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RF CMOS Products for Cellular Phone Applications Challenges and

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RF CMOS Products for Cellular Phone Applications Challenges and Powered By Docstoc
					           RF CMOS Products for Cellular Phone Applications:
                 Challenges and Architectures
           European Microwave Week 2004
Infineon
           Workshop GAAS01




           Christian Münker
           Infineon Technologies AG
                           outline
! Overview of cellular RF markets and requirements
   ! technology comparison of BiCMOS and CMOS RF
! GSM CMOS RF transceiver
   ! GSM CMOS RF transmitter
   ! GSM CMOS RF receiver
! Future trends
Technology progress in transit frequenz ft and maximum frequency fmax
as driver for RF-ICs for consumer applications on the mass market

                       1000




                                        Bipolar: ft & fmax                                                                                                 Auto radar

                                        doubling within 18 month
                       100
                                        = Moore‘s Law                                                                                               WCDMA, WLAN




                                                                                                            GSM1800 & DECT / Bluetooth
    ft & fm ax (GHz)




                        10

                                                                                   TV-VHF/UHF Tuner / GSM900




                         1


                                                                     TV-VHF Tuner
                                                                                                     CMOS: ft & fmax fast increase since 1980

                                                                                                     now stagnation of fmax
                        0,1              MW/SW & TV-IF
                          1970   1972    1974   1976   1978   1980   1982   1984    1986   1988 1990      1992   1994   1996   1998   2000   2002   2004   2006   2008   2010
                                                                                                   Year

                                                                        Bip (ft)      Bip (fmax)      CMOS (fT)         CMOS (fmax)
        Infineon 120nm CMOS Technology

•   120 nm RF Transistor with fT > 100 GHz (VDD=1.5V)
•   Oxide thickness 2.8 nm
•   400 nm analogue I/O Transistor (VDD=2.5V)
•   6 copper layers up to 550 nm thick
•   MIM CAP (2 fF/um2 )
•   Diffusion and Polysilicon Resistors
                    GSM RF Transmitter Architectures


                                             Polar modulation techniques
 Quadrature            Sigma-Delta
  modulators            modulators         Polar modulators    Polar transmitters

IF modulation /
 upconversion          Σ∆ modulation PLL   Σ∆ modulation PLL   Σ∆ modulation PLL
                       with PM modulator   with AM modulator   with PA modulation
Direct modulation

    offset LO
                                                  EER techniques

 LO frequency
   division                                   Polar loop           Polar loop
                                               modulator           transmitter

 Cartesian loop
  transmitter
             Linear Modulation Architectures

High data rates require linear modulation techniques using
  e.g. 8PSK, QAM 64, OFD (opposed to GMSK):


         Problems of Linear Transmit Architectures

•   PA Feedback to VCO: Leakage of modulated TX signal back into
    VCO creates sidebands
•   Stringent requirements for GSM / EDGE Transmit Noise in
    Receive Bands:
      – GMSK: -162 dBc/Hz (20 MHz Offset)
      – 8PSK: -157dBc/Hz (20 MHz Offset)
•   Each signal processing step after transmit signal generation (VCO)
    is extremely critical concerning noise and consumes a lot of current
Direct modulation architecture (LO frequency division)
                                        VGA for ramping
                  I                     and power control


                            ÷4                                        to
                  LO1
                                                                   antenna
                  Q                                        PA       switch
                                                        (linear)



                        h3 filter


      Direct modulation with LO division (usually by 2 or 4) is very
         suitable for highly integrated low cost solution:
      ! Provides very wide band, well defined 0/90 degree relation
      ! Only one synthesizer needed
      ! But: This concept is sensitive to PA feedback (harmonics)
Direct modulation architecture (LO frequency division)
                                            Direct modulator output spectrum



      power spectral density
                                                         nonlinear conversion


                                                                                h3 product
                                 3
                               IM product
                                                      wanted signal


                                                 f0                                          3 f0
                                                           frequency




      • Spectral regrowth due to H3
        conversion
                            Polar transmitter
                                            crystal                                      PA
                                             clock                                (switched mode)


                                                                  PD         LF                   to
                                          26 MHz                                               antenna
                                                                                                switch
                                                                  multi modulus
                                 channel                             divider
                                  word
                                                                         N
                                φ(t)                       f(t)
                 digital                            d/dt          Σ∆ modulator
               modulator
  transmit
                  and
    data
                 pulse   A(t)           AM/PM
                shaping                correction


  power ramping and
                                        AM/AM
  power level control
                                       correction                 DAC


