This example shows how to build and simulate an RC tree circuit using the RF Toolbox™.
In "Asymptotic Waveform Evaluation for Timing Analysis" (IEEE Transactions on Computer-Aided Design, Vol., 9, No. 4, April 1990), Pillage and Rohrer presented and simulated an RC tree circuit that models signal integrity and crosstalk in low- to mid-frequency MOS circuit interconnect. This example confirms their simulations using RF Toolbox software.
在下图中复制的它们的电路由11个电阻和12个电容器组成。在纸上,掠夺和罗勒:
应用坡道电压输入
Compute transient responses
绘制两个不同电容器上的输出电压,C7
andC12
。
图1:An RC tree model of MOS interconnect with crosstalk.
With RF Toolbox, you can programmatically construct this circuit in MATLAB and perform signal integrity simulations.
此示例显示:
如何使用克隆
,,,,setports
,,,,andSparameters
objects to calculate S-parameters for each desired output over a wide frequency range.
如何使用S2TF
和Zsource = 0
andzload = Inf
要计算从输入到每个所需输出的电压传输函数。
如何使用rationalfit
function to produce rational-function approximations that capture the ideal RC-circuit behavior to a very high degree of accuracy.
如何使用计时器
function to compute the transient response to the input voltage waveform.
在构建电路之前使用电阻
andcapacitor
objects, we must number the nodes of the circuit shown in figure 1.
图2:这circuit drawn with node numbers
创建一个circuit
and use the添加
function to populate the circuit with named电阻
andcapacitor
对象。
ckt =电路('相声');添加(ckt,[2 1],resistor(10,'r1')添加(CKT,[2 0],电容器(0.114E-12,,'C1')添加(CKT,[3 2],电阻器(72,,'r2')添加(电路,3 0],capacitor(1.238e-12,'C2')添加(CKT,[4 3],电阻器(34,,'r3')添加(CKT,[4 0],电容器(0.021E-12,'C3')添加(电路,5 4],resistor(96,'r4')添加([5 0]电路,电容器(0.028 e-12,'C4')添加(CKT,[6 5],电阻器(72,,'r5')添加(CKT,[6 0],电容器(0.007E-12,,'C5')添加(CKT,[7 6],电阻器(10,'r6')添加(电路,7 0],capacitor(1.048e-12,'C6')添加(电路,8 7],resistor(120,'r7')添加(CKT,[8 0],电容器(0.47E-12,,'C7')添加(CKT,[12 8],电阻器(24,,,'R8')添加(CKT,[12 0],电容器(0.2E-12,,'C8')添加(电路,10 2],resistor(48,'R9')添加(CKT,[10 0],电容器(0.007E-12,,'C9')添加(CKT,[11 10],电阻器(24,,,'r10')添加(CKT,[11 0],电容器(0.2E-12,,'C10')添加(电路,9 8],capacitor(0.1e-12,'C11')添加(电路,9 0],resistor(1000,'R11')添加(CKT,[9 0],电容器(1E-12,,'C12'))
这input signal used by Pillage and Rohrer is a voltage ramp from 0 to 5 volts with a rise time of one nanosecond and a duration of ten nanoseconds. The following MATLAB code models this signal with 1000 timepoints with asampleTime
0.01纳秒。
以下MATLAB代码也使用logspace
函数生成101个对数间隔分析频率在1 Hz和100 GHz之间的矢量。指定一组频率点可提高模拟精度。
SampleTime = 1E-11;t =(0:1000)'*sampletime;输入= [(0:100)'*(5/100);(101:1000)'*0+5];freq = logspace(0,11,101)';
To calculate the response across both theC7
andC12
capacitors, two separate S-parameter calculations must be made: first, assuming theC7
capacitor represents the output port, and second, assuming theC12
电容器代表输出端口。为每个设置计算S-参数:
复制原始电路CKT
using the克隆
功能。
使用该网络的输入和输出端口使用setports
功能。
使用Sparameters
object.
Calculate S-parameters withC7
电容器代表输出端口。
CKTC7 =克隆(CKT);setports(cktc7,[1 0],[8 0])s_c7 = sparameters(cktc7,freq);
Calculate S-parameters withC12
电容器代表输出端口。
CKTC12= clone(ckt); setports(cktC12,[1 0],[9 0]) S_C12 = sparameters(cktC12,freq);
To simulate each network:
这S2TF
功能,带option = 2
,,,,computes the gain from the source voltage to the output voltage. It allows arbitrary source and load impedances, in this caseZsource = 0
andzload = Inf
。这resulting transfer functionsTFC7
andtfC12
是频率依赖的数据向量,可以符合理性功能近似。
这rationalfit
function generates high-accuracy rational-function approximations. The resulting approximations match the networks to machine accuracy.
这计时器
函数计算由理性函数近似定义的状态空间方程的分析解决方案。这种方法足够快,可以使人们通过频道推动一百万个位。
SimulateCKTC7
circuit.
TFC7 = S2TF(S_C7,0,INF,2);FITC7 = RationalFit(FREQ,TFC7);outputc7 = timeresp(FITC7,输入,sampletime);
SimulateCKTC12
circuit.
tfC12 = s2tf(S_C12,0,Inf,2); fitC12 = rationalfit(freq,tfC12); outputC12 = timeresp(fitC12,input,sampleTime);
输出匹配掠夺和罗勒纸的23和24。绘制低频至中频MOS电路与串扰互连的坡道响应。
figure plot(t,input,t,outputC7,'行宽',,,,2) axis([0 2.5e-9 0 5.5]); title(“低到中频MOS电路与串扰互连的坡道响应”);Xlabel('Time (sec)');ylabel(“电压(伏)”);legend('Vinput',,,,'V(C7)',,,,'Location',,,,'西北');
Plot crosstalk in low- to mid-frequency MOS circuit interconnect with ramp input.
图图(t,输入,T,outputc12,'行宽',,,,2) axis([0 5e-9 0 .5]) title('Crosstalk in Low- to Mid-Frequency MOS Circuit Interconnect with Ramp Input')Xlabel('Time (sec)')ylabel(“电压(伏)”) 传奇('Vinput',,,,'V(C12)',,,,'Location',,,,'NorthEast')
Though not shown in this example, you can also use thefreqresp
功能检查行为rationalfit
在指定频率范围内的功能很好。指定范围之外的拟合有时会导致令人惊讶的行为,尤其是如果未提供0 Hz(DC)附近的频率数据。
To perform this check for the rational-function approximation in this example, uncomment and run the following MATLAB code.
% widerFreqs = logspace(0,12,1001);% respC7 = freqresp(fitC7,widerFreqs);% figure%loglog(freq,abs(tfc7),'+',widerfreqs,abs(respc7))%respc12 = freqresp(FITC12,widerfreqs);% figure% loglog(freq,abs(tfC12),'+',widerFreqs,abs(respC12))
For example on how to build and simulate this RC tree circuit using RFCKT objects, seeMOS互连和串扰Using RFCKT Objects。