Research On Multi-chain Clock Jitter Measurement Circuit Of Picosecond Based On FPGA

The clock signal is the basis of the timing logic circuit and the aorta of the whole system,which directly determines the success or failure of the data signal transmission and reception.Therefore,the clock jitter has an important influence on the whole circuit system,how to measure the jitter of a clock system and evaluate its distribution has become a hot topic in recent years,in other words,measuring clock jitter has a very important practical significance.The measurement of clock jitter is essentially measuring the time interval between adjacent edges of the measured signal.Based on the full understanding of the time interval measurement methods,this paper makes a detailed study on the traditional multi-chain clock jitter measurement method based on FPGA,and then improve its disadvantages in several aspects.Consequently,an improved multi-chain clock jitter measurement method based on FPGA is proposed.Specifically,the traditional methods were mainly improved in the following aspects: First,reinventing the structure of "fine" measurement---making full use of the dedicated carry chain in the FPGA Slice and building two delay chains with a row of Slices so that the rate of resource utilization is doubled.Second,Proposing the clock group latch method.Improve the latch logic by using a pair of inverted clock latching the state of the delay chains,so that the upper frequency limit of measured signal is nearly doubled.Third,replacing the original single clock with reverse clock group for a simple count,significantly improved the clock stability of the "rough" measurement unit;Fourth,improving the decoding structure,so that the decoding efficiency is improved significantly and the resource cost is reduced as well.Compared with the traditional method,the proposed method has the characteristics of high precision,large range,strong stability and low resource cost.In order to evaluate the performance of the proposed circuit,this paper firstly analyzes the accuracy and resolution of the circuit,and then carries on the simulation correspondingly.The simulation results show that the proposed circuit has high measurement accuracy.On this basis,the improved circuit is implemented and a test platform is built to verify its range,accuracy and nonlinearity.The test results show that when the number of chains of the improved circuit is 8,the measurement accuracy is 4.8 ps.In general,the improved circuit proposed in this paper has high measurement accuracy,large scale,simple structure,stable performance and good practical value.