The electronic transmission through a one-dimensional (1D) monomode wave guide made of asymmetric loops pasted together with segments of finite length is investigated. Existence of gaps (where the propagation of electrons is forbidden) in the band structure is reported. These gaps originate both from the periodicity of the system and the resonance states of the loops. The width of these band gaps depends on the geometrical parameters of the structure and may be drastically increased in a tandem geometry made of several successive asymmetric serial loops structures (ASLSs) which differ by their geometrical characteristics. These ASLSs may have potential applications as ultra-wide-band filters.