The Ber Estimation Based On Fast Time-Domain Simulation Algorithm

For the high-speed parallel bus, such as DDR system, the improving data rate has become a big obstacle for CPU to read and write. In order to cut the development costs, designers need to estimate its interface performance in advance: what data rate it can reach, and what is the possibility of error taken place at this data rate. Unfortunately, the eye diagram contains limited information, and the worst eye diagram does not have practical reference value. Therefore, it cannot meet the requirement for designers to judge the signal quality purely by using the eye diagram or the worst-case eye diagram. As the fast time-domain algorithm can reduce the time of simulation greatly, so it is necessary to introduce the calculation of statistical-domain into the algorithm. We should introduce BER_eye, thus it can provide new reference for engineer when pre_simulation needs to be done.By using Hspice transient simulation waveform of all nodes of DDR system, this paper proposes a method using the single-bit response(SBR) and the double-bit response(DER)of fast time-domain algorithm to calculate the bit error rate at different sample times and different sample voltages, and to draw the BER eye. Thus we can estimate the performance of DDR in statistical domain, and this algorithm can also provide more references to the engineers. The fast time-domain simulation algorithm has been used to draw the worst-case eye diagram, and its advance in accuracy and speed is very obvious, therefore, it is a new attempt to use this method to get BER and it has a strong forward looking. Meanwhile, this paper also compares the advantages and disadvantages of the two algorithms considering the speed and the accuracy, and it points out that the algorithm of DER can handle the edge that drives asymmetric and it is more practical. At last, this paper also considers the impact of the sampling jitter and noise of receiver, and puts forward an algorithm considering the impact of the sampling jitter of Gaussian distribution on the BER of the channel.And it also calculates and draws the BER_eye of the receiver.At last, the paper presents the algorithm into the engineering practice, and develop a software that can calculate the worst-case eye diagram and the BER_eye automatically.And meanwhile, an interface is set aside at the receiver, through the input parameters, we can estimate BER_eye at the receiver. This software uses the transient simulation file of Hspice, and can select the type of algorithm freely. Engineers can select the algorithm according to the practical situation. We find that the software has been walking in the forefront of this discipline on simulation speed and precision. Moreover, it has a strong engineering and theory guidance.