Getac Technology Corporation ZX70U Manual De Usuario
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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Revision 2.0 / 6/22/12
page 13/17
Balun Section:
Figure 10 - Schematic Balun Section
The output impedance of the 0 dBm (low power) outputs are 100 ohm differential. Therefore a
2:1 Balun is used to convert the RF track impedance to 50 ohm single ended. In case the ouput
power should be very low the resistor R8, R9 and R10 (Pi-Pad) can be used to attenuate the RF
signal. It would be also possible to reduce the output power via reader IC register settings but
this should be done only down to -6 dB as the local oscillator signal inside the IC would become
too low. Per default the Pi-Pad is not installed.