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withwave microwave devices - RF Cafe

Module 11 - Microwave Principles
Navy Electricity and Electronics Training Series (NEETS)
Chapter 2:  Pages 2-61 through 2-66





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.

Tunnel diode curve

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.



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-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.




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.



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.


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.


NEETS Modules
- Matter, Energy, and Direct Current
- Alternating Current and Transformers
- Circuit Protection, Control, and Measurement
- Electrical Conductors, Wiring Techniques, and Schematic Reading
- Generators and Motors
- Electronic Emission, Tubes, and Power Supplies
- Solid-State Devices and Power Supplies
- Amplifiers
- Wave-Generation and Wave-Shaping Circuits
- 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
Note: Navy Electricity and Electronics Training Series (NEETS) content is U.S. Navy property in the public domain.
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