The Antenna Guy

 For the very few folks that still come here, I moved my personal blog into Github pages. You can find my blog here . I've migrated my posts there, so you may as well remove this blog from your favorites and just add the new one, ah! :)

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

A while ago I promised to look into the effects of using VIAs (Vertical Interconnect Access) on RF tracks to change layers on PCBs. Unlike the 90º degree bends on PCB tracks, in this case there's essentially two postures about the matter. Either people are completely clueless of the potential risk of placing a via on a RF track and do it recklessly. Or they're somehow a little aware of the risks, therefore completely demonize such practice, going at extreme lengths such as increasing the track sizes immensely (making it even worst), just so to avoid the use of the via.  A long time ago I found an awesome primer about vias for high-speed and RF tracks from Keysight, you can find it here . However, it focuses mainly on multi-layer board in excess of 8 layers. Therefore, although the concepts are the same and the material is absolutely valuable no matter your scenario, it lacks the actual results you'd get in a 2 or 4 layer board.  I've been cooking this post for a while,

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: