Trisection Microstrip Delay Line Filter With Mixed Cross-Coupling

It has been discovered that a trisection bandpass filter with mixed cross-coupling K-13 has flat group delay if the condition K-13 = 0 is satisfied, which occurs when magnetic K-m and electric vertical bar K-e vertical bar components of the coupling are equal. It has been proven that the group delay of the filter increases as the values K-m = vertical bar K-e vertical bar increase. The microstrip construction of the trisection delay line filter is proposed. The analysis of this construction has been carried out, which allows controlling the values K-m = vertical bar K-e vertical bar at the zero of cross-coupling. The results of the measurements and the simulation are presented.