CN102542112A - Passive-modeling-based circuit simulation method - Google Patents

Abstract

The invention relates to a passive-modeling-based circuit simulation method and belongs to the technical field of integrated circuit design. Firstly, an electromagnetic simulation method is adopted to generate a data file, and an initial simulation mode is built with the aid of a vector fitting method according to the data file; the initial simulation model is modified and changed to an initial passive model; the precision of a final passive model serves as an optimization target, a passive restriction serves as an optimization constraint condition, the initial passive model serves as the initial solution, and the finial passive model is obtained through an optimization algorithm; and the coefficient matrix of the final passive model is inputted to a circuit simulator, and the circuit parameter is obtained through calculation. The circuit simulation method provided by the invention improves the modeling precision, shortens the modeling time, improves the efficiency and precision of circuit simulation, and enhances the astringency of the circuit simulation. The circuit simulation method can be applied to the design of the integrated circuit, improves the reliability of the circuit simulation and the efficiency of the circuit design, and shortens the time of the circuit product to the market.

Description

A kind of circuit emulation method based on passive modeling

Technical field

The present invention relates to a kind of circuit emulation method, belong to the IC design technical field based on passive modeling.

Background technology

At the higher circuit of frequency of operation, for example in the design verification flow process of millimetre-wave circuit, it is a wherein important step thereby carry out emulation according to the model that the Electromagnetic Simulation data are set up the electrology characteristic that is used to describe circuit devcie or electronic circuit.Here said circuit devcie or electronic circuit generally have passivity.And passivity refers to the average power of device or circuit and is not more than zero characteristic; Electromagnetic Simulation refers to for the circuit devcie of built-up circuit or electronic circuit carries out electromagnetics emulation; The input of Electromagnetic Simulation is physical dimension, structure and the working environment of these circuit devcies or electronic circuit; The output of Electromagnetic Simulation is the data of describing the operating characteristic of these devices under different frequency, for example S parameter or hybrid parameter.Set up the model of circuit devcie or electronic circuit according to the Electromagnetic Simulation data after, these models are used for circuit simulation, then can obtain the parameter of circuit, the performance of evaluation circuits.

Because a lot of circuit devcies or electronic circuit itself in the circuit just have passivity, can their model preferably also has passivity so, otherwise can influence the stability of circuit simulation, just influence circuit simulation and obtain true rational result.Therefore the passive circuit devcie or the model of electronic circuit need guarantee it is passive in the circuit simulation process.

Describe in the face of the passivity doing mathematics down.Transport function is two kinds of different method for expressing of model with state space equation.The transport function of model is meant the ratio of the input and the output signal Laplace transform of system, and state space is meant the space that state variable and derivative thereof by model constitute.The state space equation of device or model is made up of following two equations:

$\stackrel{\·}{x}=\mathrm{Ax}+\mathrm{Bu}$

y＝Cx+Du

Wherein, X, u, y are vectors; Represent state, input and output respectively;

represents the derivative of x, and A, B, C, D are matrix of coefficients, and wherein the size of A matrix is defined by the order of system usually.Under such state-space expression, system transter can be expressed as: H (s)=C (sI-A) ^-1B+D.Because the transport function of a model can be described under hybrid parameter (H parameter) or scattering parameter (S parameter).So provide the mathematical description of the passivity of two kinds of models under the parameters description here respectively.

For the transport function that hybrid parameter is described, the passivity of model is equivalent to satisfy following conditions:

H(s)+H ^H(s)≥0， $\∀s=j\·2\mathrm{\πf}$

Wherein, f representes frequency, H ^H(s) be the conjugate transpose of H (s).(2) formula shows, under any frequency, and H (s)+H that model is corresponding ^H(s) all be positive semi-definite, that is to say, H (s)+H ^H(s) under any frequency, all has non-negative characteristic root.

For the transport function under the S parametric description, the passivity of model is equivalent to satisfy following conditions:

I-H(s)H ^H(s)≥0， $\∀s=j\·2\mathrm{\πf}$

Wherein, I representation unit matrix.(3) formula shows, under any frequency, and H (s) H that model is corresponding ^H(s) characteristic root is all less than 1.And circuit devcie or electronic circuit are set up the model with passivity, and to find the model that as far as possible accurately meets the data that Electromagnetic Simulation obtains in fact exactly, make the transfer function H (s) of model satisfy the mathematical expression of above-mentioned passivity simultaneously.

