DEVELOPMENTS IN MOBILE PORTABLE TELEPHONES AND KEY DEVICES FOR MINIATURIZATION/

Fundamental microwave key devices used in achieving compact mobile/por table telephones (radio units) are discussed. The historical developme nt flow of the systems and radio units are introduced, with respect to the 800-/900-MHz and 1.5-GHz Japanese cellular radio systems. The des ign concept of the developed radio units is briefly described. Technic al requirements for RF circuits are reviewed and the developed key dev ices are practically applied to the circuits. Key factors in the requi rements are also shown. Finally, future trends for the key devices are surveyed from the stand point of achieving a smaller and more light w eight pocket radio unit.