The Antenna Guy

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 ...

Hey there folks!    Today I'm heading back to the RFID reader antennas topic. This time, I'm covering another typical antenna found in these readers, which is the quadrifilar antenna. In this particular case, a printed implementation of the quadrifilar antenna. These antennas are composed of four arms, either monopoles or PIFA type elements, where each of the elements is fed with a 90º phase delay in between in order to create a circularly polarized radiation. Another common place for quadrifilar antennas is the helix type antennas used for VHF and UHF band communications and GNSS applications. These are very popular among HAMs and also some commercial applications. Here's some examples: ...

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...