EVAL-ADF7021DBZ5 Datasheet, PDF (51/64 Pages) Analog Devices – High Performance Narrow-Band Transceiver IC

Data Sheet
REGISTER 4—DEMODULATOR SETUP REGISTER
IF_BW
POST_DEMOD_BW
DISCRIMINATOR_BW
ADF7021
Rx_
INVERT
DEMOD_
SCHEME
ADDRESS
BITS
IF FILTER
IFB2 IFB1 _BW
00
01
10
11
12.5kHz
18.75kHz
25kHz
INVALID
DW10 .
0
.
0
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1
.
POST DEMOD
DW6 DW5 DW4 DW3 DW2 DW1 BW
0000011
0000102
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1 1 1 1 1 1 1023
DP1 PRODUCT
0 CROSS PRODUCT
1 DOT PRODUCT
RI2 RI1
00
01
10
11
INVERT
NORMAL
INVERT CLK
INVERT DATA
INVERT CLK/DATA
DS3 DS2 DS1 DEMODULATOR SCHEME
00 0
00 1
01 0
01 1
10 0
10 1
11 0
11 1
2FSK LINEAR DEMODULATOR
2FSK CORRELATOR DEMODULATOR
3FSK DEMOD
4FSK DEMOD
RESERVED
RESERVED
RESERVED
RESERVED
TD10 .
0.
0.
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1.
CORRELATOR
TD6 TD5 TD4 TD3 TD2 TD1 DISCRIM BW
0000011
0000102
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0 1 0 1 0 0 660
Figure 66. Register 4—Demodulator Setup Register Map
To solve for DISCRIMINATOR_BW, use the following
equation:
DEMOD CLK × K
DISCRIMINATOR_BW =
400 ×10³
where the maximum value = 660.
For 2FSK,
K
=
Round

100 ×10
f _DEV
3

For 3FSK,
K
=
Round

100
2×
×10 ³
f _DEV

For 4FSK,
K
= Round_4FSK

100
4×
× 10 ³
f _DEV

where:
Round is rounded to the nearest integer.
Round4FSK is rounded to the nearest of the following integers: 32,
31, 28, 27, 24, 23, 20, 19, 16, 15, 12, 11, 8, 7, 4, 3.
fDEV is the transmit frequency deviation in Hz. For 4FSK, fDEV is
the frequency deviation used for the ±1 symbols (that is, the
inner frequency deviations).
Rx_INVERT (DB[8:9]) and DOT_PRODUCT (DB7) need to be
set as outlined in Table 17 and Table 18.
POST_DEMOD_BW = ^{211 × π × fCUTOFF}
DEMOD CLK
where the cutoff frequency (fCUTOFF) of the post demodulator
filter should typically be 0.75 × the data rate in 2FSK. In 3FSK,
it should be set equal to the data rate, while in 4FSK, it should
be set equal to 1.6 × symbol rate.
Rev. B | Page 51 of 64