Thereby the model of setting up circuit devcie or electronic circuit according to the Electromagnetic Simulation data carries out circuit simulation; Current approach mainly contains two types: class methods are that the problem description with the model of setting up circuit devcie or electronic circuit becomes protruding optimization problem, find the solution through convex optimized algorithm again.This class methods algorithm complex is very high, generally is difficult to be used in system's order and surpasses in 100 the system; Another kind of method is that this process is divided into two stages.Do not consider the requirement of passivity in phase I, directly set up precise analytic model based on the Electromagnetic Simulation data, then in second stage through the means correction model of passive correction, make it satisfy the requirement of passivity.Yet there is constringent problem mostly in these methods, that is to say to use existing method, can not obtain a no source model for some circuit.For the higher circuit of frequency of operation, a model that does not satisfy passivity will cause the mistake of circuit simulation.

Summary of the invention

The objective of the invention is to propose a kind of circuit emulation method based on passive modeling; To overcome the weak point of prior art; Propose the modeling process of the no source model of rational and effective circuit devcie or electronic circuit, and it is applied in the circuit simulation, and then obtain correct circuit parameter; Improve the reliability and the circuit layout efficiency of circuit simulation, and then shorten the Time To Market of circuit product.

The circuit emulation method based on passive modeling that the present invention proposes may further comprise the steps:

(1) method of employing Electromagnetic Simulation; Generate a data file that is used for circuit simulation; Comprise in this data file Electromagnetic Simulation environmental parameter, be used to explain the data layout and the simulation result of simulation result; According to this data file, utilize vectorial approximating method, set up the initial realistic model of this circuit;

(2) above-mentioned initial realistic model is revised, made initial realistic model become initial no source model, modification method is:

Adopt the characteristic root method of disturbance Hamilton matrix, initially do not had source model;

Or adopt the corresponding coefficient method of disturbance limit, initially there is not source model;

Or make matrix of coefficients D and a positive definite matrix mutual superposition that is used to improve initial realistic model transport function characteristic root of above-mentioned initial realistic model, initially there is not source model;

(3) precision with final no source model is an optimization aim, as optimizing constraint condition, is initial solution with the initial no source model of above-mentioned steps (2) with passivity constraint, uses optimized Algorithm, is not finally had source model:

Optimization variable: C, D

Minimize: $\underset{k}{\mathrm{\Σ}}{|H\left(s_k\right)-\hat{H}\left(s_k\right)|}_2^2$

H(s)＝C(sI-A) ^-1B+D

Constraint condition: $M=\left[\begin{array}{cc}A-{\mathrm{BR}}^{-1}C& -B{R}^{-1}{B}^H\\ C^H{R}^{-1}C& -A^H+C^H{R}^{-1}{B}^H\end{array}\right]$

real(λ)≠0， $\∀\mathrm{\λ}:|\mathrm{\λI}-M|=0$

Wherein: A, B, C, D, R are the matrix of coefficients of final no source model, H (s _k) be the data in the above-mentioned data file, real (λ _M) be the real part of the characteristic root of matrix M;

(4) with the coefficient matrices A of above-mentioned final no source model, B, C, D are input in the circuit emulator, calculate, and obtain circuit parameter.

The circuit emulation method that the present invention proposes based on passive modeling; Modeling process is wherein compared with existing passive modeling process, and its characteristics are passive modeling is divided into " accurately modeling ", " passivity of correction model " carried out with " improving the precision of no source model " three steps.With respect to existing emulation mode based on the passive modeling of protruding optimization, the algorithm complex of emulation mode of the present invention is low, and counting yield improves greatly.Revise the emulation mode that two of passivity goes on foot passive modeling process again with respect to the existing model of setting up earlier; This method can improve modeling precision in the simulation process; Therefore use more effective passivity modification method, can avoid in the existing emulation mode not convergent problem of simulation process.Therefore emulation mode of the present invention has improved modeling precision; Shorten the time of modeling; And then the efficient and the precision of raising circuit simulation, the convergence of intensifier circuit emulation is applied to circuit emulation method of the present invention in the IC design; Can improve the reliability and the circuit layout efficiency of circuit simulation, shorten the Time To Market of circuit product.

Description of drawings

Fig. 1 is the synoptic diagram of Electromagnetic Simulation data file.

Fig. 2 is the transfer curve that utilizes the initial realistic model of vectorial approximating method foundation.

