40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  SUS Lab eLog  Not logged in ELOG logo
Entry  Tue Apr 26 17:06:37 2011, Mingyuan, Tara, DailyProgress, Creak, start crackling 
    Reply  Thu Apr 28 21:55:25 2011, tara, DailyProgress, Creak, start crackling chopping.pdf
       Reply  Fri Apr 29 18:39:37 2011, tara, DailyProgress, Creak, start crackling 
          Reply  Wed May 11 22:17:35 2011, tara, DailyProgress, Creak, start crackling 1khz.pngf_t_response.png
       Reply  Fri Apr 29 21:23:15 2011, tara, DailyProgress, Creak, start crackling ad734_crackle.pdf
          Reply  Thu May 12 23:18:27 2011, ryan, tara, DailyProgress, Creak, start crackling ad734.png
Message ID: 199     Entry time: Wed May 11 22:17:35 2011     In reply to: 191
Author: tara 
Type: DailyProgress 
Category: Creak 
Subject: start crackling 

 I tested the mixer, the demodulated signal from input at 10 - 100 Hz might be too small and too distorted to get reliable data.


  As we want to square/demodulate  signal in 10 - 100 Hz BW. a low frequency mixer might be a good tool. I asked Alastair to buy this mixer for me, and it arrived today.

  The lowest acceptable frequency in the design is 500 Hz, but I don't know how well it works at 10 - 100 Hz so I tested it.


   ==Setup and result==

   I used  SR785 to generate sine wave, then split it with a T and connected the output to LO and RF of the mixer. 

   I tested that the mixer works fine at the designed frequency.  The plot below shows the result from  1kHz signal input.


Next, I changed the frequency to 10 Hz, 50Hz, and 100Hz.

  The demodulated signal is then observed in frequency domain (left column of the plot) and in time domain ( right column of the plot)

I think the peaks at driving frequencies (10Hz, 50Hz, 100Hz and their harmonics) appear because of the offset of the sine input signal.



The results for low frequency  seem to be too distorted. We will test the AD734 chips tomorrow. I got the package this afternoon.

ELOG V3.1.3-