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- Question
To ensure that only dominant mode TE10 is allowed to propagate in an air filled rectangular waveguide, the lower frequency limit and upper frequency limit are
Options- A. about 25% above fc for TE10 and 5% below fc for TE20 mode respectively
- B. about 50% above fc for TE10 and 25% below fc for TE20 mode respectively
- C. about 25% above fc for TE10 and 25% below fc for TE20 mode respectively
- D. none of the above
- Correct Answer
- about 25% above fc for TE10 and 5% below fc for TE20 mode respectively
- 1. The external magnetic field in a magnetron is such that lines are
Options- A. parallel to the axis of cathode
- B. perpendicular to the axis of cathode
- C. inclined to the axis of cathode
- D. either (b) or (c) Discuss
- 2. Consider the following statements
- Gunn diode can be used in combinational logic circuits.
- Gunn diode can be used in sequential logic circuits.
- Both Gunn diode and GaAs Mesfet can be used in logic circuits.
Options- A. 1, 2, and 3
- B. 1 and 2 only
- C. 2 and 3 only
- D. 1 and 3 only Discuss
- 3. The two terms used to describe performance of a directional coupler are
Options- A. coupling and directivity
- B. gain and coupling
- C. gain and directivity
- D. gain and isolation Discuss
- 4. In the given figure forward current wave has a magnitude of
Options- A. 0.45 A
- B. 0.3 A
- C. 0.2 A
- D. 0.1 A Discuss
- 5. If D is diameter of circular waveguide the cutoff wave-length for TE11 mode is equal to
Options- A. 1.706 D
- B. 2.11 D
- C. 0.82 D
- D. 0.41 D Discuss
- 6. A radar has a maximum range of 120 km. The maximum allowable pulse repetition frequency for unambiguous reception is
Options- A. 1250
- B. 330
- C. 2500
- D. 8330 Discuss
- 7. A disadvantage of microstrip line as the connections of compared to strip line is that former
Options- A. do not lend themselves to printed circuit
- B. are more likely to radiate
- C. are bulky
- D. are more expensive and complex Discuss
- 8. Consider the following time parameters
- Domain growth time constant.
- Transit time.
- Dielectric relaxation time in positive mobility regime.
Options- A. 1, 2, and 3
- B. 1 and 2 only
- C. 1 and 3 only
- D. 2 and 3 only Discuss
- 9. In a circular waveguide with radius r, the dominant mode is
Options- A. TM01
- B. TE01
- C. TM11
- D. TE11 Discuss
- 10. A circular polarizer converts a linearly polarized wave into a circularly polarised wave.
Options- A. True
- B. False Discuss
Microwave Communication problems
Search Results
Correct Answer: parallel to the axis of cathode
Explanation:
In a magnetron three forces act on electron viz. force due to electric field (equal to - eE), force due to magnetic field [equal to - e (v x B)] and centrifugal force (equal to mv2/r).
The path of the electron can be found by balancing these three forces. Magnetron can be of three types i.e., negative resistance device, cyclotron frequency device and travelling wave or cavity device.
In negative resistance magnetron use is made of the negative resistance between two anode segments.
It has low efficiency and is used at frequencies less than 0.5 GHz.
In cyclotron magnetron a synchronism exists between ac component of electric field and periodic oscillation of electrons in a direction parallel to the field.
It is used for frequencies higher than 100 MHz.
A cavity magnetron has a number of cylindrical cavities in the interaction region.
The cavity magnetron is the most common type of magnetron. Its features are :
1. Frequency range - 500 MHz to 10 GHz
2. Power output - 250 kW (pulses)
3. Efficiency - about 50%
It is used in radar systems, industrial heating systems and microwave ovens.
Correct Answer: 1, 2, and 3
Correct Answer: coupling and directivity
Correct Answer: 0.3 A
Explanation:
Correct Answer: 1.706 D
Explanation:
These analysis uses cylindrical coordinates.
In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode.
If D is diameter of waveguide
?c = 1.706 D for TE11 mode
?c = 1.029 D for TE21 mode
?c = 0.82 D for TE01 mode
?c = 1.306 D for TM01 mode.
Correct Answer: 1250
Correct Answer: are more likely to radiate
Correct Answer: 1, 2, and 3
Correct Answer: TE01
Explanation:
These analysis uses cylindrical coordinates.
In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode.
If D is diameter of waveguide
?c = 1.706 D for TE11 mode
?c = 1.029 D for TE21 mode
?c = 0.82 D for TE01 mode
?c = 1.306 D for TM01 mode.
Correct Answer: True
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