at right). to first null Radiation Pattern 708 7. Parabolic Antenna Beamwidth: BW ' d Where: BW = antenna beamwidth; 8 = wavelength; d = antenna diameter. The antenna equations which follow relate to Figure 1 as a typical antenna. In Figure 1, BWN is the azimuth beamwidth and BW2 is the elevation beamwidth. Beamwidth is normally measured at the half-power or -3 dB point of the main lobe unless otherwise specified. See Glossary. The gain or directivity of an antenna is the ratio of the radiation BWN BW2 intensity in a given direction to the radiation intensity averaged over Azimuth and Elevation Beamwidths all directions.
    [Show full text]
  • Radiation Pattern, Gain, and Directivity James Mclean, Robert Sutton, Rob Hoffman, TDK RF Solutions
    Interpreting Antenna Performance Parameters for EMC Applications: Part 2: Radiation Pattern, Gain, and Directivity James McLean, Robert Sutton, Rob Hoffman, TDK RF Solutions This article is the second in a three-part tutorial series covering antenna terminology. As noted in the first part, a great deal of effort has been made over the years to standardize antenna terminology. The de facto standard is the IEEE Standard Definitions of Terms for Antennas, published in 1983. However, the EMC community has developed its own distinct vernacular which contains terms not included in the IEEE standard. In the first part of this series, we discussed radiation efficiency and input impedance match. In the second part of this series, we will discuss antenna field regions and antenna gain and how they relate to EMC measurements. Geometrical Considerations In order to quantitatively discuss radiation from antennas, it is necessary to first specify a coordinate system for describing the antenna and the associated electromagnetic fields. The most natural coordinate system for this task is the spherical coordinate system. This is because at a sufficient distance from an antenna (or any localized source of electromagnetic radiation), the electromagnetic fields must decay inversely with radial distance from the antenna (see references 1 and 2). Traditional spherical coordinates consist of a radial distance, an elevation angle, and an azimuthal angle as shown in Figure 1. The elevation angle is taken as the angle between a line drawn from the origin to the point and the z axis. The azimuthal angle is taken as the angle between the projection of this line in the x-y plane and the x axis.
    [Show full text]
  • A Near Field Propagation Law & a Novel Fundamental Limit To
    Preprint – Submitted to IEEE APS Conference July 2005; © 2005 Dr. Hans Schantz A Near Field Propagation Law & A Novel Fundamental Limit to Antenna Gain Versus Size Hans Gregory Schantz ([email protected]) The Q-Track Corporation; 515 Sparkman Drive; Huntsville, AL 35816 ABSTRACT This paper presents a theoretical analysis of the near field channel in free space. Then this paper validates the theoretical model by comparison to data measured in an open field. The results of this paper are important for low frequency RF systems, such as those operating at short range in the AM broadcast band. Finally this paper establishes a novel fundamental limit for antenna gain versus size. 1. INTRODUCTION The “leading edge” of RF practice moves to increasingly higher and higher frequency in lock step with advances in electronics technology. The most commercially significant RF systems are those operating at microwave frequencies and above, such as cellular telephones and wireless data networks. Microwave frequencies have the advantage of short wavelengths, making antenna design relatively straightforward, and vast expanses of spectrum, making large bandwidth, high data rate transmissions possible. There are many applications, however, that do not require large bandwidths. These include real time locating systems (RTLS) and low data rate communications systems, such as hands free wireless mikes or other voice or low data rate telemetry links. For applications like these, lower frequencies have great utility. Lower frequencies tend to be more penetrating than higher frequencies. Lower frequencies tend to diffract around objects that would block higher frequencies. Lower frequencies are less prone to multipath.
    [Show full text]
  • Antennas Transmission Lines
    5. ANTENNAS / TRANSMISSION LINES 1 5. ANTENNAS / TRANSMISSION LINES =e tran sm itter th at generates th e RF pow er to drive th e antenna is usually lo c a te d at so m e distance fro m th e antenna term in als. =e connecting lin k between th e tw o is th e RF tra n sm ission lin e. Its purpose is to carry RF pow er fro m one place to another, and to do th is as e@ciently as possible. From th e receiver sid e, th e antenna is resp o n sib le fo r picking up any rad io sign als in th e air and passing th em to th e receiver with th e minimum am ount of distortion and maximum e@ciency, so th at th e rad io has its best chance to decode th e sign al. For th ese reaso n s, th e RF cable has a very im p o rta n t ro le in rad io system s: it must maintain th e in te g rity of th e sign als in both directions. Figure ATL 1: Radio, tra n sm ission lin e and antenna =e sim p lest tran sm issio n lin e one can envisage is th e bi⇠lar or tw in le a d , consisting of tw o conductors sep arated by a dielectric or insulator. =e dielectric can be air or a plastic lik e th e one used fo r Aat tran sm issio n lin e s used in TV antennas.
