SX1231
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
The bit rate matching between the transmitter and the receiver must be better than 6.5 %.
Notes - If the Bit Rates of transmitter and receiver are known to be the same, the SX1231 will be able to receive an infinite
unbalanced sequence (all “0s” or all ”1s”) with no restriction.
- If there is a difference in Bit Rate between Tx and Rx, the amount of adjacent bits at the same level that the
BitSync can withstand can be estimated as follows:
- This implies approximately 6 consecutive unbalanced bytes when the Bit Rate precision is 1%, which is easily
achievable (crystal tolerance is in the range of 50 to 100 ppm).
3.5.13. Frequency Error Indicator
This function provides information about the frequency error of the local oscillator (LO) compared with the carrier frequency
of a modulated signal at the input of the receiver. When the FEI block is launched, the frequency error is measured and the
signed result is loaded in FeiValue in RegFei, in 2’s complement format. The time required for an FEI evaluation is 4 times
the bit period.
To ensure a proper behavior of the FEI:
The operation must be done during the reception of preamble
The sum of the frequency offset and the 20 dB signal bandwidth must be lower than the base band filter bandwidth
The 20 dB bandwidth of the signal can be evaluated as follows (double-side bandwidth):
BR
⎛
⎞
-------
+
BW20dB = 2 × FDEV
⎝
⎠
2
The frequency error, in Hz, can be calculated with the following formula:
FEI = FSTEP × FeiValue
Rev 2 - Nov 2009
Page 30
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