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全文搬運過來的，本篇文章並未有其它意義和目的，僅作為個人參考筆記，我會標出認為有趣的部分並進行粗糙的翻譯

了解這些規則可以用來快速評估射頻產品的可行性，

• Electromagnetic energy such as microwave radiation travels one foot in one nanosecond in free space
• Linear passive devices have noise figure equal to their loss. Expressed in dB, the NF is equal to -S21(dB).
• Noise figure is dependent on the first gain stage. If there is 20 dB gain in a receiver LNA, the noise figure contribution of the subsequent stage will likely be insignificant.
• 噪聲系數取決於增益放大的第一階
• The third-order intercept point of an amplifier is generally 10 dB higher than its one-dB compression point, when measured at the output (9 dB higher at the input).
• 通常功放的3階交調點會比它的1dB壓縮點高10dB？
• Nepers? To convert neperts to decibels, multiply by ~8.68. (just use 9 for really quick conversions)
• The isolation of a Wilkinson is limited to 6 dB better that the return loss of the common port match.
• Metal loss is proportional to square-root frequency.
• 金屬損耗與頻率的平方根成比例
• Dielectric loss is proportion to frequency
  .
• 介質損耗與頻率成比例
• The P1dB point of a mixer at its RF input is often about 6 dB less than its LO drive level.
• The noise figure of a mixer is approximately equal to the magnitude of its conversion loss.
• 混頻器的噪聲系數約等於其轉換損耗的幅度
• N-way resistor power dividers are very lossy, power is transferred as (1/N)^2 compared to a lossless power divider which transfers power at (1/N).
• The number of elements in a phased array antenna can be used to estimate the total gain of the array. A 30 dB gain array needs ~1000 elements and a 20 dB gain array needs ~100, 10 dB needs ~10.
• 相控陣天線中的單元數目可以用來估計整個天線陣的增益，一個30dB增益的陣列大概需要1000個單元
• If your circuit does funny things when you close up the box, it’s oscillating!
• 如果你的射頻電路安裝到盒子裏後發生了奇奇怪怪的事情那麽它可能自激振蕩了！
• A Wilkinson power splitter can be made in sections to increase bandwidth. To determine how many sections are needed divide the center frequency by the lowest frequency; i.e. 1-10 GHz, plan on 5 to 6 sections (5.5 is not an integer).
• You can electrically measure the approximate length of a transmission line by analyzing the frequency separation between the dips in VSWR.
• If you forget to build image rejection into your receiver design, you are probably adding 3dB to your receiver’s noise figure.
• 如果你忘了在接收器設計中加入鏡像抑制，接收器的噪聲系數可能會增加3dB
• Make sure you have more gain than you need, it is easier to change an attenuator than to add more gain to the final design. (With good designs oscillations should not be to much of a problem, but be weary of just adding gain, do a proper loss budget first!)
• For microstrip, you can cut metal losses by ~1/2 by doubling the dielectric thickness.
• The coupled port on a microstrip or stripline directional coupler is closest to the input port because it is a backward wave coupler.
• For stripline and microstrip, the attenuation factor always decreases almost linearly with characteristic impedance is reduced, lower impedance = lower loss.
• 對於帶狀線和微帶線，衰減因素的的減少總是與特征阻抗的減小呈線性相關，低阻抗=低損耗
• A microstrip board height should never exceed 1/10 of a wavelength at the maximum frequency of it usage.
• Metal enclosures should have a height of less than 1/4 wavelength to attenuate radiated signals and avoid other weird things from happening. You can also buy materials designed to absorb RF signals, we prefer magnetic RAM but there are several other methods.
• Metal covers should be greater than 6 times the height the substrate thickness.
• 金屬覆蓋層的面積應大於基板厚度的6倍。？
• An acceptable voltage droop for a power amplifier during pulsed operation is 5%, which will drop the power by a similar amount (5%, or about a quarter of a dB). This should be used to determine the amount of capacitance needed.
• When designing a phase shifter multiple stages should be used for bits which induce more than 90° of delay. If designing a bit with more than a 90° phase shift use two elements, it is best to use one high pass element and one low pass element.
• E-plane of a wave-guide is “easy to bend” and the H-plane in rectangular waveguide is hard to bend.
• 波導的E-plane很容易彎曲，矩形波導的H=plane則很難彎曲
• The WR number a waveguide is simply the dimension of the broad wall in mils, divided by 10.
• The Bragg frequency is when a artificial transmission line stops acting like a transmission line. This often occurs when the artificial transmission lines unit cell is longer than 1/3 of a wavelength.
• For silicon, 110 degrees C is the maximum junction temperature for reliable operation.
• For SiGe, 110 degrees C is the maximum junction temperature for reliable operation.
• The return loss of a circulator is very nearly equal to its isolation.
• 環形器的回波損耗幾乎與其隔離相等

Quick RF Tips for General Reference