Rogers’ John Coonrod on Insertion Loss


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John Coonrod of Rogers Corporation gave a keynote presentation at the recent Geek-A-Palooza trade show, concentrating on printed circuit board fabrication’s influences on insertion loss. I sat down with John to learn more about his presentation and what OEMs and designers need to be aware of to avoid insertion loss.

Barry Matties: John, why don't we start with a little background about what you do and where you’re from?

John Coonrod: I'm part of Advanced Connectivity Solutions at Rogers Corporation. We generally make high-frequency materials normally used in PCBs—specialty boards for the high-frequency microwave and millimeter wave range of frequencies. I do electrical characterization on our materials or competitor materials, if I can get my hands on them (laughs), and I also do evaluations on any kind of new materials that we are developing for electrical performance.

Coonrod Geek 2.JPG

Matties: Nice, and you've been at Rogers for many years?

Coonrod: A long time, since 1987.

Matties: We are here at Geek-A-Palooza and you're doing a keynote. What is the topic of your presentation today?

Coonrod: The topic is insertion loss, and more specifically printed circuit board fabrication’s influences on insertion loss. Whenever you build a printed circuit board, just due to the nature of building the board, you will have some insertion loss variables. Really, what I'm going to be showing today are some of the studies I've done looking at that, and the effects of different PCB fabrication processes on insertion loss.

Matties: And in this presentation, what's going to be the takeaway for your audience?

Coonrod: More than anything else, I'm hoping this is going to be educational, because I start off with some really basic ideas about insertion loss and why it is important, and then I get into how these different PCB fabrication influences can have an effect. One of the reasons I'm doing this is for people who may not know much about insertion loss, and that way they get a good introduction and overview of it. Then the other idea, I'm hoping, is that people who do know something about insertion loss and do circuit designs will now know more about some of these variables that they may not have known about before.

Because I've run into that from time to time, where an OEM or someone will come to us and say, "Hey, your material is not working right," and then we find out it's not really the material, it's something special or something funny that happened between the design and the fabrication. The more the designers know about these things the better, I think.

Matties: Communication is key. Could you give a quick overview of insertion loss for those of our readers that may not know anything about it?

Coonrod: Insertion loss, in an RF sense and in a frequency sense, is really the total loss of the circuit. The way to think about it is when you apply RF power on one end of the circuit, and you try to take power off the other end, you don't get the same amount of power you put into it because there's some loss there, and that's really what the circuit is doing. It's kind of a complicated issue where there are several other things that come into play, but it's really just how much loss the circuit really causes to an applied RF signal.

Matties: Is the variable the design, primarily?

Coonrod: That's definitely part of it. There's really a big interaction between three important things: the materials, the design and the PCB fabrication. And that’s because, for one particular design, the PCB fabricator can build it multiple different ways and one way may impact the insertion loss differently than another way. So that is kind of my thought process here, and what I’ll be trying to show are some of these variables.

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