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Digital Cable Tuner RFlC
CN2811
High-Performance Single-Chip CATV Tuner
The InfoSurge™ CN2811 miniature single-chip silicon tuner device
replaces traditional bulky and expensive front-end tuner circuitry
for receiving and interpreting broadband signals carried over
coaxial cable for high-speed Internet access. The CN2811 silicon
tuner represents a major step towards much smaller and more
affordable cable modems. Packaged in a small 48-pin ETQFP the
,
CN2811 requires less board space than conventional tuners. The
device eliminates the bulky tuner can and most of its associated
components, and can be easily interfaced to Conexant’s CN9414
single-chip, programmable cable modem. A cable modem OEM
needs very little additional circuitry to create a complete cable
modem tuner solution.
Sold with Conexant’s CN9414 single-chip programmable cable
modem, the CN2811 device makes possible a complete system
solution that is up to 25 percent less costly and significantly
more power-efficient than other digital cable-modem solutions.
This solution is also the first to give manufacturers the flexibility
to support new feature sets and industry standards by simply
software-upgrading the cable-modem chip’s programmable
Media Access Control (MAC) layer.
Distinguishing Features
• Single-chip RF-to-IF CATV receiver
• Supports North American DOCSIS
and European EuroDOCSIS, DVB
and DAVIC standards
• Glueless interface to the Conexant
CN9414 single-chip cable modem
and QAM ICs
• Dual-conversion architecture eliminates
the need for external tunable RF filters
• Integrated IF AGC amplifiers for
gain control
• Single +5V power supply
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Digital Cable Tuner RFlC
CN2811
Complete, Power-Efficient Solution
This device offers a number of advantages over
other integrated tuner solutions that require multiple
chips, address only a limited portion of the required
functionality, consume more than twice the
power of the CN2811, and often require specialty
manufacturing processes associated with
high-frequency wireless products. In contrast, the
CN2811 consumes less than 1.5W of power, uses
mainstream manufacturing processes, and provides
a complete tuner system solution for everything from
the coaxial cable input to the output for Conexant’s
companion CN9414.
With this new tuner and its companion single-chip
cable modem, Conexant addresses the full spectrum
of cable modem requirements for today’s demanding
broadband connectivity applications. Conexant also
is the first to offer a solution for the kind of high-
volume consumer products that the industry needs
for mainstream cable modem deployment.
Versatile Design
The CN2811 tuner supports all popular cable modem
industry standards including Cable Television
Laboratories Inc. (CableLabs
®
) Data Over Cable
Service Interface Specification (DOCSIS) 1.0/1.1, and
Typical application diagram
What is a Cable Modem?
A cable modem is a device that allows high-speed data
access — from a PC to the Internet — via a cable TV (CATV)
network. It is a modem in the true sense of the word —
it modulates and demodulates signals — and it delivers
Internet data to the desktop at blazing speeds. It simply
uses the increased bandwidth of the TV cable instead of
other specifications established by the EuroDOCSIS, Digital Video
Broadcast (DVB), and Digital Audio Visual Council (DAVIC)
organizations. The CN2811 takes Radio Frequency (RF) signals
ranging from 44 to 870 MHz and converts them to Intermediate
Frequency (IF) signals at 36 or 44 MHz. All that is required for
a complete tuner solution is the addition of a pre-amplifier and
Automatic Gain Control (AGC) circuitry to condition the input
signal for the tuner, plus filters and external tank circuits.
an ordinary phone line.
Cable modems can be part modem, part tuner, part
encryption/decryption device, part bridge, part router, part
NIC card, part SNMP agent and part Ethernet hub. They
typically have two connections: one to the cable wall outlet
and the other to a computer.
The tuner is designed to interface seamlessly with other
components in a broadband access system, drawing on
Conexant’s expertise in a wide variety of physical and MAC-layer
devices and video decoder solutions. It also provides excellent
performance by using a double-conversion architecture that
eliminates the need for manual adjustments, and enhances
signal containment and channel selectivity while minimizing
environmental interference and distortion.
traditional modem. Cable modem speeds range from 500
Kbps (500,000 bits per second) to 10 Mbps (10 million bits
download information from online services up to 1,000
times faster than today’s fastest telephone modems. Here’s
a quick comparison between a cable modem and a typical
Online access via cable modems allows PC users to
Double-Conversion Process
The RF signal is first upconverted to an IF at 1228 MHz. The first
LO consists of an onboard VCO and synthesizer, with an external
tank circuit, and loop filter. Following the upconversion, the signal
is amplified and filtered by an external bandpass filter. The signal
is then downconverted to a low IF at 36 or 44 MHz. The LO for the
downconversion consists of an onboard VCO and synthesizer,
tank circuit, and loop filter. After the downconversion, the signal
is again routed off the IC for bandpass filtering and then back
onto the IC for AGC amplification and the final buffer amplifier
stages. The output of the CN2811 can be connected directly to
the CN9414 (refer to application diagram).
per second). A traditional V.90 56K modem tops out at
only 56,000 bits per second downstream. That’s a difference
of 444,000 bits per second. Hardware companies are
presently developing 30 Mbps cable modems (30,000,000
bits per second) — which are thousands of times faster
than ordinary telephone modems.
Conexant is working on what’s next in cable modem
technologies — so home or office PC users will be
able to download more information from the Internet
in less time.
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Product Features
Reference Design
(with Diplexer)
•
•
•
•
•
Input frequency range
Input level
Noise figure
Input return loss
Spurious at input
– LO
– Other
Image rejection
Spurious output
– LO leakage
– Other (0 dBmV input)
Intermods
– CTB
– CSO
Output level
Output frequency
44 MHz to 870 MHz
-18 dBmV to +18 dBmV
10 dB Max
6 dB min, 9 dB typical
-15 dBmV
-30 dBmV
-60 dBc
0 dBmV
-60 dBc
•
•
•
•
•
•
•
-57 dBc
-57 dBc
2 Vp-p
North America 44 MHz +/- 3 MHz
Europe 36.15 MHz +/- 3.5 MHz
Output impedance
< 50 ohms
Operating temperature range
0˚ to 70˚ C
www.conexant.com
General Information:
U.S. and Canada: (800) 854-8099
International: (949) 483-6996
Headquarters – Newport Beach
4311 Jamboree Rd, P Box C
.O.
Newport Beach, CA 92660-3095
Order# 100376B
01-0363
© 2001, Conexant Systems, Inc. All Rights Reserved.
Conexant and the Conexant logo are trademarks
of Conexant Systems, Inc. Other trademarks are
owned by their respective owners. Although Conexant
strives for accuracy in all its publications, this material
may contain errors or omissions and is subject to
change without notice.
THIS MATERIAL IS PROVIDED AS IS
AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NON-INFRINGEMENT.
Conexant shall not be
liable for any special, indirect, incidental or consequential
damages as a result of its use.
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