PEP-II LLRF Direct Loop Panel


This panel contains some additional functions and constants to support the operation of the direct RF feedback loop. Some of the parameters exist on the Feedback panel but are repeated here for convenience. Some of the inputs are used in the fast and slow turnon sequences while others support the direct loop frequency offset tracking option.

Based on inputs on this panel, the direct loop coefficients (II, IQ, QI, QQ) on the RF Processing (RFP) module are calculated and updated using these equations:

DAC_counts = Conv Factor * ( 10**((Loop Gain + Gain Offset)/20) )
II and QQ values = ( DAC_counts * cos(Loop Phase * pi/180) ) + offset
IQ and QI values = ( DAC_counts * sin(Loop Phase * pi/180) ) + offset
II,IQ,QI,QQ must be within -2047 to 2047 and will be clipped if beyond.
The values are updated whenever direct loop phase or any other input is changed.
The II,IQ,QI,QQ offsets are set during RFP module calibration.

This panel is accessed from the top left of the Feedback panel.