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Antenna
- 1. VIRTUAL FACULTY DEVELOPMENTPROGRAMME ANTENNAS AND MICROWAVE ENGINEERING (22.6.2020-26.6.2020) INTRODUCTION TO MICROWAVE SYSTEMS AND ANTENNAS PRESENTED BY Dr. S. ASHA, PROF/ECE/SEC
- 2. ANTENNAS AND MICROWAVEENGINEERING • UNIT-1 : INTRODUCTION TO MICROWAVE SYSTEMS AND ANTENNAS . (Dr.S.ASHA /PROF/SEC) • UNIT-II : RADIATION MECHANISMS AND DESIGN ASPECTS . (Mr.C.MAHENDRAN /ASST.PROF/ACGCET) • UNIT-III : ANTENNA ARRAYS AND APPLICATIONS . (Dr.A.AMSAVENI /PROF/KCT) • UNIT –IV : PASSIVE AND ACTIVE MICROWAVE DEVICES . (Dr.G.KAVYA/PROF/SAEC) • UNIT-V : MICROWAVE DESIGN PRINCIPLES. (Dr.M.SELVI/PROF/SEC)
- 3. AGENDA • ENGINEERING • MICROWAVE •FREQUENCY BANDS • APPLICATION • WHY ANTENNA • WHAT IS ANTENNA • ANTENNA REGIONS • ANTENNA PARAMETERS • FRISS TXN EQUATION
- 4. ENGINEERING • PHYSICS(PARTICLE,WAVE) • ELECTRON(SMALLEST/INVISIBLE/INTERATOMIC NEGATIVELY CHARGED PARTICLE ,ONE MILLIONTH OF THICKNESS OF FIBRE) • ELECTRON IS A WAVE(SINGLE/RAY/BUNCH) • ELECTRON OSCILLATION(RADIATION) • MATHEMATICS(DISTANCE,TIME) • (TIME-STATIC,DYNAMIC) • (DISTANCE ,INFORMATION)
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- 6. MICROWAVE • Electronics –Signal,Communication – EM wave, • λ = c/f c-velocity of light(3*100,000 km/sec)(Going around earth-7 and ½ times) , f-frequency (Hertz), λ –wavelength (meter).
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- 8. MICROWAVE FREQUENCY BAND •Higher the frequency more the bandwidth but shorter coverage area. • K band is not generally used in communication because it absorbs water vapour in the atmosphere easily. • To transmit large volume of data for eg high speed wireless broadband network in an office V and W band can be preferred.
- 9. MICROWAVE FREQUENCY BAND •L band and S band are used for space communication. • Five satellites of the ISRO including INSAT 3DR sent real time images to the ground station . • It played key role in saving lives in rain battered Kerala, monitoring the grave flood situation and assisting in relief work.(Image dated Aug 19,2018).
- 10. MICROWAVE APPLICATIONS • Microwavesare suitable for Wireless Transmission of signals having larger bandwidth. • SPACECRAFT (Aircraft safety and mobile navigation to avoid terrain collision , wind shear ). • MOBILE (Wireless charging of mobile phones using microwaves).
- 11. MICROWAVE APPLICATIONS • LAWENFORCEMENT & HIGHWAY SAFETY (Radar speed meters are used by Police for enforcing speed limit). • MINE ( Inspection purpose). • MICROWAVE OVEN (In households for preparation of food).
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- 13. UNIT-1(INTRODUCTION TO MICROWAVESYSTEMS AND ANTENNAS) • ENGINEERING ,MICROWAVE , ANTENNA • MICROWAVE FREQUENCY BANDS • ANTENNA REGIONS ANTENNA PARAMETERS: • CIRCUIT QUANTITIES • FIELD QUANTITIES FRISS TRANSMISSION EQUATION • LINK BUDGET AND LINK MARGIN
- 14. WHY ANTENNA • Shortdistance (Voice Communication) between two persons is sound waves. • Long distance (Wireless communication )convert sound waves into EM waves.
- 15. ANTENNA • Coordinate system- Address of a point in space . • Vector - Why? (wind blow) • Spherical system - Why?
- 16. ANTENNA • Point P(r,θ ,φ ) - (r )radial distance, (θ)-elevation angle( angle between point P and z axis) ,(φ)-azimuthal angle ( angle between projection of point P in xy plane and the x-axis).
- 17. ANTENNA • Slicing oflemon fruit. • Side to side it is cut . • Top to bottom it is cut.
- 18. ANTENNA • Isotropic –Uniform with respect to viewing angle. • Homogeneous - Uniform with respect to position.(To be the same throughout).
- 19. ANTENNA – INTERFACE •EYE – Converts electromagnetic photons into circuit current. • ANTENNA – Unlike eye interfaces between electrons on conductors with photons in space and vice versa . It can handle transition in both the directions.(Reciprocity).
