While our collective minds have been turned towards the global pandemic it’s refreshing to hear that in some quarters life has continued, and events that would have made the news in more normal times have continued to take place while they have been replaced in coverage by more urgent considerations.
In the last few weeks there has been a piece of routine American bureaucracy that flew under the radar but which will have a significant effect on global technology; the United States’ Federal Communication Commission first proposed, then ratified, the allocation of an extra 1200 MHz of spectrum in the 6 GHz band to ISM usage. This allocation process is likely to be repeated by other regions worldwide, freeing up another significant piece of spectrum for unlicensed usage.
In practice this means that there will be a whole new set of WiFi channels created, and we’ll all have a little more spectrum to play around with, so it’s worth examining in a little more detail. Continue reading “What Will You Do With An Extra 1.2 Gigahertz?”
So you’ve built yourself an awesome radar system but it’s not performing as well as you had hoped. You assume this may have something to do with the tin cans you are using for antennas. The obvious next step is to design and build a horn antenna spec’d to work for your radar system. [Henrik] did exactly this as a way to improve upon his frequency modulated continuous wave radar system.
To start out, [Henrik] designed the antenna using CST software, an electromagnetic simulation program intended for this type of work. His final design consists of a horn shape with a 100mm x 85mm aperture and a length of 90mm. The software simulation showed an expected gain of 14.4dB and a beam width of 35 degrees. His old cantennas only had about 6dB with a width of around 100 degrees.
The two-dimensional components of the antenna were all cut from sheet metal. These pieces were then welded together. [Henrik] admits that his precision may be off by as much as 2mm in some cases, which will affect the performance of the antenna. A sheet of metal was also placed between the two horns in order to reduce coupling between the antennas.
[Henrik] tested his new antenna in a local football field. He found that his real life antenna did not perform quite as well as the simulation. He was able to achieve about 10dB gain with a field width of 44 degrees. It’s still a vast improvement over the cantenna design.
If you haven’t given Radar a whirl yet, check out [Greg Charvat’s] words of encouragement and then dive right in!
A lot of hackers take the “learn by doing” approach: take something apart, figure out how it works, and re-purpose all of the parts. [Henrik], however, has taken the opposite approach. After “some” RF design courses, he decided that he had learned enough to build his own frequency-modulated continuous wave radar system. From the level of detail on this project, we’d say that he’s learned an incredible amount.
[Henrik] was looking to keep costs down and chose to run his radar in the 6 GHz neighborhood. This puts it right in a frequency spectrum (at least in his area) where radar and WiFi overlap each other. This means cheap and readily available parts (antennas etc) and a legal spectrum in which to operate them. His design also includes frequency modulation, which means that it will be able to determine an object’s distance as well as its speed.
There are many other design considerations for a radar system that don’t enter into a normal project. For example, the PCB must have precisely controlled trace widths so that the impedance will exactly match the design. In a DC or low-frequency AC system this isn’t as important as it is in a high-frequency system like this. There is a fascinating amount of information about this impressive project on [Henrik]’s project page if you’re looking to learn a little more about radio or radar.
Too daunting for you? Check out this post on how to take on your first radar project.