Appendix
MESFET model used in SPICE simulations:
*generic GaAs MESFET; 1mm cell, Imax = 200mA
.model genfet gasfet level=2 beta=.310 vto=-2.5 alpha=2.0
*use model for internal cgs voltage dependency
* + b=3.0 lambda=.05 cds=.25pf cgs=.6pf cgd=.06pf rg=1
*set internal cgs, rg to small values to eliminate cgs variation
*rg, cgs now included in circuit file
+ b=3.0 lambda=.05 cds=.25pf cgs=.001pf cgd=.06pf rg=.001
*+ b=3.0 lambda=.05 cds=.0001pf cgs=.0001pf cgd=.0001pf rg=.0001
Notes
The Spice “b” model typically has default settings which give an “aggressive” voltage dependency to the cgs capacitance. The above listing indicates a method for removing this dependency. Most of the simulations in this book use a 10-mm device, which requires a factor of 10 scaling applied to this model. This gives a device capable of delivering about 35 dBm in a loadline matched Class A design.
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Selected Bibliography
The following books are recommended for further reading in related subject areas not fully covered in this book.
Cripps, S. C., RF Power Amplifiers for Wireless Communications, Norwood, MA: Artech House, 1999. Covers basic PA design at the circuit level and PA modes (referred to as RFPA throughout this book).
Harte, L., and S. Prokup, Cellular and PCS/PCN Telephones and Systems, APDG Publishing, 1996. An introduction and technical overview of modern cellular communications systems.
Kennington, P. B., High Linearity RF Amplifier Design, Norwood, MA: Artech House, 2000. A wide-ranging treatment of PA linearization topics.
Minnis, B. J., Designing Microwave Circuits by Exact Synthesis, Norwood, MA: Artech House, 1996. Detailed treatment of broadband microwave circuit synthesis methods.
Ojanperä, T., and R. Prasad, Wideband CDMA for Third-Generation Mobile Communications, Norwood, MA: Artech House, 1998. Introduction and comprehensive treatment of 3G communications systems.
Pothecary, N., Feedforward Linear Power Amplifiers, Norwood, MA: Artech House, 1999. Specific coverage of feedforward techniques, emphasis on practical system issues.
Glossary
ac Alternating current; term used generically to describe any sinusoidal signal
ACP Alternate channel power; term used more generally to describe the spectral distortion of spread spectrum signals, which appear as continuous bands
ADC Analog-to-digital converter
AGC Automatic gain control
AM Amplitude modulation
AM-AM Term used to describe gain compression in an amplifier, whereby a given increase in input signal results in a different change in the output level
AM-PM Amplitude modulation to phase modulation; a distortion process in a power amplifier, whereby increasing signal amplitude causes additional output phase shift
BER Bit error rate; a measure used to quantify the transmission integrity of a digital communications system
BJT Bipolar junction transistor
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CAD Computer-aided design
CDMA Code division multiple access; a digital communications system which “chips” multiple signals in a pseudo-random fashion, making them appear like random noise unless a specific coding is applied
DAC Digital-to-analog converter
DPA Doherty power amplifier
DQPSK Differential quadrature phase-shift keyed; a variation of QPSK
DSP Digital signal processing
ECM Electronic countermeasures; a generic term for military broadband microwave applications
EDGE Enhanced Data rates for GSM Evolution; an evolution of the GSM system, providing data rates up to 384 Kbps
EER Envelope Elimination and Restoration
EPA Error power amplifier; used in feedforward loop
EPR Ratio, usually expressed in decibels, of main PA power to EPA power; higher values imply higher system efficiency
EVM Error vector magnitude; a more comprehensive measure of amplifier distortion which incorporates both gain compression and AM-PM
FET Field effect transistor
GaAs Gallium Arsenide; one member of a group of useful semiconductor materials which are compounds between group 3 and group 5 elements in the periodic table. These materials show higher mobility and higher saturation velocity than silicon and are therefore used in higher frequency applications.
GaN Gallium Nitride; a newly emerging semiconductor material for highpower, high-frequency applications
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GSM Global System for Mobilecommunication; most extensively used worldwide digital cellular network operating in the 900-MHz and 1,900MHz bands
HBT Heterojunction bipolar transistor; most common variation of bipolar device used for higher frequency applications
HEMT High electron mobility transistor; an FET device in which a “sheet” of high-mobility material is created by the interaction between two epitaxial layers
IF Intermediate frequency
IM, IMD Intermodulation distortion
LDMOS Laterally diffused metal oxide semiconductor; derivative of silicon RF MOS technology for higher frequency applications
LINC Linear amplification using nonlinear components
LO Local oscillator
LUT Look-up table
MCPA Multicarrier power amplifier
MIC Microwave integrated circuit; a term used in the pre-MMIC/RFIC era to describe a miniaturized chip-and-wire microwave hybrid circuit technology
MMIC Microwave monolithic integrated circuit; a term now used, by convention, to describe monolithic integrated circuits which operate above 3 GHz
MOS Metal oxide semiconductor; usually silicon-based semiconductor technology
NADC North Americal Digital Cellular; original digital cellular system used in the United States
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PAE Power-added efficiency; efficiency definition for an amplifier which accounts for the RF input drive
PEP Peak envelope power
PHEMT Pseudomorphic high electron mobility transistor; a higher frequency variant on the HEMT
PUF Power utilization factor; a term introduced in RFPA to define the “efficacy” of a PA design; defined as the ratio of power delivered in a given situation to the power delivered by the same device with the same supply voltage in Class A mode
QPSK Quadrature phase-shift keyed; a generic term for a variety of modulation systems which carry information only in the phase, not the amplitude, of the RF carrier
RFIC Radio frequency integrated circuit; a monolithically integrated device operating in the “RF” range, typically up to 3 GHz
RFPA Radio frequency power amplifier
RRC Raised root cosine; a filter of the Nyquist type, which allows a QPSK signal to be bandlimited without losing any modulation information
SCSS Short-circuited shunt stub; a distributed matching element used at microwave frequencies
SiC Silicon Carbide; a semiconductor material which offers high voltage and high velocity saturation but low mobility; potentially useful as a high power RF device technology in the low gigahertz frequency range
SPICE A general-purpose time domain nonlinear simulator, available in many implementations including shareware
SSB Single sideband; a variation on AM developed in the 1950s, in which only one modulation sideband of an AM signal is transmitted
WCDMA Wideband CDMA; a 3G system (e.g., “UTRA,” or “UMTS”), based on CDMA, with data rates up to 2 Mbps