TRC105 Datasheet, PDF (49/67 Pages) RF Monolithics, Inc – 300-510 MHz RF Transceiver

Pattern of Bits 3..1
000
001
010
011
100
101
110
111
Transmitter Power
13 dBm
10 dBm
7 dBm
4 dBm
1 dBm
-2 dBm
-5 dBm
-8 dBm
Table 60
The highest power setting allowed under the governing radio regulations is usually chosen unless the application
operates at short range and minimum DC power consumption is critical.
6.3 Determining Configuration Values for OOK Modulation
6.3.1 Bit Rate Related OOK Configuration Values
The TRC105 supports RF bit rates (data rates) from 1.5625 to 33.33 kb/s for OOK modulation. As with FSK mod-
ulation, there are several considerations in choosing an OOK data rate. The sensitivity of the TRC105 decreases
with increasing bit rate. A bit rate should be chosen that is adequate but not higher than the application requires.
The exception to this rule is when the TRC105 is operated as a frequency hopping spread spectrum transceiver in
a noisy or crowded band. Running at a higher bit rate will allow a higher channel hopping rate, which provides
more robust operation in a crowded band in tradeoff for less range under quiet band conditions.
The TRC105 RF bit rate is set by the value of the bytes loaded in MCFG03 and MCFG04. For the standard crys-
tal frequency of 12.8 MHz:
BR = 12800/(2*(C+1)*(D + 1)), with C in the range of 0 to 255, and D = 31 (default value)
Where BR is the bit rate in kb/s, F_XTAL the crystal frequency in kHz, C the value in MCFG03, and D is the value in
MCFG04. This bit rate value supports both the data and clock recovery circuit in the receiver and the bit rate
clocking in the transmitter modulator. Using the default value of D and solving the equation above for C:
C = (12800 - 64*BR)/64*BR
C must be an integer value, so BR is limited to 256 discrete values. If the value of C given in the above equation
is not an integer for your desired bit rate, round the value of C down to the nearest integer. You can then calculate
the nearest available bit rate equal to or greater than your desired bit rate.
In OOK mode, the second IF frequency F_IF2 is normally set to 100 kHz. The discussion in the rest of this section
assumes F_IF2 is 100 kHz.
Once BR and F_IF2 has been determined, the bandwidths and related configuration values for the TRC105 filters
can be determined. The recommended 3 dB bandwidth for the transmitter anti-aliasing filters is:
F_CTX = 3*F_IF2 = 300 kHz
F_CTX is configured with bits 7..4 in TXCFG1A. For the standard crystal frequency of 12.8 MHz:
F_CTX = 200*(K + 1)/8, with K in the range of 0 to 15
Where F_CTX is the 3 dB bandwidth of the transmitter anti-aliasing filters in kHz and K is the integer value of the bit
pattern in TXCFG1A bits 7..4. The equation for determining K is:
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Page 49 of 67
TRC105 - 10/16/12