Microwaves101 replied to the topic: Using a hammer instead of pliers

Fahmi

Thanks for your thoughts! Can you tell me why HFSS comes up with 46.5 ohms for a line that is known to be 50 ohms?

I know very little about HFSS... but could a "lumped port" be useful in this case?

Steve

Fahmi replied to he topic: Using a hammer instead of pliers

In order to create a good microstrip port in HFSS, please follow the following steps:
1- If you have the actual dimensions of the air cavity above the substrate then use it otherwise create a cavity that is at least 4-5 times the substrate thickness
2- Create a rectangle that is centered at the trace (width wise) and that extends from the ground plane up to either the top edge of the actual cavity or to 4-5 times the substrate thickness. The width of that rectangle should be either the actual width of the actual substrate , or at least 5 times the width of the metallic trace.
3-Assign a wave port to that rectangle , and make sure to define an integration line from the bottom of the trace to the ground plane, this way you are telling HFSS to calculate the port impedance along that integration line which happens to have the maximum E-filed.
I ran the example with the dimensions you provided and the port impedance was calculated as 46.45 Ohms, in 9-11 GHz range.
I will have to dig an old presentation by Ansoft (the previous owner of HFSS ) which details that, if I find it I will post it to the thread.

cruzaire replied to the topic: Handy Compact

Thanks rfave, that's what i needed. Regards, Tim

rfave replied to the topic: Handy Compact

(You can find anything on the Internet)

if you register at hp41.org, there's a scanned copy of the manual.

www.hp41.org/Contents.cfm

Microwaves101 replied to the topic: Handy Compact

Somewhere in this mess I have a Compact manual from 1980... would that help? (can't promise I can find it...)


Steve

Mohammad replied to the topic: RF Rectifier Simulation in ADS

Gaurav, please go through the Wilkinson Power divider Example on page 47, in the ADS cookbook to learn how to include a lumped component:

www.ece.iisc.ernet.in/~arsl/Members_Only...itDesignCookbook.pdf

Just a quick point: if you include extra transmission lines to serve as PADS for the SMD element along with a GAP element, it will greatly help you automatically generate the layout from the schematic:
drive.google.com/file/d/1VNPA14o4IgG4ebg...xXi/view?usp=sharing

If you still have any question, please start a new post.

colin_warwick replied to the topic: RF Rectifier Simulation in ADS

Hello gaurav18, Sure! Please see the following page for info on how to learn ADS www.keysight.com/find/eesof-class . There are some books and e-learning opportunities towards the bottom. Or contact our tech support EEsof_supportatkeysightdotcom

www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=2138321

gaurav18 replied to the topic: RF Rectifier Simulation in ADS

Hello sir,

I am Trying to simulate a voltage Doubler rectifier for rectenna for RF Energy harvesting in ADS (2016 version) . sir,i want to know how to create a layout from schematic by using EM co-simulation since, its having discrete components such as R, L, C, , Diodes etc . so can you please guide me or tell me steps to create layout from schematic by using EM co-simulation or vice versa. since i am project on RF Energy Harvesting so, kindly help me as soon as possible I will be very grateful to you . please find attached schematic diagram.
Thank You

Mohammad replied to the topic: RF Rectifier Simulation in ADS

Hi steve

Thank you so much for getting in touch with the authors. Actually, I really needed the answer quickly due to a deadline, therefore, I had already taken this discussion to edaboard . But it is great to hear from the authors; I really forgot to include the package parasitics, and that might be the reason for deviation from the original results.
Once, my discussion at edaboard is final, I would post the summary of my findings in this thread for the future audience to this thread.

Thanks, again.

Mohammad.

Microwaves101 replied to the topic: RF Rectifier Simulation in ADS

Answer from Apostolos....
(posted by Steve)


a) the schematic looks good. In relation to question c) the paper also uses parasitic L and C for the diode package. The datasheet should provide these values.
b) regarding efficiency. In the paper we use input available power Pav. This would correspond to the expression using dbmtow(pin).
The expression using the power probe calculates the efficiency using the input power Pin. Both efficiency definitions are correct, they are just different. Since Pav >= Pin if you use available power you get a lower bound of the efficiency.
c) I would guess the difference is the package parasitics. The datasheet or some application note gives some indicative parasitic values for the various diode packages. Also in the paper we simulated the layout in Momentum and included this in the schematic but I don’t have it
in front of me now and I don’t remember if the figure they refer to also includes the layout simulation.

I hope this helps.
Best regards,
Apostolos

Microwaves101 replied to the topic: RF Rectifier Simulation in ADS

Mohammad

Sorry this was not answered quicker... there was a slight breakdown in the message board structure and your question was not directly routed to the right people as it should have been.

We have tracked down Apostolos Georgiadis, an author of the paper you referenced, he is at RWW conference this week but I expect he will supply the information you need shortly.

Regards

Steve

madengr replied to the topic: Even Heating

No, those are just crystal oscillators. I was just suggesting 13.56 MHz as that frequency is used for high power industrial applications (it's actually an ISM frequency like microwave ovens). I figured you were wanting a microwave oven sized chamber, hence the requirement for a power amplifier such as:

www.mksinst.com/product/category.aspx?CategoryID=17

If you are just trying to heat a small tube to 97F, then you may only few 10's of watts.

I would use Teflon instead of PVC for the tube; since PVC is somewhat lossy from my experience using it for radomes in the GHz range, but I have used it for coil-forms at HF with not too much loss. Unless you want to indirectly heat the fluid via the tube, but then why not just use immersion heating in a water bath, like those sous-vide cookers?

