主要内容

RF系统的频率响应分析

打开脚本

This example uses a few techniques to calculate the steady-state frequency response for a filter-based RF system built from RF Blockset™ Circuit Envelope library blocks. The first technique performs static analysis (harmonic balance) on a circuit comprising of inductors and capacitors. The second technique does time domain simulation using a similar circuit built with the Filter library block. The third technique facilitates small-signal analysis to obtain the frequency response of a filtering system that exhibits nonlinearity at a given operation point. This example helps you validate a circuit envelope model using a static analysis in the frequency domain, a time domain simulation, and small signal analysis in cases where the system exhibits non-linearity.

Frequency Domain Analysis

model ='simrfv2_ac_analysis';Open_System（型号）;

The system consists of:

  • A Continuous Wave source and a series resistor to model a voltage source with internal source impedance.

  • Inductor and Capacitor blocks configured to model a third-order Chebyshev filter with a center frequency of 2.4 GHz.

  • 一个配置为电压传感器的外口块，以测量载荷电阻的电压。

  • A Configuration block, which sets up the circuit envelope simulation environment. As the system is linear, the harmonic balance analysis is done with a single simulation frequency and corresponds to an AC analysis.

  1. 类型open_system('simrfV2_ac_analysis')at the Command Window prompt.

  2. Double-click the block labeled 'Specify Frequency Values' to provide a vector of frequencies.

  3. Double-click the block labeled 'Calculate Frequency Response' to execute a script,SIMRFV2_AC_ANALYSIS_CALLBACK,分析了model at the specified frequencies and plots the response.

SIMRFV2_AC_ANALYSIS_CALLBACK（[模型'/subsystem']，，'OpenFCN'）；

用电路信封库块配置模型以进行谐波平衡：

  • 在“模型配置参数”对话框中，设置停止时间parameter to zero.

  • Use a Continuous Wave block to drive the system.

  • Set the载体频率parameter in the Continuous Wave, Outport blocks, and theFundamental Tonesparameter in the Configuration block to the same vector of frequencies.

关闭开放模型

bdclose(model)

Time Domain Simulation

model ='simrfV2_ac_analysis_tf';Open_System（型号）

The system consists of:

  • 输出连续随机信号的随机源发生器。

  • A Chebyshev filter constructed using the Filter library block and designed with a center frequency of 2.4 GHz and a bandwidth of 480 MHz.

  • 离散传输函数估计器块以查看时域模拟的频域输出。

  • Spectrum Analyzer to view the output.

查看过滤器块蒙版中使用的过滤器设计参数。

View the implemented filter under the Filter block mask.

open_system（[模型'/Filter']，，'force')

模拟传输系统模型。

SIM（型号，5E-5）

Compare the outputs of the first and second model.

bdclose(model)

Small Signal Analysis

model ='simrfV2_ac_analysis_ss';Open_System（型号）

The system consists of:

  • 输出连续随机信号的随机源发电机，该信号随后被减弱以确保小信号输入。

  • 恒定源添加到随机源以确定非线性操作点。这两个信号均以2.4 GHz为中心。

  • An RF System comprising two elements; A saw filter constructed using the S-parameter library block with a center frequency of 2.45 GHz and a bandwidth of 112 MHz and an amplifier with 20dB of available power gain and non-linearity described by a 3rd-order intercept point of 30dBm.

  • Discrete Transfer Function Estimator block to view the frequency domain output of a time domain simulation measured over the 2.4 GHz carrier.

  • 频谱分析仪查看输出并将其与保存的输出数据进行比较。

Since the transient signal is small while the operation point is determined based on carrier-constant large signals, it is possible to use the transient small-signal approximation. In this approximation, non-linear interaction between transient signals is ignored, however the non-linear interaction between carrier-constant signals and its effect on the small signals is captured accurately. The small signal analysis is enabled in the advanced tab of the Configuration block mask.

使用较小的信号分析，可以选择用于稳态解决方案的完整载体的子集进行瞬态模拟。在此示例中，只有2.4 GHz对瞬态分析感兴趣。减少模拟载体的数量，加速模拟。在这种情况下，小信号仿真的速度比基于非线性电路 - eNVELOPE的模拟快15倍以上。将小信号仿真结果与从文件加载的全电路包络模拟的结果进行比较，很明显，结果实际上是相同的。

SIM（模型）

将恒定块中的操作点功率从0.5瓦减小到零，将系统有效线性。曲线之间的比较说明了非线性对传递函数的影响。这些效果包括由于压缩而导致的总体幅度下降，并且在低频侧的过滤器剖面扩大。可以解释延伸是放大器多项式响应中立方项的结果，将2.4 GHz的原始RF频率折叠回自身，但是由于通过 - 通过 - 通过 - 从 - 从 -2.4 GHz。由于锯滤波器以2.45GHz为中心，因此翻转的频率响应以2.35GHz为中心。总结线性和立方体术语效应产生了扩大的轮廓。

bdclose(model)

参考

Ludwig, Reinhold and Pavel Bretchko,RF Circuit Design: Theory and Applications。Prentice-Hall，2000年。

Mass A. Stephen,Nonlinear Microwave and RF Circuits。Artech House, 2003.

See Also

Compare Time and Frequency Domain Simulation Options for S-parameters