Fig. 3 is and transfer function H (s) corresponding H (the s)+H of the initial realistic model of revising front and back with initial no source model ^H(s) characteristic root curve.

Fig. 4 uses Electromagnetic Simulation data file shown in Figure 1, utilizes existing circuit emulation method to carry out the circuit output waveform that circuit simulation obtains.

Fig. 5 uses Electromagnetic Simulation data file shown in Figure 1, utilizes circuit emulation method of the present invention to carry out the circuit output waveform that circuit simulation obtains.

Embodiment

The circuit emulation method based on passive modeling that the present invention proposes may further comprise the steps:

(1) method of employing Electromagnetic Simulation; Generate a data file that is used for circuit simulation; Comprise in this data file Electromagnetic Simulation environmental parameter, be used to explain the data layout and the simulation result of simulation result; According to this data file, utilize vectorial approximating method, set up the initial realistic model of this circuit;

(2) above-mentioned initial realistic model is revised, made initial realistic model become initial no source model, modification method is:

Adopt the characteristic root method of disturbance Hamilton matrix, initially do not had source model;

Or adopt the corresponding coefficient method of disturbance limit, initially there is not source model;

Or make matrix of coefficients D and a positive definite matrix mutual superposition that is used to improve initial realistic model transport function characteristic root of above-mentioned initial realistic model, initially there is not source model;

(3) precision with final no source model is an optimization aim, as optimizing constraint condition, is initial solution with the initial no source model of above-mentioned steps (2) with passivity constraint, uses optimized Algorithm, is optimized like method of steepest descent or Newton method, is not finally had source model:

Optimization variable: C, D

Minimize: $\underset{k}{\mathrm{\Σ}}{|H\left(s_k\right)-\hat{H}\left(s_k\right)|}_2^2$

H(s)＝C(sI-A) ^-1B+D

Constraint condition: $M=\left[\begin{array}{cc}A-{\mathrm{BR}}^{-1}C& -B{R}^{-1}{B}^H\\ C^H{R}^{-1}C& -A^H+C^H{R}^{-1}{B}^H\end{array}\right]$

real(λ)≠0， $\∀\mathrm{\λ}:|\mathrm{\λI}-M|=0$

Wherein: A, B, C, D, R are the matrix of coefficients of final no source model, H (s _k) be the data in the above-mentioned data file, real (λ _M) be the real part of the characteristic root of matrix M.Just under the real part of the characteristic root of matrix M is not 0 constraint, do not optimize C, the D entry of a matrix is plain, the new C that obtains, and D matrix and original A, the B matrix has just constituted final system.

(4) with the coefficient matrices A of above-mentioned final no source model, B, C, D are input in the circuit emulator, calculate, and obtain circuit parameter.

Particular content below in conjunction with accompanying drawing and instance further explain this method.

Be illustrated in figure 1 as a data files; This document is used to describe one three port devices, and characteristic impedance R is 50 ohm, and data are to obtain under 0 the condition at 25 degrees centigrade, dc bias current; The unit of data medium frequency is a megahertz, and the form of The data amplitude phase place is described.According to data file shown in Figure 1, utilize vectorial approximating method, set up the initial realistic model of this circuit.Fig. 2 is the transfer curve according to the model of the data file foundation of Electromagnetic Simulation shown in Figure 1.Can see that data and curves and model curve are comparatively approaching among Fig. 2, show and utilize vectorial approximating method can set up more accurate model.

The passivity of correction model then.Can use the passivity of several different methods correction model.Existing passive modification method, such as the method for the characteristic root of disturbance Hamilton matrix, or the method for the coefficient corresponding with the disturbance limit can be used.But different with the Traditional passive correction is that the inventive method is only required the passivity of correction model, can relax to a certain extent the requirement of model accuracy.Therefore go wrong when traditional method convergence, when just can not produce no source model, the passivity that can use simple effective method of the present invention to come correction model, this process is described below:

Because passivity requires H (s)+H ^H(s)>=0, H (s)+H just ^H(s) characteristic root all is non-negative.Again because H (s)=C (sI-A) ^-1B+D therefore through on matrix D, adding the matrix of a suitable positive definite, just can improve H (s)+H ^H(s) characteristic root reaches the purpose of correction model passivity.Be on D, to add α I in the example of Fig. 3, wherein I is a unit matrix.H (the s)+H of model before and after Fig. 3 has drawn and revised ^H(s) characteristic root curve.Wherein, the characteristic root curve before the solid line representative compensation, the characteristic root curve after the dotted line representative compensation can be seen through passivity correction, H (s)+H ^H(s) characteristic root has been brought up to non-negative, and model has satisfied the requirement of passivity.

