UPDATE: This project is on an indefinite pause.
For those of you who read IEEE Spectrum magazine, this month’s edition includes an article called “Coffee-Can Radar” which details author David Schneider’s experiences in building a short range radar based on the work of Dr. Gregory Charvat, who in 2011 taught a short course at MIT on Cantenna Radars. This course has spread to other institutions including to the University of California Davis, University of Vermont, Michigan State University, MIT Lincoln Labs, etc.
Dr. Charvat’s FMCW (frequency modulated continuous wave) radar project uses a collection of connectorized Mini-Circuits components for the RF section, and several traditional components on a breadboard for the back end processing and VCO (voltage controlled oscillator) control. Antennas are of the “cantenna” type, and the whole system operates in the 2.4 GHz band with an output power of ~ 10 mW.
I decided that this project called for a kit version built on a single printed circuit board. So I started thinking about how to modify the project to expand on Dr. Charvat’s work, as well as provide backwards compatibility.
In thinking about ways to expand the usability of the radar, I decided that instead of controlling the VCO with a ramp generator chip, I’d use an Arduino microcontroller with a DAC (digital to analog converter). This allows for the arbitrary generation of radar waveforms and frequency chirps, in addition to USB computer interface.
The first major component change was to integrate the RF components, which meant finding suitable surface mount parts for the LNA (low noise amplifier), mixer, VCO, buffer amplifier, and power splitter. At this stage I decided to increase the frequency to the 5.8 GHz band which allows for the use of smaller antennas.
On the back end, I switched from a discrete anti-aliasing filter to an integrated part, and added a boost converter to generate the +12V required to control the VCO over its usable range.
This past week, we started assembly of the first prototypes, which are nearly ready for testing.
The first part of the assembly is the surface mount RF components. It is planned that this portion of the circuitry will come pre-assembled, as there are too few people with reflow soldering capabilities, and packaging SMT components is time consuming.
As was mentioned in the caption, the VCO is missing. Digikey sent the wrong part, but tomorrow the right ones should arrive and will be installed. We are looking forward to the next stage which will be to fire it up and see what problems or issues we may run into. RF is never easy to get right the first time!