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Entry  Mon Jun 4 22:38:44 2012, tara, DailyProgress, BEAT, low frequency beat with 32kHz ADC beat_2012_06_04_b.pngdemod.png
    Reply  Tue Jun 5 23:30:47 2012, rana, DailyProgress, BEAT, low frequency beat with 32kHz ADC 
       Reply  Tue Jun 19 00:08:19 2012, tara, DailyProgress, BEAT, low frequency beat with 32kHz ADC 
          Reply  Wed Jun 20 16:06:50 2012, tara, DailyProgress, BEAT, low frequency beat with 32kHz ADC 
             Reply  Wed Jun 20 17:50:59 2012, rana, DailyProgress, BEAT, low frequency beat with 32kHz ADC 
                Reply  Thu Jun 21 16:04:39 2012, tara, DailyProgress, BEAT, low frequency beat with 32kHz ADC demod_2012_06_21.mat
                   Reply  Fri Aug 10 19:50:37 2012, tara, DailyProgress, BEAT, code schmidtt trigger for beat  schmidtt.pngzoom.pngschmidtt.zip
                      Reply  Thu Aug 30 02:52:01 2012, tara, DailyProgress, BEAT, code schmidtt trigger for beat  IQ_2012_08_20.png
                         Reply  Fri Aug 31 00:48:00 2012, tara, DailyProgress, BEAT, code schmidtt trigger for beat  compare_IQ_schmidtt.pngcompare_IQ_schmidtt.figIQ_compare.pngIQ_compare.figvco-frequency-noise_2010-03-12.png
                            Reply  Mon Sep 3 01:02:46 2012, tara, DailyProgress, BEAT, code schmidtt trigger for beat  IQ_compare.pngIQ_compare.fig
Message ID: 1043     Entry time: Mon Sep 3 01:02:46 2012     In reply to: 1042
Author: tara 
Type: DailyProgress 
Category: BEAT 
Subject: code schmidtt trigger for beat  

I used IQ readout method to measure the frequency noise of Marconi. The sensitivity was good, it was lower than 10^-3 Hz/rtHz up to a few hundred Hz.

 

From previous entry, I finished up the measurement and analyzed the data. I did two things:

  • Compared IQ read out with PLL technique, (green and red against black and dark green): The measurements agree well so I think IQ method is reliable.
  •  Measured Marconi noise( carrier@160MHz, modulation off) when the marconis were locked and not locked with one Rb clock( pink and neon green). When the modulation is off, we cannot use PLL to measure marconi's frequency noise. So I used IQ to measure the noise.  

IQ_compare.png

 ==comments==

From the measurements, I can conclude that IQ method has enough sensitivity at least down to 10^-3 Hz/rtHz (might be up to 1kHz) (neon green).  One thing we should keep in mind is that the frequency noise from marconi is still quite high at 1kHz, even with modulation frequency is off. So we still have problem with measure noise up to 1kHz .

Anyway, I have not determined the noise floor of IQ method yet. I will think about it. If we can keep the beat frequency drift small enough, IQ methods should be ok for beat measurement.

Attachment 2: IQ_compare.fig  5.508 MB  Uploaded Mon Sep 3 02:04:04 2012
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