Antenna and Wave Propagation PDF

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Department of Engineering E&E Section Antenna and wave propagation Course Code: EGEC4210 Reference Links https://ebookcentral.proquest.com/lib/momp/reader.actio n?docID=1645674&query=Radio+Wave+Propagation+F undamentals+%28Artem+Saakian%29 https://ebookcentral.proquest.com/lib/momp/ detail.action?docID=4205879&query=antenna https://ebookcentral.proquest.com/lib/momp/ reader.action?docID=338762&ppg=7 https://ebookcentral.proquest.com/lib/momp/ detail.action?docID=4205879&query=antenna https://ebookcentral.proquest.com/lib/momp/ reader.action? docID=433804&query=radio+imaging+system# https://ebookcentral.proquest.com/lib/momp/ detail.action?docID=4205879&query=antenna https://ebookcentral.proquest.com/lib/momp/ reader.action? docID=1645674&query=Radio+Wave+Propagation+Fund amentals+%28Artem+Saakian%31 https://ebookcentral.proquest.com/lib/momp/ Outline Introduction to communication System What is an Antenna? The role of antennas Parameters of antenna Chapter – 1 Antenna and Propagation  Introduction to Communication System Chapter – 1 Antenna and Propagation What is an Antenna?  An antenna is a circuit element that provides a transition from a guided wave on a transmission line to a free space wave and it provides for the collection of electromagnetic energy. An antenna is an electrical conductor or system of conductors Transmission - radiates electromagnetic energy into space Reception - collects electromagnetic energy from space Chapter – 1 Antenna and Propagation An antenna is a transducer that can convert both an incident polarized RF electromagnetic wave to a time-varying signal voltage (or waveform) on a transmission line and a time-varying signal voltage on a transmission line to a transmitted polarized electromagnetic wave. Chapter – 1 Antenna and Propagation Chapter – 1 Antenna and Propagation Only accelerated (or decelerated) charges radiate EM waves. A current with a time-harmonic variation (AC current) satisfies this Chapter – 1 Antenna and Propagation What is an Antenna? In two-way communication, the same antenna can be used for transmission and reception Converts Electrons to Photons of EM energy It is a transducer which interfaces a circuit and free- space In transmitter, the RF signal is generated, amplified, modulated and applied to the antenna In receiver, the antenna collects electromagnetic waves that are “cutting” through the antenna and induce alternating currents that are used by the receiver Chapter – 1 Antenna and Propagation An antenna can be characterized by several parameters which includes Chapter – 1 Antenna and Propagation Bandwidth Bandwidth is measured as the amount of data that can be transferred from one point to another within a network in a specific amount of time. Typically, bandwidth is expressed as a bitrate and measured in bits per second (bps). Chapter – 1 Antenna and Propagation Bandwidth The bandwidth of an antenna refers to the range of frequencies over which the antenna can operate correctly. The antenna's bandwidth is the number of Hz for which the antenna will exhibit an SWR less than 2:1. The bandwidth can also be described in terms of percentage of the center frequency of the band. The term “SWR” means standing wave ratio. A “SWR” meter is used to measure how well the transmit power signal emitted from a transceiver (radio) is traveling through the antenna system into the atmosphere. Chapter – 1 Antenna and Propagation Impedance Antenna impedance relates the voltage to the current at the input to the antenna. Suppose an antenna has an impedance of 50 ohms. This means that if a sinusoidal voltage is applied at the antenna terminals with an amplitude of 1 Volt, then the current will have an amplitude of 1/50 = 0.02 Amps. Since the impedance is a real number, the voltage is in-phase with the current. Problem # 1 Calculate the magnitude of impedance if Z = 50+j50. Also calculate its phase difference. Then find out the current flowing through the antenna. [Note that "j" is the square root of -1. Imaginary numbers are there to give phase information. If the impedance is entirely real [Z=50 + j*0], then the voltage and current are exactly in time-phase. If the impedance is entirely imaginary [Z=0 + j*50], then the voltage leads the current by 90 degrees in phase.] Problem # 1 - Solution Calculate the magnitude of impedance if Z = 50+j50. Also calculate its phase difference. Then find out the current flowing through the antenna. If Z=50 + j*50, then the impedance has a magnitude equal to: The phase will be equal to: That means phase of the current will lag the voltage by 45 degrees. The current waveform is delayed relative to the voltage waveform.  