The Antenna Guy

Hey there folks. Today I'm going to talk about curves in PCB tracks. I've seen a few topics here and there trying to demystify the way that tracks should curve in order to avoid all sorts of magic stuff. There seems to be a large consensus about avoiding 90º degrees bend at all costs, then there's a lot of people already claiming we've been doing stuff based on tradition only and that there's no solid reason nor practical argument to not use 90º bent tracks. So I thought I should give my two cents on this subject. I f you want to indulge in such a discussion, check out this EDA stack overflow thread . The most voted answer of said thread is certainly very detailed and mostly demystifies religious beliefs about the 90 degree angles in the tracks. But I also feel it ends up going overboard with statements such as: "In fact, this is true even at very high frequencies, which I will address further down in this post. If I...

In the first post of this blog, I pointed out to this video about a guy discovering the wonders of UHF RFID and proposing to build his own antenna. Unfortunately for me, I discovered he knows little to nothing about antennas, and his demand has been fully about trying to replicate an already made design. That's unfortunate for me, but doesn't mean the video isn't good. On the opposite, it is splendid and extremely educational. I knew all about the stuff he was talking about, and I still found it very entertaining and learned one or two other things in the process.   But then I decided I could actually write a post about designing a UHF RFID tag antenna.  So here it is! Now, there's hundreds of references on the topic, you just search on IEEExplore and you'll see (you'll find even more if you go through Google). Even commercially, there's dozens of RFID tag antenna designs. These have been developed to answer different kinds o...

So, as I mentioned on my last post , here I'll explain about those rings around the feed points on the microstrip antenna. Those rings are copper cutouts around the feed point of the antenna. Those cutouts, at high frequencies, are equivalent to a capacitor. That capacitor is used to compensate the series inductance that is introduced by the higher order modes being driven. Also, the microstrip patch antennas are coaxially fed, the pin of the coax, at high frequencies, acts as an inductor, adding to the increased inductance effect, and the longer this pin wire is, the higher that inductance. That inductance is in series with the antenna and will impact directly on it's input impedance. Here's the variation of the input impedance of the microstrip patch with the variation in height (h) between the patch and the ground plane:   ...

This is a continuation of my previous post on the air core microstrip patch antenna. It can be found  here . At this point, we need to get the patch to radiate a circularly polarized wave (and correct the added inductance of the feed pin by the increased height). Now, if looking at the microstrip patch through the cavity mode analysis, it’s possible to produce two fundamental frequencies of operation, set by the propagation mode that is activated in the patch, these are respectively TM10 and TM01. If the patch is fed along the length, we get the TM10, if it is fed along the width, we get the TM01...or is it the other way around? I always forget which is which! But it doesn’t matter, what is relevant is that we keep in mind that exciting fields in different places of the patch will excite different modes which might have or not the same resonance, but will have a phase delay between them. Feeding on o...