Circuit simulation device and circuit simulation program

Abstract

To provide a technique for improving the accuracy of simulation for an electric circuit.SOLUTION: In a circuit simulation apparatus 1, an input unit 2 receives an input of DC characteristics of a transistor. A computing unit 4 acquires time waveform of an output signal with respect to an input signal input to the transistor, on the basis of the DC characteristics of the transistor and a load line. The computing unit 4 computes, when the output signal is limited at the end of the load line, the amount of variation of the output signal exceeding the end of the load line on the basis of the time waveform of the output signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a circuit simulation device. Place and circuit simulation programs. [Background technology]

[0002] The load line method is one of the methods for simulating electric circuits. The load line method is also called load line analysis. In the load line method, nonlinear characteristics can be obtained by performing a time-axis analysis of the waveforms of current and voltage moving on the load line of a transistor. For example, Non-Patent Document 1 and Non-Patent Document 2 disclose a method for simulating electric circuits that employs nonlinear analysis based on the load line method. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] K. Mori, M. Nakayama, Y. Itoh, S. Murakami, Y. Nakajima, T. Takagi, and Y. Mitsui, "Direct Efficiency and Power Calculation Method and Its Application to Low Voltage High Efficiency Power Amplifier", IEICE Trans., vol. E78-C, No.9, pp.1229-1236, September 1995 [Non-Patent Document 2] Y. Ikeda, K. Mori, M. Nakayama, Y. Itoh, O. Ishida, and T. Takagi, "An Efficient Large-Signal Modeling Method Using Load-Line Analysis and its Application to Non-Linear Characterization of FET", IEICE Trans. Electron., vol. E84-C, No. 7, pp. 875-880, July 2000 Summary of the Invention [Problem to be solved by the invention]

[0004] The electric circuit simulation method of Non-Patent Document 1 calculates the output and efficiency of a transistor from the DC characteristics determined by the knee voltage, breakdown voltage, and saturation current of the transistor, as well as the output load conditions and bias conditions. When the input power to the transistor increases and a forward saturation current (hereinafter referred to as forward gate current) or a reverse leakage current (hereinafter referred to as reverse gate current) flows through the gate, the method of Non-Patent Document 1 calculates the voltage amplitude or current amplitude so as not to exceed the range of the DC characteristics determined by the knee voltage, breakdown voltage, and saturation current of the transistor, which may result in a decrease in the accuracy of the output and efficiency.

[0005] The simulation method of Non-Patent Document 2 also calculates the voltage amplitude or current amplitude in the same way as Non-Patent Document 1, so there is a possibility that the simulation accuracy will decrease during large signal operation.

[0006] An exemplary object of the present disclosure is to provide a technique that can improve the accuracy of simulation of an electric circuit. [Means for solving the problem]

[0007] In order to solve the above problems, a circuit simulation device according to an embodiment of the present disclosure includes an input unit that receives an input of a DC characteristic of a transistor, and a calculation unit that acquires a time waveform of an output signal for an input signal to the transistor based on the DC characteristic of the transistor and a load line. When the output signal is limited at an end of the load line, the calculation unit calculates a fluctuation amount of the output signal that exceeds the end of the load line based on the time waveform of the output signal.

[0009] Any combination of the above components, or mutual substitution of the components or expressions of the present disclosure between methods, systems, programs, etc., are also valid aspects of the present disclosure. Effect of the Invention

[0010] According to the present disclosure, a technique can be provided that can improve the accuracy of simulation of an electric circuit. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram illustrating a functional configuration of a circuit simulation apparatus according to an embodiment. [Diagram 2] 1 is a diagram illustrating a configuration of a circuit simulation device according to an embodiment. [Diagram 3] FIG. 4 is a diagram showing DC characteristics of a transistor according to an embodiment. [Figure 4] 4(a) and (b) are diagrams for explaining the operation of the transistor of the embodiment when the input signal is large. [Diagram 5] 3 is an equivalent circuit diagram of a transistor according to the embodiment. FIG. [Figure 6] FIG. 4 is a diagram showing current-voltage characteristics of a transistor in the embodiment. [Figure 7] 5A to 5C are diagrams illustrating the input power dependence of output power, amplitude distortion, and phase distortion of an electric circuit in an embodiment. [Figure 8] 2 is a flowchart showing the operation of the circuit simulation device of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and duplicated description will be omitted as appropriate.

[0013] First, the circuit simulation device of the present embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 shows the functional configuration of the circuit simulation device 1 of the embodiment. Fig. 2 shows the configuration of the circuit simulation device 1 of the embodiment.

