A Compact LTCC Multi-layer Balanced Filter for Microwave Application

A compact multi-layer balanced filter comprised of a Marchand balun and a lowpass filter realized by low temperature cofired ceramic (LTCC) technology is proposed in this paper. Firstly, the broadside-coupled stripline is applied to meet the demands towards multi-layer structures in order to make full use of the advantage of LTCC technology. Then, a technique is introduced to adjust the even mode impedance by optimizing the coupling factor, which can be utilized to improve the device's operating performance. Based on the multi-layer structure, the size of the compact LTCC balanced filter is optimized to 3.2 mm x 2.0 mm x 2.7 mm. Through simulation, the proposed balanced filter demonstrates to be in consistent with the design specification and shows its feasibility to be implemented for system-in-package (SiP). In general, the present work offers an in-depth view and serves as a significant guidance for designing a compact LTCC balanced filter with great performance for microwave application.