[分享] 微波电路经验法则

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。

1. For 1-mil gold wirebonds, inductance of the bond wire in nanohenries is roughly equal to its length in millimeters... an advantage of the Metric System that was brought to our attention by a French engineer named Yves (merci!) Let's restate this rule-of-thumb so that baseball fans can use it: 1 mil of bond wire is equal to 25 pico-Henries of inductance, or 40 mils of bondwire is equal to one nanohenry.对于直径1mil（25um）的金丝，等效的电感量（以nH为单位）约等于其长度（以mm为单位），这可是公制单位相较于英制单位的一个优点！我们换个方式来表述一下，以便棒球运动爱好者也能使用：长度1mil的键合线等效电感量约为25pH，或者说长度40mil的键合线电感量约为1nH。

2. To be considered a "lumped element", no feature of a structure can exceed 1/10 of a wavelength at the maximum frequency of its usage.要能当做一个集总参数元件来对待，那么一个电路结构的任何一个特征尺寸都不能超过该电路最高工作频率对应波长的1/10。

    

3. To be a useful substrate, the height of a microstrip board should never exceed 1/10 of a wavelength at the maximum frequency of it usage. We've made a table for you on this subject!微带电路板的介质厚度不能超过该电路最高工作频率对应波长的1/10，否则不能使用。

4. How do you know what WR number a waveguide is just by looking at it? The WR number is simply the dimension of the broad wall in mils, divided by 10.如何看一眼波导就知道其型号WR后面的数字？WR后面的数字就是波导宽边长度以mil为单位，除以10。作者注：例如WR34表示波导的宽边长度为340mil；我国的标准矩形波导命名规则是BJ##，后面数字代表主模中心频率以GHz为单位乘以10，例如BJ260表示主模中心频率为26GHz的标准矩形波导。

5. A good way to remember which is the E-plane and which is the H-plane in rectangular waveguide is when you bend it, bends in the E-plane are the "easy way", while bends in the H-plane are the "hard way".一个记住矩形波导E面和H面的好方法是：当你弯曲它，沿着E面弯折是很容易的，而沿着H面弯折就很困难。

    

6. For silicon or SiGe, 110 degrees C is the maximum junction temperature for reliable operation (1,000,000 hours is typical median time to failure criteria). With the exception of silicon LDMOS, which can operate up to 175C for 800 years, according to Leonard who works for a major LDMOS supplier (thanks!) GaAs FET (or HEMT) channel temperature should not exceed 150 C for long-term reliable operation. For gallium nitride HEMT (GaN), 175 C is a good rule for maximum channel temperature.对于Si或SiGe半导体，110℃是器件可靠工作的最大结温（平均无故障时间MTTF=1,000,000小时）。硅工艺的LDMOS是例外，据一个主流LDMOS供应商的说法，它可以在175℃温度下工作800年。GaAs的FET（或者说pHEMT）沟道温度不能超过150℃才能确保长期可靠工作。对于GaN HEMT而言，最大沟道温度175℃是一个合理值。

7. In order to cutoff spurious modes, the width of a package should generally not exceed one-half of a wavelength in free space at the maximum operating frequency.为了截止掉杂散模式，封装（腔体）的宽度一般不要超过最高工作频率对应在真空中的半个波长。

8. For microstrip and stripline curved lines, use a minimum radius of three line widths at X-band and below. At higher frequencies, use five line widths for minimum radius. Even better, use an optimum miter instead of a curve!X波段及以下的微带线和带状线最小转弯半径不要低于三倍线宽，频率更高时最小转弯半径取五倍线宽，最好的做法是使用最佳切角代替曲线转弯！

9. The 10% to 90% rise time of a pulsed signal, in nanoseconds, will be approximately equal to 0.35 divided by the bandwidth of the network, in GHz.一个脉冲信号的10%-90%上升时间，以ns为单位时，近似等于0.35除以网络的带宽，以GHz为单位。作者举例？？：假设一个低通网络的截止频率是1GHz，则传输一个矩形脉冲时，10%-90%上升时间约为0.35ns。

10. If you are trying to effect an RF short circuit using a quarter-wave stub, use a low impedance line, or better still, use a radial stub.如果你想用1/4短截线来实现射频短路，那么应该使用低阻线，而且最好是使用扇形枝节。