Hand-made Radar! TeamFireDragon 6.013 Project

Etched and Populated Radar PCB

This is a super-quick mostly-picture blog of my team’s 6.013 Electromagnetics class final project! We started work on this project by building and testing directional couplers and power splitters, which would allow us to split the RF amplifier output into transmit and reference.

Here we test one of our prototype directional couplers
Small CNC router for cutting prototypes

In order to make more exact prototypes, we used a small CNC router with an engraving bit. This allowed us to cut precise test patterns in the exact material we would be using.

Test power splitter/combiner made on the CNC router
Checking various directional behavior

In addition to a board, this radar would require two directional antennas. For these, we made “Cantennas” and tuned wire length/position for best impedance at our desired 2.4GHz operation.

Testing Cantenna

After testing, we laid out a board in KiCad. This board was single layer for ease of fabrication, and included both the directional coupler and the power combiner as copper geometry on the board.

PCB layout with test components near their board counterparts

We used toner transfer + etching for creating the circuit board. This process is shown in the next 4 images.

Mask to protect/pattern copper areas
Laminating mask onto copper board
Copper board with desired areas protected
Final board after etching

After this, I drilled holes for all of the connections to the bottom ground plane.

Drilling Holes!
Looking at where components go

We populated the board using a hot-air reflow station.

Board on reflow station before components
Board with components soldered

Now a radar depends on having a good reflected radio wave off of the target object. In order to test the radar, we constructed a corner cube out of foam and aluminum foil. Corner cubes have the awesome property that any incoming wave reflects directly towards the source, regardless of the cube orientation. This makes it an easy, reliable target for testing.

One can is transmit, one can is receive, with corner cube as target

This final picture is an oscilloscope trace seen when the corner cube is moved. This envelope is the beat between the reference 2.4GHz, and the reflected, Doppler-shifted frequency (2.40000001GHz or however fast you are moving).

Output of the radar

Finally, here is a video of the radar in action!