Oscilloscope Bandwidth!

[Myauk]

Can anybody tell me the highest frequency that can be measure with the
oscilloscopes these days.
As far as I have known, it is about 1GHz I think.
How will they capture of the waveforms of the clock signals for
microprocessor?
How can we measure the characteristics of the waveforms in High Speed
Circuits.
There are many application notes but still I need some initiatives.
I think the highest clock speed is about 4GHz.
Regards

 

[Robert Lacoste]

Can anybody tell me the highest frequency that can be measure with the
oscilloscopes these days.
As far as I have known, it is about 1GHz I think.
How will they capture of the waveforms of the clock signals for
microprocessor?
How can we measure the characteristics of the waveforms in High Speed
Circuits.
There are many application notes but still I need some initiatives.
I think the highest clock speed is about 4GHz.
Regards

You are a couple of years late...
With sampling scopes (ie working in undersampling mode on repetitive
signals) the best scope you can find are as far as I know the Lecroy
Waveexpert series... with a bandwitdh of 100GHz ! For realtime sampling you
can find products with bandwidths up to 15GHz/40Gsps (TDS6154C from Tek or
similar from Agilent), or even 18GHz/60Gsps with more specialized serial
data analyzers (Lecroy SDA18000). Of course this all depends on how deep
your pockets are...

Friendly,
Robert
www.alciom.com

 

[Myauk]

 

[David L. Jones]

Can anybody tell me the highest frequency that can be measure with the
oscilloscopes these days.
As far as I have known, it is about 1GHz I think.

Nope, try 100GHz analog bandwidth for repetitive sampling scopes, like
this one:
http://www.lecroy.com/tm/products/Scopes/WaveExpert/default.asp

How will they capture of the waveforms of the clock signals for
microprocessor?

Huh?
Same way they always have! :->

How can we measure the characteristics of the waveforms in High Speed
Circuits.

Repetitive or single shot? Do you know the difference?, it's
important...
In either case you do it with a very careful probing, and specially
designed high bandwidth probes.

There are many application notes but still I need some initiatives.
I think the highest clock speed is about 4GHz.

You want to measure a 4GHz clock signal?
If that is the case then you need a VERY serious oscilloscope, a VERY
serious amount of money, and even more serious probing. If you have to
ask this sort of question then I'd question whether or not you actually
have the ability to build or measure this sort of stuff, even if you
had the right gear.
And no, a 4GHz bandwidth scope will not allow you to view the
characteristics of a 4GHz clock signal.

Dave

 

[Marte Schwarz]

Hi Myauk,

How will they capture of the waveforms of the clock signals for
microprocessor?
How can we measure the characteristics of the waveforms in High Speed
Circuits.
There are many application notes but still I need some initiatives.
I think the highest clock speed is about 4GHz.

You will never have success for probing a 4 GHz microprocessor clock,
because this signal is not available on any pin outside the chip. Even if
you find a clock signal > 500 MHz outside a processor be aware and don't
touch this. You will destroy this clock with your probe. The useful
frequencies for monitoring wit an osci end at about 20 to 100 MHz depending
on your equipment and knowledge. All above is very special for very high
sophisticated users solvinf´g very sophisticated problems with a huge
budget.

Marte

 

[Myauk]

I am not working on it this time.
I am just curious to know about it because the application note from
Tektronix wrote something about high speed circuit designs.
The signals I am measuring are some audio signals, video signals, and
the clock signal not higher than 100MHz for the signal processing
chipset.
Any way, I am learning from your answers.
Thank you.
Regards

 

[John Larkin]

Hi Myauk,

You will never have success for probing a 4 GHz microprocessor clock,
because this signal is not available on any pin outside the chip. Even if
you find a clock signal > 500 MHz outside a processor be aware and don't
touch this. You will destroy this clock with your probe. The useful
frequencies for monitoring wit an osci end at about 20 to 100 MHz depending
on your equipment and knowledge. All above is very special for very high
sophisticated users solvinf´g very sophisticated problems with a huge
budget.