[0014] The circuit simulation device 1 uses the load line method to analyze linear and nonlinear characteristics of an electric circuit including an amplifying element such as a transistor. The electric circuit may be, for example, an amplifier such as a power amplifier. The operating frequency of the electric circuit is not particularly limited, but may be, for example, a radio frequency band. The circuit simulation device 1 simulates the time waveform of an output signal relative to the time waveform of an input signal, and simulates output power, efficiency, amplitude distortion, phase distortion, distortion characteristics, and the like based on the obtained time waveform of the output signal, and outputs these.

[0015] As shown in Fig. 1, the circuit simulation device 1 comprises an input unit 2, a modeling unit 3, a calculation unit 4, an analysis result display unit 5, and an analysis result output unit 6. These components can be realized in hardware terms by the CPU, memory, and other LSIs of any computer, and in software terms by programs loaded into memory, but here, functional blocks realized by the cooperation of these are depicted. Therefore, it will be understood by those skilled in the art that these functional blocks can be realized in various forms by only hardware, only software, or a combination of both.

[0016] The input unit 2 has a function of receiving input of DC characteristics of nonlinear circuit elements such as transistors (FIG. 3) and circuit element values ​​of an equivalent circuit (FIG. 4). The DC characteristics of a transistor are measured values, and the knee voltage V k , breakdown voltage V br, 2-terminal breakdown voltage (V br +V p ), saturation current I dss , I d -V d Contains the characteristics, where V p is the pinch-off voltage of the transistor. The circuit element values ​​of the equivalent circuit of the transistor will be described later. The input unit 2 may receive input of simulation conditions such as the value of the AC load, the frequency and input power of the input signal.

[0017] The modeling unit 3 has a function of mathematically expressing, as functions, the DC characteristics of a transistor, nonlinear characteristics such as the capacitance and resistance of the transistor's equivalent circuit, and nonlinear characteristics such as the amplitude distortion and phase distortion of an electric circuit. The calculation unit 4 has a function of analyzing the linear and nonlinear characteristics of an electric circuit in the time domain. The functions of the modeling unit 3 and calculation unit 4 will be described in detail later.

[0018] The analysis result display unit 5 has a function of displaying the linear and nonlinear characteristics of the electric circuit as graphs or numerical values ​​using the display device 7 in Fig. 2. The analysis result output unit 6 has a function of outputting the above analysis results using the storage device, input / output device, and communication device in Fig. 2.

[0019] As shown in Fig. 2, the circuit simulation device 1 includes a display device 7, a calculation device 8, a storage device 9, a communication device 10, and an input / output device 11. The calculation device 8 executes a circuit simulation program stored in the storage device 9 to comprehensively control the circuit simulation device 1 and realize each function of the circuit simulation device 1. The storage device 9 stores programs and data. The communication device 10 communicates with external devices. The display device 7 is, for example, a display, and displays various information such as analysis results of the circuit simulation device 1. The input / output device 11 includes a keyboard and mouse for inputting data to the circuit simulation device 1, and a printer for outputting various information such as analysis results of the circuit simulation device 1.

[0020] 3 to 6, the DC characteristics, equivalent circuit, and current-voltage characteristics of the transistor analyzed by the circuit simulation device 1 will be described. An example of the transistor will be described as a field effect transistor.

[0021] FIG. 3 shows the DC characteristics of the transistor of the embodiment. In FIG. 3, the DC characteristics of the transistor are shown with respect to the drain voltage V d Drain current I d The transistor has a common source and an AC load connected to its drain. The drain voltage of the transistor is V d and the drain current I d is the knee voltage V received at the input 2 k , breakdown voltage V br , 2-terminal breakdown voltage (V br +V p ), saturation current I dss The swing angle θ is within a rectangular region 30 bounded by the points of zero voltage and current, the knee voltage V k and saturation current I dss The intersection point, breakdown voltage V br and saturation current I dss The voltage at the intersection of the two terminals is the two-terminal breakdown voltage (V br +V p ) is a quadrilateral whose vertices are the points where the current is zero.

[0022] The voltage and current at the bias point 18 of the transistor are (V do ,I do ), and the voltage and current at the minimum and maximum voltage points 19 (V dmin ,I dmax ), and the voltage and current at the voltage maximum and current minimum points 20 (V dmax ,I dmin The voltage minimum and current maximum points 19 are the points where the voltage and current are zero and the knee voltage V k and saturation current I dss The voltage maximum-current minimum point 20 is located on the line connecting the intersection of the drain current I d is located on the zero line.

[0023] The solid load line 21 is a straight line with a slope of "-gl" that connects the bias point 18, the minimum voltage / maximum current point 19, and the maximum voltage / minimum current point 20. The load line 21 is an AC load line, and is determined according to the magnitude of the AC load, etc.

