TRUE/FALSE
1. By convention, microwave frequencies are 1 GHz and above.
ANS: T
2. Transmission line losses decrease at microwave frequencies.
ANS: F
3. Semiconductor transit time can be ignored at microwave frequencies.
ANS: F
4. Leads on semiconductor devices have significant inductance at microwave frequencies.
ANS: T
5. Waveguides are essentially pipes through which electromagnetic fields propagate.
ANS: T
6. Waveguides act as low-pass frequency filters for microwaves.
ANS: F
7. Waveguides often have significant radiation loss.
ANS: F
8. Waveguides do not have significant dielectric losses.
ANS: T
9. Multimode propagation causes dispersion of a pulse as it travels through a waveguide.
ANS: T
10. Usually, a waveguide should use only one mode of propagation.
ANS: T
11. Single-mode propagation causes some dispersion of a pulse as it travels through a waveguide.
ANS: T
12. Typically, waveguides carry TEM waves.
ANS: F
13. In a rectangular waveguide, TE10 is the dominant mode.
ANS: T
14. Circular waveguides are possible, but are not used in practice.
ANS: F
15. The cutoff frequency for a rectangular waveguide depends on the longer dimension of its cross section.
ANS: T
16. Group velocity is how fast a signal travels through a waveguide.
ANS: T
17. Group velocity is significantly less than the speed of light.
ANS: T
18. Phase velocity is another term for group velocity.
ANS: F
19. Group velocity increases as the signal frequency increases.
ANS: T
20. Guide wavelength is calculated using the phase velocity.
ANS: T
21. Guide wavelength is always shorter than free-space wavelength.
ANS: F
22. Phase velocity in a waveguide is always greater than the speed of light.
ANS: T
23. Waveguide impedance is a function of frequency.
ANS: T
24. Waveguide impedance is always equal to or less than 377 ohms.
ANS: F
25. Impedance matching on a waveguide can be done with a brass screw.
ANS: T
26. At microwave frequencies, a cavity in a piece of metal acts like an LC circuit.
ANS: T
27. Resonant cavities cannot be tuned.
ANS: F
28. An isolator uses multiple ports to separate signals.
ANS: F
29. Circulators rely on the magnetic properties of ferrites.
ANS: T
30. A Gunn device contains a P-N junction.
ANS: F
31. A Gunn device uses its transit time to produce microwave oscillations.
ANS: T
32. A Gunn device uses "negative resistance" to produce microwave oscillations.
ANS: T
33. An IMPATT diode is often a 4-layer device.
ANS: T
34. The frequency of oscillation of an IMPATT diode depends on its physical dimensions.
ANS: T
35. The frequency of oscillation of an IMPATT diode depends on the resonant cavity it is in.
ANS: T
36. A YIG oscillator cannot be tuned.
ANS: F
37. A magnetron is actually a type of vacuum tube.
ANS: T
38. A magnetron is a high-power fixed-frequency oscillator.
ANS: T
39. A magnetron is easily tuned.
ANS: F
40. A klystron is a vacuum tube device used for high-stability amplification of microwave signals.
ANS: T
41. Klystrons can produce power in the megawatt range.
ANS: T
42. Traveling-wave tubes can oscillate, but not amplify.
ANS: F
43. Traveling-wave tubes are distinguished by their wide bandwidths.
ANS: T
44. A parabolic dish, like a dipole, is a type of antenna.
ANS: F
45. A parabolic dish is commonly used with a "horn".
ANS: T
46. A horn is a type of impedance matcher.
ANS: T
47. A horn is a type of antenna.
ANS: T
48. A piece of Teflon in front of a horn can act as a lens.
ANS: T
49. All radar devices rely on the Doppler effect.
ANS: F
50. Radar has a maximum range, but no minimum range.
ANS: F
51. Radar can discriminate between two targets that are in the same "line-of-sight".
ANS: T
52. Absorption and scattering by a target can reduce the effectiveness of radar.
ANS: T
MULTIPLE CHOICE
1. The microwave frequency range is considered to start at:
| a. | 100 MHz | c. | 10 GHz |
| b. | 1 GHz | d. | 100 GHz |
ANS: B
2. The UHF range is:
| a. | below the microwave range | c. | above the microwave range |
| b. | inside the microwave range | d. | same as the microwave range |
ANS: A
3. The dominant mode of a waveguide depends on:
| a. | the shape of the waveguide | c. | the point of signal injection |
