[hamdani yusuf (OP)]

It's been a while since the last time I made a video on microwave transceiver. Here's a good demonstration using dipole antennae to explore the behavior of microwave when not directed by horn antenna.

[hamdani yusuf (OP)]

I've made a new video investigating diffraction of microwave using metamaterials. Previously, it was shown that an aluminum plate, which virtually reflects all of microwave power, didn't show any observable diffraction effect. This time, we tested if diffraction effect can be observed in a partially transparent obstacle which is constructed as metamaterial. The metamaterial obstacle is made from an array of aluminum stripes. There will be some follow up videos to eliminate some uncertainties around diffraction phenomenon.

[vdblnkr34]

Make a Macrowave gun, Nanowave gun, Pikowave gun.  Add some more magnets to see what it will do, remove them to see what it do, make a loner coil or bigger, add some iron core into it or ferrite. etc...

People able to melt metals in microwaves this days. They create dielectric wall and inside metal start melting, check you tube. Find out why it does that. And make very powerful metal melting machine, that melts anything on its way. 

[hamdani yusuf (OP)]

There are already many ways to melt metals. That's not the goal of starting this thread.
Microwave was chosen due to its convenient wavelength to build metamaterials to investigate its behaviours.

[vdblnkr34]

Ok. I have a question.

What material protects from this waves? Grounded peace of metal would be enough?

[hamdani yusuf (OP)]

Ok. I have a question.

What material protects from this waves? Grounded peace of metal would be enough?

Even ungrounded peace of metal sheet can prevent the wave to pass through, providing that it can generate adequate reactional electric field to cancel out the oscillating electric field of the incoming wave. In general, higher intensity wave requires thicker material to block.

[hamdani yusuf (OP)]

I've made a new video investigating diffraction of microwave using metamaterials. Previously, it was shown that an aluminum plate, which virtually reflects all of microwave power, didn't show any observable diffraction effect. This time, we tested if diffraction effect can be observed in a partially transparent obstacle which is constructed as metamaterial. The metamaterial obstacle is made from an array of aluminum stripes. There will be some follow up videos to eliminate some uncertainties around diffraction phenomenon.

Here it is. I hope you enjoy it.

[hamdani yusuf (OP)]

Edge effect on diffraction of microwave.

[hamdani yusuf (OP)]

I've recorded two new experiments using microwave transceiver. The first investigates the effect of polarized diffraction in microwave. The other one revisits the experiment with conjoined twin polarizer with slight change in the setup, but shows some significant results. Stay tuned.

[GertrudeFranklin]

So?
What do you have to say as a result?
We are waiting and curious.

[hamdani yusuf (OP)]

So?
What do you have to say as a result?
We are waiting and curious.

I've just finished the editing. But since the videos are quite large, I"ll upload them when I get access to a reliable internet connection.

Do you really want a spoiler?

Spoiler: show

- Polarization state of the  diffracted wave is determined by polarization of the source, as well as the obstacle.  It's not so surprising if you are already informed of my other experiment on polarized diffraction of light.
- The conjoined twin polarizer can rotate polarization of incoming microwave. It should not be surprising either if we consider that ordinary polarizer can do the same.
- The sequence of polarization axis of the conjoined twin polarizers determines the transmission of the microwave.
In my previous video on conjoined twin polarizer, the electrical conduction between the two polarizers seem to remove the effect of the sequence.

[GertrudeFranklin]

Ok, I got you. I'll wait

[GertrudeFranklin]

Or even if there are some little spoiler details - I am ready

[hamdani yusuf (OP)]

Here's the first one, showing the effect of polarized diffraction in microwave.

[hamdani yusuf (OP)]

Here's the other one.

In this video we will revisit the experiment of microwave transceiver on conjoined twin polarizers. This time the polarization axis of the transmitter is perpendicular to the receiver. It will show how much microwave polarization axis is rotated by the polarizers.

You can compare the result with previous experiment on separated twin polarizer in reply#77
https://www.thenakedscientists.com/forum/index.php?topic=66414.msg619477#msg619477
And the first experiment on conjoined twin polarizer in reply#78
https://www.thenakedscientists.com/forum/index.php?topic=66414.msg619552#msg619552

[hamdani yusuf (OP)]

And here are videos demonstrating conjoined twin polarizer

In the end of the experiment, it's shown that rotating the receiver can make the reading down to 0, which means that the microwave is linearly polarized instead of eliptical or circularly polarized.

It's been a while since these videos were uploaded. There is still questions I want to answer regarding the conjoined twin polarizer. What would happen if the second polarizer is half wavelength away from the first?
I realize that making the apparatus to answer this question would require a considerable time and effort.

[hamdani yusuf (OP)]

Separating those conjoined twin polarizer turned out to be harder than I thought. I ended up breaking them apart. It seems like it was easier to build a new one.

[hamdani yusuf (OP)]

Meanwhile, I get an idea to make easier experiment with microwave transceiver. I'll use two parallel metal sticks to reflect the microwave and act like two coherent  wave sources which can be made to interfere with each other. I put this here as a reminder so I won't forget to make the experiment when I have the time.
This design would allow me to freely change the number of sources and their sizes, which is hard to do using visible light.

[hamdani yusuf (OP)]

Do Guided Modes in Metal Waveguides Travel Faster than the Speed of Light?

Do guided modes in metal waveguides travel faster than the speed of light? Many think so.

This short video illustrates what is happening in a metal waveguide that leads to this somewhat false conclusion. It turns out it is only the interference pattern of waves bouncing around in the waveguide that travels faster than the speed of light. The waves themselves are travelling exactly at the speed of light. Due to the angle the waves are bouncing around, the overall speed through the waveguide is slower than the speed of light. I think the visuals in this short video will help reconcile any confusion.

[hamdani yusuf (OP)]

This ESP32 Antenna Array Can See WiFi

More information is available on the project website of the ESP32 antenna array "ESPARGOS": https://espargos.net/

Source code for Python library + demos: https://github.com/ESPARGOS/pyespargos (directory "demos/camera" for "WiFi camera" demo)

As a research assistant at the Institute of Telecommunications at the University of Stuttgart, I work on multi-antenna systems like (distributed) massive MIMO, with a focus on wireless channel measurement platforms and algorithms for processing channel measurements (classical and deep learning-based).

One day, my (incredibly talented) colleague Marc Gauger suggested to use ultra low-cost ESP32 chips instead of software defined radios for channel measurements. I was highly sceptical at first, but when he showed me a minimalistic prototype he had soldered together, I was intrigued by the idea of being able to demonstrate my algorithms in real time using WiFi signals. In a series of Bachelor's / Research theses, my excellent students Tim Schneider, David Engelbrecht and David Kellner helped me develop the ESP32 antenna array "ESPARGOS".

Measured CSI dataset used for AoA / TDoA visualization: https://espargos.net/datasets/data/es...
AoA / TDoA localization source code (needs some minor modifications to be applied to espargos-0005 dataset): https://github.com/Jeija/ToA-AoA-Augm...
Channel Charting source code for the animation in the video: https://github.com/Jeija/Geodesic-Unc...
Tutorial on Channel Charting: https://dichasus.inue.uni-stuttgart.d...

My research on (distributed) massive MIMO, Channel Charting and other algorithms for multi-antenna systems is funded by the German Federal Ministry of Education and Research (BMBF) within the project Open6GHub (grant no. 16KISK019).
I also want to express my gratitude towards ARENA2036, who hosted our measurement campaign for Channel Charting, and to my colleague and Channel Charting expert Phillip Stephan, with whom I co-authored several papers on Channel Charting and who assisted me with the creation of this video.

These experiments look interesting.