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ADS using Harmonic Balance with mixers - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


dstraight
Post subject: ADS using Harmonic Balance with mixers Posted: Sun Oct 02, 2005 6:40 pm

Captain

Joined: Sun May 09, 2004 1:23 am
Posts: 10
Location: Morgan Hill, CA (Silicon Valley, Bay Area)
Hello all,

I am having trouble simulating a mixer with ADS's Harmonic Balance. I would like to, very much, sweep the frequency source feeding the RF port of the mixer while using a single frequency source (non-swept) at the LO port. I desire to measure the IF output over the swept frequency (or, quite possibly, frequencies higher than the swept frequency depending upon which sideband I want to view at the IF port). Although I have not successfully performed a sweep with a second CW source using the Harmonic Balance engine I have been able to simulate two CW sources in the RF and IF port of the mixer. Also, I can sweep one source with the harmonic balance simulator, but it appears that I cannot use a second source while doing so. For whatever reason, things fall apart for me when I try to use two source with one being swept. Any help would be much appreciated.

I documented my issue with ADS here (once you visit the link click on each icon to make the picture larger and readable):
http://www.pbase.com/dstraight/harmonic ... and_mixers

I will also try to embed the same information in this message (but if it doesn't work then use the link supplied above - you should see four pages in this posting). If none of my links work and you're interested then email me and I'll either post again or email you back.

Many thanks,

David




<img src="http://www.pbase.com/dstraight/image/50162072/original.jpg" border="0" />

<img src="http://www.pbase.com/dstraight/image/50162073/original.jpg" border="0" />

<img src="http://www.pbase.com/dstraight/image/50162074/original.jpg" border="0" />

<img src="http://www.pbase.com/dstraight/image/50162075/original.jpg" border="0" />


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dstraight
Post subject: Posted: Sun Oct 02, 2005 6:52 pm

Captain

Joined: Sun May 09, 2004 1:23 am
Posts: 10
Location: Morgan Hill, CA (Silicon Valley, Bay Area)
Let's try embedding those pictures again....

Here they are...







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pallavi_d
Post subject: Harmonic balance and ADSPosted: Thu Oct 06, 2005 4:58 am

Captain

Joined: Thu Oct 06, 2005 3:45 am
Posts: 7
Location: India
Hi David,

If you want to sweep RF frequency and keep LO Freq constant, you can just use the template provided in ADS.
There is an example of Gilbert Cell Mixer in ADS, you can just use the sweptrf.dsn file and modify it according to your freqency range.
It should work , i have used it .
But still if you ahve further problems , do let me know, i will try to solve it.

regards,
Pallavi


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dstraight
Post subject: Re: Harmonic balance and ADSPosted: Thu Oct 06, 2005 12:47 pm

Captain

Joined: Sun May 09, 2004 1:23 am
Posts: 10
Location: Morgan Hill, CA (Silicon Valley, Bay Area)
pallavi_d wrote:
Hi David,

If you want to sweep RF frequency and keep LO Freq constant, you can just use the template provided in ADS.
There is an example of Gilbert Cell Mixer in ADS, you can just use the sweptrf.dsn file and modify it according to your freqency range.
It should work , i have used it .
But still if you ahve further problems , do let me know, i will try to solve it.

regards,
Pallavi



Hello Pallavi,

Thanks for offering a helping hand. I use ADS a lot for s-parameter simulations and occasionally delve into harmonic balance. However, I find that I do not use harmonic balance very much because I am not so familiar with how variables are used and how to set up many seemingly useful features in the harmonic balance engine. Sometimes I look at examples and sometimes that helps.

I am late for work right now, but I did look at the project (sweptrf.dsn). I can see that the project runs correctly so then copied it into another directory and only added a net called VLO at the port of the LO so that I could view signals at this port. I ran the project again and then attempted to plot spectral output of the LO and RF port of the mixer. What I found was inconsistent power levels at these ports. The plots that I produced power (in dBm) over swept frequencies and for each the LO and RF the levels were -50dBm and below. I believe the LO should be -5dBm and the RF was something higher than this.

I didn't change much other than adding the label (net) "VLO" yet the project seems to work correctly (aside from the plots I tried to generate). Can you try what I did and let me know if you see the same? I am a bit rushed right now so maybe I've missed something.

As I've mentioned I'm late for work and will not be able to look at this more until about 10pm tonight. At that time if I have the energy I'll look at this some more and perhaps post more information using nice pictures.


