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Popular posts from this blog

UHF RFID Antennas - VII - Quadrifilar antenna (Part II)

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To continue on the topic of the printed quadrifilar antennas, as promised, this post will be about the feeding network. Last post I've shown the antenna part and a quick explanation as to what the feeding network should look like, this time I'm going to cover the power distribution network that makes it all work. More specifically, I'll explore an alternative that allows the antenna construction to be more compact and with better performance. So the idea is to create a system which has one single input port and four output ports, where all the outputs have the same power and 90º sequential phase difference between them, as explained in the last post.  But how exactly does that work and why the antenna becomes circularly polarized, when the single element of the antenna has linear polarization? Well, if you generate two orthogonal electric field components with a 90º phase difference between them, then the ...
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Antenna tuning - How to juggle two bands

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Hello folks.  There's been some time since I've written my last post. I've been very busy with work and other side projects, which eventually will find their way here, but since they're far from completion, I thought to make a smaller post about a subject that is useful and I've had had in my notes for a long time. So I figured I'd just put it up on the blog so it could be useful as reference for someone, or even myself one of these days. The subject is simple, how to tune a dual-band antenna. There's a fair amount of articles and tutorials, even on YouTube, about matching networks, either LC and Pi networks. They'll teach you all you need to know about Smith charts and what not. That's all very useful, but they all have one problem, they usually focus on having impedance \(Z_1=R_1+jX_1\) become \(Z_0\) \(\Omega\) at one single frequency. But how do you do it when your antenna is suppose to operate at two different frequency bands? How to tune both b...
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UHF RFID Antennas - V - Tag dipole antennas

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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...
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