In this monograph, the author makes an attempt to fill gaps in the solution of the problem of spatial decoupling of antennas by means of impedance decoupling structures. He presents the results of research about the electromagnetic fields of aperture antennas located on the common impedance surfaces, and about the development of techniques of synthesis of impedance structures and on their basis, the creation of decoupling devices providing the required electromagnetic compatibility of antennas. On the basis of the method of integral equations we solved the problems of analysis of radiation characteristics of a single antenna in the shape of the open end of a parallel-plate waveguide located on the impedance plane and on the surface of a circular cylinder. A similar problem is solved with the account of a receiving antenna with the same construction. Using the defined variations of distribution of the complete and scattered electromagnetic fields, we developed the techniques of synthesis of impedance decoupling structures for the antennas located on the common impedance plane and circular cylinder. Results of the comparative analysis of theoretical and experimental research.