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Tue Oct 7 21:19:40 2008
MC_F calibrated spectrum
I updated the plots because I did not take into account the double path AOM effect, which doubles the frequency actuation efficiency. (2008/10/8)
I determined the MC_F counts to the PSL frequency change calibration.
The attachment 1 is the calibrated MC_F spectrum, which is, above the cross over frequency, equivalent to the frequency noise seen by the MC.
The calibration method is the following:
1) I picked spare AD and DA channels (C1:IOO-MC_TMP1 and C1:OMC-SPARE_DAC_CH_16_EXC). C1:OMC-SPARE_DAC_CH_16_EXC is labeled C1:OMC-OSC_FM on the cable.
2) C1:IOO-MC_TMP1 was calibrated by injecting a sine wave of known amplitude and measuring the amplitude in counts in dataviewer.
It was 63uV/cnt.
3) C1:IOO-MC_TMP1 was connected to the feedback BNC connector of the MC board, that is the direct monitor of the feedback voltage to the VCO.
4) C1:OMC-SPARE_DAC_CH_16_EXC was connected to the channel B excitation input of the MC board, which adds the signal to the fast feedback path.
5) Using DTT a swept sine signal was injected to the MC board through C1:OMC-SPARE_DAC_CH_16_EXC, and the transfer function from C1:IOO-MC_TMP1 to the
C1:IOO-MC_F was measured.
6) Using the calibration of C1:IOO-MC_TMP1, the transfer function from the MC_F count to the actual voltage applied to the VCO input was obtained.
7) Using the DC calibration of the VCO input voltage to the VCO frequency change (1.75MHz/V
) and the fact that there is a 1.6Hz pole and a 40.8Hz zero between the VCO input connector and the actual input of the VCO chip, the final calibration transfer function from the MC_F count to the frequency change of the PSL (that is twice the frequency change of the VCO within the bandwidth of the FSS) can be obtained (attm3).
8) The analytic form of the calibration TF is, poles at [1.6Hz, 11.42Hz, 11.42Hz] and zeros at [40.8Hz, 113Hz, 113Hz] with the DC gain of 110Hz/cnt.
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