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REGISTER 2—TRANSMIT MODULATION REGISTER
TxDATA_
INVERT
Tx_FREQUENCY_DEVIATION
DI2
DI1
TxDATA_INVERT
0
0
NORMAL
0
1
INVERT CLK
1
0
INVERT DATA
1
1
INV CLK AND DATA
TFD9
...
0
...
0
...
0
...
0
...
.
...
1
...
NRC1
R-COSINE_ALPHA
0.5 (DEFAULT)
0
1
0.7
•
The 2FSK/3FSK/4FSK frequency deviation is expressed as
follows:
For direct RF output,
Frequency Deviation (Hz) =
Tx_FREQUEN
CY_DEVIATI
16
2
With RF_DIVIDE_BY_2 (Register 1, Bit DB18) enabled,
Frequency Deviation (Hz) =
Tx_FREQUEN
CY_DEVIATI
×
0
5 .
where:
Tx_FREQUENCY_DEVIATION is set by Bits[DB27:DB19].
PFD is the PFD frequency.
•
In the case of 4FSK, there are tones at ±3 × the frequency
deviation and at ±1 × the frequency deviation.
f
TFD3
TFD2
TFD1
DEV
0
0
0
0
0
0
1
1
0
1
0
2
0
1
1
3
.
.
.
.
1
1
1
511
P6
P5
...
P2
0
0
...
0
0
0
...
0
0
0
...
1
0
0
...
1
.
.
...
.
.
.
...
.
1
1
...
1
Figure 64. Register 2—Transmit Modulation Register Map
×
ON
PFD
×
ON
PFD
16
2
POWER_AMPLIFIER
PA_BIAS
PE1
PA2
PA1
PA_BIAS
0
0
0
5µA
1
0
1
7µA
1
0
9µA
1
1
11µA
PR3
PR2
PR1
PA_RAMP RATE
0
0
0
NO RAMP
0
0
1
256 CODES/BIT
0
1
0
128 CODES/BIT
0
1
1
64 CODES/BIT
1
0
0
32 CODES/BIT
1
0
1
16 CODES/BIT
1
1
0
8 CODES/BIT
1
1
1
4 CODES/BIT
POWER_
P1
AMPLIFIER
0
0 (PA OFF)
1
1 (–16.0dBm)
0
2
1
3
.
.
.
.
1
63 (+13dBm)
•
The power amplifier (PA) ramps at the programmed rate
(Bits[DB10:DB8]) until it reaches its programmed level
(Bits[DB18:DB13]). If the PA is enabled/disabled by the
PA_ENABLE bit (Bit DB7), it ramps up and down. If it is
enabled/disabled by the Tx/Rx bit (Register 0, Bit DB27),
it ramps up and turns hard off.
•
R-COSINE_ALPHA sets the roll-off factor (alpha) of the
raised cosine data filter to either 0.5 or 0.7. The alpha is set
to 0.5 by default, but the raised cosine filter bandwidth can
be increased to provide less aggressive data filtering by
using an alpha of 0.7.
Rev. 0 | Page 47 of 60
MODULATION_
SCHEME
PA_RAMP
PA_ENABLE
OFF
ON
S3
S2
S1
MODULATION_SCHEME
0
0
0
2FSK
0
0
1
GAUSSIAN 2FSK
0
1
0
3FSK
0
1
1
4FSK
1
0
0
OVERSAMPLED 2FSK
1
0
1
RAISED COSINE 2FSK
1
1
0
RAISED COSINE 3FSK
1
1
1
RAISED COSINE 4FSK
ADF7021-V
ADDRESS
BITS
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