iNets – I've heard the name but what is it?

 Dr. Mike Heimlich, Microwave & RF Marketing, AWR

One of the true gems of EDA technology that is certainly deserving of the Rodney Dangerfield Award (“I don’t get no respect!”) is iNets™. Not that anyone doing MMIC, module or PCB design should feel guilty that they’ve been negligent by not hunting down this capability...it was originally developed for silicon RFIC.

For the well-versed AWR user, iNets are multi-pin MTRACE or MCTRACE fused with bridge code but without the symbol on the schematic. For the greater electronic design community, it’s the ability to have a wire on the schematic that is routable over many layers, with an auto via insertion capability that knows how to terminate the route on whatever pins to which it is connected. What separates iNets from dumb polygon routes is that they also enable you to decide later how they should be modeled (if at all). 

iNets first appeared in the 2006 version of AWR’s Analog Office® RFIC design software.  For the “high-frequency” silicon designer attempting feats of microwave or mm-wave fame, a major challenge is what to do with the interconnect. Given that the typical silicon RFIC has more interconnect than there are Mickey Mouse ears at Disney World, and that the substrate is lossy plus “where’s the ground?”, there’s a lot to take into consideration. So the initial incarnation of iNets let users route a wire in their schematic, which enabled them to incrementally model it as they refined their design along the way to tape out. For example, starting with all the lines being a short, users could have the iNet automatically tie together a series of RF/microwave interconnect models for them that were process dependent so as to give a first-cut measure of loss and delay at GHz frequencies. Later on, they could send it to a parasitic extraction engine or eventually do a full-up EM.

Pretty cool. This concept was then taken over to Microwave Office® for MMIC and module design. The result: iNets that we have today in the current version of AWR software.

So if you’re a MMIC designer, iNets can keep your DC lines on your schematic for inclusion later when you’re scratching your head as to why you have an oscillation in your world’s greatest PA or high gain amp. In the early stages of the design, you can just leave ‘em alone. But when you want to make the boss proud that your DC lines are not just a bad tank circuit, two mouse-clicks later you’re EXTRACTing your iNet’d DC lines to ACE™, AXIEM™, or your favorite EM solver in the EM Socket™.

For module design, getting some spirals onto the softboard is a great cost savings, and while you don’t necessarily want to nail down their size early in the flow, you may want to look at their cross-coupling.  Lay them out with an iNet and you can easily push, pull, and stretch to get a feel for the space you need.  Incrementally EM’ing them with a few of the extra lines in the vicinity is a great balance between speed and accuracy in the middle part of your design when you are trying to get the layout to fit without blowing out your space constraints.

And for the PCB designer. Welcome to nirvana. Manually route your lines, inserting the vias you want or letting the iNet router do it for you.  When you’re ready to do that final verification...WHAM! send it to ACE or an EM solver to nail the electricals before using an AWRConnected™ link to migrate it into your enterprise PCB tool and manufacturing.

Check out iNets...it's one of the best darn feature you’ll ever use when it comes to circuit designers’ layouts and probably the one you’ve heard the least about. Don’t just take my word for it, see it in action on AWR.TV and then call your local sales contact or AE to put iNets to work for you!