design of rectifier for wireless power harvesting in implanted applications

hi
i need to design of a rectifier for a rectenna that implant and for ultra low input power(-20dBm) at 900MHZ.
what model is better?
1)using single zero-bias schottky diode(HSMS285x)?
2)voltage doubler using zero-bias schottky diode(HSMS285x)?
3)bridge using zero-bias schottky diode(HSMS285x)?
4)using CMOS technology?
why?
please help me
tanx

* Consider adjusting the L:C ratio. It makes a difference to AC voltage output. Take output across the capacitor.

* If voltage is very low, try a single diode rectification (half-wave). Go on to try full-wave rectification only if you observe it will give you an advantage in power output.

* There is little or no advantage between the Villard doubler and bridge doubler (when compared by simulation).

At 900 MHz, with -20 dBm you will get no DC output under any circumstances. Schottky RF detectors need more than -10 dBm to rectify a hundred millivolts into an open DC load. Then coupling the RF field at 900 MHz from air into a living tissue is a nice problem. The implanted antenna must be designed to work within the lossy tissue and the outside antenna, rather an applicator, is a specifc problem on its own.
Start with the implanted antenna, use the known tissue permitivity to design it, and use a tissue phantom to test it. My guess is that the loss from external to the implanted antenna will be close to 20 dB. Maybe you will need one watt power source at 900 MHz to get a small DC voltage rectified into an open circuit. Loading the rectifier will degrade the complete system even more.

Good luck!

def use a voltage doubler!

you would have less signal attenuation at a lower frequency, although the antenna might get unacceptably large.

See https://support.impinj.com/hc/en-us/...0141209_R3.pdf

This uses CMOS rectifier and achieves a read sensitivity of up to -22.1 dBm with a dipole antenna.

If you have interest, search US-PATENT of impinj with keyword of "rectifier".

http://patft.uspto.gov/netacgi/nph-P...ctifier&d=PTXT

Also, see http://ieeexplore.ieee.org/xpl/login...mber%3D7418063