BCM3034 Datasheet, PDF (2/2 Pages) Broadcom Corporation. – UNIVERSAL ADVANCED DOWNSTREAM MODULATOR

OVERVIEW
PS_IN[7:0]
PS_VALID
PS_SYNC
8
Extended
ITU-T J.83
Annex A/B/C
Encoder
Programmable
Nyquist
= .12-.18
Programmable
Nyquist
= .12-.18
24-tap
Pre-
distortion
Filter
Interpolation
Filter
QDDFS
Interpolation
Filter
OB_DIN
PS_CLK
Programmable
RS
FEC
Encoder
4/16/32 QAM
Burst
Pwr. Mgmt.
Modulator
Output Clock PLL
Source Clock Generator
PLL / Clock Generation
X
sin X
SCALE
D/A
A_IF +/-
D_IF[13:0]
DAC_CLK
D/A
OB_IF +/-
The BCM3034 QAMLink Universal Modulator is a highly integrated
solution that significantly decreases the board space and cost of
modulators in digital cable-TV head-ends, digital cable modem head-
ends, digital microwave radio, SMATV and MMDS applications. The
BCM3034 features an advanced downstream QAM modulator that
includes an extended ITU-T J.83 Annex A/B/C FEC encoder, an all-
digital QAM modulator supporting up to 1024-QAM, and an integrated
10-bit D/A converter with power control. Additionally, the BCM3034
includes a second modulator that can be used for out-of-band signaling
or CPE power control.
The advanced downstream QAM modulator supports symbol rates up to
10 MBaud and symbol constellations from QPSK up to 1024-QAM,
enabling up to 100 Mbps operation. The modulator accepts either a serial
or parallel data stream, optionally recovers the data timing and encodes
the data with one of the supported coding standards. The resulting
stream of QAM symbols then enters the modulator where the data pulses
are shaped by the dual programmable linear phase square-root Nyquist
filters. Built-in coefficients are provided for these filters for industry-
standard excess bandwidth factors (alpha = 12%, 15% or 18%). The
filtered data is then passed through a 24-tap complex T/2-spaced
predistortion filter. This filter allows the user to compensate for non-
idealities, such as slope distortion, introduced elsewhere in the RF
portion of a design. Interpolation filters then upsample the signal to the
output sample rate while providing additional signal filtering. A
quadrature direct digital frequency synthesizer and I/Q modulator allows
the QAM spectrum to be mixed to a precise output center frequency. The
spectrum can then be predistorted by the integrated X/sinX filter to
compensate for DAC distortion. The final signal can be output to the
integrated 10-bit, 200-MS/s D/A converter, which includes differential
analog outputs and a gain stage that can set the output power in 0.4 dB
steps. Alternatively, a selectable 12- or 14-bit digital IF output can drive
an external D/A converter with sufficient linearity to enable final RF
sections that do not require the use of SAW filters to meet industry-
standard RF output templates.
The BCM3034 is a flexible, cost-effective worldwide solution. Because
the chip accepts variable data rates and supports multiple digital
transmission standards, manufacturers only need to develop one
modulator for worldwide usage. The integrated feature set in the
BCM3034 significantly reduces the board space in modulators, giving
manufactures a chip solution that is both cost-effective and easy to use.
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16215 Alton Parkway, P.O. Box 57013
Irvine, California 92619-7013
© 2004 by BROADCOM CORPORATION. All rights reserved.
3034-PB04-R
07/01/04
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