MATRUSRI ENGINEERING COLLEGE�DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

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SUBJECT NAME: Electromagnetic Theory & Transmission Lines (PC232EC)

FACULTY NAME: Dr. Pallavi Khare

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Electromagnetic Theory and Transmission Lines

COURSE OBJECTIVES:

1. Analyse fundamental concepts of vector analysis, electrostatics and magneto statics law and their Applications to describe the relationship between electromagnetic theory and circuit theory
2. Formulate the basic laws of static electricity and magnetism and extend them to time varying fields. To define the maxwell’s equations in differential and integral form.
3. Derive the wave equations for conducting and di-electric mediums to analyse the wave propagation Characteristics of uniform plane waves (upw) in normal and oblique incidences
4. Analyse fundamental concepts of transmission lines and to formulate the basic relationship Between distortion less transmission lines & applications.
5. To understand the concepts of rf lines and their characteristics, smith chart and its applications, Acquire knowledge to configure circuit elements, qwts and hwts and to apply the same for Practical problems

COURSE OUTCOMES:

1. Apply vector calculus to understand the behavior of static electric fields in standard configurations
2. Implement the concepts of magnetostatics in terms of Maxwell’s equation in different forms for different fields
3. Analyze and deduce EM wave propagation characteristic in guiding structure for various matching boundary condition.
4. Analyze impedance characteristic of various transmission lines and their significance with application.
5. Interpret and illustrate of different transmission lines using smith chart as a graphical tool

Review of coordinate systems. Coulomb’s law, electric field due to various charge configurations and electric flux density. Gauss’s law and its applications. Work, potential and energy, the dipole. Current and current density, laplace and poisson’s equations. Calculation of capacitance for simple configurations

SYLLABUS

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UNIT-1

UNIT-3

Steady magnetic-Biot-Savart’s law, Ampere’s law. Stoke’s theorem, Magnetic flux and magnetic flux density. Scalar and vector magnetic potentials. Electric and Magnetic fields boundary conditions. Maxwell’s equations for static and time varying fields.

UNIT-2

Uniform plane waves in free space and in conducting medium, Polarization. Instantaneous, average and complex Poynting theorem and its applications.

Reflection and Refraction: Normal and Oblique incidence on dielectrics and conducting medium.

Overview of T and π networks. Types of Transmission Lines-Two wire lines. Primary and secondary constants. Transmission Line equations. Infinite line and characteristic impedance- Open and short circuit lines and their significance. Distortion less transmission line, Concept of loading of a transmission line, Campbell's formula

SYLLABUS

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UNIT-4

Impedance at any point on the transmission line- Input impedance. RF and UHF lines, transmission lines as circuit elements. Properties of λ/2, λ/4 and λ/8 Lines. Reflection coefficient and VSWR. Matching: Stub matching. Smith chart and its applications

UNIT-5

Recommended Books

1. Matthew N.O. Sadiku, Principles of Electro-magnetics, 6th edition, Oxford University Press, 2016
2. William H. Hayt Jr. and John A. Buck, Engineering Electromagnetics, 7th edition, Tata McGraw Hill, 2006.
3. John D. Ryder, Networks Lines and Fields, 2nd edition, Pearson, 2015
4. E.C. Jordan and K.G. Balmain, Electromagnetic Waves and Radiating Systems, 2nd edition, Pearson, 2015.
5. K.D. Prasad, Antennas and Wave Propagation, Khanna Publications

Prerequisites

Needs to have basic concepts on mathematics and physics

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Introduction

Electromagnetism is one of the fundamental forces of nature. It is responsible for all of the everyday things we see, except gravity.

Light, life, and the bonding of atoms into molecules are all due to electromagnetism.

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• Since the dawn of humanity, people have been aware of electricity in lightning.

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• Electric fish and rays were known in ancient times.

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• The static electrical property of amber was investigated by the ancient Greeks.

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• These natural electrical phenomena were thought to be due to the will of the gods.

