AN-808
APPLICATION NOTE
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ABSTRACT
The goal of this application note is to determine the
feasibility of implementing a multicarrier CDMA2000
transceiver and what the major subsystem performanc-
es must be.
GENERALIZED BLOCK DIAGRAM
The block diagram in Figure 1 is the general block
diagram used in this discussion. While there are many
variations of this design, the key focus is on this ar
chi-
tecture, which represents a flexible radio platform that
can easily implement a wide variety of air standards
including WCDMA, CDMA2000, and TD-SCDMA.
Multicarrier CDMA2000 Feasibility
by Brad Brannon and Bill Schofield
MAIN RECEIVE SIGNAL PATH
FREQUENCY
ADF4106/
ADF4360
Rx SYNTHESIZER
MIXER
MIXER
LNA
BPF
LNA
BPF
AD8369
BPF
BPF
Tx/Rx
14-BIT
ADC
4/6DDC
AD6654
AD9246
AD9445
AD9446
14-BIT
ADC
4/6DDC
AD6636
ADF4106/
ADF4360
Rx SYNTHESIZER
ADL5330
AD9779
PREAMP
MCPA
VGA
POWER DETECT AND CONTROL
BPF
0�
90�
LPF
LPF
DAC
DAC
AD6633
BASEBAND
PREDISTORTION
4/6 DUC
W/PPR
ADC DDC
AD9430
BPF
ATTEN
DIVERSITY DRIVE SIGNAL PATH
TRANSMIT SIGNAL PATH
PA MONITOR PATH FOR
DIGITAL PREDISTORTION
DANUBE
TigerSHARC
®
DSP
DSP
MODEM
MODULATOR
ANTENNA
BPF
AD6654
AD9246
AD9445
AD9446
Figure 1. ADI Wideband Multicarrier TRX Common Platform CDMA2000/WCDMA/TD-SCDMA
Some variations of this architecture include high or low
IF sampling as well as direct conversion for receive.
Although the latter is not feasible for multicarriers today,
it is acknowledged as the low cost, high performance
solution of the near future. In the transmit path, direct
RF modulation is feasible for most applications if some
amount of in-phase and quadrature (IQ) balance is pro-
vided. Direct RF modulation represents the lowest cost
transmit path. For applications requiring high perfor-
mance without an IQ balance network, superheterodyne
IF upconversion is another excellent option.
REV. 0
