Module 11 - Microwave Principles |
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Module 11 − Microwave Principles
Pages i, 1−1, 1−11, 1−21, 1−31, 1−41, 1−51, 1−61, 2−1, 2−11, 2−21, 2−31, 2−41, 2−51, 2−61, 3−1, 3−11, AI−1, Index−1, Assignment 1, Assignment 2
ASSIGNMENT 1 Textbook assignment: Chapter 1, "Waveguide Theory and Applications," pages 1-1 through 1-68.
1-1. The portion of the electromagnetic spectrum which falls between 1,000 and 100,000 megahertz is referred to as which of the following regions? 1. X-ray 2. Infrared 3. Microwave 4. Ultra-violet
1-2. Microwave theory is based on the action of which of the following fields? 1. Electric field only 2. Magnetic field only 3. Electromagnetic field
1-3. Coaxial lines are more efficient than two-wire lines at microwave frequencies for which of the following reasons? 1. Because electromagnetic fields are completely confined in coaxial lines 2. Because electromagnetic fields are not completely confined in coaxial lines 3. Because coaxial lines have less resistance to current flow than two-wire transmission lines 4. Each of the above
1-4. The most efficient transfer of electromagnetic energy can be provided by which of the following mediums? 1. Waveguides 2. Twin-lead flat lines 3. Single-conductor lines 4. Coaxial transmission lines 1-5. Copper (I2R) losses are reduced by what physical property of waveguides? 1. Small surface area 2. Large surface area 3. Shape of the waveguide 4. Waveguide material used
1-6. In a coaxial line, the current-carrying area of the inner conductor is restricted to a small surface layer because of which of the following properties? 1. Skin effect 2. Copper loss 3. Conductor density 4. Temperature effect
1-7. Which of the following dielectrics is used in waveguides? 1. Air 2. Mica 3. Insulating oil 4. Insulating foam
1-8. Which of the following characteristics of a waveguide causes the lower-frequency limitation? 1. I2R loss 2. Physical size 3. Wall thickness 4. Dielectric loss 1 1-9. At very high frequencies, ordinary insulators in a two-wire transmission line display the characteristics of what electrical component? 1. An inductor 2. a resistor 3. a capacitor 4. a transformer
1-10. At very high frequencies, which of the following devices works best as an insulator? 1. Open half-wave section 2. Open quarter-wave section 3. Shorted half-wave section 4. Shorted quarter-wave section
1-11. The range of operating frequencies is determined by which of the following wave-guide dimensions? 1. The widest 2. The longest 3. The shortest 4. The narrowest
1-12. If frequency is decreased, what change, if any, will be required in the dimensions of the wave-guide bus bar? 1. Decrease in dimensions 2. Increase in dimensions 3. None
1-13. The cutoff frequency for a wave-guide is controlled by the physical dimensions of the wave-guide and is defined as the frequency at which two quarter- wavelengths are 1. shorter than the "a" dimension 2. shorter than the "b" dimension 3. longer than the "b" dimension 4. longer than the "a" dimension 1-14. In practical applications, which of the following dimensions describes the wide dimension of the wave-guide at the operating frequency? 1. 0.1 wavelength 2. 0.2 wavelength 3. 0.5 wavelength 4. 0.7 wavelength
1-15. Which of the following fields is/are present in wave guides? 1. E field only 2. H field only 3. E and H fields 4. Stationary field
1-16. a difference in potential across a dielectric causes which of the following fields to develop?
1. Electric field only 2. Magnetic field only 3. Electromagnetic field
Figure 1A. - Electric field. IN ANSWERING QUESTION 1-17, REFER to FIGURE 1A.
1-17. What information is indicated by the number of arrows between the plates of the capacitor? 1. The amount of capacitance 2. The amount of current flow 3. The strength of the electric field 4. The strength of the magnetic field 2 1-18. H lines have which of the following distinctive characteristics? 1. They are continuous straight lines 2. They are generated by voltage 3. They form closed loops 4. They form only in the wave-guide
1-19. What minimum number of boundary conditions must be satisfied for energy to travel down a waveguide? 1. One 2. Two 3. Three 4. Four
1-20. For an electric field to exist at the surface of a conductor, the field must have what angular relationship to the conductor? 1. 0 degrees 2. 30 degrees 3. 45 degrees 4. 90 degrees
1-21. What, if anything, happens to the amplitude of the wavefronts within a waveguide that DO NOT meet boundary conditions? 1. They Increase rapidly to maximum 2. They decrease slowly to the half- power point 3. They decrease rapidly to zero 4. Nothing
1-22. If the wall of a wave-guide is perfectly flat, the angle of reflection is equal to which of the following angles? 1. Angle of cutoff 2. Angle of incidence 3. Angle of refraction 4. Angle of penetration
1-23. THIs QUESTION HAS BEEN DELETED.
