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I am building up a radio harvesting circuit on WIFI signal, but I fail. Actually I am very new to antenna and RF aspects.I have several questions about the circuit.

First of all, I follow this schematic diagram from this article - http://www.hindawi.com/journals/apec/2010/591640/

enter image description here

Equipment that I have used: 6X 1N5819 DO-41 1A/40V diodes 17X 1pf ceramic capacitors 5X 0.1uH 0307 Axial-Lead Inductor 1X 2DBI 2.4-2.5GHz wifi pcb internal ipex antenna , like this:[​IMG] 1X UNI-T UT33C DMM [​IMG]

C1 is made up of 11X 1pf capacitor in series. L1 is made up of 5x 0.1uH inductor in parallel. C2=C3=C4=C5=C6=C7=1pf capacitor

The result I have encountered:

When I place the antenna vary the distance between 1cm to 3meters in any direction from my home wifi router, zero volt across Test point 3 with ground point , even zero volt test point 1,2 with ground point measured by the DMM.

I doubt at some area that I may misunderstand:

  1. What is MS in the schematic diagram that illustrated in the research ?
  2. Do I use wrong type of capacitor or diode or inductors? Since I have found some capacitors, inductors and diodes that specifically used in RF.

  3. Do I need earth the antenna ? Actually, the ground point of antenna I have connected to the earth poin that near to C7 which is also connected to DMM negative(COM) pin. And I just follow this IPEX instruction: [​IMG]

  4. Is the antenna too weak ? Since I have only 2DBI gain of antenna, however, I wonder why I even can not get 0.1mV when I place the antenna very very close to the home wifi router.

Apart from this, a very strange phenomenon occur in this circuit: When I change the diodes to 1N4004 and keep other equipment unchanged, and placing the antenna near to a charging mobile phone or wifi router (on top of the device), there is a reading, like 30-50 mV shown in DMM. I wonder is this reading due to the AC charging current?

I hope someone can help me. Thanks all

(Since I dont know how to place the diagram to the post here. So I may provide the post on other forum for reference, Please forgive me to do this. Sorry. http://www.electronicspoint.com/threads/problem-on-radio-energy-harvesting-circuit-is-cockcroft-walton-circuit-fail.275060/ ==> picture inserted by Wouter)

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  • \$\begingroup\$ I have my doubts about such circuits, but one point might be that 1N5819 is a medium-current diode, a small-signal type (for instance BAT85) might do better. \$\endgroup\$
    – Wouter van Ooijen
    Aug 14, 2015 at 8:27
  • \$\begingroup\$ Thanks for your suggestion. How about the capacitor ? Do I need to change to other capacitor ? \$\endgroup\$
    – allhksar
    Aug 14, 2015 at 8:43
  • \$\begingroup\$ Is your intent to harvest energy from Wifi (as indicated in thetitle to your question?) What is the end goal? (Just curious) \$\endgroup\$
    – cowboydan
    Aug 14, 2015 at 13:00

1 Answer 1

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At these frequences you need to use microwave diodes (BAT68 for example)and very dense, microwave grade surface mount PCB (like they show in the article). Your diodes have capacitance 200pf. It is like a piece of wire at 2Ghz. Even 1n4148 will do better.

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