[0024] The calculation unit 4 acquires a time waveform of an output signal with respect to a time waveform of an input signal to the transistor based on the DC characteristics of the transistor and the load line 21. The DC characteristics of the transistor are expressed as I d -V d The characteristics are included (not shown). d -V d The characteristic is, for example, the I d -V d The characteristic measurement values ​​are approximated by a function. The calculation unit 4 calculates the drain voltage V d and the drain current I d is swung on the load line 21, and the drain voltage V d and the drain current I d When the input to the transistor is relatively small, the drain voltage V d and the drain current I d moves on the load line 21 within the range where the voltage minimum-current maximum point 19 and the voltage maximum-current minimum point 20 are not reached. In this case, the drain voltage V d and the drain current I d The time waveform is not clipped.

[0025] The calculation unit 4 detects the input signal as it becomes relatively large, and the drain voltage V d and the drain current I d When the drain voltage V reaches the voltage minimum-current maximum point 19, d The minimum value of is the voltage V dmin The time waveform limited by and the drain current I d The maximum value of the current I dmax The calculation unit 4 obtains a time waveform limited by the drain voltage V d and the drain current I dWhen the voltage reaches the maximum and current reaches the minimum point 20, the drain voltage V d The maximum value of the voltage V dmax The time waveform limited by and the drain current I d The minimum value of is the current I dmin In other words, these time waveforms have at least one of their maximum and minimum values ​​clipped.

[0026] In an actual transistor, when the input signal becomes large, a forward gate current or a reverse gate current flows through the transistor, causing the output signal to slightly exceed the end of the load line 21, resulting in a fluctuation in the output signal. The calculation unit 4 calculates the amount of this fluctuation and incorporates the amount of fluctuation into the time waveform of the output signal.

[0027] The dashed line 22a indicates that the input to the transistor increases and the drain voltage V d and the drain current I d When the drain voltage V exceeds the voltage minimum-current maximum point 19 at the end of the load line 21, d and the drain current I d The dashed line 22b indicates the range in which the input to the transistor increases and the drain voltage V d and the drain current I d When the drain voltage V exceeds the voltage maximum-current minimum point 20 at the end of the load line 21, d and the drain current I d The line 22a indicates the range over which the voltage and current can swing, and the knee voltage V k and saturation current I dss On the line connecting the intersection of the voltage minimum and current maximum points 19 and the drain current I d The line 22b extends in the direction in which the drain current I d On the line where the drain voltage V is zero, d It extends in the direction in which

[0028] When the output signal is limited at the end of the load line 21, the calculation unit 4 calculates the amount of fluctuation in the output signal that exceeds the end of the load line 21 based on the time waveform of the output signal. It can also be said that when the output signal is limited at the end of the load line 21, the calculation unit 4 calculates the amount of fluctuation in the output signal caused by a forward gate current or a reverse gate current flowing through the transistor. The calculation of the amount of fluctuation will be described below.

[0029] 4(a) and (b) are diagrams for explaining the operation of the transistor of the embodiment when the input signal is large. FIG. 4(a) shows the operation of the transistor when the input signal to the transistor becomes large and the drain current I d When the upper half of the waveform is clipped, the time waveform 60 and I d -V d Figure 4(b) shows the characteristics of the transistor as the input voltage increases and the drain current I d The time waveform 64 and I when the lower half of d -V d The characteristics are shown in Fig. 3. Here, a load line and bias point different from those in Fig. 3 are used for explanation.

[0030] In FIG. 4(a), the load line 40 shown by the dashed line is the load line when a small signal is input in the initial state. do , current I do First, the calculation unit 4 calculates the drain current I d and the drain voltage V d In this example, since the input is large, the drain voltage V d and the drain current I d is limited by the voltage minimum-current maximum point 42 at the end of the load line 40. The drain voltage V d and the drain current I d is not limited at the voltage maximum / current minimum point 43 at the end of the load line 40.

[0031] The calculation unit 4 calculates the drain current I d is limited at the end of the load line 40, the obtained drain current I dThe time waveform of is expanded into a Fourier series to obtain the DC component of the time waveform, and the load line 40 is moved so as to pass through the value of the obtained DC component. At this time, the calculation unit 4 calculates the slope "-gl" of the load line and the voltage V at the bias point. do The calculation unit 4 keeps the drain current I constant based on the DC characteristics of the transistor and the load line after the shift (not shown). d and the drain voltage V d A new time waveform is acquired.

