MRF89XAM8A-I Datasheet, PDF (68/140 Pages) Microchip Technology – Ultra Low-Power, Integrated ISM Band Sub-GHz Transceiver

MRF89XA
3.4.10.2 Optimizing OOK Demodulator
Response for Fast Fading Signals
A sudden drop in signal strength can cause the bit error
rate to increase. For applications, where the expected
signal drop can be estimated, the OOK demodulator
parameters set by the OOKTHSV<2:0> and OOK-
THPV<2:0> bits (OOKCREG<7:5> and OOK-
CREG<4:2>) can be optimized.
For a given number of threshold decrements per bit,
specified by OOKTHPV<2:0>:
• 000 Æ once in each chip period (default)
• 001 Æ once in 2 chip periods
• 010 Æ once in 4 chip periods
• 011 Æ once in 8 chip periods
• 100 Æ twice in each chip period
• 101 Æ 4 times in each chip period
• 110 Æ 8 times in each chip period
• 111 Æ 16 times in each chip period
For each decrement of value from OOKTHSV<2:0>
bits:
• 000 Æ 0.5 dB (default)
• 001 Æ 1.0 dB
• 010 Æ 1.5 dB
• 011 Æ 2.0 dB
• 100 Æ 3.0 dB
• 101 Æ 4.0 dB
• 110 Æ 5.0 dB
• 111 Æ 6.0 dB
3.4.10.3 Alternative OOK Demodulator
Threshold Modes
In addition to the Peak OOK threshold mode, the user
can alternatively select other two threshold detectors:
• Fixed threshold: The value is selected through the
OOKCREG register (for more information, refer to
Section 3.4.10.1, Optimizing the Floor Threshold).
• Average threshold: Data supplied by the RSSI
block is averaged with the cut-off frequency.
In Equation 3-14, the higher cut-off frequency enables
a sequence of up to eight consecutive ‘0’s or ‘1’s to be
supported, while the lower cut-off frequency presented
in Equation 3-15 allows for the correct reception of up
to 32 consecutive ‘0’s or ‘1’s.
EQUATION 3-14:
OOKATHC<1:0>
=
00 ⇒ f_cutoff
=
B_----R_----V_----A_---L_----<_----6_---:_--0_--->_--
8^∗π
EQUATION 3-15:
OOKATHC<1:0> = 11 ⇒ f_cutoff = ^B----^R----^V---3^A---2-^L--_∗--^<--_π--⁶---^:--⁰---^>--
DS70622C-page 68
Preliminary
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