Archive for September, 2009

Cheap and nasty 13 dBi antenna

Tuesday, September 22nd, 2009

The other day our antenna engineer team leader told me how impressed he was with the dipole-fed Short Backfire antenna. After chatting with him I wanted to go build one myself. It is very easy to construct, cheap, small and can achieve up to 13 dBi gain! The characteristics of this antenna make it ideal for Wi-Fi applications, like boosting your wireless internet reception at home.

Short backfire - frying pan antenna

Short backfire - frying pan antenna

The above image shows a short backfire antenna that was built by an Italian engineer (Ciauz B.Loved) from a frying pan! He explains everything in detail on his website. The antenna consists of a ?/2 dipole with a large ?cake pan? like disc and small ?/2 circular disc spaced ?/4 on either side. The two discs reflect both direct and indirect illumination from the dipole producing a great medium gain antenna. The rim of the ?cake pan? increases the bandwidth at the expense of gain and reduces back radiation considerably.

Every antenna engineer should own one of these! All you need to make this antenna is Antenna Magus to design the physical parameters and some basic metal and copper materials – or go measure the diameter of your frying pan in the kitchen!

I?m looking forward to hearing feedback on how it went with your antenna creations!


Author: Robert Kellerman

Building and measuring Antenna Magus designs in the office

Monday, September 7th, 2009

Just before I left for IEEE AP-S and IEEE MTT 2009 in the States, I asked the engineers whether they could build a few prototypes that I could take with me. This was the Friday afternoon before I left. I had ordered some basic raw materials like copper tape, 5mm signage boards (with an Er of approx 1), small metal ground planes and a few of SMA connectors.

We turned the boardroom table into a workbench with soldering irons, metal cutting scissors, tape and so forth. I?d not seen the engineers so excited since the previous Foosball tournament! Each could pick an antenna of his choice, design it with Antenna Magus, run the simulation, build it and then measure the impedance on the network analyser. Some of the antennas we used were the Circular pin-fed linearly polarised patch, Inverted-F (IFA), U-slot dual-band planar inverted-F, Elliptical rectangular monopole, Suspended plate antenna (cut-out version) and the Discone. I also invited the software team and a few others who had never built their own antennas before and they were ecstatic to see how their measurements matched the Antenna Magus results.

We had a lot of fun and unlike other Friday afternoons, no one wanted to go home for the weekend (or perhaps it took a bit longer for those with less experience in mechanical construction).

Here are pictures of two antennas we built and measured:

Discone antenna designed at 3GHz, S11 measurement.

Discone antenna designed at 3GHz, S11 measurement.

Suspended plate antenna designed at 2Ghz, S11 measurement.

Suspended plate antenna designed at 2Ghz, S11 measurement.


Author: Robert Kellerman

 

Is a decent measurement of a simple antenna too much to ask for?

Wednesday, September 2nd, 2009

I love the Cantenna? (Or: Probe fed open-ended circular waveguide antenna). It has great performance for so simple a design (another of my favourites in this category is the short back-fire).? Given the abundance of websites devoted to this antenna, is it too much to expect that someone somewhere has done a comprehensive measurement of one? ?Maybe the abundance is exactly the problem ? so much SPAM that it makes the good paper impossible to find.

Without the measurement to validate that we are building our models with enough detail, it won?t get into Antenna Magus. If you know where the needle in the haystack is, please let us know!


Author: Sam Clarke