A. I. Tyumentsev, A. N. Yakovlev, I. M. Yasinsky

The article presents a T-shaped bridged network of a band-pass LC-filter which has parallel circuit in the input and in the output. We can compensate inductive and capacitive components of input resistance of filters connected in parallel to the input of the filter by changing L and C. Filter circuit is designed in such a way that its characteristic impedance increases in the condition of turning out from average frequency and so short-circulating effect on adjacent filters decreases. We received calculation formulas of the circuit elements and control calculations, which have shown that values of elements may be inconvenient in their realization. To get more comprehensible values of elements, the authors offer the modified variant of performance of the initial circuit by introduction of additional pair of condensers in the structure of the Т-shaped fragment of the circuit. Equivalence of these variants is proved; corresponding formulas of recalculation of value of elements are introduced. The opportunity of elements transformation using Norton transformations is also considered. On the basis of numerical calculations and modeling of the circuit it is shown that influence of inductor Q, which is included in parallel contour, much less in comparison with other coils. These inductors Q can be chosen equal from 10 up to 50 units without appreciable influence on resulting parameters. The authors have deduced the formulas for calculating network elements and offer the way of using it to find the most acceptable values of elements. One of simulation method is represented by its amplitude-frequency response.