73.What are the parameters to be considered for the design of an helical antenna? Derive the expression for refractive index of ionosphere and critical frequency. 12.Derive the expressions for the fields and power radiated from a half wave dipole antenna.Find its radiation resistance and directivity. 9.Explain the principle of pattern multiplication with some examples. i. EmoticonEmoticon. * To get Clear; figures / diagrams, tables / values, answers / explanations and more, download the Antennas and Wave Propagation Viva Short Questions and Answers PDF. The book begins with an introduction that discusses the fundamental concepts, notations, representation and principles that govern the field of antennas. A half wave antenna is the fundamental radio antenna of metal rod or tubing or thin wire which has a physical length of half wavelength in free space at the frequency of operation, 65.What is the radiation resistance of a half wave dipole, The radiation resistance of a half wave dipole is given by Rr=73 ohm, A loop antenna is a radiating coil of any convenient cross-section of one or more turns carrying radio frequency current.it may assume any shape (e.g. In this array the antenna elements are arranged coaxially by mounting the elements end to end in straight line or stacking them one over the other with radiation pattern circular symmetry. 55.Why a short dipole is called a oscillating dipole? The total beam area ( WA) consists of the main beam area ( WM ) plus the minor lobe area ( Wm) . It depends on i. 92. Frequency whose period is equal to the period of an electron in its orbit under the influence of the earths magnetic flux density B. Following is the list of multiple choice questions in this brand new series: MCQ in Radiation and Wave Propagation . 6.Explain in detail the different cases of the array containing two isotropic sources. The ratio of the effective aperture to the physical aperture is the aperture efficiency. Advantage: ._No minor lobes Disadvantages: ._Increased beam width ._Maintaining the large ratio of current amplitude in large arrays is difficult. The efficiency of an antenna is defined as the ratio of power radiated to the total input power supplied to the antenna. It is made up of direct wave and ground reflected wave. What is the principle of the pattern multiplication? [ ] a) Linear. Read PDF Antenna Wave Propagation Questions With Answers Recognizing the way ways to acquire this books antenna wave propagation questions with answers is additionally useful. Previous Year Exam Questions for Antenna and wave Propagation - AWP of 2018 - bput by Bput Toppers By Bput Toppers 4.0K Views Type: PYQ Rating: 0 6th Semester - 2018 BPUT Due to the earth’ s magnetic fields, the ionosheric medium becomes an isotropic and the incident plane wave entering the ionosphere will split into ordinary and extra ordinary waves/modes. a. SONAR b. Subsurface communication c. Radio navigation d. Facsimile ANSWER: Facsimile 3) Wavefront is basically a locus … What is meant by identical Point sources.? 2. wave propagation, including ground wave and ionospheric propagation, goes on to make this text a useful and self-contained reference on antennas and radio wave propagation. When the length of the short dipole is vanishingly small,then such a dipole is called a infinitesimal dipole.If dl be the infinitesimally small length and I be the current,then Idl is called as the current element. In this array the elements are fed parasitically to reduce the problem of feed line. How wideband operation is possible with this antenna. Antenna Wave & Propagation - Important Questions with Answers Waves that arrive at the receiver after reflection from the troposphere region is called Tropospheric wave. Space wave ii. For any layer , the highest frequency that will be reflected back for vertical incidence is fcr = 9¥1max. Fundamental Concept 1.1 Introduction: An antenna (or aerial) is an electrical device which converts electric power into radio waves, and vice versa. Explain the different types of polarization in detail. 85. Explain the geometry of a log periodic antenna. Directivity from beam area(WA ). Having covered the process in class these past weeks you are now well capable of taking up the quiz below with ease. D = 4p / WA. 24. Explain about the frequencies used for radar 5. Multiple Choice Questions and Answers on Antenna & Wave Propagation 1) What is the wavelength of Super high frequency (SHF) especially used in Radar & satellite communication? The phenomenon of splitting the wave into two different components (ordinary and extra-ordinary) by the earths magnetic field is called Magneto-Ions Splitting. ._It is used as receiving antenna in portable radio and pagers . Find the maximum effective area of an antenna at 2GHz when the directivity is 100. Visit Wisdom jobs to look into the various Antenna jobs available along with the training and assessment material for improving your knowledge base and sample resumes for a winning job and Antenna interview questions. Define wave velocity and Group velocity.? C. Omni-directional . 59.At what distance from the dipole is the induction field equal to the radiation field? Surface wave. What are the type of fading.? D .Kraus Book). Define dipole antenna. End fire array is defined as an arrangement in which the principal direction of radiation is coincides with the array axis. Give it a try and share your score. Antenna is also said to be an impedance transforming device. , M I S O I . The ratio of maximum radiation intensity in given direction to the maximum radiation intensity from a reference antenna produced in the same direction with same input power. iii) Loss aperture. Eg. A. Antenna array . 