This would be the first of many low-powered, retrodirective designs that the group would develop. Powered by a TI MSP 430 micro-controller, the device consisted of a dynamically switched Van Atta array in which 4 different phase lengths could be inserted into the electrical pathways. The result was a QPSK backscatter signal with large retrodirective gains.
Fun Fact: This form of modulator is referred to within the group as a Koo-Lu modulator, named after Greg Koo and Albert Lu — the inventors. Albert found the original Van Atta design and helped Greg Koo design the first implementation for his MS thesis.