Compact On-Chip Bandpass Filters Based on 1/n Mode Short-Circuited Ring Patch in Through Glass Via Technology

This article proposes a breakthrough in millimeter-wave on-chip filter design through the development of short-circuited ring patch (SCRP) structures in through glass via (TGV) technology for 5G n257/n258 applications. The innovative 1/n mode SCRP, enabled by various angular segmentations of θ, achieves a compact footprint while maintaining the centrosymmetric electromagnetic (EM) field distribution. Hybrid EM coupling between 1/n mode SCRPs for the generation of transmission zeros (TZs) is adopted and systematically analyzed using an equivalent circuit model. A set of TGV-based filter prototypes with varying θ configurations and coupling topologies is synthesized, designed, taped out, and measured for proof-of-concept. The proposed 1/n mode SCRP filters exhibit insertion loss (IL) lower than 1.5 dB, return loss (RL) better than 15 dB, and a 20-dB out-of-band rejection range exceeding two times the resonant frequency. The consistency between measured and simulated results verifies the design approach, the feasibility and versatility of the TGV manufacturing process, demonstrating a scalable platform for millimeter-wavefront-end modules requiring high rejection and miniaturization.