Power Amplifier Hybrid Design

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```							Power Amplifier Hybrid Design
ECE 191
October 7th, 2004
Mentor: Matthew Bredel

Group1: Mark Manglicmot
Eric Torkildson
Agenda
   Power Amplifier
– Hybrid PA
– Why LDMOS

   Mathematical Foundation needed
– S-parameters
– Smith Charts
– Impedance matching

   Goals for this week
Power Amplifier
   Hybrid Design:
–   Self-contained unit (i.e. stand alone black box)
–   Essentially “plug and play” feature

   LDMOS
–   Functions exactly like a regular FET, but with high
frequency features :
   2W-120W output range while operating at
frequencies up to 960MHz
   Simpler Biasing circuits
   Higher power gain
–   Lateral structurevery low feedback capacitance
compared with BJT:
–   Power gainCFB and LSOURCE
   Provides an efficient (yet tedious) way to find optimal settings for input/output matching
networks to optimize:
– PA power gain, efficiency, and other governing properties of PA’s as a function of
impedance

Eff.= η=Pout/Pin , ; Gain=Vout/Vin

Note: Gain match (i.e. conjugate match) does not necessarily lead to optimal power
match. Also, constant power contours are not circular; unlike noise and linear
mismatch (gain) circles.

Scatter Parameters
•   S parameters, like Y or Z
parameters, describe a
two-port’s linear            a
1
TWO PORT
a
2
performance completely.             b1   NETWORK     b2

•   Easier to measure and
work with at high
frequencies                      b1   S 11 S 12  a1 
b2  S 21 S 22 a 2
•   Represent reflection and                         
transmission coefficients.

b1  S11a1  S12a 2
b 2  S 21a1  S 22a 2
Matching Networks

Output Matching
Input Matching
ZIN                ZOUT

Transistor
Network

Network
Z1
Z2

ZIN*                 ZOUT*

• Matching networks help to achieve maximum power gain.
• Transform Z1 to ZIN*, and Z2 to ZOUT*, maximizing gain to the load.
The Smith Chart
 Representation of Γ=(Z-
Z0)/(Z+Z0)
 Allows complex
equations to be solved
graphically in seconds.
 Simplifies impedance
matching.
Smith Chart Basics
 Any impedance value
(+resistance & reactance) can
be plotted
 Green circles: constant
resistance
 Red arcs: constant reactance
– Arcs above centerline: +jX,
inductive reactance
– Arcs below centerline: -jX,
capacative reactance
Smith Chart Matching
 We want to match some
impedance (Z = .8+j.8,
impedance (Z=1, blue).
 Use C’s, L’s, or
microstrip lines to match.
Microstrip Transmission Lines
•   We will utilize microstrip
matching networks.
•   Microstrip impedance is
determined by geometry.
•   We may also use
capacitors to help meet the
matching goals, and stay
within the circuit’s area
limits.
Goals for this week!
   Begin simulations using Microwave Office.
– Determine optimal input and output matching circuits
– to utilized quarter-wavelength theory we will be cascading 2 or 3
TML for each network!
   Complete initial simulations and get ready for layout
by 10/15
50Ω

Input                      Output
DUT
Network           50 Ω
VSOURCE       Network

Z01’                       Z01
Z03’                     Z03
Z02’                      Z02
Project: Power Amplifier Hybrid Design

Gantt Chart (Schedule)

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