RF64 datasheet(19/76 Pages) ETC2

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ADVANCED COMMUNICATIONS & SENSING

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RF64

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In OOK mode, the phase difference between the I and Q channels is kept constant (independent of the transmitted

data). Thus, the first stage of up-conversion creates a fixed frequency signal at the low IF = Fdev (This explains

why the transmitted OOK spectrum is offset by Fdev).

OOK Modulation is accomplished by switching on and off the PA and PA regulator stages. By convention:

After the interpolation filters, a set of four mixers combines the I and Q signals and converts them into a pair of

complex signals at the second intermediate frequency, equal to 1/8 of the LO frequency, or 1/9 of the RF

frequency. These two new I and Q signals are then combined and up-converted to the final RF frequency by two

quadrature mixers fed by the LO signal. The signal is pre-amplified, and then the transmitter output is driven by a

final power amplifier stage.

3.3.2. Bit Rate Setting

In Continuous transmit mode, setting the Bit Rate is useful to determine the frequency of DCLK. As explained in

section 5.3.2, DCLK will trigger an interrupt on the uC each time a new bit has to be transmitted.

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3.3.3. Alternative Settings

Bit rate, frequency deviation and TX interpolation filter settings are a function of the reference oscillator crystal

frequency, FXTAL. Settings other than those programmable with a 12.8 MHz crystal can be obtained by selection of

the correct reference oscillator frequency.

3.3.4. Fdev Setting in FSK Mode

The frequency deviation, Fdev, of the FSK transmitter is programmed through bits MCParam_Freq_dev:

It should be noted that for communications between a pair of RF64s, that Fdev should be at least 33 kHz to ensure

a correct operation on the receiver side.

3.3.5. Fdev Setting in OOK Mode

Fdev has no physical meaning in OOK transmit mode. However, as has been shown - due to the DDS baseband

signal generation, the OOK signal is always offset by

“-Fdev” (see formulas is section 3.2.8). It is suggested that

Fdev retains its default value of 100 kHz in OOK mode.

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