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Electricity

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• Static electricity was investigated extensively during the 18th century

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• The concepts of electrostatic forces and charge were discovered

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• Volta discovered that electricity could be generated by chemical reactions, leading to the battery and the idea of voltage, which bears his name.

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Electricity

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Coulomb discovered that the force between two charged particles is inversely proportional to the square of the distance between them.

Electricity

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• Stories of magnetism from China and ancient Greece date back over 2000 years. �Natural magnets, made of magnetite, were considered to possess magical powers.

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• People soon realized that magnetite, when made into the shape of a pointer and floated on water, always pointed in a north-south direction, creating a primitive compass.

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• This led to the name lodestone, or ‘leading stone’.

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Magnetism

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The navigational compass was first recorded in China, around 1100, and then shortly afterwards in Europe.

Magnetism

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• The development of the compass led to vastly improved navigation – especially far from land – and led eventually to the Age of Discovery.

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• The first artificial magnets were produced in 1740

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• Modern magnets, based on rare earth elements, can be very powerful.

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Magnetism

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• The 19th century saw the first concrete links between electricity and magnetism.
• Øersted discovered that a wire carrying electric current produces a magnetic field.
• Ampere discovered the force between two current carrying wires.

The Golden Age

• Faraday discovered electromagnetic induction; the process by which a changing magnetic field produces an electric field.

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• The Scottish physicist, James Maxwell, published "A dynamical theory of the electromagnetic field," which linked electricity, magnetism, and light.

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• Maxwell’s theory was used to explain how oscillating electric currents in wires produce electromagnetic waves, such as radio waves.

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Electromagnetism

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• Hertz clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell.

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• He was the first to satisfactorily demonstrate the existence of electromagnetic waves.

Electromagnetism

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• Maxwell’s theory was used by Einstein to develop his theory of special relativity.

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• Einstein explained the photoelectric effect.

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• In 1940, this led to quantum electrodynamics – the part of quantum mechanics that deals with electromagnetism.

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Electromagnetism

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 in A²s⁴ kg^-1m⁻³ or C²N⁻¹m⁻² or F m⁻¹

1642-1727

Fax of a 1682 letter from Newton to Dr William Briggs,

commenting on Briggs' "A New Theory of Vision"

1736-1806

Newton & Charles Coulomb

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Fig. What is meant by 1 Coulomb?

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Electric Fields due to charge bodies

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q₃

q₁

q₂

F₃₁

F₂₁

F

F₃₁

F₁₃

F_31x

F_31y

F_21x

F_21y

F₂₁

F = (F_21x + F_31x) x + (F_21y + F_31y) y

Forces add vectorially

Superposition Principle

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• total electric flux through a closed surface is equal to the total charge enclosed by the surface.

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Gauss law

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• Used to calculate the magnetic field due to a current carrying conductor.

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• Magnitude of the magnetic field at any point P due to a small current element I.dl ( I = current through the element, dl = length of the element) is -

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Biot - Savart Law

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Comparison - Coulomb’s laws and Biot Savart laws

• Both the electric and magnetic field depends inversely on square of distance between the source and field point.

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• Charge element dQ producing electric field is a scalar whereas the current element IdL is a vector quantity having direction same as that of flow of current. 

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• According to coulomb’s law ,the magnitude of electric field at any point P depends only on the distance of the charge element from any point P.

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• According to Biot savart law, the direction of magnetic field is perpendicular to the current element as well as to the line joining the current element to the point P.

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Ampere’s circuital law

Ampere’s Circuital Law states that the line integral of H about any closed path is exactly equal to the direct current enclosed by the path.

