I want to design a circuit in order to Harvest radio-frequency (RF) signals and get a DC Output to a specific load (i.e micro Watt Battery of a sensor).
Notes to be considered :
- input will be between (uV - mV) which is low.
- frequency that i am harvesting from is the GSM frequency which is 900-915 MHz
- considering this frequency value the capacitance should be really small (pico or nano farads)
During my research i have found that the most used step-up (In terms of Voltage) configurations are mainly three types which are :
1- Transformer Topology (Which is the cheapest and less efficient for such application)
2-Diodes : Rectifiers (Which I am not interested in due to losses)
3-Voltage Doubler/ Multiplier (Which consists of diodes and capacitors such like >> Cockcroft-Walton or any other configuration)
Now the thing is that there are a lot of types of the voltage multiplier, but I could not find any certain reference that can help me through the design of the Voltage multiplier.
For example how to calculate the capacitance values lets say for multi-stage multiplier with N Stages and Vin to Vout specific ratio ?
Such as : Vin = 1V Vout = 5V N = 5-10 stages (or more depending on the output)
Cockcroft-Walton Topology with 2 stages.
Any advice will be much appreciated