[0032] The calculation unit 4 calculates the drain current I d The series of processes are repeated until the value of the DC component of the drain current I converges to a substantially constant value. The calculation unit 4 may repeat the series of processes a predetermined number of times. In FIG. 4(a), d The time waveform 60 and the load line 45 are shown by thick solid lines. The converged drain current I d The value of the DC component of the current I dav Corresponds to.

[0033] The calculation unit 4 calculates the finally obtained drain current I d The calculation unit 4 obtains the DC component A0 and the fundamental wave component A1 of the time waveform 60. The calculation unit 4 calculates the drain current I that exceeds the voltage minimum / current maximum point 47 at the end of the load line 45 based on the value that varies from the DC component A0 by the fundamental wave component A1. d The amount of change ΔI d and the drain voltage V d The amount of change ΔV d (not shown) is calculated. The drain voltage V d and the drain current I d is not limited at the voltage maximum / current minimum point 48 at the end of the load line 45.

[0034] The calculation unit 4 calculates the finally obtained drain current I d The amount of change ΔI d Adding these together, the drain current I d The amount of change ΔI dThe calculation unit 4 obtains a time waveform 62 including the finally obtained drain voltage V d The amount of fluctuation ΔV d Adding these, the drain voltage V d The amount of change ΔV d A time waveform (not shown) including

[0035] Similarly, in FIG. 4(b), a load line 50 shown by a dashed line is a load line in the initial state when a small signal is input. A bias point 51 is located on the load line 50. Initially, the calculation unit 4 calculates the drain current I d and the drain voltage V d In this example, since the input is large, the drain voltage V d and the drain current I d is limited by the voltage maximum-current minimum point 53 at the end of the load line 50. The drain voltage V d and the drain current I d is not limited at the voltage minimum / current maximum point 52 at the end of the load line 50.

[0036] The calculation unit 4 calculates the drain current I d is limited at the end of the load line 50, the obtained drain current I d The time waveform of is expanded into a Fourier series to obtain the DC component of the time waveform, and the load line 50 is moved so that it passes through the value of the obtained DC component. As described above, the slope of the load line "-gl" and the voltage V at the bias point do is kept constant. The calculation unit 4 calculates the drain current I for an input signal of the same AC component based on the DC characteristics of the transistor and the load line after the shift (not shown). d A new time waveform is acquired.

[0037] As described above, the calculation unit 4 calculates the drain current I d This series of processes is repeated until the DC component of the drain current I converges to a constant value. d The time waveform 64 and the load line 55 are shown by thick solid lines. The converged drain current I dThe value of the DC component of the current I dav Corresponds to.

[0038] The calculation unit 4 calculates the finally obtained drain current I d The calculation unit 4 obtains the DC component A0 and the fundamental wave component A1 of the time waveform 64. The calculation unit 4 calculates the drain voltage V that exceeds the voltage maximum / current minimum point 58 at the end of the load line 55 based on the value that varies from the DC component A0 by the fundamental wave component A1. d The amount of change ΔV d In the example of Figure 4(b), the drain current I d The amount of change in the drain voltage V d and the drain current I d is not limited at the voltage minimum / current maximum point 57 at the end of the load line 55.

[0039] The calculation unit 4 calculates the finally obtained drain voltage V d The maximum value of the time waveform (not shown) fluctuates by ΔV d Adding these, the drain voltage V d The amount of change ΔV d A time waveform (not shown) including

[0040] These processes are explained using formulas. Drain current I d The amplitude of the drain current I is A, the DC component obtained by expanding the clipped time waveforms 60 and 64 into a Fourier series is A0, the fundamental component is A1, and the period is T. As shown in FIG. 4(a), d At a point bT away from the peak value of d Assume that the upper half of is clipped. Also, as shown in Fig. 4(b), the drain current I d At a point aT away from the peak value of d Assume that the lower half of I is clipped. d When the time waveform in which both the upper and lower halves are clipped simultaneously is expanded in a Fourier series, the following equations (1) and (2) are obtained.

[0041]

number

[0042] In FIG. 4(a), a=1 / 2, that is, the lower half is not clipped, so A0 and A1 are given by the following equations (3) and (4), respectively.

[0043]

number

[0044] In FIG. 4B, b=0, that is, the upper half is not clipped, so A0 and A1 are given by the following equations (5) and (6), respectively.

[0045]

number

[0046] When the input to the transistor increases, the drain current I d is the voltage minimum and current maximum point 47 at the end of the load line 45, and the zero point and knee voltage V k The drain current I d The amount of change in ΔI d Then, ΔI d can be calculated from the following equation (7). Also, the drain voltage V d The amount of change ΔV d is the zero point and knee voltage V k On the line connecting the current is ΔI d It can be calculated as the amount of change in voltage when the voltage changes.

