RF Control Strategy

As more accelerators adopt superconducting cavities or require high RF field stability, the LLRF system becomes critical for meeting the accelerator performance objectives. Different control strategies have been developed to solve the RF control problems raised by different machines. In this chapter, we give an overview of the RF control strategies widely used in LLRF systems. We will briefly compare the feedback and feedforward control, the amplitude/phase and in-phase/quadrature (I/Q) control, the generator-driven resonator (GDR), self-excited loop (SEL) and phase-locked loop (PLL) control, the analog and digital control, and the single-cavity and vector-sum control. The pros and cons of the control strategies will also be discussed.