nicolas.bachelard
Newbie level 1
Dear all,
I am dealing with a physical signal where the information that I seeking of measuring is encoded in the phase \[ \Phi(t) [\tex].
This is an optical signal that I modulate in amplitude at a carrier frequency \[f_m = 1 GHz/tex].
I am looking at the phase of this signal. But this phase changes in time over roughly 10 ns.
The signal is acquired with a detector, which cuts off at 2.5 GHz.
My signal should read \[s_m cos( 2 \pi f_m t + \Phi(t))\], where \[s_m[\tex] is the amplitude of my signal and \[ \Phi(t) [\tex] the varying phase that I want.
The problem that I am facing is that the physical process that I apply to change \[\Phi(t)[\tex] also influences the influence \[s_m(t)[\tex].
This amplitude modulation together with the phase time-evolution broaden my signal in frequency (I would say of about 10 to 100 MHz around 1GHz).
I fear that this broadening ultimately influences the phase that I measure since I work so close from the cut off of my detector (2.5 GHz).
My phase-evolution is supposed to be very small (around few degrees) and I am sure that the broadening of my signal convoluted by the detector produces a much bigger phase shift.
Until now I was doing simple temporal detection using a RF oscilloscope to detect the phase but I am convinced that what I measure is the convolution of my phase with the response of the detector.
I cannot work at lower frequency. I am looking for a detection technique that ensures that the phase of my detector will not interfere with the phase. Right now I am implementing an IQ demodulation.
There I multiply the signal \[s_m cos( 2 \pi f_m t + \Phi(t))\] by \[cos( 2 \pi f_m t)[\tex] on one arm and by \[sin( 2 \pi f_m t)[\tex] on another arm and from these signal I hope I can extract [text]\Phi(t)[\tex] without the influence of my detector.
Can someone confirm that the IQ demodulation is indeed a way to shortcut the influence of my detector? If not does someone has an idea of how I can get rid of the influence of my detector?
Best
I am dealing with a physical signal where the information that I seeking of measuring is encoded in the phase \[ \Phi(t) [\tex].
This is an optical signal that I modulate in amplitude at a carrier frequency \[f_m = 1 GHz/tex].
I am looking at the phase of this signal. But this phase changes in time over roughly 10 ns.
The signal is acquired with a detector, which cuts off at 2.5 GHz.
My signal should read \[s_m cos( 2 \pi f_m t + \Phi(t))\], where \[s_m[\tex] is the amplitude of my signal and \[ \Phi(t) [\tex] the varying phase that I want.
The problem that I am facing is that the physical process that I apply to change \[\Phi(t)[\tex] also influences the influence \[s_m(t)[\tex].
This amplitude modulation together with the phase time-evolution broaden my signal in frequency (I would say of about 10 to 100 MHz around 1GHz).
I fear that this broadening ultimately influences the phase that I measure since I work so close from the cut off of my detector (2.5 GHz).
My phase-evolution is supposed to be very small (around few degrees) and I am sure that the broadening of my signal convoluted by the detector produces a much bigger phase shift.
Until now I was doing simple temporal detection using a RF oscilloscope to detect the phase but I am convinced that what I measure is the convolution of my phase with the response of the detector.
I cannot work at lower frequency. I am looking for a detection technique that ensures that the phase of my detector will not interfere with the phase. Right now I am implementing an IQ demodulation.
There I multiply the signal \[s_m cos( 2 \pi f_m t + \Phi(t))\] by \[cos( 2 \pi f_m t)[\tex] on one arm and by \[sin( 2 \pi f_m t)[\tex] on another arm and from these signal I hope I can extract [text]\Phi(t)[\tex] without the influence of my detector.
Can someone confirm that the IQ demodulation is indeed a way to shortcut the influence of my detector? If not does someone has an idea of how I can get rid of the influence of my detector?
Best