[0047]

number

[0048] In addition, when the input to the transistor increases, the drain voltage V d exceeds the voltage maximum-current minimum point 58 at the end of the load line 55, and I d = 0 line to the right. At this time, the drain voltage V dThe amount of change in ΔV d Then, ΔV d can be calculated from the following equation (8). d is the current I at the voltage maximum-current minimum point 58 on the load line 55. dmin It can be calculated as the amount of change in voltage when the voltage decreases by "fundamental wave component A1 - DC component A0".

[0049]

number

[0050] Drain current I d Even if both the upper and lower sides of are limited at the same time, a time waveform including the amount of fluctuation in the output signal can be obtained in the same manner.

[0051] In this embodiment, when the input of the transistor becomes large and a forward gate current or a reverse gate current occurs in the transistor, the amount of fluctuation in the voltage amplitude or the current amplitude can be calculated. In other words, when the input of the transistor is large, the drain current I d , drain voltage V d The time waveform of the output signal is obtained taking into account the behavior of the

[0052] FIG. 5 is an equivalent circuit diagram of a transistor in the embodiment. The mutual conductance is gm, and the drain-source resistance is R ds , where C is the gate-source capacitance. gs , the gate-drain capacitance is C dg These circuit elements are expressed as gate voltage V g and the drain voltage V d These values ​​can be given by the following equations (9)-(12), for example. In equation (10), the drain-source resistance R ds Let conductance g ds =1 / R ds The drain voltage V dand the drain current I d Since the load swings on the load line 21 and the straight lines 22a and 22b in FIG. 3, during nonlinear operation (i.e., during large signal operation), the average value for one period, that is, gm given by the following equations (13)-(16) av ,g dsav ,C gsav ,C dgav That is, the modeling unit 3 calculates the values ​​of the nonlinear circuit elements included in the equivalent circuit based on one period of the time waveform including the amount of fluctuation in the output signal calculated by the calculation unit 4. The calculation unit 4 acquires the time waveform including the amount of fluctuation in the output signal for each of the multiple input powers. The modeling unit 3 calculates the values ​​of the nonlinear circuit elements for each of the multiple input powers.

[0053]

number

number

[0054] The gate-source resistance is R i , drain-source capacitance is C ds These circuit elements are expressed as gate voltage V g and the drain voltage V d It is a linear circuit element that does not depend on

[0055] 6 shows the current-voltage characteristics of the transistor in this embodiment. In FIG. 6, the V d -I d As mentioned above, the region 30 enclosed by the dashed rectangle is the drain voltage V d , drain current I d The solid line 32 is a measured value of the current-voltage characteristic, which is the DC characteristic of a transistor. The dashed line 31 is an example of the DC characteristic of a transistor expressed mathematically as a function. The drain current I d is the drain voltage V d and the gate voltage V gExamples of equations expressed as a function of are shown in equations (17) and (18). In other words, the modeling unit 3 d -I d The measured value of the characteristic is approximated by a function.

[0056]

number

[0057] Drain current I d is the drain voltage V d and the gate voltage V g The drain current I d This makes it possible to obtain a more accurate time waveform of the output signal even in areas where no measured values ​​are available, and to more accurately calculate the mutual conductance in equations (9) and (13) and the drain-source conductance in equations (10) and (14). This improves the accuracy of the simulation.

[0058] That is, the calculation unit 4 obtains the time waveform of the output signal based on the load line and a function that approximates the measured values ​​of the DC characteristics of the transistor. This process corresponds to the calculation unit 4 calculating the electrical characteristics of the electric circuit based on a function that represents the nonlinear characteristics of the electric circuit having the transistor.

[0059] Here, in the technology of Non-Patent Document 2, the time waveform is obtained by directly using the measured values ​​of DC characteristics such as the current and voltage of the transistor, so there is a possibility that the calculation accuracy will decrease at points where there are no measured values. In contrast, in the embodiment, the DC characteristics of the transistor are expressed mathematically as a function instead of measured values, so the calculation accuracy can be improved.

[0060] Next, analysis of the AM-AM characteristics, AM-PM characteristics, and distortion characteristics of an electric circuit by the circuit simulation device 1 will be described with reference to FIG.

[0061] FIG. 7 shows the output power P out, the input power P with amplitude distortion ΔG and phase distortion Δφ in It indicates dependency. P in -P out The characteristic is known as the AM-AM characteristic, and in The -Δφ characteristic is known as the AM-PM characteristic. The amplitude distortion ΔG and the phase distortion Δφ can be calculated from the scattering parameters of the transistor equivalent circuit in Figure 5 using the following equations (19)-(22).

