PURPOSE: To make the assembling and maintenance easy, by providing a dielectric board formed with a microwave circuit on a metallic board at each function for forming a block, coupling separably the blocks, and connecting a microstrip line on the board between the blocks.

CONSTITUTION: An oscillator is constituted on the dielectric board 24 with a diode 32, a dielectric resonator 33 and the like, and a frequency converter is constituted with a diode 40 on the dielectric board 29. Further, a monitor circuit is constituted with a diode 43 on the dielectric board 30 and a coupling section with a waveguide section 45 is constituted with a microstrip antenna 44 on the dielectric board 31. The microwave circuit formed on the dielectric boards 24∼ 31 is tested and adjusted, then arranged on the metallic boards 21∼23 at blocks A∼C each, the connection between the microstrips on the board 24∼31 is performed, the test and adjustment at each block are performed and the blocks A∼C are coupled with bolts 47, 48. Further, the microstrip lines between the blocks are connected, allowing to attain ease of the assembling and maintenance.