transform GHz to MHz so I can use my Oscope

J

jw

Guest
Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a signal
that could have a frequency up to 1GHz, this is not a square wave shape, it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency divider
to shift the GHz frequency to a range (MHz) that my oscope could handle.

Are there any big reasons why this would not work?

--TIA, jw
 
jw wrote:
Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a signal
that could have a frequency up to 1GHz, this is not a square wave shape, it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency divider
to shift the GHz frequency to a range (MHz) that my oscope could handle.

Are there any big reasons why this would not work?

--TIA, jw
Click to expand...
Apart from the frequency divider changing the shape and magnitude of
the signal you want to measure the absolute value of - no, there is no
reason why it won't work. :->

Dave :)
 
Frequency divider are only useful for a frequency counter, where you
don't care the shape of the signal...
I think you have to buy a new scope...

Kubiack

jw a écrit :
Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a signal
that could have a frequency up to 1GHz, this is not a square wave shape, it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency divider
to shift the GHz frequency to a range (MHz) that my oscope could handle.

Are there any big reasons why this would not work?

--TIA, jw
Click to expand...
 
On Thu, 01 Sep 2005 02:59:30 GMT, "jw" <letron_2000no__spam@yahoo.com>
wrote:

Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a signal
that could have a frequency up to 1GHz, this is not a square wave shape, it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency divider
to shift the GHz frequency to a range (MHz) that my oscope could handle.

Are there any big reasons why this would not work?

--TIA, jw
Click to expand...
As others have noted, frequency dividers are typically
digital devices that don't preserve amplitude.
But if you just want to monitor the level of the signal
(not it's wave shape) you can rectify and low-pass filter it and
feed the DC to your scope. No, I don't have any handy
GHz rectifier circuits handy... anyone else?

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
 
Bob Masta wrote:
On Thu, 01 Sep 2005 02:59:30 GMT, "jw" <letron_2000no__spam@yahoo.com
wrote:

Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a signal
that could have a frequency up to 1GHz, this is not a square wave shape, it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency divider
to shift the GHz frequency to a range (MHz) that my oscope could handle.

Are there any big reasons why this would not work?

--TIA, jw



As others have noted, frequency dividers are typically
digital devices that don't preserve amplitude.
But if you just want to monitor the level of the signal
(not it's wave shape) you can rectify and low-pass filter it and
feed the DC to your scope. No, I don't have any handy
GHz rectifier circuits handy... anyone else?

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
Click to expand...
The OP would have to provide quite a bit more information to get a
recommendation for a homebrew circuit, like frequency range of
interest, amplitude range, and impedance. Also, how would he check the
results from any homebrew circuit, especially if
amplification/buffering was required?

It might be best for him just to do the job right and scrounge an RF
voltmeter to make the measurement. They're commonly available
used/reconditioned, and not very expensive. Some require special
probes, so the OP should do his homework before buying.

Chris
 
On 8/31/05 7:59 PM, in article m8uRe.73$pt.48@newssvr29.news.prodigy.net,
"jw" <letron_2000no__spam@yahoo.com> wrote:

Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a signal
that could have a frequency up to 1GHz, this is not a square wave shape, it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency divider
to shift the GHz frequency to a range (MHz) that my oscope could handle.

Are there any big reasons why this would not work?

--TIA, jw
Click to expand...
Others have told you why that won't work. Here is one that will.

You need to build an RF mixer to get the spectrum of interest to a frequency
below 100 MHz.

There are readily available VCOs and Balanced Mixers built for 1 GHz. Also,
you should put a (100 MHz.) low-pass filter at the output of the mixer to
eliminate the unwanted mixer product and to reduce the VCO Carrier leakage
amplitude. With only a little care, the signal will be an excellent
representation of it's form at 1 GHZ.

Don
 
Thanks, this is great! --jw

"Don Bowey" <dbowey@comcast.net> wrote in message
news:BF3C7B4C.F268%dbowey@comcast.net...
On 8/31/05 7:59 PM, in article m8uRe.73$pt.48@newssvr29.news.prodigy.net,
"jw" <letron_2000no__spam@yahoo.com> wrote:

Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a signal
that could have a frequency up to 1GHz, this is not a square wave shape,
it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency
divider
to shift the GHz frequency to a range (MHz) that my oscope could handle.

Are there any big reasons why this would not work?

--TIA, jw



Others have told you why that won't work. Here is one that will.

You need to build an RF mixer to get the spectrum of interest to a
frequency
below 100 MHz.

There are readily available VCOs and Balanced Mixers built for 1 GHz.
Also,
you should put a (100 MHz.) low-pass filter at the output of the mixer to
eliminate the unwanted mixer product and to reduce the VCO Carrier leakage
amplitude. With only a little care, the signal will be an excellent
representation of it's form at 1 GHZ.

Don
Click to expand...
 
I'll try a few things and get back if I run into trouble. thx, jw

"Chris" <cfoley1064@yahoo.com> wrote in message
news:1125582818.068289.30980@o13g2000cwo.googlegroups.com...
Bob Masta wrote:
On Thu, 01 Sep 2005 02:59:30 GMT, "jw" <letron_2000no__spam@yahoo.com
wrote:

Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a
signal
that could have a frequency up to 1GHz, this is not a square wave
shape, it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency
divider
to shift the GHz frequency to a range (MHz) that my oscope could
handle.

Are there any big reasons why this would not work?

--TIA, jw



As others have noted, frequency dividers are typically
digital devices that don't preserve amplitude.
But if you just want to monitor the level of the signal
(not it's wave shape) you can rectify and low-pass filter it and
feed the DC to your scope. No, I don't have any handy
GHz rectifier circuits handy... anyone else?

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

The OP would have to provide quite a bit more information to get a
recommendation for a homebrew circuit, like frequency range of
interest, amplitude range, and impedance. Also, how would he check the
results from any homebrew circuit, especially if
amplification/buffering was required?

It might be best for him just to do the job right and scrounge an RF
voltmeter to make the measurement. They're commonly available
used/reconditioned, and not very expensive. Some require special
probes, so the OP should do his homework before buying.

Chris
Click to expand...
 
In article <m8uRe.73$pt.48@newssvr29.news.prodigy.net>, jw wrote:
Hi,

I have an oscope that can operate at up to 100 MHz.

My situation is that I want to measure the voltage magnitude of a signal
that could have a frequency up to 1GHz, this is not a square wave shape, it
is probably more like a sign wave shape.

So I am thinking that I could accomplish this by using a frequency divider
to shift the GHz frequency to a range (MHz) that my oscope could handle.

Are there any big reasons why this would not work?
Click to expand...
yes, frequency dividers typically convert the output to a fixed voltage, not
proportional to the input.

A better move may be to use a downconverter (but that's about the limit of my
knowledge of things RF)

Bye.
Jasen
 
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