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Using the GPIO2 output of the LO SI4432 it is possible to create a fairly accurate -30dBm power reference level as the output swing of the GPIO port is 3 Volt when the current is below the drive limit.


Using a DC blocking capacitor (100nF) and a voltage divider (3k7 + 50ohm) provides a 50 ohm matched output and reduces the load on the GPIO port below the current limit.

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The PowerReference output provides a -30dBm power level at the fundamental of the selected GPIO2 output frequency

If the 3k7 resistor cannot be found a 3k9 resistor can be used. This will provide a -30.4 dBm output power
For best accuracy during power calibration you should use a -10dB or more attenuator setting to ensure the input impedance of the tinySA is close to 50 ohm. This because the input impedance of the mixer is rather ill defined.