[0062]

number

[0063] That is, the calculation unit 4 calculates scattering parameters for each of the multiple input powers based on the values ​​of the nonlinear circuit elements calculated by the modeling unit 3, and derives AM-AM characteristics and AM-PM characteristics based on the calculated scattering parameters for each of the multiple input powers. This process corresponds to the calculation unit 4 calculating the AM-AM characteristics and AM-PM characteristics of the electric circuit based on the time waveforms of the output signals for each of the multiple input powers.

[0064] Here, in the technology of Non-Patent Document 2, the scattering parameters during non-linear operation of the transistor are calculated using a commercially available simulator, so the calculation is performed offline, which may slow down the calculation speed. In contrast, in the embodiment, the scattering parameters during non-linear operation can be calculated online based on the values ​​of the non-linear circuit elements calculated by the modeling unit 3, so the simulation speed can be improved.

[0065] The AM-AM characteristics and AM-PM characteristics are basic equations for calculating intermodulation distortion, spectrum, modulation accuracy (EVM), etc. as distortion characteristics. However, when changing the input power and performing a simulation, it may take a long time to perform calculations each time using the above equations (19)-(22). Therefore, in this embodiment, the AM-AM characteristics and AM-PM characteristics that have been calculated once are mathematically expressed as functions. In other words, the modeling unit 3 approximates the calculated AM-AM characteristics and AM-PM characteristics with functions. The calculation unit 4 calculates the distortion characteristics of the electric circuit based on the functions that approximate the AM-AM characteristics and AM-PM characteristics. This process corresponds to the calculation unit 4 calculating the electrical characteristics of the electric circuit based on a function that represents the nonlinear characteristics of the electric circuit. This can improve the calculation speed. Here, the AM-AM characteristics and AM-PM characteristics are expressed by equations (23) and (24) using a regression analysis method. n ,a n-1 ,a n-2 ,···,b n ,b n-1 ,b n-2 represents coefficients, and equations (23) and (24) are expressed as n-th degree polynomials.

[0066]

number

[0067] Furthermore, when the approximation error of the function exceeds a predetermined allowable range, the calculation unit 4 stores the calculated AM-AM characteristics and AM-PM characteristics as a table, and calculates the distortion characteristics of the electric circuit based on the stored table. Various known errors can be used as the approximation error of the function. The allowable range can be appropriately determined by experiment or simulation. This makes it possible to calculate the distortion characteristics even when it is difficult to approximate the AM-AM characteristics and AM-PM characteristics by a function.

[0068] Next, the overall operation of the circuit simulation device 1 will be described with reference to Fig. 1 and Fig. 8. Fig. 8 is a flowchart showing the operation of the circuit simulation device 1 of Fig. 1.

[0069] The input unit 2 receives input of DC characteristics of nonlinear circuit elements such as transistors and circuit element values ​​of an equivalent circuit (S1). Next, the modeling unit 3 calculates the V d -I d The characteristics are modeled (S2). The calculation unit 4 acquires the time waveform of the output signal for the input signal to the transistor based on the DC characteristics and the load line of the transistor (S3). The modeling unit 3 models the nonlinear characteristics of nonlinear elements such as capacitance and resistance of the equivalent circuit of the transistor based on the time waveform of the output signal of the transistor using equations (9)-(16) (S4).

[0070] The calculation unit 4 outputs the output P out and efficiency η d is calculated from equations (25) and (26) (S5). Here, V d (t) and I d (t) represents the time change of the drain voltage and drain current, and P dc indicates the power consumption.

[0071]

number

[0072] The calculation unit 4 calculates the scattering parameters of the electric circuit from the equations (21) and (22) (S6). The scattering parameters of the electric circuit are calculated based on the input power P in Depending on the transistor's nonlinear circuit element, the mutual conductance gm and the drain-source resistance R ds , gate-source capacitance C gs , gate-drain capacitance C dg Since varies, it can be calculated in a form dependent on the input power using equations (21) and (22).

[0073] The calculation unit 4 calculates the amplitude distortion ΔG and phase distortion Δφ of the electric circuit from equations (19) and (20) based on the scattering parameters (S7). The calculation unit 4 calculates various distortion characteristics of the electric circuit, such as intermodulation distortion, spectrum, and EVM, based on the AM-AM characteristics and AM-PM characteristics (S8).

[0074] These analysis results are output as data to a display, printer, or storage device from the analysis result display unit 5 and analysis result output unit 6 in FIG.

[0075] The present disclosure has been described above based on the embodiments. It will be understood by those skilled in the art that the present disclosure is not limited to the above embodiments, that various design changes are possible, that various modifications are possible, and that such modifications are also within the scope of the present disclosure.

