ANALOG DEVICES AD6644, AD6624, AD6622, AD9754 Service Manual

ENABLING TECHNOLOGY FOR
NEXT-GENERATION SOFTWARE
BASE STATIONS

Analog Devices introduces the latest in Direct IF

Sampling (DIFS) and Direct Digital Synthesis

(DDS) technology to reduce the cost, size, and

power of traditional multicarrier radios.

Finally, the dynamic range barriers in converter

technology have been overcome to permit

an entire 25 MHz spectrum to be digitally

processed. Incremental RF carriers are easily

added (or reprogrammed) for most air interface

standards.

APPLICATIONS

Micro/Pico Cell Transceivers

In-building Wireless Base Stations

Wireless Local Loop

Software Programmable Base Stations

Phased Array Antenna Systems

Analog Devices’

SoftCell chipset cuts

the component

count for wireless

base stations.

AD6644/AD6624/AD6622/AD9772

RECEIVE SIGNAL PROCESSOR FEATURES

• Single Analog-to-Digital Converter (ADC) digitizes 25 MHz spectrum:
replaces multiple radios for reduced size and cost

• AD6644 14-bit 65 MSPS ADC: samples multiple channels with 100 dB
dynamic range and 75 dB SNR

• AD6624 Quad Digital Receive Signal Processor: four independent digital
receivers on a single chip, replacing expensive analog tuners and filters

• Digital tuner/filters are programmable for AMPS, IS136, GSM, EDGE,
PHS, and NMT. Noninteger decimation rates allow multiple air interfaces
within a single chipset

TRANSMIT SIGNAL PROCESSOR FEATURES

• Direct Digital Synthesis eliminates multiple analog modulators and the
matching problems they present

• AD6622 Quad Digital Transmit Signal Processor: independently
interpolates, filters, tunes, and combines four carriers per chip

• AD9772 14-bit 2X interpolating 400 MSPS TxDAC

®

: optimized for high

dynamic range and low distortion in a multicarrier environment

• Programmable channel filtering using linear I and Q inputs or pulse
shaping for most air interface standards

SOFTCELL™MULTICARRIER TRANSCEIVER CHIPSET

FLEXIBLE AND
PROGRAMMABLE

Analog Devices’ versatile design
enables you to manufacture
base stations for a variety of air
interface standards—using the
same core elements.

Software receivers can be
tuned to different channels and
modulation standards without
expensive hardware changes.
This all-digital approach can
also be used for fixed-access
receivers in wireless local loops.

FUTURE-PROOF
ARCHITECTURE

Once deployed, base stations
using these programmable
receivers can be readily recon­figured by network operators to
adapt to standards as they
evolve. SoftCell allows your
customers to take some of the
guesswork out of future net­work planning. As new micro­cells and picocells are added to
increase network capacity,
operators can easily implement
new frequency plans through
software.

Direct IF Sampling and
Direct Digital Synthesis plat­forms offer a flexible environ­ment for 3G developments,
including IS95 and Wideband
CDMA air interface standards.

In transmitters, the AD6622
can be configured to support
IS95 (including transmit pre­distortion phase equalizer) and
5 MHz WBCDMA signals. Digital
receivers for 1.25 MHz to 5 MHz
carriers will be supported in
follow-on products to the
AD6624.

INNOVATIVE DESIGN SAVES
TIME AND MONEY

Analog Devices’ all-digital
approach enables RF channels
to be consolidated within a
single ADC. The front-end
section is therefore smaller and
less expensive to manufacture.

Channel-select filtering takes
place in the digital signal
processor.

Characteristics for band­width, passband ripple, and
stopband rejection are speci­fied through software, rather
than by sensitive and costly­to-produce analog filters.

By reducing front-end filter­ing requirements, this chipset
solution cuts assembly costs
and eliminates the need for
extensive factory adjustments
of analog components.

COST-EFFECTIVE FOR MULTI­CHANNEL SYSTEMS

With a single AD6644 ADC
digitizing an entire 25 MHz of
spectrum, this advanced wide­band receiver can deliver a
lower cost-per-channel than
traditional receivers.

The AD6622 and AD6624
are optimized for four-channel
applications.

To increase capacity, simply
add digital transmit/receive
chips to provide additional RF
channels.

This easy add-on capability
makes Analog Devices’ SoftCell
ideal for high-volume, multi­channel cellular systems. As
the number of channels
increases, the cost per channel
is reduced because of shared
hardware costs.

SoftCell ensures that your
customers’ hardware investment
is fully protected.

HIGH SFDR FOR OPTIMUM
SENSITIVITY

This high-performance receiver
maintains a spurious-free
dynamic range (SFDR) of
100 dB over a 25 MHz band­width. The AD6644 enables the
receiver to maintain a signal-to­noise ratio (SNR) of 75 dB, prior
to digital filtering. The AD6624
Digital Receive Signal Processor
provides additional processing
gain of 20 dB – 35 dB.

ANALOG DEVICES: LEADING
BASE STATION SUPPLIER

At the forefront of next­generation receiver technology,
Analog Devices is an established
supplier of integrated circuits
used in current cellular base
station subsystem designs.

We have the largest market
share of mixed-signal integrated
circuits in base stations world­wide. And we also hold a lead­ership position in high-speed
conversion technology and high
dynamic range sampling.

SoftCell Transceiver Chipset

SOFTCELL MULTICARRIER
TRANSCEIVER CHIPSET

• AD6644 14-bit 65 MSPS
ADC

The AD6644 is an 65 MSPS,
high dynamic range 14-bit
ADC optimized to sample IF
inputs up to 70 MHz. CMOS­compatible, this high­performance ADC provides
100 dB of SFDR and 75 dB
SNR in a 25 MHz bandwidth.

• AD6624 Quad Digital
Receive Signal Processor

The AD6624 contains four
independent digital decimat­ing receivers, each providing
over 100 dB of SFDR. Each
channel contains a digital
tuner, two stages of fixed
coefficient filters, and a user­programmable decimating
filter.

• AD6622 Quad Digital
Transmit Signal Processor

This four-channel transmit
signal processor accepts I
and Q inputs and digitally
filters, interpolates, and
tunes the baseband signal to
the desired digital IF. Each
independent channel is com­bined in a single 18-bit paral­lel output that can be com­bined with additional
AD6622s to increase the
number of carriers support­ed. Pulse shaping and
matched filtering can be pro­grammed to support most air
interface standards.

• AD9772 14-bit 400 MSPS
2X Interpolating TxDAC

The AD9772 accepts wide­band digital input at rates up
to 150 MSPS, and generates
a spectrally pure IF output at
frequencies up to 60 MHz.
The resolution and ac accu­racy of the AD9772 minimize
spurious signals, improve
dynamic range, and simplify
upconversion to the next IF
frequency.

or send e-mail to:

wireless.infrastructure@

analog.com

© Analog Devices, Inc., 2000. All rights

reserved. Trademarks and registered
trademarks are the property of their
respective companies. SoftCell is a
trademark of Analog Devices, Inc.

Printed in the U.S.A. H3518a-2-2/00 (rev. A)

Visit us on the

Worldwide Web at:

www.analog.com

Digital Filter

(Channelizer)

Receiver IF

ADC

AD6644 AD6624 AD6622

Digital Filter
(Channelizer)

Digital Filter

(Channelizer)

Digital Filter

(Channelizer)

Format,

Pulse Shape

TigerSHARC

DSP

™

Format,

Pulse Shape

Format,

Pulse Shape

Format,

Pulse Shape

DUC

DUC

DUC

DUC

DAC

+

AD9772

Transmit IF