In 2023, we are replacing the LLRF system for the KEK-PF 2.5 GeV ring. The
new system is composed of digital boards such as eRTM, AMC, and {\mu}RTM, based
on the MTCA.4 standard. In our system, we adopted the non-IQ direct sampling
method for RF detection. We set the sampling frequency at 8/13 (307.75 MHz) of
the RF frequency, where the denominator (13) is the divisor of the harmonic
number (312) of the storage ring. This allows us to detect the transient
variation of the cavity voltage that is synchronized with the beam revolution.
We also plan to compensate for the voltage variation by implementing a
feedforward technique. These functions will be useful in a double RF system for
KEK future synchrotron light source. Production and installation of the new
system were complete and the new system is under commissioning. In this
presentation, we introduce our new system and report the upgrade status.Comment: Talk presented at LLRF Workshop 2023 (LLRF2023, arXiv: 2310.03199