! Not seen in mass production of cellular phones so far
! Huge dynamic range for PA control (power level + modulation rang
! Matching of amplitude / phase path is essential
! AM/PM and AM/AM modelling needed over temperature / productio
             Comparison of modulation techniques

                Quadrature      Sigma Delta   Polar        Polar
                                Modulation    Modulation   Transmitter

preferred       BiCMOS          CMOS RF       CMOS RF      CMOS RF
technology
Chip cost       high            low           low          Low


System          High            medium        medium       Low
BOM             Filter/shield                              nonlinear PA
EDGE            yes             No            yes          yes
capability                      GMSK-only
High Performance RX Front Ends for RF
              in CMOS

• Direct conversion receiver is preferred architecture for both BiCMOS
  and CMOS GSM systems (low BOM / no SAW filters)
• Critical performance parameters for RX front ends in CMOS are
    –   flicker noise
    –   matching
    –   low break through voltages
    –   low gm/I ratio / low driving capability
    –   complicated ESD and latch up security
    –   substrate crosstalk when bulk CMOS is used

• CMOS front-ends are complicated to do, but with a good system
  approach, design and layout very good results are achievable
      Challenges for CMOS Receivers
• Improvements of RF Receivers in CMOS processes
   – potential implementation of self alignment procedures to overcome
     process variation issues
   – due to high speed digital, signal processing can be done closer to
     the antenna, thus shrinking of RX is enabled
   – availability of very fast CMOS devices: 0.13µm ft=100GHz


• But: remaining RF building blocks are even more
  challenging:
   – LNA: power gain, cross talk sensitivity and matching to 50Ohms
   – Mixer: dynamic range, driving level for switching transistors for
     optimum noise,
   – flicker noise optimization
  Design Issues for CMOS RF Receivers
• Even in a highly digitized radio
  two complicated building
  blocks remain in the receiver
                                                       LO-Q

    – LNA




                                                                          Signal Processing
                                                              LPF   A/D
        •   power gain
        •   noise figure                PAD         Mixer
                                              LNA
        •   matching to 50 Ohms
        •   ESD                                               LPF   A/D


                                                       LO-I



    – Mixer
        •   flicker noise performance
        •   IP2
        •   headroom with low supply
            voltage
    High Performance RF CMOS Receivers
•    Potential solutions for LNA:
     –   Trans-impedance amplifiers
         •   good noise performance
         •   good crosstalk performance
         •   higher current consumption
         •   limited headroom
         •   low area consumption
     –   Coil LNA´s
         •   good noise performance
         •   limited crosstalk
             performance due to inductive
             coupling
         •   lower power consumption
         •   improved linearity
         •   larger die area
                                            Trans-impedance
     –   Only coil LNA achieves
                                                amplifier
         sufficient performance
Results CMOS Sigma Delta GSM Transceiver

                  Features:
•   Direct Conversion RX and TX
•   Supported Bands 850/900/1800/1900 MHz
•   Internal RX and TX VCO
•   Σ∆-Modulation Loop for GMSK
•   Constant gain receiver for 14 bit ADC
•   Part of complete GSM/GPRS Platform
•   48-pin VQFN Plastic Package
Sigma-Delta Transceiver block diagram
          Sigma-Delta Transceiver block diagram

           Digital Part                              Base-      I/IX    Q/QX

                                                     band
 CLK
 DA          3 Wire Bus Interface                                                   850/900
                                                                                     MHz
 EN


                                    Frequency Word
Digital
                   Gauss                                                       ÷4
 TX       FIFO     Filter
                                    MOD   MASH                                        RX
Data
                                                                               ÷2

                        Timing &                             VCO Band
          OLGA
                       Measurement                            Select
                                                                                    1800/1900
                                                                                      MHz



PLL
                                      MMD
                                                                                     800/900
                                                                               ÷2
                                                                                      MHz
26 MHz
                 PFD     CP
                                     Loop Filter
                                      (external)
                                                              3.8 GHz                TX
                                                                VCO                 1800/1900
                                                     VTune                     ÷4
                                                                                      MHz
Delta-Sigma Frac.-N PLL Modulation Loop
                                                   loopfilter
               ref(t)                    iCP(t)                               vco(t)
                             phase                              uT(t)
                            detector
                                                                        VCO            driver