88 .Define frequency diversity Reception. • V elocity of propagation of a wave in free space is giv en by 3 × 10 8 m/s. The beam area or beam solid angle or WA of an antenna is given by the normalized power pattern over a sphere. Antenna beamwidth is a measure of directivity of an antenna. The effective radiated power ii. 36. * Ask us, what you want? Optimum frequency for transmitting between any two points is therefore selected as some frequency lying between about 50 and 85 percent of the predicted maximum usable frequency between those points. ii. Self impedance of an antenna is defined as its input impedance with all other antennas are completely removed i.e away from it. Derive the expression for the radiated field from a short dipole. 1 cm – 10 cm c. 10 cm – 1 m d. 0.1 cm – 1 cm ANSWER: 1 cm – 10 cm 2) Which among the following is an application of high frequency? Tags. i. Curvature of earth. T e c h . In some situation the electric field E is parallel to the wave propagation that condition is called Cross field. Directivity from Pattern. iv) collecting aperture. 1. Questions and Answers in Radiation and Wave Propagation Series. (Ae). 19. 20. Professionals, Teachers, Students and Kids Trivia Quizzes to test your knowledge on the subject. W’ = I2 R Rr = W’/ I2 Where Rr is a fictitious resistance called called as radiation resistance. i.e FBR = Power radiated in desired direction / power radiated in the opposite direction. ii) For certain applications, it is highly desirable that secondary lobes should be eliminated completely or reduced to minimum desirable level compared to main lobes. Gain 3. 3. R A V E E N D R A M . It is obtained by two ways. PDF | On Apr 2, 2013, mahendra Kumar published multiple choice questions on wireless communication | Find, read and cite all the research you need on ResearchGate An antenna is a system of similar antennas oriented similarly to get greater directivity in a desired direction. _____ is an antenna with a number of half-wave antenna on it. Since radio transmission is Omni directionalin nature, the need to physically align the transmitter and receiver does not arise. What is meant by front to back ratio.? It is the addition of above three apertures. Ans:The dipole has two equal charges of opposite sign oscillating up and down in a harmonic motion.The charges will move towards each other and electric filed lines were created.When the charges meet at the midpoint, the field lines cut each other and new field are created.This process is spontaneous and so more fields are created around the antenna.This is how radiations are obtained from a short dipole. For a charge moving with uniform velocity with straight & infinite wire, ANSWER: For a charge oscillating in time motion. Derive the expression for radiation resistance of loop antenna with circumference equal to wavelength. Explain in detail about the aperture Concept, 3.Briefly explain the radiation from a short dipole. Also includes the portion of energy received as a result of diffraction around the earth surface and the reflection from the upper atmosphere. 38. Write short notes on i) Ground wave propagation ii) space wave propagation. 21.Explain the concept of Reflection and refraction wavesby the ionosphere. Frequency of the signal. Waves that arrive at the receiver after reflection in the ionosphere is called sky wave. The ratio of the major to the minor axes of the polarization ellipse is called the Axial Ratio. 5.Define Polarization? ii) Explain the term pattern multiplication. TASK: Identify the characteristics of wave propagation. Antenna and Wave Propagation multiple choice questions and ... An antenna is an electrical conductor or system of conductors. This is the Multiples Choice Questions Part 1 of the Series in Antennas as one of the Communications Engineering topic. 4. a. iii. The applications of helical antenna are: . (Ap). 1 m – 10 m b. Derive the expression for calculating field strength at a distance in space wave Propagation. Page 2/9. ANTENNAS AND WAVE PROPAGATION 2015 U N I T W I S E B I T B A N K –K . Space diversity reception. Attenuation of this wave is directly affected by the constant of earth along which it travels. Page 5 MULTIPLE CHOICE QUESTIONS UNIT-3: ANTENNA ARRAYS 1. The polarization of the radio wave can be defined by direction in which the electric vector E is aligned during the passage of atleast one full cycle.Also polarization can also be defined the physical orientation of the radiated electromagnetic waves in space.The polarization are three types. Tower . A isotropic radiator is a fictitious radiator and is defined as a radiator which radiates fields uniformly in all directions. (E Volts/m). Inverse bending may transform line of sight path into an obstructed one. Plane earth reflection. _It is used to estimate the direction of radio wave propagation. d. Parasitic array. Broad side array is defined as an arrangement in which the principal direction of radiation is perpendicular to the array axis and also the plane containing the array element. TQ, visit us again. Far field zone (Fraunhofer zone). Antenna beam width is an angular width in degrees, measured on the radiation pattern (major lobe) between points where the radiated power has fallen to half its maximum value .This is called as “beam width” between half power points or half power beam width.(HPBW). 