Specifications
Page 21
WT1231H
3.3.5. Modulation Shaping
Modulation shaping can be applied in both OOK and FSK modulation modes, to improve the narrowband response of the
transmitter. Both shaping features are controlled with PaRamp bits in RegPaRamp.
In FSK mode, a Gaus
sian filter with BT = 0.3, 0.5 or 1 is used to filter the modulation stream, at the input of the
s
igma-
de
lta modulator. If the Gaussian filter is enabled when the WT1231H is in Continuous mode, DCLK signal
on
pin DIO1/DCLK will trigger an interrupt on the uC each time a new bit has to be transmitted. Please refer to
section 5.4.2 for details.
When OOK modulation is used, the PA bias voltages are ramped up and down smoothly when the PA is turned on
and
off, to reduce spectral splatter.
No
te the transmitter must be restarted if the PaRamp setting is changed, in order to recalibrate the built-in filter.
3.3.6. Power Amplifiers
A higher power mode, when PA1 and PA2 are combined, providing up to +20 dBm to a matched load.
When PA1 and PA2 are combined to deliver +20 dBm to the antenna, a specific impedance matching / harmonic filtering
design is required to ensure impedance transformation and regulatory compliance.
All PA settings are controlled by RegPaLevel, and the truth table of settings is given in Table 10.
Table 10 Power Amplifier Mode Selection Truth Table
Pa0On Pa1On Pa2On
Mode Power Range Pout Formula
1 0 0
PA0 output on pin RFIO -18 to +13 dBm -18 dBm + OutputPower
0
1 0
PA1 enabled on pin PA_BOOST -2 to +13 dBm -18 dBm + OutputPower
0
1 1
PA1 and PA2 combined on pin PA_BOOST +2 to +17 dBm -14 dBm + OutputPower
0 1 1 PA1+PA2 on PA_BOOST with high output
power +20dBm settings (see 3.3.7)
+5 to +20 dBm -11 dBm + OutputPower
Other combinations Reserved
Notes
- To ensure correct operation at the highest power levels, please make sure to adjust the Over Current Protection
Limit accordingly in RegOcp, except above +18dBm where it must be disabled
- If PA_BOOST pin is not used (+20dBm applications and less), the pin can be left floating.