Exploring the Example

The model consists of five simple models of an amplifier, each of which is set up to perform specific measurements.

通过双击放大器块打开放大器模型。第一放大器型号如下所示：

输入首先与高斯噪声源组合，然后通过高阶多项式运行以模拟非线性失真。

You can modify the amount of additive noise on the input by clicking on the Noise Source and modifying the variance of the Gaussian distribution.

You can modify the parameters of the amplifier by changing the polynomial coefficients. The coefficients are arranged from highest-to-lowest order. If you edit the last coefficient you change the DC voltage offset of the amplifier. If you change the next-to-last coefficient, you change the voltage gain of the amplifier. If you change other coefficients, you can change the higher-order harmonics of the amplifier.

Harmonic Distortion

You can measure harmonic distortion by stimulating the amplifier with a sinusoidal input and viewing the harmonics in a spectrum analyzer. The harmonic distortion measurements can be invoked from the Measurements option in the Tools menu, or by clicking its corresponding icon in the toolbar (shown depressed in the figure, below).

在失真测量面板中查看结果您可以看到基础和谐波的幅度以及它们的SNR，SINAD，THD和SFDR值，这些标志是基本输出功率所引用的。

Third Order Intermodulation Distortion

放大器通常具有显着的奇数谐波。如果刺激两个紧密间隔的正弦管的放大器，则可以在输出处产生互调产品。下载188bet金宝搏通常，失真产品衰减远离基本色调，其中最大值对应于输下载188bet金宝搏入波形的三阶总和和差分频率。您可以通过从失真测量面板中的下拉菜单中选择互调失真测量来测量输出三阶互调（TOI）失真。

Also in the Distortion Measurement panel you see the intermodulation products highlighted and the output TOI displayed. Adjust the polynomial coefficients in the amplifier to change the harmonics shown in the signal.

ACPR.

If you stimulate an amplifier that is broadcasting a communications channel, you may see spectral growth leaking into the bandwidth of neighboring channels due to intermodulation distortion. You can measure how much power leaks into these adjacent channels by measuring the adjacent channel power ratio (ACPR). You can see the measurements both before and after the amplifier by toggling the measurement input in the Trace Selection Dialog. ACPR measurements can be selected from the drop-down menu in the Channel Measurements dialog. This dialog can be invoked from the Measurements option in the Tools menu, or by clicking its corresponding icon in the toolbar (shown depressed in the figure, below).

调整放大器中的多项式系数，以获得由于互调失真引起的集电电量的不同量。您可以在指定的偏移频率下观察ACPR读数。

在上面的示例中，您可以在输入源（蓝色迹线）和放大器4（黄色迹线）之间看到大约0.5 dB的压缩。输入通道的峰平均功率比（PAPR）为3.3 dB，而输出通道的PAPR为2.8 dB。这种动态范围的损失表明，施加到放大器的输入功率太大。

谱图

You can view time-varying spectral information by using the Spectrogram Mode of the spectrum analyzer. If you stimulate the amplifier with a chirp waveform you can observe how the harmonics behave as time progresses. Select "Spectrogram" from the "Type" dropdown menu in the Spectrum Settings dialog, which is invoked from the Spectrum Settings dialog in the View menu (not shown).

You can use cursors to make measurements of the period of the chirp and to confirm that the other spectral components are harmonically related. The Cursor Measurements dialog can be invoked from the Measurements option in the Tools menu, or by clicking its corresponding icon in the toolbar (shown depressed in the figure, above).

Peak Finder

您可以使用峰值查找器测量对话框跟踪时变频谱分量。您可以显示和可选地标记最多100个峰值。可以从“工具”菜单中的“测量”选项中调用峰值查找器对话框，或通过单击工具栏中的相应图标（如图所示，在上面的图中显示）。

参考