• G. Huang, J.M. Byrd, L.R. Doolittle, J.W. Staples, R.B. Wilcox
  LBNL, Berkeley, California

High precision phase measurement is important for many areas of accelerator operation. In a heterodyne digital receiver, one source of phase error is due to the thermal variation of the input stage. We have developed a technique to calibrate this drift. A CW calibration signal is sent through the same components together with the RF signal to measure and compensate the component drift. At intermediate frequency (IF), we use FPGA based digital signal processing to measure and reconstruct the RF signal after applying appropriate correction. Using this technique, we can measure the phase of a 2856 MHz signal with an accuracy of 15 mdeg. We describe how this is approach is applied to the femto-second timing distribution system.