Optimizing circuits using EM analysis

Click here to go to our main page on optimization

New for April 2018

Optimizing circuits is one of the coolest things you can do as a microwave engineer. You unleash the infinite monkeys, but guide them on their journey with goals, constraints, and knowledge of what your circuit is capable of. How do you know what your circuit is capable of?  Just look at past efforts, chances are you are not developing anything that is truly novel. Or ask an engineer with grey hair.

What do engineers do while the optimizer is running?  Managers probably assume we all work on reports, proposals, spreadsheets and the like.  But your computer is on its knees, the fan is on high and the CPU and memory are 99% consumed.  Maybe you read the news, maybe you try some yoga poses, or maybe you play a different kind of keyboard.  

But how do you tie optimization to EM analysis? Maybe hire some muddy chipmunks to start chewing on the artwork while leaving footprints? Actually, it is possible to optimize inside the EM environment, we will cover that topic later.

You need some way to parameterize the circuit, and then apply optimization to the parameters.  This can be done in the schematic environment, with an extraction tool, as explained below. In this video, the instructor is using Axiem as the EM tool, inside of Microwave Office.  The schematic controls the EM artwork, but the RF prediction linked to the schematic is purely EM.  That's the magic trick you need to pull this off.  There is a lot of good advice in the video: make sure you check the box that says "auto-snap on parameter changes" for example.

Note that for any complicated circuit, EM optimization is going to take some time... like overnight, or worse. For optimizing EMed circuits, it is best to break the product down into small pieces, and try to limit the number of variables.  You already have a great starting point from your linear analysis, here you are just applying the final tweaks to get back the performance that your linear analysis predicted.  In many cases, you don't need to optimize the width of a transmission line, just the length.

Performing an EM optimization in AWR Design Environment (Microwave Office) by Aaron Sher

During the EM run, Aaron amuses himself on a keyboard.  That first musical piece sounds a little like a long-lost Bach Minuet... but we sound-hounded it and came up with no matches.  We asked him about it.  You are listening to his original compositions!

Author : Unknown Editor