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Using EMANIM to Visualize Radio Waves

By Keith Parsons, Contributor
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Those of us involved in Wi-Fi have a tough job. We have to work on something we can’t touch, see or feel, so we have to visualize the RF in our heads. Using a tool like EMANIM allow for changing different parameters and visualizing the various results.

EMANIM Classic Interface

András Szilágyi has now offered his EMANIM visualization tool as an HTML webpage so you can access and learn from it from any platform.

If you are interested in how the various radio waves we use on a daily basis in our work as wireless LAN professionals, this is a great resource. It’s not only great for the visualizations, but also for the explanations. The software allows a nearly unlimited amount of customization, so you can play with the look, colors, camera angles, wave sizes and frequencies.

I’m pretty sure I’ve only barely touched the surface of what is possible with this tool.

For my work in helping teach folks how to better design wireless LANs, I’ve found a need to first teach fundamental concepts. Using EMANIM, students can quickly understand relationships that might be difficult to describe with only words. Without such a piece of software, I’ve been left using :hand motions" to describe some fairly complex movements.

Let’s start with the basics of frequency and amplitude. Below is a "Tall" – "Slow" wave form. Height refers to the amplitude. We use the metric of RSSI in the Wi-Fi world to show the amplitude of the radio wave we receive at a Wi-Fi NIC.  In the Wi-Fi world, we have a very limited set of frequencies (currently either the 2.4GHz or 5GHz band).

High Amplitude – Low Frequency

In our world, we are using very fast waves—moving billions of times per second—that have very small amplitudes. They're measured in thousands or even billions of a single watt. Using EMANIM, I can visualize a simple view of a quiet, yet very fast frequency wave.

Low Amplitude – High Frequency

Another concept that is sometimes more difficult to understand with just hand motions is the idea that radio waves can be either vertically polarized or horizontally polarized.

EMANIM makes it quite easy to show the differences between vertical polarization (red) and horizontal polarization (green).

Vertical Polarization in Red – Horizontal Polarization in Green

Note: The word is "polarization" NOT "polarity"! Polarity has to do with + and -, black and red, positive and negative. Polarization is about vertical v. horizontal wave forms.

One of the nearly 20 different variable parameters is the ability to model the RF absorption of a material on the amplitude of an RF waveform. This is very much like what happens when Wi-Fi hits a wall. You can see the frequency didn’t change, only the amplitude (signal strength) changed.

Effect of RF Absorption on RF Amplitude

Rather than me continuing…go and experience this yourself!

Enjoy.

If you’d like to try it yourself, go to Szilágyi, András: EMANIM: Interactive visualization of electromagnetic waves

For additional information, visit an Animated Tutorial on Electromagnetic Wavesalso from the same author.

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