[0076] For example, in the embodiment, an example has been shown in which the circuit simulation device 1 analyzes an electric circuit having a field effect transistor, but the circuit simulation device 1 may analyze an electric circuit having other amplifying elements such as a bipolar transistor.

[0077] One aspect of the present disclosure is as follows.

[0078] [Item 1] an input unit that receives an input of a DC characteristic of a transistor; a calculation unit that acquires a time waveform of an output signal with respect to an input signal to the transistor based on a DC characteristic and a load line of the transistor, the calculation unit calculates, when the output signal is limited at the end of the load line, an amount of fluctuation in the output signal exceeding the end of the load line based on a time waveform of the output signal; A circuit simulation device comprising: According to this aspect, the amount of fluctuation in the output signal exceeding the end of the load line is calculated, so that the accuracy of the simulation can be improved.

[0079] [Item 2] the transistor is a field effect transistor, the output signal includes a drain current and a drain voltage of the field effect transistor; The calculation unit is when the drain current is limited at the end of the load line, a series of processes is repeated, in which a DC component of the acquired time waveform of the drain current is acquired, the load line is moved so as to pass through the value of the acquired DC component, and a new time waveform of the drain current for an input signal of the same AC component is acquired based on the DC characteristics of the transistor and the load line after the movement; A DC component and a fundamental component of the finally obtained time waveform of the drain current are obtained, and a fluctuation amount of the final drain current or drain voltage exceeding the end of the load line is calculated based on a value obtained by fluctuating the DC component by the fundamental component. 2. The circuit simulation device according to item 1, In this case, the accuracy of the simulation can be improved.

[0080] [Item 3] the calculation unit calculates electrical characteristics of the electric circuit based on a function representing a nonlinear characteristic of the electric circuit having the transistor; 3. The circuit simulation device according to item 1 or 2. In this case, the accuracy of the simulation can be improved.

[0081] [Item 4] a modeling unit that calculates values ​​of nonlinear circuit elements included in the equivalent circuit of the transistor based on one period of a time waveform including a fluctuation amount of the output signal calculated by the calculation unit, the calculation unit calculates scattering parameters of the electric circuit having the transistor based on the values ​​of the nonlinear circuit elements calculated by the modeling unit; 4. The circuit simulation device according to any one of items 1 to 3. In this case, the speed and accuracy of the simulation can be improved.

[0082] [Item 5] the calculation unit acquires a time waveform including a fluctuation amount of an output signal for each of a plurality of input powers, and calculates an AM-AM characteristic and an AM-PM characteristic of an electric circuit having the transistor based on the acquired time waveform of the output signal; The circuit simulation device includes: A modeling unit is further provided that approximates the calculated AM-AM characteristics and the calculated AM-PM characteristics by functions, the calculation unit calculates the distortion characteristic of the electric circuit based on the function; 4. The circuit simulation device according to any one of items 1 to 3. In this case, since the distortion characteristics can be calculated using a function, it is not necessary to recalculate the AM-AM characteristics etc. every time the input power conditions are changed, and therefore the simulation speed can be improved.

[0083] [Item 6] the calculation unit stores the calculated AM-AM characteristics and AM-PM characteristics as a table when an approximation error of the function exceeds a predetermined allowable range, and calculates the distortion characteristics of the electric circuit based on the stored table. 6. The circuit simulation device according to item 5, In this case, the distortion characteristic can be calculated even when approximation by a function is difficult.

[0084] [Item 7] receiving an input of a DC characteristic of a transistor; acquiring a time waveform of an output signal with respect to an input signal to the transistor based on a DC characteristic and a load line of the transistor; When the output signal is limited at the end of the load line, calculating an amount of fluctuation of the output signal exceeding the end of the load line based on a time waveform of the output signal; A circuit simulation method comprising:

[0085] [Item 8] receiving an input of a DC characteristic of a transistor; acquiring a time waveform of an output signal with respect to an input signal to the transistor based on a DC characteristic and a load line of the transistor; When the output signal is limited at the end of the load line, calculating an amount of fluctuation of the output signal exceeding the end of the load line based on a time waveform of the output signal; A circuit simulation program for causing a computer to execute the above.

[0086] [Item 9] An electric circuit simulation device using a simulation method for analyzing the nonlinear characteristics of an electric circuit using a load line method for analyzing the time waveforms of voltage and current swinging on the load line of a transistor.

[0087] [Item 10] 10. The electric circuit simulation device according to item 9, characterized in that the simulation speed and accuracy are improved by using a behavior model that expresses the nonlinear characteristics of the electric circuit as a function rather than as a measured value.

