HSP50306_04 Datasheet, PDF (1/8 Pages) Intersil Corporation – Digital QPSK Demodulator

®
HSP50306
July 2004
Digital QPSK Demodulator
Features
• 25.6MHz or 26.97MHz Clock Rates
• Single Chip QPSK Demodulator with 10kHz Tracking
Loop
• Square Root of Raised Cosine (α = 0.4) Matched
Filtering
• 2.048 MBPS Reconstructed Output Data Stream
• Bit Synchronization with 3kHz Loop Bandwidth
• Internal Equalization for Multipath Distortion
• 6-Bit Real Input: Digitized 10.7MHz or 2.1MHz IF
• Level Detection for External IF AGC Loop
• 0.1s Acquisition Time
• 10^-9 BER
• <116mA on +5.0V Supply
Applications
• Cable Data Link Receivers
• Cable Control Channel Receivers
Ordering Information
PART NUMBER
HSP50306SC-27
TEMP.
RANGE (°C)
PACKAGE
0 to 70 16 Ld SOIC
PKG.
DWG. #
M16.3
Description
The HSP50306 is a 6-bit QPSK demodulator chip designed
for use in high signal to noise environments which have some
multipath distortion. The part recovers 2.048 MBPS data from
samples of a QPSK modulated 10.7MHz or 2.1MHz carrier.
The chip coherently demodulates the waveform, recovers
symbol timing, adaptively equalizes the signal to remove
multipath distortion, differentially decodes and multiplexes the
data decisions. 8-A lock signal is provided to indicate when
the tracking loops are locked and the data decisions are valid.
To optimize performance, a gain error feedback signal is
provided which can be filtered and used to close an I.F. AGC
loop around the A/D converter.
The QPSK demodulator derives all timing from CLKIN. The
chip divides this clock by 2 to provide the sample clock for the
external A/D converter. The -27 version operates at a clock
input of 26.97MHz and demodulates a 10.7MHz QPSK signal
to recover the 2048 KSPS data. The -25 version operates at a
clock input of 25.6MHz and demodulates a 2.1MHz QPSK
signal to recover the 2048 KSPS data. Variation from these
CLKIN frequencies will progressively degrade the receive
data rate, the receive IF, acquisition sweep rate, acquisition
sweep range and loop bandwidths as the deviation increases
from normal CLKIN. Details on the maximum allowable devia-
tion are found in the Input Characteristics section. The
HSP50306 processes 6-bit offset binary data. 4-bit data pro-
vides adequate performance for many applications.
Block Diagram
I
DIN0-5
AGCOUT
ADCLK
CLKIN
RESET
TEST
6
COS SIN
LEVEL
DETECT
NCO
CARRIER
LOOP FILTER
Q
BIT PHASE
DETECTOR
TIMING
GENERATOR
BIT SYNC
LOOP FILTER
4 TAP
ADAPTIVE
EQUALIZER
I
DIFF.
Q DECODE/
MUX
CARRIER
PHASE
DETECT
LOCK
DETECT
DATAOUT
LOCK
CLKOUT
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Copyright Harris Corp. 1998, Copyright Intersil Americas Inc. 2004. All Rights Reserved
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