本文翻译自Microwaves101 | Microwave Rules of Thumb，汇总了一些微波电路中的经验法则（Rules of Thumb），所谓经验法则，就是一些长期总结出来的规律，多数情况下适用，但并不是任何时候都适用，请读者自行斟酌。

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1. Keep your fat fingers out of expensive hybrid modules, or someone might break your thumb! Seriously, how many times in your life have you seen an idiot point to something in a module and crush a dozen wirebond?让你的胖手指离昂贵的混合集成电路模块远一点，否则有人可能会掰断你的拇指！严肃地说，你这辈子多少次遇到过一个蠢货指了一下模块中的某个部位导致坏了一堆绑定线？

2. The minimum noise figure of a FET varies linearly with frequency, up until Fmax. This related rule came from John, who also supplied a reference (thanks!) The minimum noise figure of a BJT varies quadratically with frequency, up until Fmax.一个FET的最小噪声系数（NFmin）随频率是线性变化的，直到Fmax。一个BJT的最小噪声系数则是随频率按平方关系变化，直到Fmax。
   This rule was quoted from Bahl, I. and Bhartia, P. 2003, Microwave Solid State Circuit Design, 2 Ed, John Wiley & Sons, New Jersey, p.377

3. The loss of a branchline coupler is reduced as the square-root of frequency, given that the same substrate and metallization is used. This is one outcome of the skin depth effect.假设衬底和金属材料都保持不变，则分支线耦合器的损耗随频率的平方根减小。这是趋肤效应的结果。

4. Five skin depths of a good conductor will keep your losses to a minimum in microstrip.使用厚度至少5倍趋肤深度的导体就可以使你的微带线损耗最小。

5. If you are using copper boards with half-ounce or thicker copper, you don't have to worry about skin depth problems unless you are working below 200 MHz. To clarify that obtuse statement (thanks to Sylvia), if you are working at microwave frequencies, using more than ½ ounce copper does not improve loss as you can reached the maximum surface conductivity. But if you are working on the bias circuits for high power, current-hungry solid-state amplifiers down at DC, then adding more copper can decrease the loss, as ALL of the copper is used in conduction. The “skin depth problem” is that you didn't achieve at least three (preferably five) skin depths so you didn't do your best to minimize loss.如果你使用1/2盎司或者更厚的覆铜板，那么只要工作频率不低于200MHz你就不用担心趋肤深度问题。如果工作在微波频段，比1/2盎司更厚的铜皮并不会减小损耗，因为你已经达到了最大的表面导电率。但如果你是在给高功率、大电流的固态功放设计直流偏置电路，那么增加铜厚可以减小损耗，因为所有的铜厚都会参与导电。所谓“趋肤深度问题”是说除非你使用至少三倍（最好是五倍）趋肤深度，否则你还没尽力达到最小损耗。

6. Electromagnetic energy such as microwave radiation travels one foot in one nanosecond in free space. In teflon-dielectric coax cables, it travels one foot in about 1.5 nanoseconds. In waveguide, speed is a function of frequency due to dispersion.微波辐射这类的电磁能量在真空中1ns传播1英尺。在特氟龙介质的同轴线中传播1英尺大约需要1.5ns。在波导中，由于存在色散，电磁波的传播速度是频率的函数。

7. The return loss of a circulator is very nearly equal to its isolation.环形器的回波损耗几乎等于它的隔离度。

8. The third-order intercept point of an amplifier is generally 10 dB higher than its one-dB compression point, when measured at the output. This corresponds to 9 dB higher when measured at the input. There are notable exceptions, often the latest pHEMT devices have higher TOI than you'd expect... So if your amp starts to compress around +20 dBm (out) then the TOI is probably around +30 dBm.放大器的输出三阶交调截点（OIP3）通常比1dB压缩点（OP1dB）高10dB左右，如果以输入功率看则是高9dB。但也有明显的例外：最新的pHEMT器件具有比你期望更高的三阶交调截点（TOI）。因此如果你的放大器在输出20dBm时开始压缩，那么其输出三阶截点很可能大约为30dBm。

9. The isolation resistor on a quadrature coupler (such as a Lange) on the output of a power amp should be able to handle 25% of the total power if you want the amplifier to still (sort of) work if one amp blows up. Otherwise 10% of the total power for a tuned hybrid, or 5% of the power if the entire amp is on a MMIC.如果你希望（平衡式功率放大器的）一只放大器坏掉后还能勉强工作，那么用在功放输出端的正交（90deg）耦合器（例如Lange）中的隔离电阻要能承受25%的总功率。否则已调配混合电路（Hybrid）总功率的10%，或者功放总功率的5%都会落在MMIC功放芯片上。

10. For a given switch-arm design, a SPDT switch will have 6 dB more isolation than a comparable SPST switch, as long as the "through" arm of the switch is properly terminated.对于一个给定的开关臂设计，只要开关的“直通”臂是适当端接的，单刀双掷开关（SPDT）会比一个同等的单刀单掷开关（SPST）的隔离度高6dB。