Arduino radar search system 
a wireless charging pad, which is often located in a sheltered location where there is a greater chance of lost GPS signals. I have put an omni-antenna on the charging pad and a rotating high-directivity antenna array with a step-motor and an Arduino computer on the hexacopter. This setup has the advantage of low power consumption and is similar to how ships at sea find a lighthouse. The antenna radar offers extra insurance that the hexacopter can locate the charging pad. By rotating a patch antenna array, which possesses high-gain characteristics, the patch array can receive the power transmitted by another omni-antenna or monopole fixed on the charging pad, allowing the hexacopter to identify in which direction the charging pad is located. By using the friis equation, the remaining distance to the charging pad can be calculated.