Microwave Communication - Section 1 (3)
Microwave Communication - Section 1
| 17. |
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Answer: Option B Explanation: Printed circuit techniques is used for micro strip line. |
| 18. |
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Answer: Option A Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20% 4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc. |
| 19. |
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Answer: Option D Explanation: XC should be at least ten times greater than R. Therefore for 50 Ω resistor at 3 GHz, C should be less than 0.1 pF. |
| 20. |
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Answer: Option D Explanation:
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| 21. |
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Answer: Option D Explanation:
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| 22. |
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Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments. |
| 23. |
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Answer: Option A Explanation: A Microstrip line has a single dielectric substratc with ground plane on one side and a strip on the other face. Its special feature is easy access to top surface so that minor adjustments can be made after circuit fabrication. The high dielectric constant of the substrate reduces guide wavelength and circuit dimensions. A microstrip line is the most commomly used transmission structure for microwave integrated circuits. |
| 24. |
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Answer: Option B Explanation: t is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments. |