    [Show full text]
  • EE302 Lesson 13: Antenna Fundamentals
    EE302 Lesson 13: Antenna Fundamentals Antennas An antenna is a device that provides a transition between guided electromagnetic waves in wires and electromagnetic waves in free space. 1 Reciprocity Antennas can usually handle this transition in both directions (transmitting and receiving EM waves). This property is called reciprocity. Antenna physical characteristics The antenna’s size and shape largely determines the frequencies it can handle and how it radiates electromagnetic waves. 2 Antenna polarization The polarization of an antenna refers to the orientation of the electric field it produces. Polarization is important because the receiving antenna should have the same polarization as the transmitting antenna to maximize received power. Antenna polarization Horizontal Polarization Vertical Polarization Circular Polarization Electric and magnetic field rotate at the frequency of the transmitter Used when the orientation of the receiving antenna is unknown Will work for both vertical and horizontal antennas Right Hand Circular Polarization (RHCP) Left Hand Circular Polarization (LHCP) Both antennas must be the same orientation (RHCP or LHCP) 3 Wavelength () You may recall from physics that wavelength () and frequency (f ) of an electromagnetic wave in free space are related by the speed of light (c) c cf or f Therefore, if a radio station is broadcasting at a frequency of 100 MHz, the wavelength of its signal is given c 3.0 108 m/s 3 m f 100 106 cycle/s Wavelength and antennas The dimensions of an antenna are usually expressed in terms of wavelength (). Low frequencies imply long wavelengths, hence low frequency antennas are very large. High frequencies imply short wavelengths, hence high frequency antennas are usually small.
    [Show full text]
  • Antennas in Practice
    Antennas in Practice EM fundamentals and antenna selection Alan Robert Clark Andr´eP C Fourie Version 1.4, December 23, 2002 ii Titles in this series: Antennas in Practice: EM fundamentals and antenna selection (ISBN 0-620-27619-3) Wireless Technology Overview: Modulation, access methods, standards and systems (ISBN 0-620-27620-7) Wireless Installation Engineering: Link planning, EMC, site planning, lightning and grounding (ISBN 0-620-27621-5) Copyright °c 2001 by Alan Robert Clark and Poynting Innovations (Pty) Ltd. 33 Thora Crescent Wynberg Johannesburg South Africa. www.poynting.co.za Typesetting, graphics and design by Alan Robert Clark. Published by Poynting Innovations (Pty) Ltd. This book is set in 10pt Computer Modern Roman with a 12 pt leading by LATEX 2". All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of Poynting Innovations (Pty) Ltd. Printed in South Africa. ISBN 0-620-27619-3 Contents 1 Electromagnetics 1 1.1 Transmission line theory . 1 1.1.1 Impedance . 3 1.1.2 Characteristic impedance & Velocity of propagation . 3 Two-wire line . 4 One conductor over ground plane . 5 Twisted Pair . 5 Coaxial line . 5 Microstrip Line . 6 Slotline . 6 1.1.3 Impedance transformation . 6 1.1.4 Standing Waves, Impedance Matching and Power Transfer 8 1.2 The Smith Chart . 9 1.3 Field Theory . 10 1.3.1 Frequency and wavelength . 10 1.3.2 Characteristic impedance & Velocity of propagation .
    [Show full text]
  • Using Antennas to Extend and Enhance Wireless Connections
    Wireless Networking Using Antennas to Extend and Enhance Wireless Connections 4dBi Desktop Antenna, 5dBi Swivel Antenna, 9dBi Directional Antenna Technical Note This note was developed to provide practical information about the use of U.S. Robotics antenna accessories with 802.11b/802.11g wireless LAN products. The U.S. Robotics Family of Wireless Antennas described in the following sections is designed to connect to any wireless device that uses Reverse SMA (female) connectors. Overview A critical determinant to the successful implementation of a wireless LAN solution often revolves around providing appropriate antennas to support home and office environments. Wireless connection speeds and reliability are dependent on both distance and signal obstructions. These obstructions can be the walls, floors and ceilings of various constructions, as well as other less obvious items such as metal filing cabinets. In real-world use the distances you might attain will vary according to these conditions. U.S. Robotics developed various antenna options to assist in optimizing wireless LAN solutions based on 802.11g and 802.11b wireless LAN standards. The maximum distance information provided for each antenna is based on engineering computations included in an appendix to this document. Desktop Computer Wireless Enhancement Antenna Solution - US Robotics 4dBi Desktop Antenna (USR5480) The U.S. Robotics 4dBi desktop antenna is designed to attach to 802.11b and 802.11g wireless PCI cards via its reverse polarity SMA (female) connector. Since PCI cards are normally installed into desktop PCs, the directly attached antenna must deliver a signal through the metal PC case and often compete with the “noisy” behind-the-desktop environment.
