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 Km and electric |K
_e
| components of the coupling are equal. It has been proven that the group delay of the filter increases as the values K
_m
= |K
_e
| 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 Km = |Ke| at the zero of cross-coupling. The results of the measurements and the simulation are presented.