Main Content

Transmission Lines, Delay-Based and Lumped Models

Open Script

This example shows how to simulate delay-based and lumped-elementTransmission Lineusing blocks in the RF Blockset™ Circuit Envelope library. The example is sequenced to examine circuit envelope and passband differences, delay-based lossy transmission line sectioning, and lumped element implementation of delay.

基于无损延迟传输线的系统架构

In this section, two RF Blockset™ models,simrf_xline_pb.andsimrf_xline_ce.那illustrate lossless delay-based transmission line effects and the computational benefit of circuit envelope techniques.

model_pb ='simrf_xline_pb';model_ce.='simrf_xline_ce';load_system（model_ce）open_system（model_pb）

该模型，simrf_xline_pb.那represents a passband signal as:

$$ i（t）\ cos {2 \ pi f_c t} - q（t）\ sin {2 \ pi f_c t} $$

The input is a pulse-modulated sinusoidal passband signal. For this particular case, I(t) equals zero, and Q(t) is the pulse modulation. The carrier frequencies are set to zero in the RF Blockset Inport and Outport blocks.

Open_System（[model_pb'/输入信号']）;

电路包络模型，simrf_xline_ce.那represents an envelope signal as:

$$I(t) + j Q(t)$$

同样，I（t）等于零，并且Q（t）是脉冲调制，但是载波信号未被指定为输入信号的一部分。模拟载体，载波频率parameter is set to$ f_c $在RF Blockset Inport和Outport块中。

open_system([model_ce'/输入信号']）;

在电路包络模型中移除显式正弦载波允许模拟以减少相对于通带模型的时间步。

跑ning the Lossless Delay-Based Transmission Line

  1. TypeOpen_System（'simrf_xline_pb'）oropen_system('simrf_xline_ce')在命令窗口提示符下。

  2. 选择Simulation>跑。

在模拟之后，在输入和输出信号的曲线图中可以观察到传输延迟。

open_system([model_ce'/Circuit Envelope']）;SIM（model_ce）;

The carriers in modulated waveforms appear in passband signals, but only the modulation envelopes appear in circuit-envelope signals. Passband signals can be reconstructed from circuit envelope signals as:

$$ Re（（i（t）+ j q（t））e ^ {j2 \ pi f_c t}）$$

However, reconstruction of the passband signal this way requires additional time steps for the carrier.

SIM（model_pb）;hine = plot（spb_data（：，1），spb_data（:,2），sce_data（：，1），sce_data（:,2），' - '）;legend('通带'那'电路包络'的）title('输入通带和电路包络信号'的）xlabel('时间'的）ylabel('电压'的）ylim([-1.1 1.1])

haxis = get（hline（1），'Parent'）;绘图（HAXIS，SPB_DATA（：，1），spb_data（:,3），sce_data（：，1），sce_data（:,3），' - '） 传奇（'通带'那'电路包络'的）title(“通带和电路包络信号的输出”的）xlabel('时间'的）ylabel('电压'）ylim（[ - 。 - 。55 .55]）

基于延迟的损耗传输线

一种用于建模分布式损耗传输线的传统方法N.级联的双端口段。每个段由理想的无损延迟线和阻力组成，其中段延迟等于总线延迟除以N.和segment resistance equals the total line resistance divided byN.。As the number of segments increases, the lumped model will more accurately represent the distributed system. This methodology requires a compromise between simulation time and model accuracy for increasingN.。In RF Blockset, theN.umber of segments， 这每单位长度的电阻和线条长度are specified as dialog box parameters in the transmission line block.

model_seg =.'simrf_xline_seg';Open_System（model_seg）

System Architecture for Lossy Delay-Based Transmission Line

基于损失的延迟传输线模型，simrf_xline_seg，由两个平行的武器组成，由RF块组圆形源激发。顶部臂采用单个段传输线，而底部臂使用由3个段组成的线。源和负载电阻不等于传输线的特性阻抗。这些差异影响输出响应的形状。例如，当源和负载电阻小于特性阻抗时，输出响应将被过度调整。

open_system([model_seg'/输出电压']）;sim(model_seg);

从三到四到四个和比较响应的底部臂中的线段数表明三个段足以进行这种配置。

close_system（[model_seg'/输出电压']）;st_data3 = st_data;set_param（[model_seg'/传输（3个段）'],'numsegments'那'4'）sim（model_seg）;绘图（HAXIS，ST_DATA3（：，1），st_data3（:,4），st_data（：，1），st_data（:,4），' - '） 传奇（'3段'那'4段'的）title('Delay-Based Lossy Transmission Line Output Signals'的）xlabel('时间'的）ylabel('电压'的）

System Architecture for Lumped Element Transmission Line

Differences between the lumped element and delay-based transmission lines are now examined. Consider the modelsimrf_xline_ll.，对话框参数的位置model_type.是Delay-based and lossy为顶部手臂和Lumped parameter L-sectionfor the other two arms. The每单位长度的电感and每单位长度的电容parameters values for the L-section lines are similar to a 50$ \ omega $同轴电缆。这些线的基本第一阶近似是$ z_0 = \ sqrt {l / c} $and$T_D = \sqrt{L*C} * Length.$

model_ll ='simrf_xline_ll';Open_System（model_ll）

跑ning the Lumped Element Transmission Line

  1. Typeopen_system('simrf_xline_ll')在命令窗口提示符下。

  2. 选择Simulation>跑。

以下图表显示了集总元素段的数量如何影响输出。使用集总元件传输线块时必须平衡速度和精度。

Open_System（[model_ll200年' /信封电路输出电压MHz Carrier']）;sim（model_ll）;

Cleaning Up

关闭模型并删除工作区变量。

关闭（获得（Haxis，'Parent'的）的）清除haxishline;bdclose（{model_pb model_ce model_seg model_ll};清除sce_data.SPB_DataST_DataST_Data3sll_data.;清除model_pbmodel_ce.model_seg.model_ll;

References

Sussman-Fort and Hantgan,SPICE Implementation of Lossy Transmission Line and Schottky Diode Models。IEEE Transactions on Microwave Theory and Techniques, Vol. 36, No. 1, January 1988

真正的kenneth m，数据传输线及其特征。应用笔记806，1992年4月

也可以看看

比较S参数的时间和频域模拟选项