Ultrawide Stopband, Low-Loss, and Miniaturized Low-Pass Filter Using SISL 3-D Inductor and Metasubstrate

In this article, a novel strategy is proposed to design an ultra-wide stopband, low-loss, and miniaturized low-pass filter (LPF) based on three-dimensional (3D) inductor and metasubstrate on substrate integrated suspended line (SISL) platform. In order to achieve miniaturization of LPF based on SISL technology, firstly, we designed a periodic bone-shaped metasubstrate with a high effective permittivity of larger than 10. Based on the metasubstrate structure, we can also significantly reduce the size of conventional capacitors. Then we designed a 3D inductor to achieve highQ-factor while also realizing a compact design of the inductor. Finally, to verify the effectiveness of our proposed concept and the design methods for miniaturizing capacitors and inductors, three LPFs with a cutoff frequency of 100 MHz are designed, containing the SISL LPF with 2D inductors without metasubstrate, the SISL 2D inductors and double-layer metasubstrates LPF, and the SISL 3D inductors and double-layer metasubstrates LPF. Compared with the SISL LPF with 2D inductors without metasubstrate, the SISL 2D inductors and double-layer metasubstrates LPF shows a size reduction of 84.4% due to the double-layer metasubstrates. Moreover, the proposed LPF designed on the SISL 3D inductors and double-layer metasubstrates using FR4 shows a compact size of 0.01 λg × 0.006 λg × 0.002 λg with a size reduction of 86.2% due to the designed double-layer metasubstrates and 3D inductors, stopband rejection better than 40 dB up to 14.2fc, and low loss of less than 0.15 dB with self-packaging advantage.