Ultracompact Effective Localized Surface Plasmonic Bandpass Filter for 5G Applications

In this article, we present a novel ultracompact plasmonic bandpass filter (BPF) based on a recently proposed concept of effective localized surface plasmons (ELSPs). By virtue of the insensitiveness of the ELSPs resonator's dipolar mode resonance frequency to the variations of its cross-sectional area and shape, we can significantly miniaturize the occupied area of the filter. Moreover, the unloaded quality factor of the ELSPs resonator can be flexibly tuned and adjusted to be much larger than that of conventional microstrip and substrate integrated waveguide (SIW) resonators. For demonstration, we design and implement two Sub-6G BPFs centered at 3.3 and 3.4 GHz with the size of only 0.006 and 0.021λ
₀
²
. The measured in-band insertion loss (IL) and fractional bandwidth are 0.8 dB and 5.6% for the third-order BPF, and 0.7 dB and 5.9% for the fourth-order BPF, respectively. Excellent agreements between the measured and simulated results verify our design. The proposed ELSPs BPFs pave the way to realize ultracompact and high-performance functional devices for fifth-generation (5G) applications.