IEEE Solid-State Circuits Magazine - Fall 2016 - 80

TABle 1. A CoMPAriSon BeTWeen eT AnD DP CirCuiT oPerATion
ChArACTeriSTiCS.
oPerATing
ChArACTeriSTiC

DP MoDulATion

Output signal envelope control Input RF signal

DPS

Input signal modulation

Only PM is needed

Precise, from specification

DPS accuracy

Low, when above a minimum

Critical always

Output power = 0?

No problem

Difficult

Power supply noise

Rejected

Passed through directly

Circuit stability

Critical and difficult

Unconditional

Thermal stability

Requires compensation

Unconditional

Energy efficiency

High

Higher (best possible for PA)

RF PA transistor operation

CCS (L-mode)

Switching (C-mode)

Device output matching

Complex conjugate

Real line, if any

Wideband noise, dominant
source(s)

PA noise figure and gain

Phase noise (RF input),
power supply

Input signal magnitude
accuracy

Critical

Anywhere within C-mode
range

Load current control

Regulated by the RF transistor

DPS and load impedance
accuracy

Envelope time alignment

Tight, if emphasizing
efficiency

Tighter

effectively a sampled data system,
where carrier half-cycles sample the
signal envelope. The timing of these
carrier samples contains the signal
phase information. Reconstruction
filters may or may not be needed to
get the desired output signal.
That is the case unless the signal
we are amplifying has multiple carriers. Then the Fourier transform
requires circuit linearity if we are
to avoid intermodulation among
the multiple carriers. This situation
occurs for any OFDM signal, for LTE,
and for other multicarrier amplifiers including CA. In this case,

FA L L 2 0 16

[3]

the operating requirements map
only on to ET, and not onto DP. It is
unfortunate that signal selection by
a standards committee restricts our
circuit implementation options. Yet
there it is. The more that we understand these constraints, the faster
we can develop competitive products in reasonable time.
Game on!

References

[1] E. McCune, "A technical foundation for
RF CMOS power amplifiers: Part 2," IEEE
Solid-State Circuits Mag., vol. 7, no. 4,
pp. 75-82, 2015.
[2] E. McCune, "A technical foundation for
RF CMOS power amplifiers: Part 3," IEEE

IEEE SOLID-STATE CIRCUITS MAGAZINE

[4]

[5]

[6]

[7]

Solid-State Circuits Mag., vol. 8, no. 1,
pp. 44-50, 2016.
E. McCune, "A technical foundation for
RF CMOS power amplifiers: Part 5," IEEE
Solid-State Circuits Mag., vol. 8, no. 3,
pp. 81-85, 2016.
F. Raab, P. Asbeck, S. Cripps, P. Kenington, Z. Popovic, N. Pothecary, J. Sevic, N.
Sokal, "Power amplifiers and transmitters for RF and microwave," IEEE Trans.
Microwave Theory Tech., vol. 50, no. 3,
pp. 814-826, Mar. 2002.
Z. Wang, Envelope Tracking Power Amplifiers for Wireless Communications. Norwood, MA: Artech House, 2014, Sec.
2.2, p. 54.
E. Lindberg, "The Barkhausen criterion (observation?)," in Proc. IEEE Workshop Nonlinear Dynamics of Electronic
Systems, Dresden, Germany, 2010,
pp. 15-18.
E. McCune, Dynamic Power Supply Transmitters. Cambridge, U.K.: Cambridge
Univ. Press, 2015, Table 6-2, p. 181.

About the Author
Earl McCune (emc2@ w ireless
andhighspeed.com) received his B.S.
degree from the University of California, Berkeley, his M.S. degree from
Stanford University, and his Ph.D. degree from the University of California,
Davis. His experience in RF circuits,
signals, and systems spans more than
40 years. He cofounded two Silicon
Valley startups: one doing direct digital synthesis beginning in 1986, which
merged with Proxim in 1991, and the
second, Tropian, doing switch-based
RF transmitters beginning in 1996,
which was acquired by Panasonic ten
years later. He has 83 issued patents
in the United States. He has authored
two books, Practical Digital Wireless
Signals and Dynamic Power Supply
Transmitters. He has been an IEEE
Microwave Theory and Techniques Society Distinguished Lecturer since 2013.

http://www.andhighspeed.com

Table of Contents for the Digital Edition of IEEE Solid-State Circuits Magazine - Fall 2016