RF Rectifier simulation and implmentation

chuckey said:

I do not understand why you have two sets of diodes, what does the second set do?
Frank

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BiNa2605 said:

When you use more stage of the Cockcroft-Walton the DC output voltage will be increase. I think you have a good result for the simulation. ADS software is so good, that is a pitty I am not use it.

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I don't know what the diode you use (HMS 2852)? Have you compare the property of the component in the software and the real device?

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thylacine1975 said:

> should build some vias instead for black wire in the pic. to the ground)?

Definitely!!!
Those wires aren't included in your ADS model and are a gross departure from the idealised ground connections shown in your schematic.

I've found achieving practical RF "ground" connections in a microstrip design such as yours to be quite challenging, especially with thick (~1.6mm) PCB. I've had reasonable success at 3+ GHz by paralleling two vias at each intended "ground" connection in a hand-made PCB, made by drilling 2x 0.6mm holes as close together as practicable (~1mm) and inserting short stubs of tinned copper wire, soldered top and bottom and trimmed flush with the cladding.

If you're going to remake your board, yes, I'd also reduce the copper pad sizes (represented by the MLIN's in your model) to the minimum dimension able to accommodate the 0603 SMDs. While ADS's empirically-derived numeric models for physical artwork are exceptionally good, they're not perfect and they're subject to assumptions made about the substrate. For a design made on a random piece of FR-4 fibreglass board without plated through vias, reducing the circuit geometry to the minimum size possible to diminish the [unintended] contributions of any distributed/stripline components will improve the agreement between simulation and reality.

Finally, be careful with the load presented to the output of your Cockroft-Walton multiplier. While they work well, they have notoriously high output impedances (always much worse than expected, in my experience!) and the output will droop badly when loaded with even modest resistances. I'd start at 10+ Kohms.

Good luck!

Oh, and the body of that SMA input connector *is* soldered to the plane on the underside of the PCB, isn't it?

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kpc said:

Hi,
Whay is your PCB material? Is it FR4?

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mtwieg said:

The inductance in those ground wires are an obvious issue, drill some vias instead. I would redo the layout so the top side ground pour is much larger, and put many vias in it. Also I don't see L5 in your layout, though it may not be necessary.

I'm surprised your simulation is predicting a good S11, is that a small signal measurement? And 30% isn't too bad for a RF>DC converter. Keep in mind that high quality passive mixers have ~6dB conversion loss, which is 25% "efficiency."

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