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System measuring amplitude & phase difference of 2 signa

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yolande_yj

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I have two signal with the same frequency (about 1 to 6 GHz, 0dBm), one is reference siganl and the other is what I need to measure. I need a system (not an instrument) that can measure the amplitude and phase difference between these two signals, can anyone give me suggestions? Thanks
 

Mazz

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Not an easy task.
Usually a problem found to measure I & Q.
One way is to have calibrated paths to a combiner, with a certain known and trimmable phase and amplitude difference between two paths: when the output is ZERO (a good sensitivity is achieved with spectrum analizer), the two signals are opposite at combiner input. You can deembed single paths and calculate signals amplitude and phase.

I hope it can help.
Mazz

p.s. maybe Sergio Mariotti can give you more help; he's really skilled in lab.
 

    yolande_yj

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yolande_yj

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Re: System measuring amplitude & phase difference of 2 s

Mazz said:
Not an easy task.
Usually a problem found to measure I & Q.
One way is to have calibrated paths to a combiner, with a certain known and trimmable phase and amplitude difference between two paths: when the output is ZERO (a good sensitivity is achieved with spectrum analizer), the two signals are opposite at combiner input. You can deembed single paths and calculate signals amplitude and phase.

I hope it can help.
Mazz

p.s. maybe Sergio Mariotti can give you more help; he's really skilled in lab.
Thanks Mazz,
If only the phase difference is measure, forget the amplitude, how?
Can you give me a link or a paper about measuring I & Q?
 

davicente

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Re: System measuring amplitude & phase difference of 2 s

Analog devices has a chip(AD8302 I think) which gives you voltages proportional to phase and gain diferences between two input signals. I can't remember the maximum frequency, but browse Analog to see if it can help you

Bye

Added after 1 minutes:

Analog devices has a chip(AD8302 I think) which gives you voltages proportional to phase and gain diferences between two input signals. I can't remember the maximum frequency, but browse Analog to see if it can help you

Bye
 

BigBoss

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Re: System measuring amplitude & phase difference of 2 s

A compherensive solution is to use linear downconverters for both signals and measurement could be done much lower frequency. If the signals are very far from other this technique may not be very convenient but otherwise it's a quick solution..
 

Mazz

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Sorry no paper about it. Only experience.
Another good solution, as usual, is the one proposed by BigBoss.
Downconvert both to a freq that can be read by an oscilloscope. Take care to both downconvert paths, they must be equal. And oscilloscope readings are not very accurate (if you need <1 deg accuracy, forget it).
I hope it can help.
Mazz
 

dozer

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Re: System measuring amplitude & phase difference of 2 s

you did say that the 2 signals were of the same frequency.

did you mean this literally?

i.e., they are the -exact- same freq?

if so, i believe that a simple DBM (mixer) would give you a DC output proportional to the phase diff. between the inputs.

you didn't specify what range of phase differential you might encounter; nor with what accuracy you need to measure it; so it's difficult to give more specific recommendations....
 

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