blake_ch17.pdf

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Chapter 17: Microwave Devices

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 injectionb. 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 possibleb. 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 sectiond. 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


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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 onlyc. 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


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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. magnetronb. 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 rangingb. 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


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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.


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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.


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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 d E = d H = 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-µsec duration pulses.

ANS:300 meters

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