AN149
Rev 1.0 | 3/12
www.cmostek.com
1 Tx and Rx Parameter Configuration
1.1 Basic Parameter Configuration
Figure 1. RF Parameter Configuration Interface
The registers corresponding to these parameters are stored in the frequency bank, the symbol rate bank,
and the Tx bank, It
needs to be calculated by complex calculation. The user does not need to understand the
calculation process and the specific
meaning of the register.
RFPDK interface parameters are easy to understand. The following configurations need attention.
How to set the Deviation:
Generally speaking, the following 3 points are recommended when configuring the Deviation:
1.
4kHz < Deviation < 200 kHz, and Symbol rate * 0.5 + Deviaiton<= 250 kHz
2.
Symbol rate * 0.25 <= Deviation
，
that is, the modulation index must not be less than 0.5 (MSK).
3.
In the case of meeting the above two conditions, if Symbol rate * 0.5 <= Deviation <= Symbol rate *
2, it can achieve the best
sensitivity.
How to set the crystal PPM
The user inputs the crystal tolerance values for Tx and Rx respectively in RFPDK. If inp/-20 ppm
respectively, it means that the worst case between the transmitter and receiver is the crystal frequency
difference of 40 ppm. The user should consider the worst case to set these two tolerance values, which affect
every bandwidth setting within the receiver.