- 20. TRANSMISSION LINE TOANTENNA
- 21. WHAT IS ANTENNA •ANTENNAE or AERIAL • Transducer(electrical energy into electromagnetic energy and vice versa). • Transition device between guided wave(plane wave) and free space wave(spherical wave) and vive versa. • Conductor which radiates(electrons accelerated and retarded repeatedly),(flow of energy) . • WEBSTERS dictionary., IEEE Std(metallic tubing device i.e rod or wire for radiating or receiving radio waves). • Spatial Filter.( It has the property of being more sensitive to one direction than other which provides ability to spatially filter signals from its environment). • Polarization Filter.(It has the property of being more sensitive to one polarization than other which provides ability to filter signals based on polarization). • Impedance Transformer.(Intrinsic impedance of free space is (η) E/H =377 Ω)., (Characteristic impedance of transmission line (ZO) V/I = 50 Ω ) . • Propagation mode Adapter.(It must serve as a probing device in addition to directional and impedance transformation device).
- 22. WAVE PROPAGATION • SURFACEWAVE - (Ground wave) follows contour of earth . • SKY WAVE - Signal is reflected from ionized layer of atmosphere back down to earth .
- 23. ANTENNA REGIONS • RNFR-Reactive Near Field Region • FRESNEL -Radiative Near Field Region (Transition). • FRAUNHOFER - Radiative Far Field Region . • L – length of the antenna, λ –wavelength
- 24. ANTENNA PARAMETERS • Circuitlow frequency- V(V),I (A) • Field high frequency –E(V/m),H(A/m)
- 25. PRINCIPAL PATTERN • Theradiation pattern is a graphical (pictorial) ,mathematical representation of the radiation properties of an antenna as a function of space coordinates. (E/H Plane Patterns) • Graphically, we surround the antenna by a sphere and evaluate the electric / magnetic fields (far field radiation fields) at a distance equal to the radius of the sphere. • For a dipole, this leads to the doughnut pattern in 3D because of the dependence of Eθ on sin θ.
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- 27. RADIATION PATTERN • MAJORLOBE : Radiation lobe containing direction of maximum radiation (main beam). • MINOR LOBE : Is any lobe except major lobe. • SIDELOBE : Radiation lobe in any direction other than the intended lobe . • BACK LOBE : Radiation lobe which makes an angle of approximately 180 degrees with respect to beam of an antenna
- 28. RADIATION PATTERN • HALFPOWER BEAMWIDTH : The angular separation between two identical points on opposite side of pattern maximum . The term beamwidth usually refers to HPBW. • FIRST NULL BEAMWIDTH : The angular separation between the first nulls of the pattern is called FNBW.(FNBW). • The beam width decreases , then side lobe increases and vice versa. • It describes resolution capabilities ,to distinguish two adjacent sources or targets.
- 29. ISOTROPIC PATTERN • Itis a hypothetical reference. • In reality this antenna cannot exist , but is used to compare real antennas with each other . All real antennas have gain that is compared to this reference. • The Sun radiates energy equally in all directions.
- 30. DIRECTIONAL PATTERN • Designedto be pointed or focused ,in a single direction , somewhat like a flash light .(The light of the flashlight is strongest at the center of beam and tapers off toward the edges). • When there is clear LOS from the antenna to the cell tower. • When all required cell towers are off in the same direction.
- 31. OMNI DIRECTIONAL • The360 degree characteristic of omni antenna is similar to the light bulb throwing light in all directions . • They radiate in the horizontal plane. • When there is no LOS from the antenna to the cell tower.(Areas with mountains or Dense forests). • When signal is acquired from cell towers in multiple directions.(Antenna attached to moving car).
- 32. ISOTROPIC/OMNI DIRECTIONAL/DIRECTIONAL • Theisotropic radiator has got ball(round) shaped radiation. • Omni directional radiate in the horizontal plane, donot radiate in the vertical plane. • Directional antenna is focused in a single direction.
- 33. BEAM SOLID ANGLE •RADIAN is a measure of plane angle. 1 rad subtends an arc of length r. • Since the circumference of a circle is 2πr, the number of radians in a complete circle is C/r = 2π rad. • STERADIAN is a measure of solid angle. 1 sr subtends a spherical area of area r2 . • Since a complete sphere has a surface area of 4πr2, there are A/r2 = 4π sr in a sphere.
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- 38. ANTENNA GAIN • Thegain of an antenna takes into account the efficiency and directional abilities. But directivity describes only directional properties controlled by the pattern. • Defn: measurement of antennas ability to direct or concentrate the radiated signal emitting from it.(dBi -decibels relative to isotropic radiator) • Why?-in specification sheet, gain is quoted than directivity because it takes in to account the actual losses that occur.(Reflection losses, Polarisation losses).
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