Best DDS sig gen card

That almost calls for a selfbuilt solution. A DDS is quickly done, and 5 of them fit nicely into an FPGA. Just add a DAC and you're there.

Rene

--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

Hello Rene,

Well, sure it can be built quickly. But then there are those jobs that many of us dread such as creating a reliable USB interface and writing the GUI and control software.

Mark, I suppose this might be above the price line you had in mind but these guys make such generators:

This might be interesting:

As to AM/FM/phase and all that I don't know if there is enough market. Maybe these things come with flexible enough SW. I don't know Softmark but you might just want to contact them about it.

Regards, Joerg

I don't think the AD DDS parts will do much other than FSK.

I did an FPGA based arbitrary waveform generator that had all the pieces needed to make a DDS generator with AM/SSB/FM/phase. It is actually possible to modulate the arbitrary waveform onto a carrier. It uses 10% of an XC3S400 plus 14 of the 16 blockrams (for the 16384 point ARB table). It works quite nicely, but I never did make a nice interface for it. It was a senior design project from my BSEE degree. I have been meaning to put the verilog up on the net, but never have. Send me an email if you are interested in it. I used the CORDIC algorithm for the mixer.

The paper I submitted is at

(2.6 MB PDF).

-- Darrell Harmon

Hello Darrell,

Most are just used as simple frequency generators.

Thanks for the offer by I don't need a DDS card right now. Mark, the original poster might.

Nice web site. This particular PDF didn't load, always stopped with a blank sheet. Your spectrum analyzer project could be interesting. There should be a significant market if it could be realized without the parts you mentioned as being prohibitively expensive. Currently there is no "faceless" PC-based spectrum analyzer I know of that covers the usual EMC band and can be connected via USB.

Regards, Joerg

Hi Joerg,

My suspicion for awhile has been that Agilent, Tek, and R&S aren't particularly interested in that market because the revenue would be so much less.

What frequencies do you consider to be "the usual EMC band?" Up to ~3GHz? Or lower?

---Joel

Hello Joel,

Well, yes, and that's why I thought that the 2nd tier companies would jump on the opportunity. All you have to provide is a plastic box with a BNC jack on one side and a USB jack on the other, some electronics in the middle and a nice SW package.

150kHz through 1GHz suffices for most EMC work and it doesn't need a dynamic range from here to the Klondike. There also isn't much of a need to go below the 9kHz CISPR bandwidth which should make it even less expensive. Frequency stability is not that important either.

Some people think that an EMC analyzer should be able to detect FM or TV modulation to distinguish between "real" EMC problems and spoofers. But after a couple decades on the beat I have to say that ain't so, we know how to waive our hands to figure that out :-)

Regards, Joerg

"Joerg" a écrit dans le message de news:DVq8g.70478$F snipped-for-privacy@newssvr29.news.prodigy.net...

mentioned

PC-based

much

~3GHz? Or

Hameg had a small box exactly like that (with a bonus CRT :-). I think it is (was?) in the $2K range, with or without a track gen.

--
Thanks,
Fred.

Hello Fred,

They do and it's a nice box. We bought it at my previous job and IIRC the $2k was without the tracking generator which you don't need for EMC work anyway. Susceptibility is done with lots more power and I typically use a regular bench generator to drive the big amp.

However, $2k is still a lot for a device that gets banged up during travel and the Hameg is too large if you want to fly with carry-on only. When doing that I try not to be a space hog and cram it all into a pilot's case. By the time the razor, several shirts and a sports jacket has been tossed inside there ain't much space left. A little EMC pod for the laptop would really be nice.

Regards, Joerg

I am not sure what is happening with that PDF. I use ps2pdf to make them and I have never had a problem. Maybe your version of Acrobat reader doesn't like it.

If the network analyzer portion was removed, my design would be much simpler. The FPGA could be eliminated and replaced with a digital down converter. The only difficult or expensive parts would be the 2.15 to

3.95 GHz 1st LO and the 1st IF bandpass filter. The current filter is machined from a block of copper. This is great for performance, but not for cost. It may be possible to sacrifice some image rejection or go to a more complex architecture to avoid this filter. I have heard of some VCO designs covering nearly an octave. If not, it could be split into bands. Of course, all of this adds complexity.

I believe the whole thing could fit on a 4x6 inch board. I may consider doing it sometime in the future so others could assembly one. That is assuming they are not afraid of a 176LQFP. At least there would be no BGA FPGA. The one I am building now is just for learning purposes and having fun. I have about $1000 in it. This is about 30% the 2 4 layer board prototypes, 30% digikey and the rest is connectors and mechanical bits like the case. Assuming it all works out and my time is free, it will be a good deal, but considering my time at McDonalds pay, I could have bought an Agilent.

-- Darrell Harmon