Research On Key Technologies Of Multi-channel Large Range High Precision Event Timer

The event timer is used to convert the time information of the event to a digital quantity.Its core technology is time-to-digital converter(TDC).The event timer is widely used in aerospace,quantum communication experiments,lidar ranging and other fields.The precision of the event timer is closely related to the technical level of these fields.Some applications require multi-channel event timers to be measured in parallel to improve efficiency.The multi-channel event timer with large range and high precison measures the time information of multiple channel events by the same device at the same time.Compared with the single channel event timer,it can meet the need of multi-channel timing and effectively reduce the volume and weight of the system.According to the demand of multi-channel high-precision event timer,the common design method of TDC is analyzed,and the design of multi-channel high-precision event timer is realized by the combination of coarse and fine.The coarse count is obtained by the direct count of the system clock,and the fine count is designed by the tap delay chain.According to the existing experimental platform in the laboratory,the delay chain is constructed by using CARRY4 in Xilinx Aritex-7.Aiming at the "bubbling" phenomenon caused by the inherent carry ahead characteristic of the special carry chain,the sequence number of the taps have been reordered.In order to improve the coding efficiency,this paper uses the half search method to change the thermometer code into binary code.In order to reduce the influence of process,voltage,and temperature on the delay of the delay chain,the code density test is used to calibrate the fine count and the on-chip ring oscillator is used to detect the change of delay to compensate the influence of temperature on the delay of the carry chain in real time.The TDC designed in this paper has 1 start measurement channel and 18 stop measurement channels with a range of 671 ms and a dead time of 30 ns.This paper bulids a system level verification platform to evaluate the performance of TDC.The experimental results show that difference between the19 delay chains is very small,the average delay of a single delay chain is about36.8 ps,the differential nonlinearity is 4.7 LSB(Least Significant Bit),and the integral nonlinearity is 5.1 LSB.The precision of TDC system is better than5.933 ns when tested in a large range of 600ms;the precision of TDC system is better than 2.969 ns when tested in a large range of 50 ms;The precision of TDC system is 39.2 ps when it is tested in 180 ns,and the precision of single channel TDC is 27.7 ps.