The novel microwave wideband quasi-elliptic bandpass filter, in which the initially uncoupled strip transmission lines are used is considered in the present study. The proposed filter is based on the reentrant structure in which the metallic body with a floating potential is asymmetrical. Generally speaking, the internal and external dielectric fillings must be of unequal relative permittivity. As a result, the additional symmetrical transmission zeros are reached at the lower and upper stop bands of the pass band leading to the quasi-elliptic response function that improves the bandpass filter selectivity. The general TEM circuit model for the proposed filter, in terms of the multi-port series connection, is presented and then used to predict the initial electrical and geometrical quantities. A printed circuit prototype has been manufactured using a conventionally printed circuit board implementation. The measured results are in an acceptable agreement with the simulation-derived ones, and that improves the degree of freedom in the frequency selective unit design.