mrf89xa Microchip Technology Inc., mrf89xa Datasheet - Page 67

• Manufacturer Part Number: mrf89xa
• Description: Ultra-low Power, Integrated Ism Band Sub-ghz Transceiver
• Manufacturer: Microchip Technology Inc.

OOK mode: The 99% energy bandwidth of an OOK
modulated signal is approximated, as shown in
Equation 3-11.
EQUATION 3-11:
The POLCFV<3:0> bits (PFCREG<7:4>) set f
center frequency of the polyphase filter when activated.
f
Intermediate Frequency of the receiver (IF2). That is
the reason for low IF frequency of the OOK receiver
denoted by IF2 can always be replaced by f
calculations or monitoring purposes.
The following setting is recommended:
The
(FILCREG<3:0>) determines f
frequency. Therefore, f
Equation 3-12.
EQUATION 3-12:
FIGURE 3-7:
© 2010 Microchip Technology Inc.
o
should always be chosen to be equal to the low
f
POLCFV<3:0> = 0011.
o
= 100 kHz
450
400
350
300
250
200
150
100
value
50
0
2
0
•
BW
(
f
c
stored
–
99%,ook
f
o
)
>
ACTUAL BW OF BUTTERWORTH FILTER
2
c
BW
=
should be set according to
as
99%,ook
------ -
t
bit
2
=
BUTFILV<3:0>
c
2 BR
, the filter cut-off
+
•
LO
4
drifts
Butterworth Filter BW, FSK
o
for any
o
Val BUTFILV<3:0> [d]
6
, the
Preliminary
bits
8
Again, f
described in Section 3.4.6 “Channel Filters Setting
in OOK Mode”.
3.4.5
f
used in FSK reception, is programmed through the
BUTFILV<3:0> bits (FILCREG<3:0>). However, the
entire receiver chain influences this cut-off frequency.
The channel select and resultant filter bandwidths are
illustrated in Figure 3-7.
Table 4-2 in Section 4.6 “Crystal Specification and
Selection Guidelines” suggests filter settings in FSK
mode along with the corresponding passive filter band-
width and the accepted tolerance on the crystal
reference.
c
, the 3dB cut-off frequency of the Butterworth filter
c
as a function of the BUTFILV<3:0> bits, is
10
CHANNEL FILTERS SETTING IN
FSK MODE
12
Actual
BW
MRF89XA
Theoretical
BW
14
DS70622B-page 67
16