LAUSR

A low-temperature co-fired ceramic (LTCC) coupled resonator decoupling network (CRDN) with asymmetric input/output (I/O) couplings for suppressing interference between two adjacent frequency bands is proposed in this paper. Based on LTCC multilayer technology, a second-order CRDN module is realized by strongly coupled semi-lumped LC resonators in a very small volume of 3.2 mm $\times2.5$ mm $\times1.2$ mm. A wide range of mutual admittance and different self-admittances of the CRDN can be realized by adjusting the asymmetric I/O couplings. Thus, a satisfactory decoupling performance covering two contiguous bands, as well as good matching in each band, can be realized without additional matching networks. To prove the concept, two planar inverted-F antennas working in TD-LTE and Wi-Fi frequency bands, along with the corresponding decoupling network, are designed, fabricated, and tested. The measured results have demonstrated that more than 15-dB isolation improvement can be achieved within the two operating bands, showing the feasibility of this ”one-fit-all” integrated solution. More importantly, the design methodology and circuit topology presented in this paper are general and can be applied to practical multi-input multi-output system applications.