Module 11 - Microwave Principles
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
, 2−31 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 TWT is a wide-bandwidth, velocity-modulated tube used primarily as an amplifier. The electron beam is bunched by a signal applied to the HELIX. The bunching causes an energy transfer from the electron beam to the traveling wave on the helix.
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
ELECTRON-RESONANCE MAGNETRON. A diagram of a magnetron is shown at the right.
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.
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-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.
A-12. The accelerator grid and the buncher grids.
A-13. The catcher cavity.
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-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-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-38. The negative-resistance magnetron has a split plate.
A-39. The application of the proper magnetic field.
A-40. To reduce the effects of filament bombardment.
A-41. Rising-sun block.
A-43. Working electrons.
A-44. Greater power output.
A-45. Loops and slots.
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-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-66. A field of much greater intensity.
A-67. The frequency.
A-69. The negative-resistance property.
A-70. To form a small region of p-type material.
A-72. Lower forward resistance and low noise.
A-73. Variable resistance.
A-74. A switching device.
NEETS Table of Contents
- Introduction to Matter, Energy,
and Direct Current
- Introduction to Alternating Current and Transformers
- Introduction to Circuit Protection,
Control, and Measurement
- Introduction to Electrical Conductors, Wiring
Techniques, and Schematic Reading
- Introduction to Generators and Motors
- Introduction to Electronic Emission, Tubes,
and Power Supplies
- Introduction to Solid-State Devices and
- Introduction to Amplifiers
- Introduction to Wave-Generation and Wave-Shaping
- Introduction to Wave Propagation, Transmission
Lines, and Antennas
- Microwave Principles
- Modulation Principles
- Introduction to Number Systems and Logic Circuits
- Introduction to Microelectronics
- Principles of Synchros, Servos, and Gyros
- Introduction to Test Equipment
- Radio-Frequency Communications Principles
- Radar Principles
- The Technician's Handbook, Master Glossary
- Test Methods and Practices
- Introduction to Digital Computers
- Magnetic Recording
- Introduction to Fiber Optics