    [Show full text]
  • Antenna Parameters and Figures of Merit (FOM)
    9/5/2017 Topic 2 – Antenna Parameters and Figures of Merit (FOM) EE‐4382/5306 ‐ Antenna Engineering Outline • Introduction • Radiation Pattern • Radiation Power Density • Radiation Intensity • Directivity • Antenna Efficiency • Gain, Realized Gain • Bandwidth • Polarization • Input Impedance • Radiation Efficiency • Effective length and equivalent Area • Friis Transmission Equation Constantine A. Balanis, Antenna Theory: Analysis and Design 4th Ed., Wiley, 2016. Stutzman, Thiele, Antenna Theory and Design 3rd Ed., Wiley, 2012. Antenna Parameters and FOM 2 1 9/5/2017 Introduction 3 What is a figures of merit for an antenna? The figures of merit of an antenna are numbers that lets us describe the performance of a real antenna. Some of these parameters are compared to the ideal isotropic antenna, while others are not. Some of the parameters are interrelated, and not all of them need to be expressed to describe the full performance of an antenna. Antenna Parameters and FOM Slide 4 2 9/5/2017 Radiation Pattern Antenna Parameters and FOM 5 What is the radiation pattern? “A mathematical function or a graphical representation of the radiation properties of an antenna as a function of space” Properties: • Usually defined in the far‐field region of the antenna • Many other parameters, such as power density, directivity, radiation intensity, and others, are properties of the antenna radiation Antenna Parameters and FOM Slide 6 3 9/5/2017 2D Radiation Pattern Slide 7 Antenna Parameters and FOM 2D Radiation Pattern (circular) Antenna Parameters and FOM Slide 8 4 9/5/2017 2D Radiation Pattern (linear) Antenna Parameters and FOM Slide 9 3D Radiation Pattern Antenna Parameters and FOM Slide 10 5 9/5/2017 3D Radiation Pattern Antenna Parameters and FOM Slide 11 The isotropic radiator Hypothetical lossless antenna that emits radiation equally in all directions dBi Units for antenna gain, directivity, etc.
    [Show full text]
  • Transmitting and Receiving Antennas
    740 16. Transmitting and Receiving Antennas The total radiated power is obtained by integrating Eq. (16.1.4) over all solid angles 16 dΩ = sin θ dθdφ, that is, over 0 ≤ θ ≤ π and 0 ≤ φ ≤ 2π : π 2π Prad = U(θ, φ) dΩ (total radiated power) (16.1.5) Transmitting and Receiving Antennas 0 0 A useful concept is that of an isotropic radiator—a radiator whose intensity is the same in all directions. In this case, the total radiated power Prad will be equally dis- tributed over all solid angles, that is, over the total solid angle of a sphere Ωsphere = 4π steradians, and therefore, the isotropic radiation intensity will be: π 2π dP Prad Prad 1 UI = = = = U(θ, φ) dΩ (16.1.6) dΩ I Ωsphere 4π 4π 0 0 Thus, UI is the average of the radiation intensity over all solid angles. The corre- 16.1 Energy Flux and Radiation Intensity sponding power density of such an isotropic radiator will be: dP UI Prad The flux of electromagnetic energy radiated from a current source at far distances is = = (isotropic power density) (16.1.7) 2 2 given by the time-averaged Poynting vector, calculated in terms of the radiation fields dS I r 4πr (15.10.4): 16.2 Directivity, Gain, and Beamwidth 1 1 e−jkr ejkr PP= × ∗ = − ˆ + ˆ × ˆ ∗ − ˆ ∗ Re(E H ) jkη jk Re (θθFθ φφFφ) (φφFθ θθFφ) 2 2 4πr 4πr The directive gain of an antenna system towards a given direction (θ, φ) is the radiation intensity normalized by the corresponding isotropic intensity, that is, Noting that θˆ × φˆ = ˆr, we have: ˆ + ˆ × ˆ ∗ − ˆ ∗ = | |2 +| |2 = 2 U(θ, φ) U(θ, φ) 4π dP (θθFθ φφFφ) (φφFθ θθFφ) ˆr Fθ Fφ ˆr F⊥(θ, φ) D(θ, φ)= = = (directive gain) (16.2.1) UI Prad/4π Prad dΩ Therefore, the energy flux vector will be: It measures the ability of the antenna to direct its power towards a given direction.
    [Show full text]