NEETS MODULE 11 CHAPTER 1 WAVEGUIDE THEORY AND APPLICATION
Q-1. What is the region of the frequency spectrum from 1000 MHz to 100,000 MHz called?
Q-2. Microwave theory is based upon what concept
Q-3. Why are coaxial lines more efficient at microwave frequencies than two-wire transmission lines?
Q-4. What kind of material must be used in the construction of waveguides?
Q-5. The large surface area of a waveguide greatly reduces what type of loss that is common intwo-wire and coaxial lines?
Q-6. What causes the current-carrying area at the center conductor of a coaxial line to be restricted toa small layer at the surface?
Q-7. What is used as a dielectric in waveguides?
Q-8. What is the primary lower-frequency limitation of waveguides?
Q-9. At very high frequencies, what characteristics are displayed by ordinary insulators?
Q-10. What type of insulator works well at very high frequencies?
Q-11. The frequency range of a waveguide is determined by what dimensison?
Q-12. What happens to the bus bar dimensions of the waveguide when the frequency is increased?
Q-13. When the frequency is decreased so that two quarter-wavelengths are longer than the "a" (wide)dimension of the waveguide, what will happen?
Q-14. What interaction causes energy to travel down a waveguide?
Q-15. What is indicated by the number of arrows (closeness of spacing) used to represent an electricfield?
Q-16. What primary condition must magnetic lines of force meet in order to exist?
Q-17. What happens to the H lines between the conductors of a coil when the conductors are closetogether?
Q-18. For an electric field to exist at the surface of a conductor, the field must have what angularrelationship to the conductor?
Q-19. When a wavefront is radiated into a waveguide, what happens to the portions of the wavefrontthat do not satisfy the boundary conditions?
Q-20. Assuming the wall of a waveguide is perfectly flat, what is the angular relationship between theangle of incidence and the angle of reflection?
Q-21. What is the frequency called that produces angles of incidence and reflection that areperpendicular to the waveguide walls?
Q-22. Compared to the velocity of propagation of waves in air, what is the velocity of propagation ofwaves in waveguides?
Q-23. What term is used to identify the forward progress velocity of wavefronts in a waveguide?
Q-24. What term is used to identify each of the many field configurations that can exist in waveguides?
Q-25. What field configuration is easiest to produce in a given waveguide?
Q-26. How is the cutoff wavelength of a circular waveguide figured?
Q-27. The field arrangements in waveguides are divided into what two categories to describe thevarious modes of operation?
Q-28. The electric field is perpendicular to the "a" dimension of a waveguide in what mode?
Q-29. The number of half-wave patterns in the "b" dimension of rectangular waveguides is indicated bywhich of the two descriptive subscripts?
Q-30. Which subscript, in circular waveguide classification, indicates the number of full-wave patternsaround the circumference?
Q-31. What determines the frequency, bandwidth, and power-handling capability of a waveguideprobe?
Q-32. Loose or inefficient coupling of energy into or out of a waveguide can be accomplished by the useof what method?
Q-33. What is the result of an impedance mismatch in a waveguide?
Q-34. What is used to construct irises?
Q-35. An iris placed along the "b" dimension wall produces what kind of reactance?
Q-36. How will an iris that has portions along both the "a" and "b" dimension walls act at the resonantfrequency?
Q-37. What device is used to produce a gradual change in impedance at the end of a waveguide?
Q-38. When a waveguide is terminated in a resistive load, the load must be matched to what property ofthe waveguide?
Q-39. What is the primary purpose of a dummy load?
Q-40. The energy dissipated by a resistive load is most often in what form?
Q-41. What is the result of an abrupt change in the size, shape, or dielectric of a waveguide?
Q-42. A waveguide bend must have what minimum radius?
Q-43. What is the most common type of waveguide joint?
Q-44. What is the most likely cause of losses in waveguide systems?
Q-45. What is the primary purpose of a directional coupler?
Q-46. How far apart are the two holes in a simple directional coupler?
Q-47. What is the purpose of the absorbent material in a directional coupler?
Q-48. In a directional coupler that is designed to sample the incident energy, what happens to the twoportions of the wavefront when they arrive at the pickup probe?
Q-49. What happens to reflected energy that enters a directional coupler that is designed to sampleincident energy?
Q-50. What two variables determine the primary frequency of a resonant cavity?
Q-51. Energy can be inserted or removed from a cavity by what three methods?
Q-52. Inductive tuning of a resonant cavity is accomplished by placing a nonmagnetic slug in whatarea?