It would be an interesting experiment to try, essentially a parallel plate capacitor, using Styrofoam as a sample holder. You'd need a transmatch between the amp and plates.

John replied to the topic: Even Heating

madengr, all your links were very helpful. It looks like these Stalam fellows in Italy are the world leader in these RF drying machines, but, as you say, they are very big machines for industrial assembly lines and, giving you some idea of how big (and expensive) they are, they can only produce 100 per year.

Your lead about making a homemade one from a 13.56 MHz source is interesting. Is this the kind of source you're talking about:

www.newark.com/avx/k50-hc1cse13-5600mr/o...-5mm-cmos/dp/33K9509

www.digikey.com/product-search/en/crysta...852334?k=13.56%20MHz

John replied to the topic: Even Heating

Desert Sage, thanks so much for your very helpful reply! I didn't know if anyone would respond.

Desert Sage wrote: The first question: Is it possible? Yes.

Woohoo! That's good news.

A more important question would be is it practical?

Yes, that is the bottom line question in the end.

The second question: Is there anyone doing this commercially? Not to my knowledge.

OK, good to know.

After making sure they were all lined up (so I could use linear polarization) I would look for the resonant frequency of the little straws (and their filling) and pick a frequency accordingly (use resonance to my advantage). At that point it is relatively easy to control the power level driving the heating. It would be a much more difficult problem if the little straws were strewn about and/or they all have different resonance frequencies.

No problem lining them up! The straws will be heated one at a time, and their location and orientation can be controlled to be the same every time. In fact, I was thinking that the cylindrical chamber that the straw slides into could itself be what I think you call the "reaction chamber" -- that is, the reaction chamber would be very small, just big enough for one straw to fit into. Straws are 5 inches long by 0.1 inches diameter, by the way.

I would suspect if the little straws were precisely manufactured to precise dimensions and coated with a lossy material (on the outside) the problem would get significantly easier. Good thermal conductivity (of the precision straws) would ensure there would be no hot/cold spots.


Now, I didn't make it clear, but I'm sure you guessed: it is actually the filling we care about heating, not the straw itself. The filling is biological; essentially an aqueous solution. So thermally, it will behave kind of like liquid egg whites. The straw is made of a PVC material. I am not sure what you mean by "a lossy material" -- lossy in what way, and is PVC lossy? The straws are definitely precision manufactured to set dimensions -- approx. +/- .002".

madengr replied to the topic: Even Heating

Ha ha , I was about to jump in. Look into RF drying, as they place the material between capacative plates; i.e. in a uniform, near field.

www.stalam.it/en/technologies/radio-freq...and-micro-wawes.html

Problem is all these seem to be large systems. Not that you couldn't make one as multi-kW, 13.56 MHz sources are ubiquitous since they are used in semiconductor and vacuum processing.

See Labotron RF3000:

www.sairem.com/the-ovens-52.html

As far as measuring the temp, a thermistor or thermocouple might work, but then you have to contend with high RF fields. You can get those liquid crystal tape thermometers (I have one on my beer brewing jug) and they are pretty precise. I assume they have some kind of formulation for each temperature. Or maybe an IR thermometer or fiber optic:

www.omega.com/temperature/pdf/FOB100.pdf

Desert Sage replied to the topic: Even Heating

I was hoping someone else would jump in here but here I go.

The first question: Is it possible? Yes. A more important question would be is it practical?

The second question: Is there anyone doing this commercially? Not to my knowledge.

Here are my thoughts. You talk about little straws. After making sure they were all lined up (so I could use linear polarization) I would look for the resonant frequency of the little straws (and their filling) and pick a frequency accordingly (use resonance to my advantage). At that point it is relatively easy to control the power level driving the heating. It would be a much more difficult problem if the little straws were strewn about and/or they all have different resonance frequencies. I would suspect if the little straws were precisely manufactured to precise dimensions and coated with a lossy material (on the outside) the problem would get significantly easier. Good thermal conductivity (of the precision straws) would ensure there would be no hot/cold spots.

bucci replied to the topic: Penetration depth versus frequency for humans

It is not possible to give an unique answer, as the penetration depth depends on the type of tissue. You can refer to the site niremf.ifac.cnr.it/tissprop/ for an exhaustive list of available data. An on line calculator provides, for each type of tissue and frequency interval, both the electrical parameters and the penetration depth, namely the depth at which the field amplitude is attenuated 2.71 times.

parkerMV replied to the topic: WG Excitation

This is an interesting question from a theoretical perspective, having read up a little on the field of nonlinear optics.
In general, it is MUCH MUCH easier for radio-frequency electromagnetic waves to jump to a second harmonic than visible wavelengths.
Any time you have a resonance cavity and energy of a different wavelength bounces around in that cavity, it's going to want to convert into the type of wave that is most fitting to the cavity. That is why [in other applications] it is often said that the cavity "amplifies" a certain wavelength.

drevier replied to the topic: WG Excitation

Excellent and thanks for the advice. I did a brief experiment in HFSS and ramped a WR340 from 2-18 GHz to see the effect. I was shocked to see something that has a TE20 mode at 14 GHz (and only 14 GHz, not any other frequency) while all the other frequencies exhibited something much closer to TE10. This, per your explanation, would be due to meshing/calculation imperfections then. I'll try meshing it more and seeing what it yields.

Thanks

Desert Sage replied to the topic: WG Excitation

In a theoretically perfect world you could excite one mode without exciting the other. However, in the real world this is near if not exactly impossible. Any small deviations from perfection will excite the other mode(s). You could try and suppress the mode but it will still result in energy lost in that mode.

An old VP of engineering once told me if it can (excite the) mode, it will (excite the) mode. I have found that to be sage advice.