A Prototype Doppler Radar

Matt Reynolds with the prototype doppler radar

This photo shows the radar head itself (top left of photo) along with the processing unit (rack chassis on bench). The radar operates in the 2.4GHz ISM band, with an emitted power of less than ten milliwatts. The antenna is a four-element phased micropatch array. The RF oscillator, two mixers operated in a quadrature mode, and a baseband video amplifier are contained on a single piece of double-sided FR4 printed circuit board. The micropatch antenna is printed on the same substrate, keeping the total component cost for the radar head itself at around ten dollars.

The baseband processing unit has inputs for two such RF heads, and contains an analog correlator that demodulates the quadrature signal to produce outputs corresponding to a directed velocity for each radar as well as a long-term integrated output that can be used as a threshold in user interface experiments. The analog outputs are digitized and are available on both an RS-232 serial bus as well as a MIDI interface.

Detection range for this radar extends to about fifteen feet in an open area.