SWRS046I November 2006 – September 2018 CC1020
PRODUCTION DATA.
The data modulator can also provide OOK (On-Off Keying) modulation. OOK is an ASK (Amplitude Shift Keying) modulation using 100% modulation depth. OOK modulation is enabled in RX and in TX by setting TXDEV_M[3:0] = 0000 in the DEVIATION register. An OOK eye diagram is shown in Figure 5-29.
The data demodulator can also perform OOK demodulation. The demodulation is done by comparing the signal level with 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 5-14). Manchester coding must always be used for OOK.
NOTE
The automatic frequency control (AFC) cannot be used when receiving OOK, as it requires a frequency shift.
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 very 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 2.4 kBaud.
Typical figures for the receiver sensitivity (BER = 10–3) are shown in Table 5-14 for OOK.
9.6 kBaud |
DATA RATE
[kBaud] |
FILTER BW
[kHz] |
SENSITIVITY [dBm] | |
---|---|---|---|
433 MHz
MANCHESTER MODE |
868 MHz
MANCHESTER MODE |
||
2.4 | 9.6 | –116 | — |
4.8 | 19.2 | –113 | –107 |
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 |