To provide a more compact balun transformer.

The compact balun transformer has primary and secondary conductor loops. Each of these loops is substantially prepared in a flat spiral structure. However, one of these loops, a primary or secondary loop, is suitably prepared in a multilayer (lamination) structure. At least one lamination layer of a primary or secondary layer in the multilayer structure causes one of loops to increase impedance. The increased impedance for impedance matching brings about an advantage such that no parasitic capacitance exists between primary and secondary layers, which usually occurs in the mutilayer structure. In other embodiments, both conductor loops are installed in the multilayer structure. Such a structure is especially useful for the balun circuit of 1 to 1 impedance matching state and a little lower frequency.

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