Marte

Fet probes now go into the low GHz with fractional pF capacitance.
Right now I'm using a Tek SD-14 sampling probe, an ebay find, which
has better than 3 GHz bandwidth at the probe tip and about 0.3 pF
loading.

John

 

[tlbs101]

Can anybody tell me the highest frequency that can be measure with the
oscilloscopes these days.
As far as I have known, it is about 1GHz I think.
How will they capture of the waveforms of the clock signals for
microprocessor?
How can we measure the characteristics of the waveforms in High Speed
Circuits.
There are many application notes but still I need some initiatives.
I think the highest clock speed is about 4GHz.
Regards

In the early 1990's, EG&G/Energy Measurments came up with an analog
oscilloscope tube (not a sampling 'scope) and the accompanying
amplifiers and interfaces that was good to 18 GHz, and would still
function out to 54 GHz (the highest frequency the Naval test lab could
produce). These oscilloscopes were to be used in nuclear weapon
testing, but the US quit testing nuclear weapons in 1992. Five were
built. I was privileged to see one of these units in operation in
1993. To see a 55 pico-second one-shot (not sampled) rise time was
pretty cool.

In the 1980's and 1990's, some French company had also produced analog
oscilloscopes with 10+ GHz bandwidths for use at CERN and other
high-energy physics experiments.

Bottom line: fast analog oscilloscopes exist, but at a high price.

 

[John Larkin]

In the early 1990's, EG&G/Energy Measurments came up with an analog
oscilloscope tube (not a sampling 'scope) and the accompanying
amplifiers and interfaces that was good to 18 GHz, and would still
function out to 54 GHz (the highest frequency the Naval test lab could
produce). These oscilloscopes were to be used in nuclear weapon
testing, but the US quit testing nuclear weapons in 1992. Five were
built. I was privileged to see one of these units in operation in
1993. To see a 55 pico-second one-shot (not sampled) rise time was
pretty cool.

A 55 ps risetime computes to about a 6.5 GHz bandwidth.

In the 1980's and 1990's, some French company had also produced analog
oscilloscopes with 10+ GHz bandwidths for use at CERN and other
high-energy physics experiments.

My friend Bernard still makes it:

http://www.greenfieldtechnology.com/product-standard.html

It uses a traveling-wave-deflection scan converter tube inside. It
used to be relabeled and sold by Tektronix.

Bottom line: fast analog oscilloscopes exist, but at a high price.

Tek 7104's (1 GHz, microchannel plate CRT) are available on ebay. Nice
scopes.

John

 

[Myauk]

Massive Precious Knowledge for me.
Thank you so much.
I got initiative to own my first oscilloscope.
I hope I need to buy one for my experiments!
Regards

 

[Myauk]

Massive Amount of Precious Knowledge for me!
Thanks.

 

[redbelly]

A 55 ps risetime computes to about a 6.5 GHz bandwidth.

John, I'm getting a different answer. From what I can remember, 55 ps
would give a 250 GHz bandwidth:

55 ps risetime (10%-90%) computes to about 25 ps 1/e time (or "RC time
constant")
25 ps time constant computes to a bandwidth of 1/25ps = 40 G-rad/s
= 2*pi*40 GHz = 250 GHz

18 GHz should correspond to a 770 ps risetime.

Am I figuring this correctly?

Mark

 

[Costas Vlachos]

John, I'm getting a different answer. From what I can remember, 55 ps
would give a 250 GHz bandwidth:

55 ps risetime (10%-90%) computes to about 25 ps 1/e time (or "RC time
constant")
25 ps time constant computes to a bandwidth of 1/25ps = 40 G-rad/s
= 2*pi*40 GHz = 250 GHz

18 GHz should correspond to a 770 ps risetime.

Am I figuring this correctly?

Mark

The rise time and bandwidth of a signal are approximately related by the
following equation:

Signal bandwidth = 0.35 / Signal rise time

For a 55 ps signal we have:

BW = 0.35 / 0.055 ns = 6.36 GHz

Now, to *measure* this signal with some useful accuracy we need an
oscilloscope with a much higher bandwidth than 6.36 MHz.

