Build a $360 synthetic aperture radar with MIT’s OpenCourseware


A few profs from MIT’s Lincoln Lab are giving those poor MIT undergrads something to do over winter break: they’re teaching a three-week course on building a laptop-powered radar system capable of radar ranging, doppler, and synthetic aperture imaging. Interestingly, the radar system that teams will build for the class has a BOM totaling $360, and they’re also putting the entire class online if you’d like to follow along and build your own.

From the lecture notes from the course, the radio system is made out of an off-the-shelf  LNA, oscillator, and  splitter. By connecting two coffee can ‘cantennas’, it’s possible to record a .WAV file from the signal coming from the radar and use MATLAB to turn that audio signal into a doppler radar.

It’s a very ambitious project that goes deep down the rabbit hole of RF and analog design. One of the lecturers made a YouTube demo of the radar in ranging mode; you can check that out after the break.

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More continuous wave radar fun

[Gregory Charvat] continues to have a great time testing out radar systems. He and a friend have pointed the radar out the garage door and are using it to see who can reach a high running velocity.

The last time we looked in on [Greg’s] work he had acquired an old police radar unit and wired it up to use with a laptop. The hardware he’s working with now is a lot more bulky and we don’t think it will be hitting the road with him anytime soon (although it is on wheels). The video after the break starts off which an overview of the test system which is mounted in a waist-high rack. He illustrates how Labview is monitoring the radar inputs and then moves on to show off the hardware which is actually harvesting the data. The box is quite versatile, able to run five different systems and includes a slew of different connector types.

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Hacking an old radar gun to interface with a laptop

[Gregory Charvat] decided to see what he could do with this old Police radar gun. It is an X-band device that broadcasts continuous waves and measures the Doppler shift as they echo back. He cracked it open to see if he could interface the output with a computer.

After a little poking around he’s able to get it connected to a 12V feed from his bench supply, and to monitor the output with an oscilloscope. He established that it draws about 0.5A in current he built a companion board which uses AA batteries for power, and provides an audio output which can be plugged into his laptop’s audio-in jack. This technique makes reading the device as easy as recording some audio. From there a bit of simple signal processing lets him graph the incoming measurement.

In the video after the break you’ll see his inspection of the hardware. After making his alterations he takes it into the field, measuring several cars, a few birds, and himself jogging.

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Seeing through walls using WiFi

Turns out you don’t need to be Superman to see through walls. Researchers at University College London have developed a way to passively use WiFi as a radar system. Unlike active radar systems (which themselves send out radio waves and listen for them to echo back), passive radar systems cannot be detected.

The system is small enough to fit in a briefcase, and has been tested through a one-foot-thick brick wall. It can detect position, speed, and direction of a person moving on the other side of that wall, but cannot detect stationary object. [Karl Woodbridge] and [Kevin Chetty], the engineers behind the prototype, think it can be refined to pick up motion as minuscule as a person’s rib cage moving with each breath. For some reason we get the picture in our mind of that body scanner from the original Total Recall.

[via Reddit]

[Image Credit]

Video-based radar for your car

[Gustaf] has been playing around with machine vision for a while and sent in his latest project in on our tip line. It’s a video based car radar system that can detect cars in a camera’s field of vision while cruising down the highway.

Like [Gustaf]’s previous experiments with machine vision where he got a computer to recognize and count yellow cylinders and green rectangles, the radar build uses ADABoost and the AForge AI/Machine Vision C# framework. [Gustef] used an evolutionary algorithm to detect the presence of a car in a video frame, first by selecting 150 images of cars from a pre-recorded video, and the another 1,850 images were selected by a computer and confirmed as a car by a human eye.

With 2000 images of cars in its database, [Gustaf]’s machine vision algorithm is able to detect a car in real-time as he drove down a beautiful Swedish highway. In addition to overlaying a rectangle underneath each car in a video frame and an awesome  Terminator-style HUD in the upper right corner, [Gustaf] also a distance display above the hood of his car.

It’s an awesome build that makes us wonder if [Gustef] is building an autonomous car. Even if he’s not, it really makes us want to install a video HUD in our whip, just to see this in action.

Automatic airplane tracking; what radar-systems engineers do for kicks

[G. Eric Rogers] is a radar-systems engineer who just happens to live within sight of the aircraft approach path for the local airport. We wonder if that was one of the criteria when looking for a home? Naturally, he wanted his own home-based system for tracking the airplanes. He ended up repurposing a motorized telescope for this purpose.

The system does not actually use Radar for tracking. Instead, the camera strapped to the telescope is feeding a video experimenter shield. A tracking algorithm analyzes the video and extrapolates vector data. From there, the base unit can be controlled by the Arduino via an RS232 interface.

There are some bugs in the system right now. The Arduino has something of an ADHD problem, losing interesting and going to sleep in the middle of the tracking process. [Eric’s] workaround uses the RS232 board to periodically reset the Arduino, but he hopes to squash this bug soon.

Build your own radar system

How we missed this one is anybody’s guess, but one of the presentations at DEFCON last year covers a DIY radar build. [Michael Scarito] talks about the concepts behind radar, and then goes on to show that it’s not too hard or expensive to build a setup of your own. We’ve embedded his 45 minute talk after the break.

The two large pieces of hardware above should look familiar. They’re descendents of a favorite hacking project, the cantenna. The can-based long-range antenna is most popular with WiFi applications, but we’ve seen it used for Bluetooth as well and it’s not surprising to see it here. The rest is a lot of sensing hardware and enough math crammed into the coding to make your ears droop.

If you make it far enough (exactly 39 minutes into the talk) [Michael] shares some links for more information on the build. We think living vicariously is enough for us, but if you manage to build your own setup don’t forget to post a project log!

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