ANALOG DEVICES AD6640, AD6620 Service Manual

AD6640/AD6620

Multi-Channel Multi-Mode Receiver Chipset

“FUTURE-PROOF” BASE STATIONS
WITH NEXT-GENERATION DIGITAL
RADIO

Analog Devices’ breakthrough design for digital
radio receivers lets you bring programmable
wideband radio base stations to market with
complete confidence.

This advanced “software” receiver is based on
Analog Devices’ function-rich, high-performance
AD6640 and AD6620 chips. The AD6640 is a
wideband analog-to-digital converter capable
of sampling at 65 MSPS. The AD6620 is a
65 MSPS decimating receiver chip that enables
the same radio to be tuned to different channels
and even different air interface standards.

Industry-leading high dynamic range wideband
sampling enables the AD6640 to digitize an
entire 25 MHz of spectrum at one time.

The result: A single all-digital wideband radio
replaces multiple analog radios for a smaller,
more flexible, more readily configurable solu­tion that helps your customers remove the
uncertainty from network planning.

Analog Devices’

all-digital solution

lets you produce base

stations for multiple

air standards using

the same core

elements.

FEATURES

• One ADC digitizes multiple RF channels: replaces multiple analog radios
for reduced receiver size

• Digital tuner/filter chips replace analog synthesizers and channel-select
filters for reduced complexity and lower manufacturing costs

• On-chip programmable digital filters: easily reconfigured for new air
standards such as AMPS, IS136, CDMA, GSM, PCS1900, PHS

• Enables high-frequency IF sampling at 70 MHz

• Maintains 80-100 dB SFDR over a bandwidth of 25 MHz

• Minimal hardware requirements for increasing capacity: simply add
digital tuner/filter chips to demodulate additional RF channels

• Small outline, surface-mount plastic packaging (44-pin TQFP, 80-pin
PQFP): reduces receiver size, simplifies micro- and pico-cell designs

• Easily interfaces to general-purpose DSPs

• Complete radio reference designs reduce your engineering investment

Fixed

LO

BPF

BPF

n channels

AD6620's

70 MHz IF
25 MHz Bandwidth

ADC

Tuner/

Filter

Tuner/

Filter

Tuner/

Filter

Tuner/

Filter

DSP

BSC

or

MSC

AD6640

BPF

COST-EFFECTIVE FOR MULTI­CHANNEL SYSTEMS

With a single AD6640 ADC
digitizing an entire 25 MHz of
spectrum, this advanced wide­band receiver can deliver a
lower cost-per-channel than
traditional receivers.

To increase capacity, simply
add digital tuner/filter chips to
demodulate additional RF chan­nels. For example, 30 AD6620
tuner/filter chips can be con­nected to an AD6640 ADC to
accommodate a 30-channel
AMPS system.

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

This approach 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
80-100 dB over a 25 MHz band­width. The AD6640 enables the
receiver to maintain a signal-to­noise ratio (SNR) of 70 dB, prior
to digital filtering. The AD6620
digital filter chip then adds
processing gain of 20-35 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.

ANALOG DEVICES IN
COMMUNICATIONS

Analog Devices is committed to
supplying the communications
industry with the highest­performance solutions at the
lowest possible cost. We meet
the needs of today’s broadband
wired and wireless markets
with leadership capabilities in
analog, digital and mixed signal
processing, RF signal process­ing, data conversion, interfaces
and total system design.

MULTI-CHANNEL MULTI­MODE RECEIVER CHIPSET

Analog Devices’ advanced
wideband digital receiver
chipset consists of:

• AD6640 wideband ADC chip
The AD6640 is a high-speed,
low-power monolithic 12-bit
analog-to-digital converter
with all necessary functions
included on-chip to provide
a complete conversion solu­tion. It runs on a single +5 V
supply and provides CMOS­compatible digital outputs at
65 MSPS.

This high-performance ADC
maintains 80+ dB SFDR and
70 dB SNR over a bandwidth
of 25 MHz.

Units are packaged in a 44-pin
Thin Quad Plastic Flatpack
(TQFP).

• AD6620 decimating receiver
chip

The AD6620 is a 65 MSPS
decimating receiver chip that
maintains an SFDR greater
than 100 dB. Its four cascaded
signal processing elements are
a digital tuner, two fixed coeffi­cient filters and a programma­ble coefficient decimating filter.

A high-resolution Numerically
Controlled Oscillator (NCO)
allows flexibility in frequency
planning; the RAM-based
architecture allows easy recon­figuration for multi-mode
applications.

The AD6620 is designed for
easy integration; built-in circuit­ry enables multiple chips to be
connected in a single system.

Units are packaged in an
80-pin Plastic Quad Flatpack
(PQFP).

REFERENCE DESIGNS

AD6640/AD6620 multi-channel
wideband receiver reference
designs indicate all required
external components in the
optimal PCB layout which min­imizes adjacent channel inter­ference. Designs, along with a
complete set of application
notes and technical white
papers, are available for
900 MHz cellular and 1.9 GHz
PCS air interface standards.

FLEXIBLE AND
PROGRAMMABLE

Analog Devices’ versatile
receiver design enables you
to manufacture base stations
for a variety of air interface
standards — including
PCS1900, CDMA, IS136, PDC,
AMPS, ETACS and NMT —
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.

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

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 costly-to­produce 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.

Complete reference designs
further ease your development
efforts. These designs show the
optimal PCB layout for reducing
noise and minimizing adjacent
channel interference.

Multi-Channel Multi-Mode Receiver