Q-53. What are the two basic types of T junctions?
Q-54. Why is the H-type T junction so named?
Q-55. The magic-T is composed of what two basic types of T junctions?
Q-56. What are the primary disadvantages of the magic-T?
Q-57. What type of junctions are formed where the arms of a hybrid ring meet the main ring?
Q-58. Hybrid rings are used primarily for what purpose?
Q-59. Ferrite devices are useful in microwave applications because they possess what properties?
Q-60. Which of the two types of electron motion (orbital movement and electron spin) is more importantin the explanation of magnetism?
Q-61. The interaction between an external field and the binding force of an atom causes electrons to dowhat?
Q-62. The resonant frequency of electron wobble can be changed by variation of what force?
Q-63. Rotating the plane of polarization of a wavefront by passing it through a ferrite device is called what?
NEETS MODULE 11 CHAPTER 2 MICROWAVE COMPONENTS AND CIRCUITS
Q-1. What happens to the impedance of interelectrode capacitance as frequency increases?
Q-2. What undesirable effect is caused by the inductance of the cathode lead?
Q-3. How does transit time affect the relationship of the grid voltage and the plate current at highfrequencies?
Q-4. Moving tube electrodes apart to decrease interelectrode capacitance causes an increase in theeffect of what property?
Q-5. The kinetic energy of an electron is directly proportional to what property?
Q-6. What will be the effect upon an electron traveling in the opposite direction to the lines of force inan electrostatic field?
Q-7. How is a beam of electrons velocity-modulated?
Q-8. What portion of an electron gun causes the electrons to accelerate or decelerate?
Q-9. What is the effect upon an electron that enters the buncher gap when the potential across thegrids is at 0 volts?
Q-10. What determines the placement of the catcher cavity?
Q-11. What is the basic principle of operation of a klystron?
Q-12. The electrons in the beam of a klystron are speeded up by a high dc potential applied to whatelements?
Q-13. The two-cavity klystron uses what cavity as an output cavity?
Q-14. A two-cavity klystron without a feedback path will operate as what type of circuit?
Q-15. What can be added to the basic two-cavity klystron to increase the amount of velocity modulationand the power output?
Q-16. How is the electron beam of a three-cavity klystron accelerated toward the drift tube?
Q-17. Which cavity of a three-cavity klystron causes most of the velocity modulation?
Q-18. In a multicavity klystron, tuning all the cavities to the same frequency has what effect on thebandwidth of the tube?
Q-19. The cavities of a multicavity klystron are tuned to slightly different frequencies in what method oftuning?
Q-20. What element of the reflex klystron replaces the output cavity of a normal klystron?
Q-21. When the repealer potential is constant, what property of the electron determines how long it willremain in the drift space of the reflex klystron?
Q-22. The constant-speed electrons of an electron bunch in a reflex klystron must remain in the repellerfield for what minimum time?
Q-23. If the constant-speed electrons in a reflex klystron remain in the repeller field for 1 3/4 cycles,what is the mode of operation?
Q-24. Debunching of the electron bunches in the higher modes of a reflex klystron has what effect onoutput power?
Q-25. What limits the tuning range around the center frequency of a reflex klystron in a particular modeof operation?
Q-26. What is the primary use of the twt?
Q-27. The magnet surrounding the body of a twt serves what purpose?
Q-28. How are the input and output directional couplers in a twt connected to the helix?
Q-29. What relationship must exist between the electron beam and the traveling wave for bunching tooccur in the electron beam of a twt?
Q-30. What structure in the twt delays the forward progress of the traveling wave?
Q-31. The folded waveguide in a bwo serves the same purpose as what component in a twt?
Q-32. What serves as a grid in a magnetron?
Q-33. A cylindrical copper block with resonant cavities around the circumference is used as whatcomponent of a magnetron?
Q-34. What controls the output frequency of a magnetron?
Q-35. What element in the magnetron causes the curved path of electron flow?
Q-36. What is the term used to identify the amount of field strength required to cause the electrons tojust miss the plate and return to the filament in a circular orbit?
Q-37. A magnetron will produce oscillations when the electrons follow what type of path?
Q-38. What is the primary difference in construction between the basic magnetron and the negativeresistancemagnetron?
Q-39. What starts the oscillations in a negative-resistance magnetron?
Q-40. Why is the negative-resistance magnetron often operated with reduced filament voltage?
Q-41. What type of electron-resonance anode block does not require strapping?
