Rectenna

Discussion in 'Wireless & RF Design' started by philm01, Jul 27, 2014.

  1. philm01

    Thread Starter Member

    Mar 22, 2014
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    0
    Hello everyone,

    I have a few RF engineering design questions and I am hoping that someone from the community would be able to assist me.

    SO basically, I am designing a rectenna circuit to harvest power from a 2.4 GHz wifi signal. Currently, I have an AC source in series with a 50 ohm resistor to represent the Antenna (which I know that it is off but I am not sure how to properly model it) Attached is the pspice circuit that I am using (I am using the free student version). Please, feel free to download and simulate.

    So I have been doing research and alof of the circuits have been using a single diode to rectify to DC. I therefore conclude that it is best to go that route because everyone else is doing this and this is my first time designing such a circuit. Plus, I thought that getting help would be "easy".

    I do some simple simulations using a jave simulator and it shows that it should be acting like a half wave rectifier but according to my results, it is not. The waveform is still +- V. I emailed a few people and they said that I need to create a clamp circuit. I did and this works a little bit better but I am having a hard time impedance matching the circuit because once I do this, it kills the clamping circuit. Which, impedance matching the cirucit is a major component. So, my question is, how do I go about impedance matching it (if possible?)

    Ultimaly, I have three questions:

    1) With the diode (rectifier), how exactly do I impedance match it? There are at least 3 different parameters and multiple combinations, which one is the correct configuration?

    2) I also have to impedance match the load but what do I impedance match it to? The rectifier or the antenna? Or do I need to make sure that the impedance of the load and antenna are impedance matched to the antenna's impedance?

    3) Alot of papers have shown that they are using a single order filter to smooth out their DC. But my single order filters are not able to do that. I have to use higher order filters, but they kill the efficiency of the system. How do I go about creating a filter that will smooth out to DC without killing the efficiency? (I think that this may have to deal with the rectifier.)

    I hope that someone will reply soon. I will be happy to answer any questions to clear anything up. Than you

    Please note that I am not using a 1N6263, I changed it to a HSMS-820 and the model text is already in there replacing the text for the 1N6263
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    428
    the diode dosnt have to be impedance matched, its impedance will change with level of voltage across it. the circuit element that the diode is connected across should be matched to the rest of the antenna then the diode will output the voltage determined by the power level and distance from the other antenna, which will not be much.
     
  3. philm01

    Thread Starter Member

    Mar 22, 2014
    33
    0
    Ok, so let me clarify, basically, my 165 ohm load needs to be matched to the 50 ohm antenna? Correct?

    Interesting that you say that I do not have to impedance match the AC resistance of the diode to the antenna. I emailed a professor who actively works in the field and he says that I need to match the differential resistance of the diode to my voltage range.

    I guess I will try it a different way considering that I haven't tried it before. We will see what happens.

    Any thoughts as to way he said that though?
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    since you dont know how much voltage and current the diode will have, how can you guess the "differential resistance" ? voltage drop and resistance of a diode are dynamic, deven going into negative resistance at certain voltages.
     
  5. philm01

    Thread Starter Member

    Mar 22, 2014
    33
    0
    Yes, you are correct, I am not sure at what voltages I would be working with. But, I do know what the power of the transmitter is and what the resistance of some of the components are.

    So, I could get a rough estimate of what the voltages are. And from that, I could use the IV curve and get the current and from there, the differential resistance.

    Is that a legal way of doing it or am I stretching it too much?
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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  7. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    Hey Roman, you could use a rectenna to power your balloon project. I am sure Cartman wouldn't mind.
     
    THE_RB likes this.
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