对下面文章重点段落进行翻译原文和翻译都要给出选取三段较长文字进行翻译满足信、达、雅的翻译要求Intermodulation Distortion of a BipolarCommon-Emitter Amplifier With Arbitrary EmitterImpedance and Input Matching Network

原文：

Intermodulation distortion (IMD) is one of the most important nonlinear distortion mechanisms in bipolar amplifiers. It is caused by the nonlinear characteristic of the bipolar transistor. In the case of a common-emitter amplifier, the base current is modulated by the input signal and the output signal. The resulting current flowing through the emitter resistance causes a voltage drop across the resistance which is proportional to the current. Due to the nonlinear characteristic of the bipolar transistor, the voltage drop across the emitter resistance is not linearly related to the current flowing through it. As a result, the output signal contains not only the desired signal but also intermodulation products (IMPs) which are generated by the nonlinear mixing of the input signals. The frequency of the IMPs is equal to the sum and difference frequencies of the input signals.

To reduce the IMD of a common-emitter amplifier, the input matching network and the emitter impedance should be carefully designed. The input matching network should provide a good impedance match between the source and the amplifier to minimize the reflection and maximize the power transfer. The emitter impedance should be chosen to provide a good compromise between the gain and the linearity of the amplifier. A high emitter resistance increases the gain but also increases the IMD. A low emitter resistance reduces the gain but also reduces the IMD.

The effect of the emitter impedance on the IMD can be understood by considering the third-order IMD (IMD3) of a common-emitter amplifier with arbitrary emitter impedance. The IMD3 is caused by the mixing of two input signals at frequencies f1 and f2. The output signal contains not only the desired signal at frequency f0 = f1 + f2 but also two IMD3 components at frequencies 2f1 – f2 and 2f2 – f1. The magnitude of the IMD3 components depends on the emitter impedance. If the emitter impedance is too low, the IMD3 components are dominated by the second harmonic distortion (HD2) and the third harmonic distortion (HD3) of the emitter resistance. If the emitter impedance is too high, the IMD3 components are dominated by the cross-modulation distortion (CMD) caused by the nonlinear mixing of the input signals in the transistor. For a given emitter current, there exists an optimum emitter resistance which minimizes the IMD3.

翻译：

互调失真（IMD）是双极晶体管放大器中最重要的非线性失真机制之一。它是由于双极晶体管的非线性特性所引起的。在共射放大器的情况下，输入信号和输出信号调制了基极电流。流过发射极电阻的电流导致电阻上的电压降与电流成正比。由于双极晶体管的非线性特性，发射极电阻上的电压降与流过它的电流不是线性相关的。因此，输出信号不仅包含所需信号，还包含由输入信号的非线性混合产生的互调产品（IMPs）。IMPs的频率等于输入信号的和与差频率。

为了减小共射放大器的IMD，输入匹配网络和发射极阻抗应该被仔细设计。输入匹配网络应该提供一个良好的阻抗匹配，以最小化反射并最大化功率传输。发射极阻抗应该被选择为在放大器的增益和线性之间提供良好的折中。高发射极电阻增加了增益，但也增加了IMD。低发射极电阻降低了增益，但也降低了IMD。

发射极阻抗对IMD的影响可以通过考虑具有任意发射极阻抗的共射放大器的三阶IMD（IMD3）来理解。IMD3是由频率为f1和f2的两个输入信号混合引起的。输出信号不仅包含频率为f0 = f1 + f2的所需信号，还包含两个IMD3分量，其频率分别为2f1 – f2和2f2 – f1。IMD3分量的幅度取决于发射极阻抗。如果发射极电阻太低，IMD3分量将被发射极电阻的第二次谐波失真（HD2）和第三次谐波失真（HD3）所支配。如果发射极电阻太高，IMD3分量将被晶体管中输入信号的非线性混合所引起的交叉调制失真（CMD）所支配。对于给定的发射极电流，存在一种最优发射极电阻，可以最小化IMD3