| b. | the power level of the signal | d. | none of the above |
ANS: A
4. The dominant mode of a rectangular waveguide is:
| a. | TE 01 | c. | TE 10 |
| b. | TM 01 | d. | TM10 |
ANS: C
5. The dominant mode of a circular waveguide is:
| a. | TE 01 | c. | TE 11 |
| b. | TM 01 | d. | TM11 |
ANS: C
6. Circular waveguides use TM 01 mode because:
| a. | it is dominant | c. | it is the only mode possible |
| b. | of its circular symmetry | d. | it is more efficient |
ANS: B
7. The characteristic impedance of a waveguide:
| a. | is fixed |
| b. | depends on the frequency it carries |
| c. | depends on the longer dimension of its cross section |
| d. | both b and c |
ANS: D
8. Power can be coupled into or out of a waveguide:
| a. | with a magnetic field probe | c. | through a hole in the waveguide |
| b. | with an electric field probe | d. | all of the above |
ANS: D
9. Directional couplers for waveguides are characterized by:
| a. | their insertion loss | c. | their directivity |
| b. | their coupling specification | d. | all of the above |
ANS: D
10. Striplines and microstrips are used to:
| a. | couple sections of waveguide | c. | couple components on a circuit board |
| b. | couple waveguides to antennas | d. | none of the above |
ANS: C
11. A resonant cavity is a type of:
| a. | tuned circuit | c. | antenna |
| b. | defect in a waveguide | d. | none of the above |
ANS: A
12. A TEE connector used with waveguides is:
| a. | an H-plane TEE | c. | a "magic" TEE |
| b. | an E-plane TEE | d. | all of the above |
ANS: D
13. TWT stands for:
| a. | Transverse Wave Transmission | c. | Traveling-Wave Tube |
| b. | Transverse-Wave Tube | d. | Traveling-Wave Transmission |
ANS: C
14. An "isolator" is a device that:
| a. | isolates frequencies in a waveguide |
| b. | allows a signal to pass in one direction only |
| c. | separates signals among various ports |
| d. | prevents microwaves from leaking out of a waveguide |
ANS: B
15. A "circulator" is a device that:
| a. | rotates signal polarity in a waveguide |
| b. | allows a signal to pass in one direction only |
| c. | separates signals among various ports |
| d. | prevents microwaves from being "trapped" in a waveguide |
ANS: C
16. GaAs stands for:
| a. | gallium arsenide | c. | gallium astenite |
| b. | gallium assembly | d. | none of the above |
ANS: A
17. IMPATT stands for:
| a. | impact avalanche and transit time | c. | implied power at transmission terminal |
| b. | induced mobility at transmission time | d. | none of the above |
ANS: A
18. YIG stands for:
| a. | Yttrium-Iron-Gallium | c. | Yttrium-Iron-Garnet |
| b. | Yttrium-Iron-Germanium | d. | none of the above |
ANS: C
19. A YIG can be tuned by applying:
| a. | an electric field | c. | mechanical pressure |
| b. | a magnetic field | d. | an "exciter" signal |
ANS: B
20. The device commonly used in microwave ovens is the:
| a. | TWT | c. | magnetron |
| b. | klystron | d. | YIG |
ANS: C
21. The device commonly used in satellite communications is the:
| a. | TWT | c. | magnetron |
| b. | klystron | d. | YIG |
ANS: A
22. The device commonly used in UHF transmitters is the:
| a. | TWT | c. | magnetron |
| b. | klystron | d. | YIG |
ANS: B
23. A microwave phased array is often made using:
| a. | slots | c. | Fresnel lenses |
| b. | Yagis | d. | all of the above |
ANS: A
24. RADAR stands for:
| a. | radio ranging | c. | radio detection and ranging |
| b. | radio depth and ranging | d. | remote detection and ranging |
ANS: C
25. RADAR uses:
| a. | pulsed transmission | c. | the Doppler effect |
| b. | continuous transmission | d. | all of the above |
ANS: D
26. The maximum effective range for pulsed radar:
| a. | increases with increasing repetition rate | c. | decreases with increasing pulse period |
| b. | decreases with increasing repetition rate | d. | none of the above |
ANS: B
27. The minimum effective range for pulsed radar:
| a. | increases with increasing pulse duration | c. | is always a tenth of the maximum range |
| b. | decreases with increasing pulse duration | d. | none of the above |
ANS: A
COMPLETION
1. ____________________ is the effect of a pulse "spreading out" as it travels through a waveguide.
