PC based DIY Oscilloscopes, logical analyzers, spectrum analyzers, etc...

[Abstract Dissonance]

I'm wondering if anyone has information about DIY equipment listed in the
title. After all, the heart of all those would simply be an ADC?

I'm looking for something that has a bandwidth of atleast 100Mhz that is
very simple to do(doesn't have to be fancy). Basically I just need to get
the data into the PC... after that its pretty easy to emulate the above.

I figure that one just needs and ADC, a PGA, a probe, and a pic to configure
the ADC and PGA. I'm not sure about which interface to use though. I was
thinking about USB2.0 or something similar but it would require additional
components. (I'm not sure if USB has some type of streaming protocol or
not... in any case it probably wouldn't be a good idea unless it is the only
device using it). Maybe some type of PCI interface would work?

Any ideas?

Thanks,
Jon

 

[[email protected]]

I'm wondering if anyone has information about DIY equipment listed in the
title. After all, the heart of all those would simply be an ADC?

I'm looking for something that has a bandwidth of atleast 100Mhz that is
very simple to do(doesn't have to be fancy). Basically I just need to get
the data into the PC... after that its pretty easy to emulate the above.

I figure that one just needs and ADC, a PGA, a probe, and a pic to configure
the ADC and PGA. I'm not sure about which interface to use though. I was
thinking about USB2.0 or something similar but it would require additional
components. (I'm not sure if USB has some type of streaming protocol or
not... in any case it probably wouldn't be a good idea unless it is the only
device using it). Maybe some type of PCI interface would work?

Probe -> ADC -> FPGA/CPLD -> Computer-I/O

Computer-I/O can be ethernet, firewire, usb, pci, pic-e etc.. depending on your
choice for complexity, speed, and latency.

USB has an isochronous mode that will transmit frames without retransmitting
any faulty ones. That mode should fit this purpose.
USB have serious overhead problems thoe.

I hope you know your groundplanes, shielding, impedance matching etc..

 

[Joerg]

Hello Jon,

I'm wondering if anyone has information about DIY equipment listed in the
title. After all, the heart of all those would simply be an ADC?

If you come across a USB spectrum analyzer for EMI pre-compliance work
(150kHz through 1GHz) let me know. There is a huge market for this stuff
but companies that make spectrum analyzers do not seem to understand.
Even the small ones don't.

 

[EE123]

Hello Jon,



If you come across a USB spectrum analyzer for EMI pre-compliance work
(150kHz through 1GHz) let me know. There is a huge market for this stuff
but companies that make spectrum analyzers do not seem to understand.
Even the small ones don't.

--
Regards, Joerg





Joerg;

There is a huge market for this stuff
but companies that make spectrum analyzers do not seem to understand.
Even the small ones don't.

Are you looking for "fewer features" just to do pre-EMI?
Lower cost?

Can you elaborate?

Dave

 

[Nico Coesel]

Hello Jon,



If you come across a USB spectrum analyzer for EMI pre-compliance work
(150kHz through 1GHz) let me know. There is a huge market for this stuff
but companies that make spectrum analyzers do not seem to understand.
Even the small ones don't.

Patience. Working on it

 

[martin griffith]

Hello Jon,



If you come across a USB spectrum analyzer for EMI pre-compliance work
(150kHz through 1GHz) let me know. There is a huge market for this stuff
but companies that make spectrum analyzers do not seem to understand.
Even the small ones don't.

seen this
http://www.tti-test.com/products-tti/rf/spectrum-analyzer.htm ?
It even plays MP3s while you are working, and picks up blooteeth viri
as well


martin

 

[Joerg]

Hello Martin,

seen this
http://www.tti-test.com/products-tti/rf/spectrum-analyzer.htm ?
It even plays MP3s while you are working, and picks up blooteeth viri
as well

Yes, I have seen those. A company in Germany (Aaronia) makes a whole
range of them.

I am looking for something cheaper and most of all smaller. No display,
no battery, no keyboard. A laptop or PDA that you already have to
schlepp along anyway can do all that. Or, pretty soon I guess, a fancy
cell phone.

 

[Joerg]

Hello Dave,

Are you looking for "fewer features" just to do pre-EMI?

Yes. You don't need narrow IF filters. In fact, you don't need a whole
lot of parameter settings at all. Experienced users know what's going to
leak, they just need to know how bad it is.

Typically the situation is: Client got black eye at the compliance lab.
Sends you the plots, you look at them, choke a little, cuss a little,
and book a flight. All you really need to know is i.e. that 360MHz is
the third of the processor clock and it need to be muffled by another
15dB plus a 10dB "angst" margin.

