Subpicosecond-resolution time-to-digital converter with multi-edge coding in independent coding lines

We present the design, implementation and test results of an integrated time-to-digital converter based on a new method with multi-edge coding in independent coding lines. The method allows to achieve high resolution below 1 ps and short conversion time of about 3 ns. When used in an interpolation time counter it provides standard measurement uncertainty below 6 ps. The converter has been implemented in a readily available and cheap programmable device Spartan-6 (Xilinx). Applying a multiple coding for time digitization in independent coding lines let us decrease the number of parallel coding lines needed to obtain the same high resolution by averaging. This leads to significant reduction of required logical resources of programmable device. Additionally, the high rate of conversion (above 1 million conversions per sec.) has been achieved.