rich.abbott@LIGO.ORG - posted 20:23, Wednesday 30 January 2019 - last comment - 21:39, Wednesday 30 January 2019(46714)
Phase Noise Analysis of 203.125MHz CLF VCO
Calum, Daniel, Rich An analysis was made of the phase noise content of the VCO serving the as Squeezer CLF actuator. A comparison is included below of the VCO nominal parameters from E1700010. Attached is a plot of the single sideband phase noise. Specification 10Hz -110dBc 100Hz -140dBc 1kHz -160dBc 10kHz -165dBc Measured 10Hz (not measured) 100Hz -132dBc 1kHz -145dBc 10kHz -160dBc As can be seen from the measured vs the specification, the noise is a bit higher than expected. This is still far below the measured CLF noise, but needed to be checked. The data was compensated for the fact that 2 identical oscillators were beat together during the measurement (3dB correction), and compensated for single sideband (3dB correction). During the course of the measurement, the slope of the phase detecting mixer was determined to be 1.1268 volts per radian.
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Even so the original specs were as above, we later moved to an AT cut crystal to give us more tuning range (see T1800062). This also resulted in a lower phase noise specification:
100 Hz -103 dBc/Hz
1 kHz -133 dBc/Hz
10 kHz -148 dBc/Hz
100 kHz -158 dBc/Hz