This entry will detail the geometry of multi-static passive RADAR and describe how it obtains a target solution. For this report, a multi-static passive TDOA RADAR configuration will consist of a single receiving station that monitors for direct signals from the transmitters and indirect, multi-path signals reflected from potential targets. Other configurations are possible but the two-dimensional solution described here requires three transmitter-receiver combinations. To obtain a target the system measures the time difference of arrival (TDOA) of the multi-path signal is compared to the direct path signal from the same transmitter. Solutions for possible targets are calculated using the measured TDOA timings.