Archive for August, 2010

There must be an easier way to read off design values from an IEEE paper

Wednesday, August 25th, 2010

Illustrating the traditional graph tracing method.

Illustrating the traditional graph tracing method.


Don?t you find it interesting that one of the most important steps in designing most antennas requires a pencil, ruler and often a magnifying glass in order to obtain the correct values to use in design algorithms? Living in the year 2010 (and not in the years ?before television?) one would think that the method of reading-off graph data from a published IEEE paper should have developed to be at least digitized. But most people still use the same old pencil and ruler method and then have to approximate the value which for some reason always lies on the steepest gradient of the graph resulting in high margin for error.

One of our engineers wrote a very handy Matlab tool which allows you to import a graph as a jpeg image and records the coordinates when clicking on the trace with your mouse, interpolating the X ? Y data, so it saves you the effort of printing the graph and reading off the values by hand. If you think you can use this tool drop me an email and I?ll send it to you.

Such a tool would probably be a very handy feature in Antenna Magus?watch this space.

Author: Robert Kellerman

Comparison between a Cantenna and Coaxial cavity horn

Wednesday, August 18th, 2010

A few posts ago I showed some pictures and results of the Cantenna (also known as the Pin-fed Circular Waveguide Antenna) made from a Pringles potato chip container compared with a copper replica. Click here to read the post. We also compared the gain patterns of the copper cantenna (mentioned in the previous post) with a Coaxial cavity horn using the same wave guide dimensions as the Cantenna. Well actually Wilco (a 2nd year engineering student who did some vacation work for us) came up with a clever idea. He used the same copper Cantenna for the waveguide section and made the cavity section to slide over the cantenna forming the Coaxial cavity as shown in the next few images.

Copper cantenna and slideble cavity section which forms the coaxial cavity horn.

Copper cantenna and slideble cavity section which forms the coaxial cavity horn.


Coaxial cavity horn

Coaxial cavity horn


Measurements were done in an anechoic chamber

Measurements were done in an anechoic chamber

It was interesting to see the effect of the added cavity compared with the waveguide (Cantenna) by itself. Most of the back radiated power is directed toward the main beam which now has a much wider, almost flat shape which is ideal for being used as a reflector feed.

Comparison between the Cantenna and Coaxial cavity E-plane pattern measurements

Comparison between the Cantenna and Coaxial cavity E-plane pattern measurements

Author: Robert Kellerman

Taking a peek at your iPhone antenna ? the cost effective way

Friday, August 6th, 2010

As something of an antenna enthusiast, I was delighted to discover a source of reliable information about the antennas in many commercial devices ? including the iPhone. The Hong Kong Applied Science and Technology Research Institute (ASTRI) (www.astri.org) has taken apart many commercial phones, done measurements on them, and built 3D CAD models of them. Accurate impedance and pattern measurements are also done in anechoic chambers and published on their website for free. It is great to see a reliable, scientific, study of these devices, rather than anecdotal evidence from an enthusiast in their garage with 50% speculation, 50% measurement resolution error and 50% fact.

It is worth blocking time in your schedule to go to their website and look through some of the documentation. Follow this link to view their antenna R&D gallery.

Author: Sam Clarke