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Module 11 - Microwave Principles |
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Module 11 - Microwave Principles
Pages i−ix, 1−1 to 1−10, 1−11 to 1−20, 1−21 to 1−30, 1−31 to 1−40, 1−41 to 1−50, 1−51 to 1−60, 1−61 to 1−68, 2−1 to 2−10, 2−11 to 2−20, 2−21 to 2−30, 2−31 to 2−40, 2−41 to 2−50, 2−51 to 2−60, 2−61 to 2−66, 3−1 to 3−10, 3−11 to 3−20, AI−1 to AI−6, Index−1 to Index−2, Assignment 1 - 1−8, Assignment 2 - 9−16
The MAGNETRON is a DIODE OSCILLATOR capable of delivering microwave energy at very high power levels. Three fields exist within a magnetron that influence operation: (1) the DC ELECTRIC FIELD between the anode and cathode; (2) the AC ELECTRIC FIELD produced by the oscillating resonant cavities and on the same plane as the dc field; and (3) the MAGNETIC FIELD produced by the permanent magnet which is perpendicular to the dc electric field. Magnetrons are of two basic types, the NEGATIVE-RESISTANCE MAGNETRON and the
2-61
SOLID-STATE MICROWAVE DEVICES are becoming increasingly widespread in microwave equipment with new developments almost daily. Most of the currently available solid-state devices are two-terminal diodes with the capability to generate or amplify microwave energy. Many of the solid-state devices, such as the TUNNEL DIODE and the BULK-EFFECT DIODE, apply the property of NEGATIVE RESISTANCE to amplify microwave signals or generate microwave energy. A characteristic curve illustrating the negative-resistance property of the tunnel diode is shown at the right.
The VARACTOR is a two-terminal diode that acts as a variable capacitance and is the active element of PARAMETRIC AMPLIFIERS. The parametric amplifier is a low-noise microwave amplifier that uses variable reactance to amplify microwave signals. The illustration shows an example of a NONDEGENERATIVE PARAMETRIC AMPLIFIER. 2-62
ANSWERS TO QUESTIONS Q1. THROUGH Q74.
A-1. Impedance decreases. A-2. Degenerative feedback. A-3. Transit time causes the grid voltage and plate current to be out of phase. A-4. Transit time. A-5. Velocity. A-6. The electron will be accelerated. A-7. By alternately speeding up or slowing down the electrons. A-8. The buncher grids. A-9. There is no effect. A-10. The frequency period of the buncher grid signal.
A-11. Velocity modulation. 2-63 A-12. The accelerator grid and the buncher grids. A-13. The catcher cavity. A-14. Amplifier. A-15. Intermediate cavities between the input and output cavities. A-16. A large negative pulse is applied to the cathode. A-17. The middle cavity. A-18. The bandwidth decreases. A-19. Stagger tuning. A-20. The reflector or repeller. A-21. Velocity. A-22. Three-quarter cycle. A-23. Mode 2. A-24. Power is reduced. A-25. The half-power points of the mode. A-26. Voltage amplification. A-27. Used to focus the electrons into a tight beam. A-28. The directional couplers are not physically connected to the helix. A-29. The traveling wave must have a forward velocity equal to or less than the speed of the electrons in the beam. A-30. The helix. A-31. Helix. A-32. A magnetic field. A-33. Anode or plate. A-34. The resonant cavities. A-35. The permanent magnet. A-36. The critical value of field strength. A-37. Circular. A-38. The negative-resistance magnetron has a split plate. A-39. The application of the proper magnetic field.
2-64 A-40. To reduce the effects of filament bombardment. A-41. Rising-sun block. A-42. Series. A-43. Working electrons. A-44. Greater power output. A-45. Loops and slots. A-46. Inductive. A-47. A cookie-cutter tuner. A-48. Baking in. A-49. The tunneling action. A-50. The tuned circuit or cavity frequency. A-51. To increase the stability. A-52. Prevent feedback to the tuned input circuit. A-53. Stability problems. A-54. Variable capacitor. A-55. Reactance. A-56. The low-noise characteristic. A-57. By varying the amount of capacitance in the circuit. A-58. Supplies the electrical energy required to vary the capacitance. A-59. Exactly double the input frequency. A-60. The pump signal of a nondegenerative parametric amplifier is higher than twice the input signal. A-61. Idler- or lower-sideband frequency. A-62. The sum of the input frequency and the pump frequency. A-63. Larger microwave power outputs. A-64. The electrons become immobile. A-65. Threshold. A-66. A field of much greater intensity. A-67. The frequency. 2-65 A-68. PNIN. A-69. The negative-resistance property. A-70. To form a small region of p-type material. A-71. Lower. A-72. Lower forward resistance and low noise. A-73. Variable resistance. A-74. A switching device. 2-66 NEETS Table of Contents
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