HFA3861AIN Intersil Corporation, HFA3861AIN Datasheet - Page 16

• Manufacturer Part Number: HFA3861AIN
• Description: Processor, Direct Sequence Spread Spectrum Base band Processor
• Manufacturer: Intersil Corporation

PN Correlators Description
There are two types of correlators in the HFA3861A
baseband processor. The first is a parallel matched
correlator that correlates for the Barker sequence used in
preamble, header, and PSK data modes. This PN correlator
is designed to handle BPSK spreading with carrier offsets up
to ±50ppm and 11 chips per symbol. Since the spreading is
BPSK, the correlator is implemented with two real
correlators, one for the I and one for the Q Channel. The
same Barker sequence is always used for both I and Q
correlators.
TX_AGC_IN (18)
TX_IF_AGC (35)
ANTSEL (39)
ANTSEL (40)
V
I
REF
REF
(21)
(16)
6-BIT
6-BIT
DAC
16
ADC
V
(12, 17, 22, 31)
DD
(62) TX_PE
FIGURE 11. DSSS BASEBAND PROCESSOR, TRANSMIT SECTION
(ANALOG)
GENERATOR
TIMING
MCLK
REGISTER
CONTROL
TX AGC
MCLK
(42)
(9, 15, 20, 25, 28)
GND (ANALOG)
HFA3861A
BARKER/CCK
MODULATOR,
TRANSMIT
FILTER
CONTROL
These correlators are time invariant matched filters otherwise
known as parallel correlators. They use one sample per chip for
correlation although two samples per chip are processed. The
correlator despreads the samples from the chip rate back to the
original data rate giving 10.4dB processing gain for 11 chips per
bit. While despreading the desired signal, the correlator
spreads the energy of any non correlating interfering signal.
The second form of correlator is the correlator function used
for detection of the CCK modulation. For the CCK modes,
the correlation function uses a Fast Walsh Transform to
STATE
V
TX
(2, 8, 37, 57)
DD
(DIGITAL)
(44)
PREAMBLE/HEADER
(45)
SCRAMBLER
GENERATOR
TX_DATA
CRC-16
TEST PORT
(46) (47) (48) (49) (50) (51)
(1, 7, 36, 43, 56)
GND (DIGITAL)
DAC
DAC
TXI (23, 24)
TXQ (29, 30)
(59) TX_RDY
(55) TXCLK
(58) TXD
(3) SD
(4) SCLK
(64) SDI
(5) R/W
(6) CS
(52) RXCLK
(60) CCA