Fully Inkjet-Printed Dual-Mode Ring Bandpass Filter Using a Cross-Bridge Structure Embedded With a Metal–Insulator–Metal Capacitor

A fully inkjet-printed ring-resonator bandpass filter on a liquid crystal polymer was realized by using metal-insulator-metal (MIM) structures and via-hole interconnections. Two short stub feeding lines and a ring resonator were coupled using a cross-bridge structure embedded with an MIM capacitor to provide a high-selectivity passband, low insertion loss, and a more compact size. A stepped-impedance line was used as a perturbation to excite the dual mode of the ring resonator. Using the proposed method, a 29% fractional bandwidth was realized with four transmission zeros to improve the selectivity. In the passband, the minimal insertion loss and maximal return loss were -2.2 and -34.2 dB at 12.7 GHz, respectively. Fully inkjet-printed technology is recognized as a method of fabrication that results in a compact and low-cost 3-D integrated circuit package.