ANS: Dispersion
2. The electric field is ____________________ along the walls of a rectangular waveguide.
ANS: zero
3. The waveguide mode with the lowest cutoff frequency is the ____________________ mode.
ANS: dominant
4. In TE10 mode, the ____________________ field peaks in the middle of the waveguide cross section.
ANS: electric
5. In TE20 mode, the electric field has ____________________ peaks in the waveguide cross section.
ANS: two
6. In a circular waveguide, ____________________ mode is used because of its circular symmetry.
ANS: TM01
7. A waveguide acts as a ____________________-pass filter.
ANS: high
8. In a waveguide, group velocity is always ____________________ than the speed of light.
ANS: slower
9. In a waveguide, phase velocity is always ____________________ than the speed of light.
ANS: faster
10. In a waveguide, impedance ____________________ as frequency increases.
ANS: decreases
11. A ____________________ TEE is a combination of E-plane and H-plane TEES.
ANS: hybrid
12. The Q of a resonant cavity is very ____________________ compared to lumped LC circuits.
ANS: high
13. A wavemeter is a resonant ____________________ with an adjustable plunger.
ANS: cavity
14. A Gunn device oscillates because of its negative ____________________.
ANS: resistance
15. Both magnetrons and TWTs are slow ____________________ tubes.
ANS: wave
16. Both klystrons and TWTs are ____________________-beam tubes.
ANS: linear
17. A ____________________ antenna is just a waveguide with a hole in it.
ANS: slot
18. A ____________________ antenna is a flat piece of copper on an insulating substrate with a ground plane on the other side.
ANS: patch
19. The radar cross section of a target is typically ____________________ than its actual size.
ANS: smaller
20. The frequency of the returned signal will be ____________________ than the transmitted signal if the target is moving toward the radar antenna.
ANS: higher
SHORT ANSWER
1. Calculate the TE10 cutoff frequency for a rectangular waveguide if the longer dimension of its cross section is 5 cm.
ANS:
3 GHz
2. Calculate the group velocity in a waveguide carrying a signal that is twice its cutoff frequency.
ANS:
260 ´ 106 meters per second
3. Calculate the phase velocity in a waveguide carrying a signal that is twice its cutoff frequency.
ANS:
346 ´ 106 meters per second
4. Calculate the wavelength of a 2-GHz signal in a waveguide with a 1-GHz cutoff frequency.
ANS:
173 millimeters
5. Find the gain in dBi of a 10-GHz horn antenna with dE = dH= 60 mm.
ANS:
14.8
6. Find the maximum unambiguous range for a pulsed radar sending 10k pulses per second.
ANS:
15 km
7. Find the minimum unambiguous range for a pulsed radar sending 2-msec duration pulses.
ANS:
300 meters
1 comments:
Nicely Explained
waveguide components
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