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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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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ... All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged. My Hobby Website: AirplanesAndRockets.com
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