Single-Chip Dual-Band Filters Based on Spurious-Free Dual-Resonance Sc0.15Al0.85N Laterally Coupled Alternating Thickness (LCAT) Mode Resonators

Single-chip dual-band radio-frequency (RF) MEMS filters, as well as their constituting dual-resonance modified laterally coupled alternating thickness (LCAT) mode resonators based on Sc0.15Al0.85N are demonstrated. The dependence of the resonant frequency ($f_{s}$), the effective coupling coefficient (${k^{2}}_{eff}$) and the quality factor ($Q_{a}$) of both modes on the electrode pitches of the modified LCAT mode resonators are analyzed, and measurement results show that ${k^{2}}_{eff}$ and $Q_{a}$ of both modes can achieve over 5% and 700, respectively, with optimized pitch. The dual-band filter is designed to consist of modified LCAT resonators with 2 different pitches to achieve the low band around 3.3 GHz and high band over 4 GHz on a single chip. The measured bandwidths of the dual-band filter are 66 MHz and 33 MHz, respectively. The performance of the dual-band filter indicates that the presented resonators and filters are promising for the carrier aggregation (CA) technology in 5G applications.