I am working on RF energy harvesting. Now I am trying to calculate the impedance of the rectifier, in order to do the impedance matching. An antenna (50 ohm) receives RF signal (915 MHz) and finally become DC by the rectifier and stored into the capacitor.
In the figure, the value of L1, C1, sensor node needed to be found.
- How to calculate the impedance of the rectifier?
- Should I consider the impedance of the wireless sensor node? If needed, how to measure the impedance of the sensor node?
- Is a DC-DC converter necessary between the C3 and sensor node?
- As the antenna receive 915MHz rf signal, the frequency of the AC current in the rectifier is also 915MHz?
I had built a rectifier without impedance matching and had done an experiment. I had measured the voltage change of C2,C3 but the result is strange. The voltage of the C3 will remain 2V for about 250ms. However, theoretically, the voltage should be double of the V(c2) which is 100mv.
Another is why the period of the charge time of C2 is 10ms? I thought it should be 1/4 of the period of the AC source (1/915MHz). Or am I misunderstand it? These questions seem to be stupid.. forgive me.. LOL.