High-Precision Time Digitizer Based on Multiedge Coding in Independent Coding Lines

Abstract

We present the design, implementation, and test results of an integrated time digitizer based on a new conversion method that applies multiedge coding in independent coding lines. The proposed method eliminates an existing technological limitation of resolution inherent in the methods based on standard time coding delay lines, which causes that the value of resolution cannot be lower than the propagation time of the fastest delay element in the line. The developed method allows increasing the resolution proportionally to the number of signal edges coded and lines involved. An interpolating time counter designed by applying the six-edge coding in three independent coding lines provides subpicosecond resolution (902 fs), high precision (<;6 ps), and wide measurement range (2 s). A short conversion time of the method and the use of local RAM memory for storing measurement results allowed for significant shortening of the digitizer dead time and achieving the measurement rate up to 6 million measurements per second. The digitizer is implemented in an easily available and cheap field programmable gate array device manufactured in the 45-nm CMOS technology.