AbstractIn the rectenna array used for rectification of the microwaves received on the ground in the solar power satellite system, it is required that the rectenna elements have a high dc power conversion efficiency and that the element spacing is optimized so that the arriving microwave power is received efficiently and the number of elements can be reduced. In this paper, a microwave rectifier is fabricated in an integrated form with a microstrip line on a teflon substrate. A circular microstrip patch antenna is used. A high rectification efficiency, 66.7 percent is obtained at a microwave input of 750 mW and 75.7 percent for input of 500 mW.With this rectenna element, a 7 × 7 lattice array is formed and the variation of the receiving efficiency (the ratio of the power converted to dc to the input microwave power) is measured by varying the element spacing. On the other hand, the receiving efficiency is calculated for a given element spacing of this rectenna array from the circuit equation of the antenna system by deriving the mutual coupling between the elements. The relationship between the element spacing of a finite array and the receiving efficiency is obtained both experimentally and theoretically. This computation method is extended to the case with many elements so that the change of the receiving efficiency is investigated