射频工程师面试的时候通常会问一些什么样的技术问题？

willardjoe

射频工程师面试的时候通常会问一些什么样的技术问题？
阻抗匹配？
Smith Chart？

willardjoe

咨询各位大虾。

willardjoe

<P>50欧姆同轴线的50欧姆的物理意思是什么？</P>

不要命的男人

同轴线的特性阻抗是52Ohm

devoterf

<P 0cm 0cm 0pt; LAYOUT-GRID-MODE: char"><FONT face="Times New Roman">The History Of 50Ohms<p></p></FONT></P>A lot of people ask, so here's the answer to the eternal question, "How did 50 W get to be the standard RF transmission line impedance?" Here are a few stories. Bird Electronics will send you a printed copy of their version if you ask for it. This from Harmon Banning of W.L. Gore &amp; Associates, Inc. cable: There are probably lots of stories about how 50 Ohms came to be. The one I am most familiar goes like this. In the early days of microwaves - around World War II, impedances were chosen depending on the application. For maximum power handling, somewhere between 30 and 44 Ohms was used. On the other hand, lowest attenuation for an air filled line was around 93 Ohms. In those days, there were no flexible cables, at least for higher frequencies, only rigid tubes with air dielectric. Semi-rigid cable came about in the early 50's, while real microwave flex cable was approximately 10 years later. Somewhere along the way it was decided to standardize on a given impedance so that economy and convenience could be brought into the equation. In the US, 50 Ohms was chosen as a compromise. There was a group known as JAN, which stood for Joint Army and Navy who took on these matters. They later became DESC, for Defense Electronic Supply Center, where the MIL specs evolved. Europe chose 60 Ohms. In reality, in the US, since most of the "tubes" were actually existing materials consisting of standard rods and water pipes, 51.5 Ohms was quite common. It was amazing to see and use adapter/converters to go from 50 to 51.5 Ohms. Eventually, 50 won out, and special tubing was created (or maybe the plumbers allowed their pipes to change dimension slightly).Further along, the Europeans were forced to change because of the influence of companies such as Hewlett-Packard which dominated the world scene. 75 Ohms is the telecommunications standard, because in a dielectric filled line, somewhere around 77 Ohms gives the lowest loss. (Cable TV) 93 Ohms is still used for short runs such as the connection between computers and their monitors because of low capacitance per foot which would reduce the loading on circuits and allow longer cable runs.Volume 9 of the MIT Rad Lab Series has some greater details of this for those interested. It has been reprinted by Artech House and is available.

52rd_1

这论坛上面的细节问题随便问一个都可能难住你，关键是看你平时有没有实际操作过，比如有位兄弟提到的LNA在数据表中频带调试下半部分正常，若改成调上边部分当如何操作。另外可能也会问一些基础的东西，如为什么匹配阻抗多选50欧而不选75欧，测量时多测试功率而不是电压等等

hanny

得看公司是做什么的了
RF范围太大了

maxconn

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vinkingking

难啊，要积累！！

vlivli

呵呵！我所遇到的一般不会谈太深的东西，我想别人也不会仅仅靠几个问题来验证了，更多的是关注你原来做过什么，有多少年的工作经验。如果是招你进去做新项目的话，肯定还会问些这方面的情况，看你对这些东西的感知度。