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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
Figure 1-76. - Faraday rotation. SUMMARY 1-61 the primary operating frequency. Energy is transported through waveguides by the interaction of
electric and magnetic fields, abbreviated E FIELD and H FIELD, respectively. The density of the E field varies at
the same rate as the applied voltage. If energy is to travel through a waveguide, two BOUNDARY CONDITIONS must be
met: (1) An electric field, to exist at the surface of a conductor, must be perpendicular to the conductor, and
(2) a varying magnetic field must exist in closed loops parallel to the conductors and perpendicular to the
electric field.
1-62 description of the various TE and TM modes. The dominant mode for rectangular waveguides is shown in
the figure.
WAVEGUIDE/IMPEDANCE MATCHING is often necessary to reduce reflections caused by a MISMATCH between the waveguide and the load. Matching devices called IRISES, shown in the illustration, are used to introduce either capacitance or inductance (or a combination of both) into a waveguide. Conductive POSTS and SCREWS can also be used for impedance matching in waveguides.
1-63
DIRECTIONAL COUPLERS are devices that permit the sampling of the energy in a waveguide. Directional couplers may be constructed to sample energy in one direction only or in both directions. The energy removed by the directional coupler is a small sample that is proportional to the magnitude of the energy in the waveguide. An example of a directional coupler is shown in the illustration.
1-64
FERRITE DEVICES combine magnetic properties with a high resistance to current flow.
Ferrites are constructed from compounds of ferrous metal oxides to achieve the desired characteristics. The fact
that the spin axes of electrons will wobble at a natural resonant frequency when subjected to an external magnetic
field is the basic principle of operation of ferrite devices. The position of a typical ferrite device within a
waveguide is shown in the figure.
1-65 ANSWERS TO QUESTIONS Q1. THROUGH Q63. A-1. Microwave region. A-2. Electromagnetic field theory. A-3. The electromagnetic fields are completely confined. A-4. Conductive material. A-5. Copper loss. A-6. Skin effect. A-7. Air. A-8. Physical size. A-9. The characteristics of the dielectric of a capacitor. A-10. A shorted quarter-wave section called a metallic insulator. A-11. The "a" dimension. A-12. The bus bar becomes wider. A-13. Energy will no longer pass through the waveguide. A-14. The interaction of the electric and magnetic fields. A-15. The relative strength of the field. A-16. Magnetic lines of force must form a continuous closed loop. A-17. The H lines cancel. A-18. The field must be perpendicular to the conductors. A-19. Decrease to zero. A-20. The angles are equal. A-21. Cutoff frequency. A-22. Slower. A-23. Group velocity. A-24. Mode of operation. A-25. Dominant mode. A-26. 1.71 times the diameter. A-27. Transverse electric (TE) and transverse magnetic (TM). 1-66 A-28. TE. A-29. Second. A-30. First. A-31. Size and shape. A-32. Slots and apertures. A-33. Standing waves that cause power losses, a reduction in power-handling capability, and an increase in frequency and sensitivity. A-34. Metal plates. A-35. Inductive. A-36. As a shunt resistance. A-37. Horn. A-38. Characteristic impedance. A-39. Absorb all energy without producing standing waves. A-40. Heat. A-41. Reflections. A-42. Greater than 2 wavelengths. A-43. Choke joint. A-44. Improperly connected joints or damaged inner surface. A-45. Sampling energy within a waveguide. A-46. 1/4 wavelength. A-47. Absorb the energy not directed at the pick-up probe and a portion of the overall energy. A-48. The wavefront portions add. A-49. The reflected energy adds at the absorbent material and is absorbed. A-50. Size and shape of the cavity. A-51. Probes, loops, and slots. A-52. The area of maximum H lines. A-53. E-type and H-type. A-54. The junction arm extends in a direction parallel to the H lines in the main waveguide. A-55. E-type and H-type. 1-67 A-56. Low power-handling capability and power losses. A-57. Basic E-type junctions. A-58. High-power duplexes. A-59. Magnetic properties and high resistance. A-60. Electron spin. A-61. Wobble at a natural resonant frequency. A-62. The applied magnetic field. A-63. Faraday
rotation. 1-68 NEETS Table of Contents
Related Pages on RF Cafe - Properties of Modes in a Rectangular Waveguide
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