Simulation Method For The Analysis Of Signal Integrity In Integrated Circuits

The layout structure can be simulated by the traditional electromagnetic field simulation method to obtain the S parameters,and the circuit structure composed of the Spice model can be simulated by the traditional circuit analysis method to obtain its time domain and frequency domain characteristics.The actual signal integrity analysis usually includes both the layout and the circuit.In order to combine electromagnetic field simulation and circuit simulation,this paper proposes an method to Spice model and S-parameter model to realize direct current(DC),frequency domain and time domain analysis.This paper is based on the open source NGSpice library to integrate the Spice model and Sparameters to realize time-frequency domain simulation.The main innovation is to propose a new method of frequency domain simulation of Spice model and S-parameter model.In circuit analysis,the first step is to do a DC analysis of the entire circuit.This method converts the S parameters into an equivalent resistance network,so that static operating point of the circuit containing the S parameters can be determined by the DC analysis of the NGSpice library.In alternating current(AC)analysis,the S parameter and the circuit composed of basic components are treated as two parts,and the circuit composed of basic components has been determined to work in the NGSpice library by giving the initial value of the static operating point.Process and convert the current and voltage obtained into Y parameters.This paper proposes a comprehensive solution method for Y-parameters based on Kirchhoff's law,and achieves the final external frequency domain characteristics through multiple interconnected Y-parameter networks.Electromagnetic field simulation usually takes a long time.For occasions that need to frequently change the geometric parameters of the layout and re-simulate,this paper proposes a method to establish an artificial intelligence(AI)model to quickly obtain the S-parameters of the layout,then combine circuit components for joint simulation.The AI model is the S-parameters obtained by electromagnetic field simulation through a large number of the same type of layout,and is established using the deep learning method.For time domain and eye diagram simulation,this paper also proposes a set of methods to obtain time domain results from S parameters through Fourier transform(FFT)and inverse Fourier transform(IFFT).The innovation of this method is that the frequency domain data of output is obtained by taking the frequency domain data of the input signal as the excitation of the Y parameter,and the IFFT is used to transform it into a time domain waveform.This method supports multi-port input and output systems,and can truly reflect the influence of S-parameter internal crosstalk.This article also describes the method of cutting and superimposing a random sequence through the timedomain output response of a system to generate an eye diagram,and proposes a method for converting the time-domain output response of a step signal through the system into a time-domain reflectance(TDR)result.