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RF-OM
Joined: 03 Aug 2007
Posts: 607
Helped: 113
Location: The Earth
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 12 Aug 2008 0:03 Re: Where can i fabricate microstrip and help with GENESYS |
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| You made mistake in hairpin-with LNA worksheet. You need to assign S-parameter file to the block you chose. You chose dataset, but S-parameter file should be instead . Double click on LNA and go to Simulation tab there you may chose right S-parameter file. Do the same for the second LNA. After this you will be able to simulate your LNAs with filter. Based on filter plots there should not be any problems with matching. If you need to change footprint go to General tab and you will see line for footprint in lower part of the window. In very unlikely case if you need to do match you can add L-matching circuits and play with them. Datasets are not as good as S-parameter files because they have only magnitudes. Filter itself looks good but Monte Carlo shows strong dependents on component accuracy. You need to keep it in mind. Be raedy to see from EM simulation that filter is shifted down for about 10 to 20%. In this case you need to redesign the filter with shifting by the same shift up.
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selva500
Joined: 27 Apr 2008
Posts: 30
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| 12 Aug 2008 14:00 Re: Where can i fabricate microstrip and help with GENESYS |
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Hi,
I tried using the datafile instead of dataset option to upload the LNA S-parameter files but i still get the same response for my filter. The bandwidth of 100 MHz becomes really narrow so that it only focuses on the center frequency. I even tried uploading the file under the parameter option in the LNA part and still the response is similar. I'm wondering if you got a different response when u tried using the datafile option? Or is this a feature of the LNA that it focuses only towards the center frequency of the filter. Im not too sure about this.I have uploaded my latest workspace at:
http://www.mediafire.com/?fk98itzre3e
Hopefully you can point out to me what is it that I have done wrong as I'm a bit confused now because all 3 methods give me the same response. I would appreciate it if you could maybe modify my workspace and upload it so i can have a look at it if possible. Only if you are able to though.
As for the footprint. I dont have the footprint for the LNA yet, which is why im using it as a short circuit in the layout. Im assuming i have to design the footprint myself as i contacted Hittite and they dont seem to have footprints available for the component. Is there a place that i could maybe download the footprint for the LNA? It is a 3 x 3 mm QUAD FLATPACK NO-LEAD (QFN) package.
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RF-OM
Joined: 03 Aug 2007
Posts: 607
Helped: 113
Location: The Earth
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| 12 Aug 2008 18:02 Re: Where can i fabricate microstrip and help with GENESYS |
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I simulated your circuit with S-parameter files and get totally different response (high pass kind). Then I checked your filter file (filter alone). Your picture was very good but when I simulated it picture became different and high pass kind. It looks like something is wrong with your filter. I look on schematic and found that there are a lot unreal numbers like 0.36 mil length. This filter cannot be realized. Probably it is better for you to use your first interdigital filter. Try it with LNA S-parameter files and you should get better results.
Added after 12 minutes:
I also try to simulate your LNAs alone. Each of them has bog slope after about 1.5 GHz. When tey are connected together the slope is 10 dB from 1.4 GHz to 3 GHz. Is this slope acceptable for your project? Return loss also became not so good below 1.6 GHz.
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selva500
Joined: 27 Apr 2008
Posts: 30
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| 05 Sep 2008 5:29 Re: Where can i fabricate microstrip and help with GENESYS |
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Hello again,
It is interesting how you seem to get a high pass response with my filter as I have actually manufactured this filter already and the bench test still gives me a band pass response albeit with slightly higher return loss compared to the simulation. I'm not sure why this is happening as my simulations always return band pass response. The only problem i have when i simulate the filter and LNA together is the pass band becomes extremely narrow, Im not so sure why this is happening. Ideally i would like the pass band to be what it was originally without the inclusion of the LNA. As my filter is operating around the 2.2 GHz mark, the return loss below 1.6 GHz does not worry me too much.
The problem i am facing now is getting the layout footprint for the LNA. It is a 3 x 3 mm QUAD FLATPACK NO-LEAD (QFN) package. The package outline can be found here:
http://www.hittite.com/content/documents/package_pcb_layout/lp3_package_info.pdf
I cant seem to find the footprint layout for this type of package for the Genesys software (dxf/gerber format). Im not sure how to design the footprint myself as I've never been taught how to do so and have no experience in it whatsoever. I dont want this issue messing up my project. I was hoping someone could tell me where I could possibly find this footprint or maybe even help me out with it. It would be greatly appreciated![/u]
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webdog
Joined: 13 Nov 2001
Posts: 111
Helped: 9
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| 06 Sep 2008 0:07 Where can i fabricate microstrip and help with GENESYS |
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I had a quick go at the file... and noticed that the filter is extremely narrow, hence very lossy. Something has happened with your circuit. I did regenerate the filter and acheived 100 MHz b/w, then added the Hittite data from your de-embedded data, as I had no s2p files. Now I get the proper gain and passband!
Attached file is three screen grabs, first is what your circuit looks like, second is what I get when I recreate the filter using M-filter. Third picture shows how it looks like with the two amplifiers attached.
