| 摘要 |
PURPOSE:To stabilize performance and to realize mass-production by forming transmission transformers on both surfaces of a ferrite substrate and providing a short ring to the ferrite substrate. CONSTITUTION:Transmission line transformers 21 and 22 consisting of coils 8 and 12, and 9 and 11 are formed on both surfaces S1 and S2 of the ferrite substrate 1. The short 6 ring is provided to the substrate 1 to prevent both transmission line transformers from being coupled together magnetically. Then, the coils 7 and 8, and 11 and 12 are connected mutually by connection lines 9, 13, and 14 through through holes 4-6. Thus, a balun coil is formed to eliminate the need for winding operation and realize mass-production. Further, variances of the degree of coupling of the coils and characteristic impedance are reduced and characteristics in a high frequency band are improved because of the short ring to stabilize the performance.
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