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

For implementing professional receiver preselectors it is often used a bank of bandpass filters operating in parallel with respect to the input. For reducing filters mutual bypassing interference a differential system can be used. Known differential systems use a mode of operation providing maximum isolation between input impedances of two filter banks resulting in reducing the transmission coefficient on operating frequencies. As in real conditions input impedances of filters of one bank on the operating frequencies of the filters of the second bank are reactive it is possible in specific cases to improve the transmission coefficient on operating frequencies by the proper selection of balanced impedance and relationship between the filters load impedance and signal source impedance values. For this purpose the differential system is represented as a two-port network, its generalized parameters are defined that are used for calculating parameters of complex balanced impedance and transfer function for the specified transmission direction. Some modes of operation of such system are considered that allow the transmission coefficient improvement within the passband.