RF64W datasheet(20/76 Pages) HOPE

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ADVANCED COMMUNICATIONS & SENSING

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RF64

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3.3.6. Interpolation Filter

After digital to analog conversion, both I and Q signals are smoothed by interpolation filters. This block low-pass

filters the digitally generated signal, and prevents the alias signals from entering the modulators. Its bandwidth can

be programmed with the register RXParam_InterpFiltTx, and should be set to:



Where Fdev is the programmed frequency deviation as set in MCParam_Freq_dev, and BR is the physical Bit Rate

of transmission.

Notes:

Low interpolation filter bandwidth will attenuate the baseband I/Q signals thus reducing the power of the FSK

signal. Conversely, excessive bandwidth will degrade spectral purity.

For the wideband FSK modulation, for example when operating in DTS mode, the recommended filter setting

can not be reached. However, the impact upon spectral purity will be negligible, due to the already wideband

channel.

3.3.7. Power Amplifier

The Power Amplifier (PA) integrated in the RF64 operates under a regulated voltage supply of 1.8 V. The

external PA choke inductor is biased by an internal regulator output made available on pin 29 (VR_PA). Thanks to

these features, the PA output power is consistent over the power supply range. This is important for mobile

applications where this allows both predictable RF performance and battery life.

3.3.7.1. Rise and Fall Times Control

In OOK mode, the PA ramp times can be accurately controlled through the MCParam_PA_ramp register. Those

bits directly control the slew rate of VR_PA output (pin 29).

Table 11: PA Rise/Fall Times

MCParam_PA_ramp

tVR_PA

tPA_OUT (rise / fall)

3 us

2.5 / 2 us

8.5 us

5 / 3 us

15 us

10 / 6 us

23 us

20 / 10 us

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