                          div(t)              multi modulus
                                                 divider



                                                  delta sigma
                                                    MASH
                                                            target
                                        modulation       frequency
   bits gaussian        predistortion
          filter            filter                    +
                                           channel
                                                                        fref = 26 MHz
                                                                        20 bit accuwidth in MASH
Concept of Predistortion Filter
             u ref ( t )
                                       iCP ( t )        uZ ( t )              uout ( t )
             φref (t )
                                                                                  φ out ( t )


                           udiv (t )

                           φdiv (t )
 data
                                                                   (N   mod , j   )
                                                      ∆Σ
 (α i )
 y channel



               Φ out (s )                               1
                          =N⋅                                      = N ⋅ G (s )
               Φ ref (s )     1+
                                                       N     s
                                                   K P KVCO Z (s )


          fout (s ) = Nmod (s ) ⋅ fref ⋅ G(s ) ⋅ G(s ) = Nmod (s ) ⋅ fref
                                                                    −1
Voltage Controlled Oscillator Core




            •   Differential Cross Coupled
            •   MOS Tuning Element
            •   VCO gain 60 MHz +/-10%
            •   1300 MHz frequency range
                        VCO Frequency Band Select
                                  10 Bit VCO: Frequenz vs. Binärwort

                 4100




                 3860
Frequenz [MHz]




                 3620




                 3380




                 3140




                 2900
                        0




                            128




                                  256




                                           384




                                                    512




                                                             640




                                                                       768




                                                                             896




                                                                                   1024
                                                 Binärwort


                    Frequency Accuracy: 2 MHz per bit
                 Loop Dynamic Requirements




                                                400 kHz
          power spectral density
              [dBc/Hz]                                    -90 ... -95 dBc/Hz

                                                          app. -111 dBc/Hz
                                   MARGIN




                                       frequency offset


⇒ high loopfilter suppression needed at 400 kHz,
  but the modulation needs to have a wide bandwidth!
Driver Amplifier

  • Differential Output
    – 1.5 V Supply Voltage
    – Drives 50 Ohm Load
    – Broadband (flat over band)
    – Low Noise

  • Separate 900/1800 MHz Outputs
    – 8.5 dBm @ 900 MHz
    – 8 dBm @ 1800 MHz
           SD Modulation Spectrum




High margin to GSM Specification due to low phase noise
                  PLL Settling Time
                      Marker 1 [T1]   66.46154 # s   CF      900 MHz    Error Signal
            Ref Lvl   Phase              0.68 deg    SR   270.833 kHz   Phase
                d
             10 dBm                                                     Standard      GSM

       25
                                                                                              A
 PHASE




                                                                                             TRG
  "




      T1
                                  1




                                                                                   TS2→
            TS1
      -25
            0 s                              TIME                                  180 # s




analog PLL settling time < 80 µs
Chip Photograph


      TX


      RX-Filter
                  LNA


VCO
          Performance Summary
                    GSM850/GSM900     GSM1800/1900
Gain                    57 dB                57 dB
Noise Figure            2.6 dB                3 dB
1 dB Compression        -22 dBm             -22 dBm
IIP2                    50 dBm              50 dBm
RX Phase Noise        -129 dBc/Hz          -123 dBc/Hz
 @ 600 kHz
TX Phase Noise         -96 dBc/Hz       -100 dBc/Hz
 @ 40 kHz            < -162 dBc/Hz     <-157 dBc/Hz
 @ 20 MHz
Phase error              1.4 °               1.6 °
TX Output Power        8.5 dBm               8 dBm
Power consumption
  TX                              210 mW
  RX                              250 mW
                     Future trends

  Reconfigurability for Multi Mode / Multi Function
4 Terminals
Talk/Voice Centric
                           Browse                     Computer




Audio                                                      TV
                            UNIVERSA
                                L
                            WIRELESS
                             MODEM



                                                       Games



               Video
    Single chip CMOS Multiband/Multimode Transceiver
Transmit/Receive Bands:   Single-Chip Transceiver
                          (Digital & HF Frontend)
 RX: 800 - 2200 MHz
                                RX DFE              ADC   RX analog
 TX1: 776 - 958 MHz
 TX2: 1710 - 1990 MHz

Standards:
 GSM/EDGE
 UMTS
 CDMA2000/IS95




                            TX DFE                  DAC   TX analog

				
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posted:10/18/2011
language:English
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