Diode problem

Rectenna schematics

Used 1N4148 in combination with 100 microfarad cap, circuit gave output 14.5V and 45uA on 200 Ohms load.

But, when I use 1N4007 or FR207, they do not work, nothing on multimeter.

Can anybody explain it? Why diodes do not work? Please, feel free to clarify details of my question.

P.S impedance matching network is not included yet

Transmitter is a horn antenna (approximately 20 dBi), receiver is a half-wave dipole antenna approximately 2 dBi, radiated power (800 watts from microwave oven at 2.45 GHz), distance between reciever and transmitter is 1 meter

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    \$\begingroup\$ Mmmm 45uA into 200ohm is around 0.4uW out of 800W. I believe there could be something wrong. \$\endgroup\$ – carloc Mar 24 '19 at 15:37
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    \$\begingroup\$ 800W from a horn antenna? I hope you're taking proper safety precautions. Skyworks makes some diodes that may be very suitable for relatively small currents. \$\endgroup\$ – Spehro Pefhany Mar 24 '19 at 15:47
  • \$\begingroup\$ Hewlett Packard made the HP5083-2135 schottky diode \$\endgroup\$ – analogsystemsrf Mar 24 '19 at 17:18

Most probably it’s the reverse transition (or recovery) time of the diode. The 1N4148 is exceptionally fast (in the order of a few nano seconds) and, this means that within a few nano seconds of the AC signal reversing polarity, the diode is fully blocking and therefore acting as a proper rectifier should when reversed.

Devices like the 1N400x series can have reverse transition times of tens of microseconds and the impact of using one of these is that it just won’t block high frequency signals.

If you are trying to detect 2.45 GHz, the 1N4148 is starting to run out of steam so I would consider changing technology especially if you are trying to harvest power. The 1N400x is totally dead (and sunk to the bottom) in the water at microwaves.

For FR207, reverse recovery time is quoted at 500 ns so, it also began sinking somewhere above 100 kHz.

| improve this answer | |
  • \$\begingroup\$ Andy, what do you think about HSMS-2800 SOT-23? According to many researches I looked through, mostly used diodes for rectenna application are from HSMS-28xx family. \$\endgroup\$ – Max Rock Mar 27 '19 at 18:26
  • \$\begingroup\$ I'm not sure about that device. Mouser says its obsolete and the self-capacitance seems a little high for microwave applications. Additionally, the data sheet says it's for high voltage applications. I'd be thinking about these folk \$\endgroup\$ – Andy aka Mar 28 '19 at 8:33

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