Publication: IEICE TRANSACTIONS on Electronics Publication Date: 1998/06/25 Vol. E81-CNo. 6pp. 856-861 Type of Manuscript: Special Section PAPER (Special Issue on Microwave and Millimeter-Wave Module Technology) Category: Functional Modules and the Design Technology Keyword: quasi-optics, coherent power combining, metal grooved-mirror, Fabry-Perot resonator,