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James Clerk Maxwell

Professor of Natural Philosophy – King’s College, London

Unified theory of Electricity, Magnetism & Light

in classical Physics

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Electrostatic: Copiers(Xerography)

• Battery and battery chargers
• Semiconductor Device control
• Electro-painting
• Charged couple device(CCD) cameras and many more

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Magnetism: Compasses

• MRI
• Maglev Train
• Loudspeaker

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Application of Electromagnetism

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Electromagnetic Spectrum

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RADIOWAVES

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• In 1887, Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory.
• Their frequencies range from 300GHz to as low as 3kHz.
• Radiofrequency is a rate of oscillation in the range of radio waves, it refers to electrical rather than mechanical oscillations.
• Radiofrequency energy is used in medicine e.g. MRI and RFA.

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Heinrich Hertz

RADIOWAVES

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MRI and RF (Radio Frequency)

• Used to produce images of soft tissues, fluid, fat and bone.

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• Uses strong superconducting magnet with a magnetic field strength 40,000 x that of the Earth’s.

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• It is used to diagnose many problems e.g. helps identify tumors.

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Diagram of an MRI scanner

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Diagram explaining how MRI works

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MICROWAVES

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• In 1888, Heinrich Hertz was the first to demonstrate the existence of radio waves by building a spark gap radio transmitter that produced 450 MHz microwaves.

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• Microwaves have typically 300GHz to 300MHz

Heinrich Hertz

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MICROWAVES

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• Hyperthermia therapy is a type of medical treatment in which body tissue is exposed to slightly higher temperatures to damage and kill cancer cells or to make cancer cells more sensitive to the effects of radiation and certain anti-cancer drugs.

Cancer cells being targeted by microwaves

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Microwave Heat Therapy

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INFRARED

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VISIBLE LIGHT

• Can be detected by the human eye.
• Wavelengths range from 750-400nm.
• In the 17^th Century, Isaac Newton explained the optical spectrum in his book ‘Opticks’. He divided the spectrum into seven named colours: ROYGBIV.
• The actual concept of a visible ‘spectrum’ was defined in the early 19^th century when light outside the visible range was discovered e.g. Johann Ritter with Ultraviolet Light.

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Sir Isaac Newton

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VISIBLE LIGHT

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• Allows us to look inside the human body through a narrow, flexible scope.
• It is mostly used to diagnose problems in the oesophagus, stomach and intestines, including ulcers, bleeding and tumours.
• Typically optical fibres are used to transfer light to the end of the endoscope and a miniature video camera records the image, and viewed on a video screen.

Endoscope inside the body

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Endoscopy/ Keyhole Surgery

• Premature babies sometimes have jaundice.
• This makes them look yellow and is due to excess bilirubin, the yellow pigment in bruises.
• It is usually harmless but can be treated using blue light.
• The blue light breaks down the bilirubin so that it can be excreted as urine.

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Blue Light Jaundice Treatment

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ULTRA-VIOLET

• EM radiation between 10-400 nm.
• Johaan Wilhelm Ritter- 1801.
• Primary source from Sun.

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Sun over UV filter.

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Ultraviolet Radiation

Ultraviolet light in treatment of Psoriasis and Vitiligo

Psoriasis

Vitiligo

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X-RAYS

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• They were discovered serendipitously by German Physicist Wilhelm Roentgen in 1895.
• Roentgen was working with electron beams in discharge tubes.
• In the early days many patients and doctors developed radiation sickness since they were shining x-rays in all directions for large amounts of time.

Wilhelm Roentgen

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Discovery of X-Rays

The free electron collides with the tungsten atom, knocking an electron out of a lower orbital. A higher orbital electron fills the empty position, releasing its excess energy as a photon.

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The free electron is attracted to the tungsten atom nucleus. As the electron speeds past, the nucleus alters its course. The electron loses energy, which it releases as an X-ray photon.

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X-Ray photon emission from Tungsten

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CT-Scan Setup

CT-Scan

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GAMMA RAYS

• EM Radiation high frequency
• High energy photon- kill cancer cells
• Produced by decay from high energy states of atomic nuclei
• Discovered in 1900 by Paul Villard. (right)

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Paul Villard

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GAMMA RAYS

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