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.
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Note: Many answers contain passages quoted in whole or in part from the text.
quiz is based on the information presented in
Envelope Tracking Power Amplifiers for Wireless Communications, by Zhancang Wang.
"Envelope tracking technology is seen as the most promising efficiency enhancement technology for RF PA for 4G
and beyond wireless communications. More and more organizations are investing and researching on this topic with huge
potential academic and commercial values. This is the first book on the market to give complete introduction, theory,
and design considerations on envelope tracking for wireless communications. This resource presents microwave design
engineers with a full introduction to the subject and covers underlying theory and practical design considerations.
Note: Some of these books are available as prizes in the monthly
RF Cafe Giveaway
I am continually amazed at the brilliance of people who work tirelessly to advance the state of the art of technology,
medicine, transportation, and many other areas. They manage to succeed in spite of myriad obstacles placed in their
collective way by infuriating levels of government regulation and government-imposed societal manipulation
(e.g., political correctness). Scanning through the many engineering books I receive
from Artech House, Cambridge University Press, et al, is a truly humbling experience as I witness the incredible talent
and determination of my fellow humans. We owe them a great debt of gratitude. This book is a prime example of which
On a comical note, I noticed that the translation to English while overall excellent, did produce some notable
instances where similes did not come out quite right; e.g., on page 100 the description of something being 'the short
pole' [in the tent] came out as "'the short board' to limit overall ..." Being the 'long pole' in the tent is often
also used (but not in this book).
1. What happens to the power from an RF amplifier's DC power supply?
a) It gets converted to heat
b) RF amplifiers do not use DC
c) It is unaffected
It gets converted to RF power
2. What are the two types of efficiency definitions for an RF power amplifier?
a) Thermal efficiency and layout efficiency
b) Power added efficiency (PAE) and drain/collector
c) RF efficiency and volume efficiency
d) Time domain efficiency and frequency domain
3. Where did the Class S power amplifier get its name?
a) It falls between the Class R and Class T amplifier topologies
b) The 'S comes from its founder's
(A.M. Sandman) last name
c) The 'S' stands for 'sizzling' hot
d) The 'S' emphasizes the plurality
of the topology
4. What is the distinguishing feature of a Doherty amplifier?
a) It operates in Class-D mode
b) Low cost
c) It doe snot require an external power source
d) Load impedance varies according to the power level
5. What makes envelope tracking (ET) so attractive in mobile communications?
a) High efficiency over a wide range of power levels
b) It can operate on LiPo batteries
Operates from DC to light
d) It is popular amongst space alien believers
6. What is the name given to the diagram that portrays the parameter tradeoff in envelope tracking
a) Eye diagram
b) I-Q modulation plot
c) Envelope tracking merit pyramid
(envelope tracking parameter tradeoff diagram)
7. What is the overall envelope tracking system efficiency most dependent upon?
a) Accurate delay compensation between the RF signal and the envelope power supply
c) Inductor 'Q'
d) Ambient temperature
8. When is the nonsynchronous impedance transformer a good option for use?
a) With synchronous communications systems
b) When a synchronous transformer is too expensive
c) In applications where a ¼-wave transformer is physically too long
d) When cost is the primary
9. What is a common method used in digital front ends (DFEs) to mitigate efficiency degradation
due to high peak-to-average-power-ratio (PAPR) signals?
a) Software Defined Radio (SDR)
b) Linear modulation
c) Digital modulation
Crest factor reduction (CFR) algorithms reduce PAPR before entering the RF power amplifier stage
10. How does envelope tracking (ET) boost RF PA efficiency?
a) By using high capacity batteries
b) By replacing a fixed DC supply with a dynamic supply voltage
that tracks the RF envelope shape
c) By assigning a location code for online data package tracking
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