86.What is meant by diversity reception.? b. Faraday rotation in Sky wave Propagation. What are the factors that affect the propagation of radio waves.? Interference of normal radiation & radio wave propagation, If the path difference of two waves with single source traveling by different paths to, arrive at the same point, is λ/2, what would be the phase difference between, Which ionization layer exists during day time & usually vanishes at night due to highest, What is the possible range of height for the occurrence of sporadic E-region with, layer of appleton region acts as a significant reflecting medium for, The knowledge of which parameter is sufficient for deriving the time varying, According to Webster’s dictionary, what is an. If an e.m.f is applied to the terminals of an antenna no.1 and the current measured at the terminals of the another antenna no.2, then an equal current both in amplitude and phase will be obtained at the terminal of the antenna no.1 if the same emf is applied to the terminals of antenna no.2. It is the area over which the power is extrated from the incident wave and delivered to the load is called effective aperture. 2. This means that if a sinusoidal voltage is input at the antenna terminals with amplitude 1 Volt, the current will have an amplitude of 1/50 = 0.02 Amps. Variation of signal strength occur on line of sight paths as a result of the atmospheric conditions and it is called .It can not be predicted properly. Frequency diversity reception. While a rigorous analysis of an antenna is highly mathematical, often a simplified analysis is sufficient for understanding the basic principles of operation of an antenna. However, their powe… rectangular,square,triangular and hexagonal), 67.Give an expression of radiation resistance of a small loop Radiation resistance of a small loop is given by Rr=31,200 (A/_ 2)2, 68.How to increase the radiation resistance of a loop antenna. Draw the block diagram of a Pulsed radar and explain its operation 2. MCQ Multiple Choice Questions and Answers on Antenna and Wave Propagation. Absorption character of ionosphere for the paths between transmitter and receiver. Similar point sources with equal maximum amplitudes are called identical point sources. Derive basic radar’s equation 4. EM wave Acoustic wave TEM wave TE 10 wave 3. Relation between and Skip Distance, Multi-hop Propagation. Antenna asics Multiple hoice Test Student’s name: Total points: 1. ._, Useful tool in designing antenna ._It approximates the pattern of a complicated array without making lengthy computations. Visit our Antenna job interview questions and answers page designed by our experts … 28. ._Many satellites including weather satellites,data relay satellites all have helical antennas . Normal mode of operation 2. Letan antenna has an impedance of 50 ohms. 56.What do you understand by retarded current? Which of the following waves has the lowest propagation speed? 25. Polarization diversity. ANTENNAS AND WAVE PROPAGATION 2015 MULTIPLE CHOICE QUESTIONS UNIT-1: ANTENNA BASICS 1. It is defined as an antenna is a circuit device with a resistance and temperature on the one hand and the space device on the other with radiation patterns, beam angle ,directivity gain and aperture. It is defined as the fictitious resistance which when inserted in series with the antenna will consume the same amount of power as it is actually radiated.The antenna appears to the transmission line as a resistive component and this is known as the radiation resistance. Explain Ground wave Propagation. Axial Ratio, 74.What are the types of radiation modes of operation for an helical antenna The two types of radiation modes of operation possible for an helical antenna are: 1. Computer networks is one of the most important chapter for any candidate pursuing career in information technology field. The need for a binomial array is i). ... 21. Electrically Large loop antennas is one in which the overall length of the loop approaches the wavelength. Near field zone (Fresnel zone) ii. Since,the short electric dipole is so short,the current which is flowing through the dipole is assumed to be constant throughtout its length.The effect of this current is not felt instantaneous at a distance point only after an interval equal to the time required for the wave to propagate over the distance r is called the retardation time. 2. They are Elliptical polarization ,circular polarization and linear polarization. In uniform linear array as the array length is increased to increase the directivity, the secondary lobes also occurs. • E and H oscillate in phase and ratio of their amplitudes is constant and is equal to: 40. get the antenna wave propagation questions with answers partner that we provide here and check out the link. Multi path fading. An array is linear when the elements of the array are spaced equally along the straight line. Antenna is a transition device or a transducer between a guided wave and a free space waveor vice versa. Scattering aperture(As.) Derive the expression for radiation field and radiation resistance. The key features are − 1. Yagi uda antenna. Find the radiated power of an antenna if 10 Amp current exists and its radiation resistance 32 ohm. 53.Why a short dipole is also called an elemental dipole? 1. At low frequencies, the waves can pass through obstacles easily. The antenna is a radiating device in which power is radiated into space in the form of electromagnetic wave. Ans: A short dipole is one in which the field is oscillating because of the oscillating voltage and current.It is called so, because the length of the dipole is short and the current is almost constant throughtout the entire length of the dipole.It is also called as Hertzian Dipole which is a hypothetical antenna and is defined as a short isolated conductor carrying uniform alternating current. MUF = fcr_VHF_ i. Antennas convert -to-a) Derive the expression for radiation resistance of small loop antenna. The frequency of the radio wave determines many of the characteristics of the transmission. It is the area of the antenna which dissipates power as heat. MCQ in Radiation and Wave Propagation Part 1 as part of the Communications Engineering (EST) Board Exam. A pinoybix mcq, quiz and reviewers. 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