Six-Pole Parallel-Coupled Microstrip CQ Filter with Source-Load and Source/Load to Resonator Cross Coupling

The six-pole cascade quadruplet microstrip filter with source-load and source/load to nonadjacent resonator cross coupling is proposed to achieve generalized Chebyshev responses. The presented coupling scheme achieves similar skirt selectivity as that of a sixth-order fully canonical form filter. In addition, the proposed filter is less sensitive than that of canonical form filter. The initial design can be easily obtained by the design procedure of conventional parallel-coupled filter. With source to the third resonator and load to the fourth resonator cross couplings, two quadruplets are formed. Moreover, a source-load cross coupling forms the third quadruplet. The three quadruplets produce three pairs of finite transmission zeros. By controlling the strength of the cross couplings, the position of the three pairs of zeros can be decided arbitrarily. A design example is provided in this paper. Furthermore, simulation and measurement results are well matched.