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Wireless Communications Fundamentals
Answers to RF Cafe Quiz #6

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All RF Cafe quizzes would make perfect fodder for employment interviews for technicians or engineers - particularly those who are fresh out of school or are relatively new to the work world. Come to think of it, they would make equally excellent study material for the same persons who are going to be interviewed for a job.

Some of these books used in quizzes are available as prizes in the monthly RF Cafe Giveaway.

Note: Many answers contain passages quoted in whole or in part from the text.



Return to RF Cafe Quiz #6


1. Which of the following WLAN standards is on a different frequency band than the others?

a) 802.11a

802.11b/g/n are all in the 2.4 GHz ISM band, 802.11a is in the 5 GHz ISM band.



2. What does the term "ruggedness" refer to in wireless power amplifiers?

c) Ability to withstand load mismatch

A typical ruggedness spec is no damage into a 10:1 VSWR load



3. Which FCC regulation governs the unlicensed ISM band?

a) Part 15

FCC Part 15 governs the unlicensed ISM band for intentional, unintentional, and incidental radiators.



4. In which semiconductor technology are the majority of cellphone PAs manufactured?

c) GaAs/InGaP

Many WLAN PAs are built in SiGe and Si, and one or two experimental phone PAs are being built in Si, but the vast majority of phone PAs are built in GaAs HBT or InGaP HBT.



5. What is a major advantage of LTCC substrates?

d) All the above

Because of the high dielectric constant of the material, relatively large distributed components can be integrated into the substrate, which decreases the number of discrete components needed. The higher thermal conductivity also helps with heat dissipation.



6. Which phone standard supports the highest data rate?

c) EDGE

iDEN=64kbps, GPRS=21.4kbps/time slot, EDGE=384kbps, GSM=14.4kbps



7. Which component is typically not part of a front-end module (FEM)?

a) Power amplifier

Transmit modules (TxM) incorporates a FEM + PA



8. Which two systems are most likely to experience concurrent operation problems?

b) Bluetooth + WLAN

Bluetooth and WLAN (802.11b/g/n) both operate on the 2.5 GHz ISM band.



9. An isolator is typically required at the output of the PA for which transmitter system

d) CDMA/W-CDMA

CDMA/W-CDMA power amplifiers, due to their highly linear region of operation, cannot tolerate a very high mismatch (VSWR) and must be protected with an isolator.


10. What is the commonly claimed nominal operational range for Bluetooth?

d) All the above

Sure it's stupid (and true), but a little levity in an interview can lighten the load.
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