Q-42. Without strapping, the resonant cavities of a hole-and-slot anode are connected in what manner?
Q-43. What are the electrons called that give up energy to the ac field in a magnetron?
Q-44. Why is the pi mode the most commonly used magnetron mode of operation?
Q-45. What two methods are used to couple energy into and out of magnetrons?
Q-46. Magnetron tuning by altering the surface-to-volume ratio of the hole portion of a hole-and-slotcavity is what type of tuning?
Q-47. Capacitive tuning by inserting a ring into the cavity slot of a magnetron is accomplished by whattype of tuning mechanism?
Q-48. Name the procedure used to reduce excessive arcing in a magnetron?
Q-49. What causes the negative-resistance property of tunnel diodes?
Q-50. What determines the frequency of a tunnel-diode oscillator?
Q-51. Why is the tunnel diode loosely coupled to the cavity in a tunnel-diode oscillator?
Q-52. What is the purpose of the circulator in a tunnel-diode amplifier?
Q-53. What limits the usefulness of high-gain, tunnel-diode frequency converters?
Q-54. The varactor is a pn junction that acts as what type of electronic device?
Q-55. The underlying principle of operation of the parametric amplifier is based on what property?
Q-56. What is the most important feature of the parametric amplifier?
Q-57. How is amplification achieved in the circuit shown in figure 2-43?
Q-58. What is the purpose of the pump in a parametric amplifier?
Q-59. The pump signal frequency must be of what value when compared to the input signal of a simpleparametric amplifier?
Q-60. What is the primary difference between the pump signal of a simple parametric amplifier and thepump signal of a nondegenerative parametric amplifier?
Q-61. In a nondegenerative parametric amplifier the difference between the input frequency and thepump frequency is called what?
Q-62. What is the output frequency of an upper-sideband parametric-frequency converter?
Q-63. What is the primary advantage of bulk-effect devices over normal pn-junction semiconductors?
Q-64. What happens to the electrons of a gallium-arsenide semiconductor when they move from thenormal low-energy conduction band to the high-energy conduction band?
Q-65. The point on the current curve of a gallium-arsenide semiconductor at which it begins to exhibitnegative resistance is called what?
Q-66. The domain in a gallium-arsenide semiconductor has what type of electrical field when comparedto the other regions across the body of a semiconductor?
Q-67. What characteristic of a gunn oscillator is inversely proportional to the transit time of the domainacross the semiconductor?
Q-68. What is the junction arrangement of the original avalanche transit-time diode?
Q-69. What causes dc bias energy to be absorbed by avalanche electrons and given up to themicrowave field applied to an avalanche transit-time diode?
Q-70. During the manufacture of a point-contact diode, what is the purpose of passing a relativelylarge current from the catwhisker to the silicon crystal?
Q-71. What is the capacitive reactance across a point-contact diode as compared to a normal junctiondiode?
Q-72. What are the most important advantages of the Schottky barrier diode?
Q-73. At frequencies above 100 megahertz, the intrinsic (i) region causes a pin diode to act as what?
Q-74. The pin diode is primarily used for what purpose?
NEETS MODULE 11 CHAPTER 3 MICROWAVE ANTENNAS
Q-1. Microwave antennas and low-frequency antennas are similar in what ways?
Q-2. What term is used to express the efficiency of an antenna?
Q-3. What term is used to express the measurement of the degree of mismatch between a line and itsload?
Q-4. What type of antenna radiates in and receives energy from all directions at once?
Q-5. What is the term that is used to describe narrowness in the radiated beam of an antenna?
Q-6. What characteristic allows the same antenna to both transmit and receive?
Q-7. What type of reflector is most often used in directive antennas?
Q-8. Microwaves can be focused and reflected in the same way as what other type of waves?
Q-9. How many major lobes are radiated by a parabolic reflector?
Q-10. A horizontally truncated paraboloid antenna is used for what purpose?
Q-11. The beam from a horizontally positioned cylindrical paraboloid is narrow in what plane?
Q-12. What is the purpose of a collimating lens?
Q-13. How does a waveguide-type lens focus spherical wavefront microwave energy?
Q-14. What type of lens decelerates a portion of a spherical wavefront?
Q-15. What is a set of antenna elements called?
Q-16. What type of antenna has all elements connected to the same energy source?
Q-17. What determines the beam elevation angle of an antenna that is electronically scanned in elevation?
Q-18. What is the polarization of the energy radiated by a vertical slot?
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