Design and implementation of a miniaturized LTCC diplexer based on lumped elements

ABSTRACT This paper proposes a transmission zero prediction method for LTCC filters to shorten the design period. In order to reduce the influence of parasitic coupling between elements, we use the flexibility of 3D model design to place the elements in three areas that are far apart in the vertical direction of the substrate, and control the position of the transmission zeros to achieve high out-of-band suppression. The overall size of the diplexer is 1.6 mm×0.8 mm×0.6 mm. Simulation result shows that the insertion loss of the low band is less than 0.4 dB, and the isolation of which is greater than 40 dB. The insertion loss of the high band is less than 0.83 dB, and the isolation of which is greater than 38 dB. Compared with the existing LTCC diplexer reports, our design has the advantages of compact structure, high isolation, low insertion loss and high out-of-band suppression.