1-24. How does the group velocity of an electromagnetic field in a waveguide compare to the velocity of a wavefront through free space? 1. Group velocity is faster 2. Group velocity is slower 3. Their velocities are the same
1-25. The group velocity of a wavefront in a waveguide may be increased by which of the following actions? 1. Decreasing the frequency of the input energy 2. Increasing the frequency of the input energy 3. Increasing the power of the input energy 4. Decreasing the power of the input energy
1-26. The various field configurations that can exist in a waveguide are referred to as 1. wavefronts 2. modes of operation 3. fields of operation 4. fields of distribution
1-27. The most efficient transfer of energy occurs in a waveguide in the what mode? 1. Sine 2. Dominant 3. Transverse 4. Time-phase
1-28. How is the cutoff wavelength for a circular waveguide figured? 1. 1.17 times the radius of the waveguide 2. 1.17 times the diameter of the waveguide 3. 1.71 times the diameter of the waveguide 4. 1.71 times the radius of the waveguide 3 1-29. The field configuration in waveguides is divided into what two categories? 1. Half-sine and dominant 2. Transverse electric and transverse magnetic 3. Transverse electric and dominant 4. Transverse magnetic and half-sine
1-30. With a mode description of TE1, 0, what maximum number of half-wave patterns exist across the "a" dimension of a waveguide? 1. One 2. Two 3. Three 4. Four
1-31. With the mode description, TE1, 1, what maximum number of half-wave patterns exist across the diameter of a circular waveguide? 1. One 2. Two 3. Three 4. Four
1-32. To inject or remove energy from a waveguide, which of the following devices could you use? 1. Slot 2. Loop 3. Probe 4. Each of the above 1-33. Loose coupling is a method used to reduce the amount of energy being transferred from a waveguide. How is loose coupling achieved when using a probe? 1. By doubling the size of the probe 2. By increasing the length of the probe 3. By decreasing the length of the probe 4. By placing the probe directly in the center of energy field
1-34. Loop coupling is most efficient when the loop is placed at what point in which of the following fields? 1. At the point of maximum electric field 2. At the point of minimum electric field 3. At the point of minimum magnetic field 4. At the point of maximum magnetic field
1-35. Increasing the size of the loop wire increases which of the following loop capabilities? 1. Efficiency 2. Bandwidth coverage 3. Power-handling capability 4. Each of the above
1-36. a waveguide which is not perfectly impedance matched to its load is not efficient. Which of the following conditions in a waveguide causes this inefficiency? 1. Sine waves 2. Dominant waves 3. Standing waves 4. Transverse waves
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Figure 1B. - Waveguide iris.
IN ANSWERING QUESTION 1-37, REFER to FIGURE 1B.
1-37. The iris shown in the figure has what type of equivalent circuit? 1. Parallel-LC 2. Shunt-resistive 3. Shunt-inductive 4. Shunt-capacitive
1-38. a waveguide iris that covers part of both the electric and magnetic planes acts as what type of equivalent circuit at the resonant frequency? 1. As a shunt inductive reactance 2. As a shunt resistance 3. As a shunt capacitive reactance 4. Each of the above
1-39. a horn can be used as a waveguide termination device because it provides which of the following electrical functions? 1. a reflective load 2. An absorptive load 3. An abrupt change in impedance 4. a gradual change in impedance 1-40. For a waveguide to be terminated with a resistive load, that load must be matched to which of the following properties of the waveguide? 1. The bandwidth 2. The frequency 3. The inductance 4. The characteristic impedance
1-41. a resistive device with the sole purpose of absorbing all the energy in a waveguide without causing reflections is a/an 1. iris 2. horn 3. antenna 4. dummy load
1-42. a resistive load most often dissipates energy in which of the following forms? 1. Heat 2. Light 3. Magnetic 4. Electrical
1-43. Reflections will be caused by an abrupt change in which of the following waveguide physical characteristics? 1. Size 2. Shape 3. Dielectric material 4. Each of the above
1-44. a waveguide bend which is in the E or H plane must be greater than two wavelengths to prevent 1. cracking 2. reflections 3. energy gaps 4. electrolysis 5 1-45. a flexible waveguide is used in short sections because of the power-loss disadvantages. What is the cause of this power loss? 1. Walls are not smooth 2. E and H fields are not perpendicular 3. Cannot be terminated in its characteristics impedance 4. Wall size cannot be kept consistent
1-46. The choke joint is used for what purpose in a waveguide? 1. To reduce standing waves 2. To restrict the volume of electron flow 3. To prevent the field from rotating 4. To provide a temporary joint in a waveguide during maintenance or repair