Problem # 1 - Solution Calculate the magnitude of impedance if Z = 50+j50. Also calculate its phase difference. Then find out the current flowing through the antenna. The voltage (with frequency f) at the antenna terminals is given by The electric current will then be equal to: Chapter – 1 Antenna and Propagation Antenna Impedance – Important Features Antenna Impedance relates the voltage and current at the input to the antenna. The real part of the antenna impedance represents power that is either radiated away or absorbed within the antenna. The imaginary part of the impedance represents power that is stored in the near field of the antenna. This is non- radiated power. An antenna with a real input impedance (zero imaginary part) is said to be resonant. Note that the impedance of an antenna will vary with frequency. Various Potentials involved in the operation of Antenna Scalar Electric Potential : V Defined as the work done on the test charge per unit charge in moving a charge from the infinity to the point. Unit = Volt = Joules/Coulomb Various Potentials involved in the operation of Antenna From Coulomb's Law Various Potentials involved in the operation of Antenna Various Potentials involved in the operation of Antenna Magnetic Vector Potential Various Potentials involved in the operation of Antenna Biot Savart’s Law The Biot Savart Law is an equation describing the magnetic field generated by a constant electric current. It relates the magnetic field to the magnitude, direction, length, and proximity of the electric current. Biot–Savart law is dependable with both Ampere’s circuital law and Gauss’s theorem. The Biot Savart law is fundamental to magneto-statics, playing a role similar to that of Coulomb’s law in electrostatics. Various Potentials involved in the operation of Antenna Biot Savart’s Law The Biot Savart Law is an equation describing the magnetic field generated by a constant electric current. It relates the magnetic field to the magnitude, direction, length, and proximity of the electric current. Biot–Savart law is dependable with both Ampere’s circuital law and Gauss’s theorem. The Biot Savart law is fundamental to magneto-statics, playing a role similar to that of Coulomb’s law in electrostatics. Various Potentials involved in the operation of Antenna Biot Savart’s Law The Biot Savart Law is an equation describing the magnetic field generated by a constant electric current. It relates the magnetic field to the magnitude, direction, length, and proximity of the electric current. Biot–Savart law is dependable with both Ampere’s circuital law and Gauss’s theorem. The Biot Savart law is fundamental to magneto-statics, playing a role similar to that of Coulomb’s law in electrostatics. This is the basic form of Biot Savart’s Law Now, putting the value of constant k So Magnetic vector Potential, Ḃ, due to the current flow in the entire circuit is obtained by integrating ∫dḂ Various Potentials involved in the operation of Antenna Biot Savart’s Law So Magnetic vector Potential, Ḃ, due to the current flow in the entire circuit is obtained by integrating ∫dḂ Retarded Potentials Retarded Potentials Assignment # 1 Ampere’s circuital law Gauss’s theorem Magneto-statics Vs electrostatics Coulomb’s law in electrostatics  Bibliography Text Books: 1. John D. Kraus and Ronald J. Marhefka and Ahmad S.Khan, ―Antennas and wave propagation,‖ TMH, New Delhi, 4th Ed., (special Indian Edition), 2010. 2. E.C. Jordan and K.G. Balmain, ―Electromagnetic Waves and Radiating Systems,‖ PHI, 2nd Edn, 2000. Reference Books: 1. C.A. Balanis, ―Antenna Theory- Analysis and Design,‖ John Wiley & Sons, 2nd Edn., 2001. 2. K.D. Prasad, Satya Prakashan, ―Antennas and Wave Propagation,‖ Tech. India Publications, New Delhi, 2001. 3. E.V.D. Glazier and H.R.L. Lamont, ―Transmission and Propagation - The Services Text Book of Radio,‖ vol. 5, Standard Publishers Distributors, Delhi. 4. F.E. Terman, ―Electronic and Radio Engineering,‖ McGraw-Hill, 4th edition, 1955. 5. John D. Kraus, ―Antennas,‖ McGraw-Hill (International Edition), 2nd Edn., 1988.