Note you cannot have the opimizing goals set your way when having two amplifers, as the gain will be so much higher, this is true also in the stopband. The circuit will collapse during optimization.
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selva500
Joined: 27 Apr 2008
Posts: 30
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| 06 Sep 2008 2:09 Re: Where can i fabricate microstrip and help with GENESYS |
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Many thanks for that. Im not so sure what u mean when u say that i cannot have the opimizing goals set your way when having two amplifers, as the gain will be so much higher, this is true also in the stopband. The circuit will collapse during optimization.
How do you get the response of the filter with the amplifiers attached without optimizing it. Or how does the circuit know that there are amplifiers attached to it. I thought the way of getting the filter response is to use the optimization feature. Is there another way of doing this w/o optimization? Also the insertion loss at the start of the passband seems to be high, is there a way to mitigate this at all? It may be helpful if you cud send your workspace if you dont mind. Do you have any suggestions regarding the footprint at all? Thanks again.
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webdog
Joined: 13 Nov 2001
Posts: 111
Helped: 9
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| 06 Sep 2008 11:01 Where can i fabricate microstrip and help with GENESYS |
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What I tried to say is that you cannot have the same stop band attenuation with and without amplification. You have to alter the optimization goals to reflect that you have added gain into the circuit.
After attaching the amps, you get the circuit response, pressing recalc button, and it will be updated.. you can then optimize the circuit, but using new goals.
As for the footprint, you have all the information in the Hittite document, it's just to copy that in the footprint editor.
BTW the gain from the two de-embedded amps do differ a lot in the passband... why? They should be pretty equal?? Could this data be the root cause of the poor match in low-end of passband? I have not the s2p-files for the Hittite components.
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RF-OM
Joined: 03 Aug 2007
Posts: 607
Helped: 113
Location: The Earth
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| 09 Sep 2008 18:30 Re: Where can i fabricate microstrip and help with GENESYS |
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To selva500,
Sorry, I was too busy these days to check EDA site. I got high pass response by simulating what you gave me (if I remember it right). Regarding layout: I never create footprint in Genesys itself. What I did is to ask professional PCB designer create footprint for me and then transfer it to dxf file to use with EM simulators. Frankly speaking I do not remember how I use dxf with Genesys, may be with other programs. Usually you can find similar footprint in Genesys and try to simulate with this footprint. Results will be close if parasitic parameters for these footprints are close.
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selva500
Joined: 27 Apr 2008
Posts: 30
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| 15 Sep 2008 14:48 Re: Where can i fabricate microstrip and help with GENESYS |
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Hi
I have been trying to simulate an interdigital filter with the LNA attached to it. The linear simulation looks reasonably good but when it comes to the EMPower simulation things don’t go as well. Im not too sure why this is happening. Does EMPower account for the LNA attached to the filter because as I see it I don’t think it does. Is there a way I can set this set up? And Im not sure why the EM response is not so good either (S11 is very high and S21 is narrow bandwidth), I don’t see anything wrong with the circuit and I regenerated this circuit from scratch, it isn’t based on any of my previous designs either. I have attached my workspace and the s2p files for the LNA in the link below. I would appreciate it if someone could have a look.
http://www.mediafire.com/?i3xohjklpab
Another question I have is when I finally integrate the LNA and connect it to the filter. Do I need some sort of impedance matching from the LNA to filter and back to the LNA again or I connect it straight to the feed lines (I don’t think the TL from the LNA will be the same width as the feed lines) or can I just omit the feed lines and connect the TL from the LNA straight to the resonators?
Lastly, the LNA is a No-Lead LP3 package. I assume there wont be any legs on the component to solder it on to the PCB. How do I then attached the LNA to the PCB. Is there a way to solder it manually or must it be done by a device of some sort?
Many thanks for your help.
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selva500
Joined: 27 Apr 2008
Posts: 30
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| 18 Sep 2008 6:50 Re: Where can i fabricate microstrip and help with GENESYS |
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| Any thoughts anyone?
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selva500
Joined: 27 Apr 2008
Posts: 30
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| 23 Sep 2008 2:45 Re: Where can i fabricate microstrip and help with GENESYS |
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Hello,
I've sort of figured out why EMPower simulation is not as good as the linear one when the LNA is connected to it. When i connect up the LNA in the schematic and optimize it, the circuit is optimised for the scenario when the LNA is connected. But since the LNA is invisible to EMPower, the EM response isnt very good. Is there a way that I could set up EMPower to take into account the LNA when running the simulation? How do i do this? Currently, I have set the LNA to be replaced by a short circuit in the layout. Do i have to set it up so that the footprint shows up? I wouldnt think that this will make a difference will it? It will be good if I can see the EM response with the LNA attached. I would really appreciate it if someone could tell me how I can do this.
Another question which I have posted before is, Do I need some sort of impedance matching from the LNA to filter and back to the LNA again or I connect it straight to the feed lines (I don’t think the TL from the LNA will be the same width as the feed lines) or can I just omit the feed lines and connect the TL from the LNA straight to the resonators (ie will there be any matching issues)?
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