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Zheng, Q.

Paper Title Page
THP100 Self Tuning Regulator for ISAC 2 Superconducting RF Cavity Tuner Control 1024
 
  • K. Fong, M.P. Laverty, Q. Zheng
    TRIUMF, Vancouver
 
 

The ISAC 2 superconducting rf cavities use self-excited, phase-locked mode of operation. As such the microphonics are sensitive to the alignment of the phase control loop. Although initial alignments can minimize the effect of microphonics, long term drifts, particularly in the power amplifiers, can cause the control loop to misalign and an increase in sensitivity to microphonics. The ISAC 2 control system monitors several points in the control loop to determine the phase alignment of the power amplifiers as well as the rf resonant cavities. Online adaptive feedbacks using Self Tuning Regulators are employed to bring the different components back into alignment.

 
THP101 AM-PM Conversion Induced Instability in I/Q Feedback Control Loop 1027
 
  • K. Fong, M.P. Laverty, Q. Zheng
    TRIUMF, Vancouver
 
 

Most rf feedback control systems today uses the I/Q demodulation and modulation scheme because of its simplicity. Its performance, however, depends on the alignment of the feedback loops. If the loop contains elements that have a high AM-PM conversion such as a class C amplifier, then the misalignment is dynamic and power dependent. In the extreme case the I/Q loops can become unstable and the system settled into a limit-cycle oscillation.