Single-Chip Low Power RF Transceiver for Narrowband Systems ...

the "carrier sense" level (programmed as
CS_LEVEL in the VGA4 register). The
signal is then decimated and filtered in the
data filter. Data decision and bit
synchronization are as for FSK reception.
In this mode AGC_AVG in the VGA2
register
must be set to 3. The channel
bandwidth must be 4 times the Baud rate
for data rates up to 9.6 kBaud. For the
highest
data rates the channel bandwidth
must
be 2 times the Baud rate (see Table
27). Manchester coding must always be
used
for OOK.
Note that the automatic frequency control
(AFC)
cannot be used when receiving
OOK, as it requires a frequency shift.
Data rate
[kBaud]
Figure 32. OOK eye diagram.
9.6 kBaud.
Filter BW
[kHz]
CC1021
The AGC has a certain time-constant
determined by FILTER_CLK, which
depends on the IF filter bandwidth. There
is a lower limit on FILTER_CLK and hence
the AGC time constant. For low data rates
the
minimum time constant is too fast and
the AGC will increase the gain when a "0"
is received and decrease the gain when a
"1" is received. For this reason the
minimum data
rate in OOK is 9.6 kBaud.
Typical figures for the receiver sensitivity
(BER = 10 −3 ) are shown in Table 27 for
OOK.
433 MHz
Manchester mode
Sensitivity [dBm]
868 MHz
Manchester mode
9.6 38.4 -103
-104
19.2 51.2 -102 -101
38.4 102.4 -95 -97
76.8 153.6 -92 -94
153.6 307.2 -81 -87
Table 27. Typical receiver sensitivity as a functi
modulation, BER = 10 −3 on of data rate at 433 and 868 MHz, OOK
, pseudo-random
data (PN9 sequence).
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