In a just finished master thesis [8] a test system for this
sensor class was developed, see figure 10. The battery control
unit is extended by an RFID-Reader IC for 13,56 MHz with
the respective PCB circuit. This reader is the transmitter for
the downlink to the sensors. The corresponding transponder
front end circuit on the sensors consists of discrete components
[4]. Main advantage is the passive operation with very low
power consumption and the possibility to enable the DC-DC
conversion by the downlink receiver, see circuit overview on
figure 11. So the entire sensor, not only the microcontroller,
can remain in a low power sleep mode until the battery control