Rectennas are part of wireless power transmission (WPT) systems and are intended to receive microwave energy and convert it to DC energy. Efficiency of the WTP system is largely determined by the rectenna, which is an unphased array of receiver-rectifier elements (RREs), each of which consists of a receiving antenna and a rectifier circuit. Parameters of RRE mainly determine such indices of rectenna quality as efficiency, level of over-radiation at frequencies of higher harmonics, reliability, cost and suitability for serial production. Today, the optimization of both the parameters of individual RRE and the characteristics of the entire array as a whole remains relevant for the array. Of course, such optimization can be implemented only as a result of mathematical modeling.