SuBill
Junior Member level 3
Dear all,
I'm doing an RF energy harvesting circuit in UHF band. My question is about the voltage multiplier. My 2-stage multiplier (using 2 HSMS-285C diodes) follows Karthaus-Fischer's voltage-doubler.
A 0.1F supercapacitor is put right at the output of the multiplier. This DC voltage will be provided to run an MCU and a sensor. The minimal voltage for operation of MCU and the sensor are 1.9V and 2.56V, respectively.
As in theory, the DC output voltage of the multiplier will be:
Vout = 4 * VRFpeak - 4 * Vfwd (forward voltage of the diodes) - Vload . So say, if Vpeak is 300mV, the maximum voltage I will get is 1.2V, ignoring Vfwd and Vload.
Here is the problem. When I measured the input AC voltage at the receiver antenna (Powercast) terminal, I got a very small signal with the maximum amplitude of 200 - 350mV. BUT I could get 2.6 VDC with full load as told above (MCU & sensor on full operation). Not all the times I could get this result, but sometimes I could. Please refer my picture below.
Probe1: Vin, RF
Probe 2: Vout
Please help me explain this phenomena. It seems my measurements went wrong, or my theory got sth wrong. Thank you very much.
I'm doing an RF energy harvesting circuit in UHF band. My question is about the voltage multiplier. My 2-stage multiplier (using 2 HSMS-285C diodes) follows Karthaus-Fischer's voltage-doubler.
A 0.1F supercapacitor is put right at the output of the multiplier. This DC voltage will be provided to run an MCU and a sensor. The minimal voltage for operation of MCU and the sensor are 1.9V and 2.56V, respectively.
As in theory, the DC output voltage of the multiplier will be:
Vout = 4 * VRFpeak - 4 * Vfwd (forward voltage of the diodes) - Vload . So say, if Vpeak is 300mV, the maximum voltage I will get is 1.2V, ignoring Vfwd and Vload.
Here is the problem. When I measured the input AC voltage at the receiver antenna (Powercast) terminal, I got a very small signal with the maximum amplitude of 200 - 350mV. BUT I could get 2.6 VDC with full load as told above (MCU & sensor on full operation). Not all the times I could get this result, but sometimes I could. Please refer my picture below.
Probe1: Vin, RF
Probe 2: Vout
Please help me explain this phenomena. It seems my measurements went wrong, or my theory got sth wrong. Thank you very much.