--
Regards,
Costas
_________________________________________________
Costas Vlachos Email: [email protected]
SPAM-TRAPPED: Please remove "-X-" before replying

 

[Costas Vlachos]

The rise time and bandwidth of a signal are approximately related by the
following equation:

Signal bandwidth = 0.35 / Signal rise time

For a 55 ps signal we have:

BW = 0.35 / 0.055 ns = 6.36 GHz

Now, to *measure* this signal with some useful accuracy we need an
oscilloscope with a much higher bandwidth than 6.36 MHz.

In my last sentence I meant 6.36 GHz of course!

--
Regards,
Costas
_________________________________________________
Costas Vlachos Email: [email protected]
SPAM-TRAPPED: Please remove "-X-" before replying

 

[John Devereux]

John, I'm getting a different answer. From what I can remember, 55 ps
would give a 250 GHz bandwidth:

55 ps risetime (10%-90%) computes to about 25 ps 1/e time (or "RC time
constant")
25 ps time constant computes to a bandwidth of 1/25ps = 40 G-rad/s
= 2*pi*40 GHz = 250 GHz

= 40 G-rad/s = w = 2.pi.f

so f = 40G/2.pi = ~6.5GHz.

(You multiplied by 2 pi instead of dividing).

18 GHz should correspond to a 770 ps risetime.

Am I figuring this correctly?

No

Don't worry, I did exactly the same thing a few months ago. For a
while I was trying to design a photodiode amplifier that was 40 times
as fast as it needed to be. Doh.

 

[tlbs101]

A 55 ps risetime computes to about a 6.5 GHz bandwidth.

That was the fastest rise-time pulse generator we had in the lab, at
the time. I was told the 'scope could do much better (i.e. showing a
real-time sine wave display at 54 GHz at some Naval test and
measurement lab).

My friend Bernard still makes it:

http://www.greenfieldtechnology.com/product-standard.html

It uses a traveling-wave-deflection scan converter tube inside. It
used to be relabeled and sold by Tektronix.

Thanks for the link. I always wondered about who 'they' were.

The EG&G 'scope, I am told, was a breakthrough for the guys in Woburn,
Mass. because they changed their way of thinking about the electron-gun
and deflection system: from fine tuning a TWT, to treating the system
like an electron linear accelerator.

Tek 7104's (1 GHz, microchannel plate CRT) are available on ebay. Nice
scopes.

Right! I forgot about the 7100 series systems.

Tom

 

[John Larkin]

Massive Precious Knowledge for me.
Thank you so much.
I got initiative to own my first oscilloscope.
I hope I need to buy one for my experiments!
Regards

I've finally become a full convert to digital, color, LCD scopes. My
personal scope (in my office) is a Tek TDS2012, which handles 90% of
what I do. The digital storage, averaging, and FFT things are neat, as
it the fact that you can hold it in one hand.

John

 

[redbelly]

= 40 G-rad/s = w = 2.pi.f

so f = 40G/2.pi = ~6.5GHz.

(You multiplied by 2 pi instead of dividing).

Frackin' A, you're right. Doh!

Thanks,

Mark

 

[redbelly]

The rise time and bandwidth of a signal are approximately related by the
following equation:

Signal bandwidth = 0.35 / Signal rise time

For a 55 ps signal we have:

BW = 0.35 / 0.055 ns = 6.36 GHz

Thanks Costas, I've got it now. My 2*pi factor went the wrong way.

0.35 = (ln(0.9)-ln(0.1)) / (2*pi)

Regards,

Mark

 

[David L. Jones]

The rise time and bandwidth of a signal are approximately related by the
following equation:

Signal bandwidth = 0.35 / Signal rise time

For a 55 ps signal we have:

BW = 0.35 / 0.055 ns = 6.36 GHz

Now, to *measure* this signal with some useful accuracy we need an
oscilloscope with a much higher bandwidth than 6.36 MHz.

Most of the useful energy in an edge is contained within the bandwidth
defined by (roughly) 0.5 / tr which in this case would be 9.1GHz, so a
10GHz scope might suffice.

Dave