A Miniaturized 3-D Integrated Low-Pass Filter Using a Novel Flexibly Configurable Three-Port Capacitor Based on TSV Technology

A miniaturized three-port capacitor structure based on through-silicon via (TSV) technology is proposed for high-density 3-D integrated radio frequency (RF) circuits. By integrating three interdigital capacitors into a single structure with a common electrode, the proposed capacitor reduces the number of interconnection ports by 50%, significantly improving area efficiency and signal integrity. The structure is validated through full-wave simulation and equivalent circuit modeling, showing good capacitive performance and high self-resonant frequency. A compact low-pass filter (LPF) is demonstrated using the proposed capacitor, achieving a cutoff frequency of 3.99 GHz, insertion loss of 0.18 dB, and return loss better than 25 dB within an area of 0.32 × 0.31 mm².