[0088] [Item 11] 11. The electric circuit simulation device according to item 9 or 10, characterized in that the average of one period of the time waveform of each voltage and current swinging on the load line is adopted as the value of the nonlinear circuit element constituting the electric circuit, and the average is used as it is for calculating the scattering parameters during large signal operation, thereby improving the simulation speed and accuracy.

[0089] [Item 12] 12. The electric circuit simulation device according to any one of items 9 to 11, characterized in that the simulation accuracy is improved by analyzing the nonlinear characteristics of the electric circuit, including the fluctuation of the drain voltage and the drain current, taking into account the forward gate current and the reverse gate current that occur when a transistor or the like operates in large signal mode.

[0090] [Item 13] 13. The electric circuit simulation device according to any one of items 9 to 12, characterized in that the AM-AM characteristics and AM-PM characteristics of the electric circuit are expressed by a behavior model based on functions, thereby improving the calculation speed of intermodulation distortion, spectrum, and modulation accuracy.

[0091] [Item 14] Item 14. The electric circuit simulation device according to item 13, characterized in that when it is difficult to express the AM-AM characteristics and AM-PM characteristics of an electric circuit by a behavior model based on functions, the AM-AM characteristics and AM-PM characteristics are compiled into a single lookup table, and the table is read to enable calculation of intermodulation distortion, spectrum, and modulation accuracy.

[0092] [Item 15] 15. The electric circuit simulation device according to any one of items 9 to 14, characterized in that the electric circuit simulation programs are compiled into a single piece of software, making it possible to perform calculations on a single piece of hardware. [Explanation of symbols]

[0093] 1...circuit simulation device, 2...input section, 3...modeling section, 4...calculation section, 5...analysis result display section, 6...analysis result output section, 7...display device, 8...calculation device, 9...storage device, 10...communication device, 11...input / output device.

Claims

1. an input unit that receives an input of a DC characteristic of a transistor; a calculation unit that acquires a time waveform of an output signal with respect to an input signal to the transistor based on a DC characteristic and a load line of the transistor, the calculation unit calculates, when the output signal is limited at the end of the load line, an amount of fluctuation in the output signal exceeding the end of the load line based on a time waveform of the output signal; A circuit simulation device comprising:

2. the transistor is a field effect transistor, the output signal includes a drain current and a drain voltage of the field effect transistor; The calculation unit is when the drain current is limited at the end of the load line, a series of processes is repeated, in which a DC component of the acquired time waveform of the drain current is acquired, the load line is moved so as to pass through the value of the acquired DC component, and a new time waveform of the drain current for an input signal of the same AC component is acquired based on the DC characteristics of the transistor and the load line after the movement; A DC component and a fundamental component of the finally obtained time waveform of the drain current are obtained, and a fluctuation amount of the final drain current or drain voltage exceeding the end of the load line is calculated based on a value obtained by fluctuating the DC component by the fundamental component.

2. The circuit simulation device according to claim 1.

3. the calculation unit calculates electrical characteristics of the electric circuit based on a function representing a nonlinear characteristic of the electric circuit having the transistor; 3. The circuit simulation device according to claim 1, wherein the first and second inputs are connected to the first and second inputs.

4. a modeling unit that calculates values ​​of nonlinear circuit elements included in an equivalent circuit of the transistor based on one period of a time waveform including a fluctuation amount of the output signal calculated by the calculation unit, the calculation unit calculates scattering parameters of the electric circuit having the transistor based on the values ​​of the nonlinear circuit elements calculated by the modeling unit; 3. The circuit simulation device according to claim 1, wherein the first and second inputs are connected to the first and second inputs.

5. the calculation unit acquires a time waveform including a fluctuation amount of an output signal for each of a plurality of input powers, and calculates AM-AM characteristics and AM-PM characteristics of an electric circuit having the transistor based on the acquired time waveform of the output signal; The circuit simulation device includes: A modeling unit is further provided that approximates each of the calculated AM-AM characteristics and AM-PM characteristics by a function, The calculation unit calculates the distortion characteristic of the electric circuit based on the function.

3. The circuit simulation device according to claim 1, wherein the first and second inputs are connected to the first and second inputs.

6. the calculation unit stores the calculated AM-AM characteristics and AM-PM characteristics as a table when an approximation error of the function exceeds a predetermined allowable range, and calculates the distortion characteristics of the electric circuit based on the stored table.

6. The circuit simulation device according to claim 5.

7. receiving an input of a DC characteristic of a transistor; acquiring a time waveform of an output signal with respect to an input signal to the transistor based on a DC characteristic and a load line of the transistor; When the output signal is limited at the end of the load line, calculating an amount of fluctuation of the output signal exceeding the end of the load line based on a time waveform of the output signal; A circuit simulation program for causing a computer to execute the above.

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