I would like to go for 2 stages to get the desired voltage but before going forward I need an impedance matching between antenna and rectifier. I understand matching can be achieved through LC or TL based but I need to find the impedance of the rectifier, how can I find the impedance of the rectifier?Impedance matching is supposed to maximize power throughput. Incoming voltage & current may be at levels not usable by your following circuitry. Therefore the aim (when harvesting RF energy) is usually to raise volt amplitude even though it means current must be reduced in the same fashion. By doing that power throughput is maximized, because voltage & current levels are optimized for your following circuitry.
To get any signal (power) through your circuitry, its volt level must overcome the diode threshold. Your schamatic is a Villard voltage doubler. You would need several such charge-pump stages in order to impedance match 50 ohm incoming to 50k outgoing. With so many such stages you'd lose power instead of maximizing power.
Some kind of LC arrangement is better able to match impedances in this case.
Any f domain analysis only with a diode which changes impedance in time over the entire cycle is invalid. Also considering the level 0 model in the ELF range is also invalid for 2.4GHz.Hi,
You can use LSSP and HB and Zin analysis to measure rectifier's input impedance at a given frequency and input power. Run these analysis and then set the source impedance to be the conjugate of the measured Zin, repeat this process again until you get a good matching result shown on the S11 graph at the input frequency, That is the final input impedance.
Here it is explained very well in details with pics.
Alothman, Abdullah. (2021). Re: How to calculate Impedance of diode in rectenna design?. Retrieved from: https://www.researchgate.net/post/How_to_calculate_Impedance_of_diode_in_rectenna_design
That's why the classical ADS "rectenna" homework exercise uses HB (harmonic balance) analysis and realistic microwave capable diode models. Learning objective of the exercise is to practice this analysis method, not to reinvent the wheel.Any f domain analysis only with a diode which changes impedance in time over the entire cycle is invalid. Also considering the level 0 model in the ELF range is also invalid for 2.4GHz.
I've not done that method, yet I know the efficiency and impedance of the model changes with input power or e-field or flux level. The diode has an effective duty factor on conductance with fixed L and variable R(I), C(V). Thus one must be aware of the assumptions.That's why the classical ADS "rectenna" homework exercise uses HB (harmonic balance) analysis and realistic microwave capable diode models. Learning objective of the exercise is to practice this analysis method, not to reinvent the wheel.
Can you explain why I need to conjugate the measured Zin?Hi,
You can use LSSP and HB and Zin analysis to measure rectifier's input impedance at a given frequency and input power. Run these analysis and then set the source impedance to be the conjugate of the measured Zin, repeat this process again until you get a good matching result shown on the S11 graph at the input frequency, That is the final input impedance.
Here it is explained very well in details with pics.
Alothman, Abdullah. (2021). Re: How to calculate Impedance of diode in rectenna design?. Retrieved from: https://www.researchgate.net/post/How_to_calculate_Impedance_of_diode_in_rectenna_design
perfect.Consider Zin = Rin + Xin
and a source with conjugated impedance
Zsource = Rsrc + X src = Rin - Xin
Connecting Zin to Zsource cancels Xin and effectively connects Rin to Rsrc, achieving impedance matching.
According to maximum power transfer theorem, Maximum power is transferred from source to the load when the load resistance is equal to the resistance of the source. As stated by dear FvM , When the load is complex, if source impedance is conjugate of the load, Imaginary parts are cancelled and real parts are equal which results in perfect match and no input wave is reflected to the source.Can you explain why I need to conjugate the measured Zin?
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