A Miniaturized and Packaged LTCC Filtering Balun Using Lumped Elements

In this paper, a low temperature co-fired ceramic (LTCC) filtering balun based on lumped elements is presented. It is composed of a lumped filter and a lumped balun cascaded via a vertical metal through-hole. The filtering balun operates at 2.45 GHz with the fractional bandwidth of 15%. Within the passband, simulated results demonstrate that the magnitude difference and phase difference of the filtering balun are within 0.4 dB and 5°, respectively. Frequency selection characteristics and balanced-to-unbalanced conversion are well achieved, and its package size is 4.8 mm × 4.2 mm × 1.5 mm or 0.095λ
g
× 0.083λ
g
× 0.029λ
g
.