Introduction to antenna and microwave systems

1. VIRTUAL FACULTY DEVELOPMENT PROGRAMME
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 MICROWAVE ENGINEERING
• 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/SCE)

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)

5. 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).

6. EM FREQUENCY SPECTRUM

7. 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.
CONTD…

8. 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).contd

9. MICROWAVE APPLICATIONS
• Microwaves are 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).contd

10. MICROWAVE APPLICATIONS
• LAW ENFORCEMENT & HIGHWAY SAFETY (Radar speed meters are used by Police for enforcing
speed limit).
• MINE ( Inspection purpose).
• MICROWAVE OVEN (In households for preparation of food).

11. UNIT-1(INTRODUCTION TO MICROWAVE SYSTEMS AND
ANTENNAS)
• ENGINEERING ,MICROWAVE , ANTENNA
• MICROWAVE FREQUENCY BANDS
• ANTENNA REGIONS
ANTENNA PARAMETERS:
• CIRCUIT QUANTITIES
• FIELD QUANTITIES
FRISS TRANSMISSION EQUATION
• LINK BUDGET AND LINK MARGIN

12. WHY ANTENNA
• Short distance (Voice Communication) between two persons is sound waves.
• Long distance (Wireless communication )convert sound waves into EM waves.

13. ANTENNA
• Coordinate system - Address of a point in space .
• Vector - Why? (wind blow)
• Spherical system - Why?

14. 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).

15. ANTENNA
• Slicing of lemon fruit.
• Side to side it is cut .
• Top to bottom it is cut.

16. ANTENNA
• Isotropic – Uniform with respect to viewing angle.
• Homogeneous - Uniform with respect to position.(To be the same throughout).

17. 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).

18. TRANSMISSION LINE TO ANTENNA

19. 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).

20. WAVE PROPAGATION
• SURFACE WAVE - (Ground wave) follows contour of earth .
• SKY WAVE - Signal is reflected from ionized layer of atmosphere back down to earth .
• MICROWAVE -

21. 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

22. ANTENNA PARAMETERS
• Circuit low frequency- V(V),I (A)
• Field high frequency –E(V/m),H(A/m)

23. PRINCIPAL PATTERN
• The radiation 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.

24. RADIATION PATTERN

25. RADIATION PATTERN
• MAJOR LOBE : 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

26. RADIATION PATTERN
• HALF POWER 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.

27. ISOTROPIC PATTERN
• It is 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.

28. DIRECTIONAL PATTERN
• Designed to 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.

29. OMNI DIRECTIONAL
• The 360 degree characteristic of omni antenna similar to light bulb throwing light in all directions
is used in below situations
• 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).

30. ISOTROPIC/OMNI DIRECTIONAL/DIRECTIONAL
• The isotropic 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.

31. 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.

34. DIRECTIVITY

35. ANTENNA EFFICIENCY

36. ANTENNA GAIN
• The gain 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).

37. EFFECTIVE APERTURE

38. FRISS TRANSMISSION EQUATION