文档介绍：Power Amplifier Design
RF & work Design Basics
——Master’s Course Seminar
Lecturer: Wu Qun (Prof.,.)
硕士学位课系列讲座 March 2003
-1-
Agenda
z Introduction
z Overview of RF Design
Process
z Case Study: RF Front-End
− Power Amplifier
z Measurement for Design
− Active Device Parameter
Extraction
z Summary
硕士学位课系列讲座 March 2003
-2-
Power Amp Design
GHz PCS-Band Amplifier
z Gain > +24 dB
z 1-pression > +25 dBm
z Psat > +27 dBm
Main challenge: designing for maximum power output
During brainstorm process, decided:
z two stages needed to get desired gain
z stage one:
Îsilicon transistor
Îpassive bias
z stage two:
driver power
Îpower FET stage stage
Îactive bias
硕士学位课系列讲座 March 2003
-3-
Bias Considerations - Active vs. Passive
z passive - simpler, less space, cheaper but not as well controlled
z active - extra circuitry, but more repeatable
z hint: watch out for over-biasing junctions (FET gate-bias example)
changed to -6V to prevent gate
over-voltage condition
硕士学位课系列讲座 March 2003
-4-
Designing the Output Stage for
Maximum Output Power
z output impedance varies as function of output power
z ideal impedance exists for maximum output power
z two technique provides information for output-stage matching
; load-pull technique
; load-line analysis
Low power
S 22
High power
硕士学位课系列讲座 March 2003
-5-
Load-Pull Technique
z vary magnitude and phase of load presented to circuit
z power output is measured at each impedance point
z can use behavioral model (based on measurements)
Input Output
impedance impedance
and and
Pmax
power power
measurement measurement −1dB
system system −2dB
−3dB
X X
X X DUT
Input Output
Tuner Tuner
Constant output power contours
Can be very expensive and time-intensive versus output load impedance
(input power constant)
硕士学位课系列讲座 March 2003
-6-
Load-Line Analysis
z determines resistance that gives highest power
z curr