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How do I measure signals in the GHz range?

S

Saul Bernstein

Jan 1, 1970
0
Hello,

I've got a storage oscilloscope here with a bandwith of 6 GHz. Unfortunately
only the default probes with 500 MHz bandwidth are included.

Now I would like to measure signals in the range of 2.5 gigabit per second.
Thus, I am looking for suitable probes with sufficient high bandwidth. But I
think bandwidth is not all there is to consider. There is also the question
whether to use active or passive probes and probably impedance and
capacitance will also play a mayor role.

In addition, the signals I would like to measure on the board are routed
differentially (selfevident at the frequencies!), so that differential probe
would surely be the suitable choice here. But wouldn't it be possible to
measure asymmetrically to ground potential, anyway?

Guys, how do I find the right solution for my task? Unfortunately I'm an
absolute newbie in measurement technique so pardon me for bothering you. I
already hit some books but I couldn't find out, anyhow.

Thanks for support. Saul
 
R

René

Jan 1, 1970
0
Hello,

I've got a storage oscilloscope here with a bandwith of 6 GHz. Unfortunately
only the default probes with 500 MHz bandwidth are included.

Now I would like to measure signals in the range of 2.5 gigabit per second.
Thus, I am looking for suitable probes with sufficient high bandwidth. But I
think bandwidth is not all there is to consider. There is also the question
whether to use active or passive probes and probably impedance and
capacitance will also play a mayor role.

In addition, the signals I would like to measure on the board are routed
differentially (selfevident at the frequencies!), so that differential probe
would surely be the suitable choice here. But wouldn't it be possible to
measure asymmetrically to ground potential, anyway?

Guys, how do I find the right solution for my task? Unfortunately I'm an
absolute newbie in measurement technique so pardon me for bothering you. I
already hit some books but I couldn't find out, anyhow.

Thanks for support. Saul
Though I never tried GHz range stuff, I did use the resistive probe as
described:

http://www.signalintegrity.com/Pubs/straight/probes.htm

And cheap too :)
 
In addition, the signals I would like to measure on the board are routed
differentially (selfevident at the frequencies!), so that differential probe

What's so "self-evident" about it? Your sat TV receiver works at 12GHz
and is 100% unbalanced.

You don't say what the measurements are supposed to be for. When
working with data at these rates, the correct tool these days is a
BERT, or J-BERT, not a scope.

Unless your "scope" is a BERT with a missing personality module...
 
L

larwe

Jan 1, 1970
0
Hello,

I've got a storage oscilloscope here with a bandwith of 6 GHz. Unfortunately
only the default probes with 500 MHz bandwidth are included.

Heterodyne the 2.5GHz signals down to 200MHz or so ;)
 
H

Hans-Bernhard Bröker

Jan 1, 1970
0
[F'up2 was missing --- fixed]

What's so "self-evident" about it? Your sat TV receiver works at 12GHz
and is 100% unbalanced.

Pardon the French, but that's nonsense. Nothing in a sat receiver works
at 12 GHz. That's self-evident if you take just a quick look at the
antenna cable --- no way a 12 GHz signal can survive 10+ meters of that
coax cable and connectors.

The only place 12 GHz take place in a sat TV setup is in the LNB (for
those who don't know: that's the gadget at the end of that arm, near the
center of the dish). From there onwards the signal is in the 1..2 Ghz
range, at most.
 
[F'up2 was missing --- fixed]

What's so "self-evident" about it? Your sat TV receiver works at 12GHz
and is 100% unbalanced.

Pardon the French, but that's nonsense. Nothing in a sat receiver works
at 12 GHz. That's self-evident if you take just a quick look at the
antenna cable --- no way a 12 GHz signal can survive 10+ meters of that
coax cable and connectors.

The only place 12 GHz take place in a sat TV setup is in the LNB (for
those who don't know: that's the gadget at the end of that arm, near the
center of the dish). From there onwards the signal is in the 1..2 Ghz
range, at most.

You're right, I meant the LNB. But there's nothing self-evident about
going differential at a certain frequency.
And I consider the antenna and LNB to be part of the receiver. :)
If a signal won't survive in a coax, it won't survive any better just
because you use two...
 
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