1-47. a circular waveguide is normally used in a rotating joint because rotating a rectangular waveguide would cause which of the following unwanted conditions? 1. Oscillation 2. Large power loss 3. Decrease in bandwidth 4. Field-pattern distortion 1-48. In your waveguide inspections, you should be alert for which of the following problems? 1. Corrosion 2. Damaged surface 3. Improperly sealed joints 4. Each of the above 1-49. What type of corrosion occurs when dissimilar metals are in contact? 1. Contact corrosion 2. Metallic corrosion 3. Electrical corrosion 4. Electrolytic corrosion
1-50. Internal arcing in a waveguide is usually a symptom of which of the following conditions? 1. Change in mode 2. Electrolysis at a joint 3. Moisture in the waveguide 4. Gradual change in frequency 1-51. What is the primary purpose of a directional coupler? 1. To sample the energy in a waveguide 2. To change the phase of the energy in the waveguide 3. To change the direction of energy travel in the waveguide 4. To allow energy in the waveguide to travel in one direction only
1-52. What is the electrical distance between the two holes in a simple directional coupler? 1. Oscillation 2. Large power loss 3. Decrease in bandwidth 4. Field-pattern distortion
1-48. In your waveguide inspections, you should be alert for which of the following problems? 1. Corrosion 2. Damaged surface 3. Improperly sealed joints 4. Each of the above
1-49. What type of corrosion occurs when dissimilar metals are in contact? 1. Contact corrosion 2. Metallic corrosion 3. Electrical corrosion 4. Electrolytic corrosion 1-53. When the two portions of a reflected wave reach the pickup probe of an incident-wave directional coupler, what is their phase relationship? 1. 45º out of phase 2. 90º out of phase 3. 120º out of phase 4. 180º out of phase
1-54. The highest frequency at which a conventional circuit can oscillate is reached when which of the following values can be reduced no further? 1. Total resistance 2. Total inductance only 3. Total capacitance only 4. The total capacitance and inductance 6 1-55. For a device to be considered a resonant cavity, it must fulfill which of the following requirements? 1. Be enclosed by conducting walls 2. Possess resonant properties 3. Contain oscillating electromagnetic fields 4. All of the above
1-56. What property gives a resonant cavity a narrow bandpass and allows very accurate tuning? 1. Low Q 2. High Q 3. Inductive reactance 4. Capacitive reactance
1-57. What factor(s) determines the primary frequency of a resonant cavity? 1. Size only 2. Shape only 3. Size and shape 4. Q of the cavity
1-58. Tuning is the process of changing what property of a resonant cavity? 1. The Q 2. The power output 3. The cutoff frequency 4. The resonant frequency
1-59. An adjustable slug or screw placed in the area of maximum E lines in a resonant cavity provides what type of tuning? 1. Volume 2. Inductive 3. Resistive 4. Capacitive 1-60. What are the two basic types of waveguide T junctions? 1. H-type and T-type 2. H-type and E-type 3. H-type and magic T 4. E-type and magic T
1-61. a waveguide junction in which the arm area extends from the main waveguide in the same direction as the electric field is an example of what type junction? 1. E-type magic T 2. H-type magic T 3. H-type T junction 4. E-type T junction
Figure 1C. - H-type T junction.
IN ANSWERING QUESTION 1-62, REFER to FIGURE 1C.
1-62. When an input is fed into the "b" arm in the figure, which of the following output signal arrangements is/are available? 1. Out-of-phase signals from arms "a" and "c" 2. In-phase signals from arms "a" and "c" 3. An output from the "a" arm only 4. An output from the "c" arm only 7 1-63. E-type and H-type junctions are combined in which of the following devices? 1. Magic T 2. Rat race 3. Feed horn 4. Hybrid ring
1-64. Low power-handling capabilities and internal power losses are the primary disadvantages of which of the following devices? 1. Magic T 2. Rat race 3. Duplexer 4. Hybrid ring
1-65. The hybrid ring is usually used as what type of device in radar systems? 1. Mixer 2. Detector 3. Duplexer 4. Impedance matcher
1-66. Ferrite devices are useful in electronic and microwave applications because they possess magnetic properties and offer which of the following other properties? 1. Negative resistance to current flowbr>2. Low resistance to current flow 3. High resistance to current flow 4. High conductance for current flow 11-67. Electrons exhibit which of the following types of motion? 1. Spinbr>2. Orbital 3. Both 1 and 2 above 4. Linear
11-68. Electrons in a ferrite can be caused to wobble on their axes by which of the following actions? 1. Decreasing the internal resistancebr>2. Increasing the internal resistance 3. Applying a magnetic field 4. Applying an electric field
11-69. The energy in a ferrite attenuator that is attenuated is dissipated as which of the following energy forms? 1. Heatbr>2. Light 3. Magnetic 4. Electrical
11-70. The amount of rotation in a Faraday- rotation type ferrite phase shifter is dependent upon which of the following ferrite properties? 1. Length of the materialbr>2. Diameter of the material 3. Strength of the material 44. Internal resistance of the material 8 /p>
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