Many thanks,

David


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dstraight
Post subject: Posted: Thu Oct 06, 2005 4:27 pm

Captain

Joined: Sun May 09, 2004 1:23 am
Posts: 10
Location: Morgan Hill, CA (Silicon Valley, Bay Area)
Okay, I decided to drive home for lunch so that I could gather a few screen captures (I am lucky in that I live and work in the same town).

Below is a schematic of the example design (SweptRF.dsn) from the Mixers_prj project and below this we see graphs of the resultant simulation.

As stated in my last post I've only added one net at the LO port of the mixer and named it "VLO" then I produced a plot of the VLO and Vrf (verses swept RF frequency, Frf) as shown in the graphs below. The third screen capture shows the most detail.

As can be seen from these graphs the project appears to be running correctly, but when I try to look at the signals going into the mixer I do not see anything that would make sense. In the graphs RF power should say -20dBm at 1GHz and LO power should read -5dBm at 1GHz-70MHz= 930MHz, but as the two graphs show LO power is below -50dBm and RF power is below -60dBm.

Perhaps the graphs that I have drawn take frequency samples that do not sample exactly at 1GHz and 930MHz thus explaining absence of power. I do not know.








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pallavi_d
Post subject: Harmonic balance for Mixers in ADSPosted: Fri Oct 07, 2005 8:21 am

Captain

Joined: Thu Oct 06, 2005 3:45 am
Posts: 7
Location: India
Hello David,

If you want to see the IF spectrum , just use the template Convgain.dsn (again an example, but it helps) modify it according to the IF freq you want and see the results.

To sweep the RF freq , as i have already told use sweptrf.dsn
I also worked on it today(on sweptrf.dsn) and if you want to see the spectrum at RF and LO port , only naming the nodes as Vlo and Vrf won't work.

In the data display window write an equation:

RF_spectrum=dBm(HB.Vrf) , similarly for LO spectrum and you will see the plots over harmonic index.

When i plotted them over RF freq , i get to see the power level at RF port at particular frequencies(it is constant as i haven't swept the rf power )

You can use all the example designs for mixer and modify it according to the plots you want to see.

I dont know if you are satisfied with my answer, but still let me know your feedback.

regards,
Pallavi


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dstraight
Post subject: Posted: Fri Oct 07, 2005 11:42 am

Captain

Joined: Sun May 09, 2004 1:23 am
Posts: 10
Location: Morgan Hill, CA (Silicon Valley, Bay Area)
Hello Pallavi,

Many thanks taking the time to help me with this. It is much appreciated. I am hoping to learn harmonic balance well enough so that I can use it for work as there are many features that seem very useful (such as NoiseCons for mixers). But, one thing at a time.

By suggestion I created two variables each for the RF and LO and also created plots showing power verse harmonic index. I can see that the power levels correspond well with set values on the original schematic.

This is probably a stupid question, but how do I relate harmonic index to frequency?

Also, I tried placing a marker on some of these frequencies and I did notice that the frequency of the swept RF "Frf" was displayed. As can be seen in the graph multiple frequencies were lined up on top of each other (probably due to sweeping, number of harmonics of each source and maximum order to solve).

I did notice that the power level was slightly higher than expected. For example, I've placed the cursor showing -19.5dBm (Frf=3GHz) at harmonic index 6. Likewise, -3.8dBm (Frf=3GHz) at harmonic index= 5. I would have expected to see -20dBm and -5dBm respectively.

Do you have any idea why the power level is higher than what the source says it should be?


David




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pallavi_d
Post subject: Harmonic Balance in ADSPosted: Sat Oct 08, 2005 2:56 am

Captain

Joined: Thu Oct 06, 2005 3:45 am
Posts: 7
Location: India
Hi David,

I have no problem spending time on your query as i am myself working on MMIC mixer in ADS,it is also helpful for me.
Ok , the relation between frequency and harmonic index is:
Freq= c1*f1+c2*f2+c3*f3+............+cn*fn

where c1,c2........cn are harmonic index
I am also giving you a link which gives u the pdf .
maybe u have read it , if not just go through it , it will be helpful

xanadu.ece.ucsb.edu/~long/ ece145a/ADS_Harmonic_Balance_w03.pdf

Regarding the power level its showing , it again has to do with harmonic index.This article can provide the answer.

regards,
Pallavi



Posted  11/12/2012
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