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Microwave Techniques
The paper will help M.Phil/Ph.D candidates to learn: • Lab techniques in Microwaves • Basic principles of measurements of different quantities • Working of various microwave devices from a practical point of view • Accuracy of measurements by different methods • Selection of the suitable method of measurement for different purposes
a) Slotted Coaxial line techniques : Coaxial line, coaxial slotted section, Characteristic Impedance, coaxial attenuator, matched termination, detector and indicating meter Voltage Standing Wave Ratio, Measurement of VSWR for the unmodulated exciting wave by a crystal rectifier and Micro ammeter for the cases when VSWR is (i) very low (ii) moderate and (iii) high. Measurement of VSWR for the modulated exciting wave by crystal rectifier and VSWR meter. b) Detector Characteristics: Crystals as Detectors for Microwaves, Crystal mounting, Microwave Crystal parameters; Study of square law behavior and determination of operating range and detection efficiency of microwave crystal detector. Bolo meters and their mounting, Thermocouple c) Slotted waveguide techniques: Dominant modes in rectangular waveguides, Energizing a waveguide in a dominant mode; Group and Phase velocities; Characteristic wave impedance, Slotted waveguide section with a carriage and probe, Attenuators and Matched loads, short circuit terminations, Frequency meter. Characteristics of wave propagation in a waveguide and relationship between guide wavelength (λg) and free space wavelength (λ0 ), Wall currents.
Microwave sources used in the Laboratory: (a) Reflex Klystron: Its construction and operation, Transit time and mode number, Power-frequency characteristics, Mechanical and electrical tuning output efficiency, Modulation in Klystron, Power coupling, Basic Precautious, firing of the Reflex Klystron. Study of mode characteristics of a reflex Klystron (b) Gunn Oscillator: Gunn Effect, Gunn Oscillator, Modulation; I-V characteristics, Power and Frequency, Characteristics of a Gunn Oscillator, Modes of operation.
(a) Directional Coupler : Characteristics of a Directional coupler, Directivity and coupling of a Directional coupler, Types of couplers: Bathe hole coupler, Double hole and multi-hole couplers Directional coupler parameters. Measurement of main line and auxiliary line VSWR; measurement of coupling and insertion loss (b) Microwave Antennas : E-H Horns, E-plane, H-plane and pyramidal horns, Radiation Pattern: Beam width, Gain. Study of the E-plane and H-plane radiation pattern of a pyramidal horn antenna and estimation of beam width and directional gain of the antenna
a) Attenuation Measurement: Attenuators, Attenuator characteristics: Input VSWR, Insertion loss, and frequency sensitivity of attenuation. Attenuation Measurement: Direct or power measuring method, substitution method, Impedance measuring method b) Power Measurement : Methods of measuring microwave power for (i) high power (ii) low power (iii) very low power. Errors in power measurement, Peak and average power. Use of thermistor for power measurement, power meter.
Dielectric Measurement: Dielectric constant, loss factor, Von Hipple or shorted waveguide method, Heston and Smythe method for low loss liquids, Surber method for medium and high loss liquids, Poly’s method for high loss liquids, Corfield Coaxial line method. (b) Two point method (a) loss less dielectric (b) lossy dielectric Measurement of dielectric constant by two point method of (a) low loss solid dielectrics (b) Liquids solutions; Measurement of dielectric constant of solids and liquids by Von-Hipple method (a) General sample length (b) Sample length in multiples of λd/2; Measurement of dielectric content of powders. Use of Impedance Bridge/Network Analyzer for dielectric measurement.
1. M.L.Sisodia and G.S. Raghuvanshi, “Basic Microwave Techniques and Laboratory Mannual (New Age Internatia and Publishers, New Delhi, 2007) 2. O.B. Richard, “Laboratory Manual for Microwave Measurements” (Prentice Hall Incs., England Cliff, N.J. 1968) 3. M. Sucher and J. Fox “ Handbook of Microwave Measurements” Vol., I, II and III ( John Wailey, New York: 1963) 4. T.S. Laverghetta “Microwave Measurement and Techniques” (Artech House, Washington Street, Massachusetts: 1976) 5. E.H. Thomas, “Handbook of Microwave Techniques (Prentice Hall Inc., Englewood Cliffe, NJ: 1976) 6. A. Von Hipple, “Dielectric Materials and Applications” (John Wiley & Sons Inc, New Delhi: 1953)
1. D.C. Grem. “Transmission System TEC Level –II” (Pitman Pub. Co. Ltd. 39, Parker Street, London: 1978) 2. G.C. Southworth, “Waveguide Transmission” ( D Van Nostrand, London: 1950) 3. T.S. Laverghetta “Microwave Measurement and Techniques” (Artech House, Washington Street Massachusetts: 1976) 4. M.L. Sisodia and G.S. Raghuvanshi, “Microwave Circuits and Passive Devices” (Wiley Eastern Ltd, New Delhi, 1987) 5. A.B. Brownwall and R.E. Beam, “Theory and Application of Microwaves (Mc. Graw Hill Book Co. : 1967) 6. A.L. Lance, “Introduction to Microwave Theory and Measurements” (1964) 7. R.F. Soohoo, “Microwave Electronics”, (Addison-Wesley Pub. Co. : 1971) 8. A. Vander Zil, “Solid State Physical Electronics” (Prentice Hall of India Pvt. Ltd.: 1971) 9. H.A. Watson, “Microwave Semiconductor Devices” (Mc Graw Hill Book Co.: 1969) 10. H.J. Reech etal., “Microwave Principles” (Affiliated East-West, Press, New Delhi: 1970) 11. R.E. Collins “Microwave Electronics for Engineers”………………………. 12. G. Whealer, “Introduction to Microwave” (Prentice Hall Inc.: 1963, Indian Reprint 1976) 13. J. Helszajn, “Passive and Active Microwave Circuits” (John Wiley & Sons: 1978) 14. E.C. Jordan and K.G. Balman “Electromagnetic Waves and Radiating System” (Prentice Hall of India: 1976) 15. A.Z. Fradin, “ Microwave Optics” (R.C. Glass Pergamon Press Inc., New Delhi: 1961) 16. H.A. Atwalter, “Introduction to Microwave Theory” (Mc Graw Hill, Book Co, Toby: 1932) 17. S.M. Sze, “Physics of Semiconductor Devices” )Wiley Eastern Ltd, New Delhi: 1979) 18. M.J. Hoves and D.V. Morgan “Microwave Devices” (John Wiley and Sons: 1976) 19. E.L. Gintzton “Microwave Measurements” (Mc Graw Hill Book Co. : 1957) 20. C.G. Montgomery, “Techniques of Microwave Measurement” (Mc Graw Hill : 1947) 21. O.B. Rechard, “Laboratory Manual for Microwave Measurements” (Prentice Hall Inc., Englewood Cliffs, N.J : 1968)