Lower cost?

Yes, but most of all size. It would be nice to have something the size
of a pack of cigarettes or two that plugs into USB.

Can you elaborate?

Pretty much what Martin suggested but without display, battery and
keyboard. And smaller.

 

[Joerg]

Hello Nico,

Patience. Working on it

Let us know when it matures.

 

[[email protected]]

seen this

Yes, I have seen those. A company in Germany (Aaronia) makes a whole
range of them.

I am looking for something cheaper and most of all smaller. No display,
no battery, no keyboard. A laptop or PDA that you already have to
schlepp along anyway can do all that. Or, pretty soon I guess, a fancy
cell phone.

How fast shall the swep be done ..?

I've seen 50 MHz USB2 "scopes" already on the market (VERY small). Maybe such
could be programmed to do your spectrum measurements?
(frequency might be the akilles heel thoe I suspect

 

[Stanislaw Flatto]

I'm wondering if anyone has information about DIY equipment listed in the
title. After all, the heart of all those would simply be an ADC?

I'm looking for something that has a bandwidth of atleast 100Mhz that is
very simple to do(doesn't have to be fancy). Basically I just need to get
the data into the PC... after that its pretty easy to emulate the above.

Any ideas?

Thanks,
Jon

Math = for sampling and reconstructing a sinusoidal wave you need _at
least_ two samples per cycle, usually you use more, because you want to
see distortions and so on. So your ADC has to be able to pass the
processed info in digital word to some storage before the next sampling
occurs. The rest is trivial as your display can reconstruct this info at
its own pace.
How simple it is you will find out!

Good luck

Stanislaw
Slack user from Ulladulla.

 

[Tim]

Abstract Dissonance wrote

I'm wondering if anyone has information about DIY equipment listed in the
title.

We have the logic analyzer stuff at DIYish prices. See www.rockylogic.com

 

[Joerg]

How fast shall the swep be done ..?

It doesn't matter much, a few seconds would be ok.

I've seen 50 MHz USB2 "scopes" already on the market (VERY small). Maybe such
could be programmed to do your spectrum measurements?
(frequency might be the akilles heel thoe I suspect

Not really. You need a mixer and a sweep oscillator. Similar to what a
scanner radio does. Also, it has to have enough dynamic range so it
isn't thrown off the rocker by a strong local TV signal or a cell tower,
or by someone in the building using a cell phone.

 

[Jim]

Joerg, here is a wwebsite that has a design for a spectrum analyzer, and
a complete kit if parts, that looks as if it would work for your
requirements.

http://www.zianet.com/erg/

And here is the website that goes into the technical details....
Actually, this fellow did the original design and the other one liked it so
much he produced a set of PC boards and the components.

http://users4.ev1.net/~wsprowls/


Personally, I am impressed and seriously thinking of building one.


Jim Pennell

--

18:40 Pacific Time Zone
Jun 14 2006

International Time
01:40 UTC
15.06.2006

 

[Ben Jackson]

Yes. You don't need narrow IF filters. In fact, you don't need a whole
lot of parameter settings at all. Experienced users know what's going to
leak, they just need to know how bad it is.

This reminds me of ed, whose only error is '?', about which it has
been said: The experienced user will know what is wrong.

 

[David L. Jones]

I'm wondering if anyone has information about DIY equipment listed in the
title. After all, the heart of all those would simply be an ADC?

I'm looking for something that has a bandwidth of atleast 100Mhz that is
very simple to do(doesn't have to be fancy). Basically I just need to get
the data into the PC... after that its pretty easy to emulate the above.

Forget analog bandwidth for a minute, what sample rate do you need?
100MS/s is about the top you get in low priced units. That gives you an
effective single shot bandwidth in the order of 10MHz. If you want
100MHz single shot analog bandwidth you need at least 1GS/s, you can't
do that yourself.
You can push it to a few hundred MS/s is you rolled your own, but it's
not easy.
If you don't know what "single shot bandwidth", "effective bandwidth",
and "repetitive sampling" are, you should learn before you embark on
such a project.
Repetitive sampling sucks, you don't want to go there, although if you
really need 100MHz analog bandwidth you will have no choice.
The hardest part is the analog front end. You need an input buffer and
a selectable gain stage. If you want it for a single input voltage
range it makes your life easier, but I would go to all that trouble and
not include a proper CRO front end attenuator.

