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Last week (or a few weeks ago) we talked about the concept of input impedance and how the impedance changes along the transmission line as a function of the line length, l. This week, we're going to show this change with some different segments of transmission line. No transmission line, a quarter wavelength transmission line, and a half wavelength transmission line. We are going to assume a lossless transmission line for simplicity. First, let's start with a line length of 0

In any sizable production based environment, there’s usually more than one RF test station and that station usually has a dedicated VNA. For low mix high volume labs, incoming product is almost always slated to run on more than one station since there’s quite a handful (sometimes hundreds) of units per lot/purchase order. Each VNA has a dedicated state file (sometimes a set of state files) to test that specific part number and the difficulty of managing these state files scal

You’ve heard of characteristic impedance, you’ve heard of load impedance, and you might’ve even heard of wave impedance, but have you heard of input impedance? I think input impedance is one of the coolest concepts in transmission line theory and is one of the most important concepts on your journey to understanding RF. Input impedance describes how impedance varies along the transmission line from a particular point (say, the source) to the load. It’s the impedance looking I

So, you just got your first VNA for the lab and there's incoming RF product that needs testing. How do you make sure every RF site is tested using the same parameters? The answer is VNA state files. Think of VNA state files like a video game save state. Every time you load the game, it pulls up the exact same spot you saved. VNA state files work the same way, except instead of a deathclaw lunging at you from 80 feet away (FNV reference), you're restoring RF measurement condit

Microstrip and stripline are some of the most common transmission lines used in high frequency printed circuit boards. Each has its own tradeoffs, but what actually makes them different from one another? It comes down to field containment. At higher frequencies, the signal on the line isn't just voltage and current but electromagnetic fields that exist between and around the conductors themselves. This introduces a guided mode of wave propagation. For stripline structures, th

When I first started as an RF test engineer, I was brand new to RF measurement equipment. I had the theoretical RF framework from college and some design/simulation experience, but I never actually measured an RF circuit. On day one, I learned one of the most important aspects of measuring an RF circuit - calibrating the vector network analyzer (VNA)! The intent of calibration is to remove the systematic measurement errors introduced between the VNA and the DUT, including cab

RF and Electromagnetism in general is such a rich field filled with many beautiful concepts, equations, and phenomena. It's so rich and beautiful, we sometimes forget the history behind it and the individuals that made the field what it is today. Enter James Clerk Maxwell - born in Scotland in 1831 and attended the University of Cambridge in his later years. In 1873, Maxwell came to the conclusion that light was a form of electromagnetic energy. From this conclusion came his

I've found a lot of people working on the outskirts of the RF field ask this important, fundamental question. Whether that be business leaders, managers, and even other engineers supporting the field, this is a question us RF engineers must have an immediate answer to when asked. Here's what I say whenever I get asked this question... There are four forces of nature. Gravity, the strong nuclear force, the weak nuclear force, and the electromagnetic force. Electromagnetism in