Power Amplifier Hybrid Design

							Power Amplifier Hybrid Design
              ECE 191
         October 7th, 2004
     Sponsor: Northop Grumman
      Mentor: Matthew Bredel

      Group1: Mark Manglicmot
          Eric Torkildson
                        Agenda
   Power Amplifier
     – Hybrid PA
     – Why LDMOS
     – Load-pull test fixtures

   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 :
     –   Advantages:
              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
              Load Pull Test Fixture
   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.




       Typical Load-pull setup                                        Extracted Data
            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,
            red) to a 50Ω load
            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
                        Matching                   Matching          RLoad~
                                                   Network           50 Ω
          VSOURCE       Network




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



Gantt Chart (Schedule)