I figure that one just needs and ADC, a PGA, a probe, and a pic to configure
the ADC and PGA. I'm not sure about which interface to use though. I was
thinking about USB2.0 or something similar but it would require additional
components. (I'm not sure if USB has some type of streaming protocol or
not... in any case it probably wouldn't be a good idea unless it is the only
device using it). Maybe some type of PCI interface would work?

USB is the key, but you need sample buffering. You would not stream it
via USB in real time, no one does that.
Everyone buffers it inside an FPGA these days if you only need a few KB
of sample memory (which is not very good), or using external SDRAM for
larger sample buffers.

Dave

 

[Joerg]

Hello Jim,

Joerg, here is a wwebsite that has a design for a spectrum analyzer, and
a complete kit if parts, that looks as if it would work for your
requirements.

http://www.zianet.com/erg/

And here is the website that goes into the technical details....
Actually, this fellow did the original design and the other one liked it so
much he produced a set of PC boards and the components.

http://users4.ev1.net/~wsprowls/

Thanks. Interesting, but why on earth do most of these contain a
bazillion little circuit boards that must be interconnected. Makes no
sense to me. The best approach would be one board, one BNC connector and
one USB plug.

Personally, I am impressed and seriously thinking of building one.

If I was retired I'd do that as well. But I'd rather buy something right
now.

 

[[email protected]]

I'm wondering if anyone has information about DIY equipment listed in the
title. After all, the heart of all those would simply be an ADC?

I'm looking for something that has a bandwidth of atleast 100Mhz that is
very simple to do(doesn't have to be fancy). Basically I just need to get
the data into the PC... after that its pretty easy to emulate the above.

I figure that one just needs and ADC, a PGA, a probe, and a pic to configure
the ADC and PGA. I'm not sure about which interface to use though. I was
thinking about USB2.0 or something similar but it would require additional
components. (I'm not sure if USB has some type of streaming protocol or
not... in any case it probably wouldn't be a good idea unless it is the only
device using it). Maybe some type of PCI interface would work?

Any ideas?

http://www.dsoworld.co.uk/
http://www.johann-glaser.at/projects/DSO/
http://www.geocities.jp/ojisan_koubou/allpurpose/index.html
http://www.fpga4fun.com/digitalscope.html
http://alternatezone.com/electronics/dsoamk3.htm

You'r not the first one.

Btw, should anyone else care to lookup more projects in this area, pls
post the links..

Consider if you want storage or realtime. If storage is your way then it's no
big deal with transfers as it can happen in any speed. However for realtime
your pipe(s) better keep up with capacity and latency.

Also consider what interface you want to use to get the data into the pc.

There's other gotchas.. like if you do 3Gsps 8bit. Then PCI-e bus be 79%
busy with sampleing data. And you can't save anything because your bus is
simple stuffed. Unless there's two of them. Be happy you don't need 1TByte/s
like cern.ch
For 3GByte/s you would need something like Raid-0 with 40 discs. For 1TB/s
you would need to divide signal and then use raid systems.

 

[[email protected]]

Joerg skrev:

Hello Jon,



If you come across a USB spectrum analyzer for EMI pre-compliance work
(150kHz through 1GHz) let me know. There is a huge market for this stuff
but companies that make spectrum analyzers do not seem to understand.
Even the small ones don't.

Would a 2Gs ADC and an FFT on the PC be any good? the ADCs at that
speed
doesn't provide too many bits, so the dynamic range would be limited.
maybe with some selectable input filters and bandpass sampling?

-Lasse

 

[Joerg]

Hello Lasse,

Would a 2Gs ADC and an FFT on the PC be any good? the ADCs at that
speed
doesn't provide too many bits, so the dynamic range would be limited.
maybe with some selectable input filters and bandpass sampling?

Not really. You need well north of 80dB of true dynamic range because
there is so much pollution nowadays. Cell phones everywhere, plus
wireless this, that and the other thing.

The other issue is power. Such an ADC would take one big slurp and your
laptop battery is gone.

Best would be something like a scanner. One analyzer I built back at the
university used a ladder of simple varicap-tuned oscillators and one
mixer. This created a "zero IF" scheme where you'd always get a double
peak but for this kind of application it might be ok. Unfortunately I
built if for the RF institute so I had to leave it there. Sigh. Well, it
didn't quite go to a GHz anyway.

Later I built something like that around a Plessey SL6440 but again not
for myself. Man, those were incredible mixers. History, AFAIK. Somehow
much of the good stuff doesn't seem to make it. But I still do have some
of those Plessey mixers. They boast a dynamic range from here to the
Klondike.