No matter be to select any method for use, can initial realistic model accurately original but that do not satisfy passivity be modified to one and on precision, decrease but passive initial no source model.

Afterwards, improve the precision of model.Initial no source model for producing in second step the present invention proposes optimized Algorithm and improves model accuracy.Use a model precision as optimization aim, use the passivity constraint as constraint condition, the model that produces with second step finds higher the separating of precision of satisfying the passivity constraint through optimized Algorithm, and separates as final model with this as initial solution.

Optimization variable: C, D

Minimize: $\underset{k}{\mathrm{\Σ}}{|H\left(s_k\right)-\hat{H}\left(s_k\right)|}_2^2$

H(s)＝C(sI-A) ^-1B+D

Constraint condition: $M=\left[\begin{array}{cc}A-{\mathrm{BR}}^{-1}C& -B{R}^{-1}{B}^H\\ C^H{R}^{-1}C& -A^H+C^H{R}^{-1}{B}^H\end{array}\right]$

real(λ)≠0， $\∀\mathrm{\λ}:|\mathrm{\λI}-M|=0$

Wherein: A, B, C, D, R are the matrix of coefficients of final no source model, H (s _k) be the data in the above-mentioned data file, real (λ _M) be the real part of the characteristic root of matrix M.Just under the real part of the characteristic root of matrix M is not 0 constraint, do not optimize C, the D entry of a matrix is plain, the new C that obtains, and D matrix and original A, the B matrix has just constituted final system.

At last, with the coefficient matrices A of above-mentioned final no source model, B, C, D are input in the circuit emulator, calculate, and obtain circuit parameter.

Use the Electromagnetic Simulation data file shown in Fig. 1; Directly carry out circuit simulation according to existing emulation mode; The circuit output waveform figure that obtains is as shown in Figure 4; If use and of the present inventionly to set up model after utilizing the Electromagnetic Simulation data file, carry out circuit simulation again, with the circuit output waveform figure that obtains like Fig. 5.Two output waveforms all are different on parameters such as oscillation starting points, amplitude, and through the measurement to side circuit, it is correct judging waveform shown in Figure 5, and the emulation mode that this explanation the present invention proposes helps obtaining correct circuit parameter.

Claims (1)

1. circuit emulation method based on passive modeling is characterized in that this method may further comprise the steps:

(1) method of employing Electromagnetic Simulation; Generate a data file that is used for circuit simulation; Comprise in this data file Electromagnetic Simulation environmental parameter, be used to explain the data layout and the simulation result of simulation result; According to this data file, utilize vectorial approximating method, set up the initial realistic model of this circuit;

(2) above-mentioned initial realistic model is revised, made initial realistic model become initial no source model, modification method is:

Adopt the characteristic root method of disturbance Hamilton matrix, initially do not had source model;

Or adopt the corresponding coefficient method of disturbance limit, initially there is not source model;

Or make matrix of coefficients D and a positive definite matrix mutual superposition that is used to improve initial realistic model transport function characteristic root of above-mentioned initial realistic model, initially there is not source model;

(3) precision with final no source model is an optimization aim, as optimizing constraint condition, is initial solution with the initial no source model of above-mentioned steps (2) with passivity constraint, uses optimized Algorithm, is not finally had source model:

Optimization variable: C, D

Minimize: $\underset{k}{\mathrm{\Σ}}{|H\left(s_k\right)-\hat{H}\left(s_k\right)|}_2^2$

H(s)＝C(sI-A) ^-1B+D

Constraint condition: $M=\left[\begin{array}{cc}A-{\mathrm{BR}}^{-1}C& -B{R}^{-1}{B}^H\\ C^H{R}^{-1}C& -A^H+C^H{R}^{-1}{B}^H\end{array}\right]$

real(λ)≠0， $\∀\mathrm{\λ}:|\mathrm{\λI}-M|=0$

Wherein: A, B, C, D, R are the matrix of coefficients of final no source model, H (s _k) be the data in the above-mentioned data file, real (λ _M) be the real part of the characteristic root of matrix M;

(4) with the coefficient matrices A of above-mentioned final no source model, B, C, D are input in the circuit emulator, calculate, and obtain circuit parameter.

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