Exploiting Hi-Lo Inter-Digital DGS for High-Order Microstrip Bandpass Filters
Journal
2016 IEEE 5th Asia-Pacific Conference on Antennas and Propagation (APCAP)
ISBN
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85015314381&doi=10.1109%2fAPCAP.2016.7843110&partnerID=40&md5=b49cf27b7ef82d1dd047a5529afd0a25
Date Issued
2016
Author(s)
Yihdar Chen
Abstract
With the fast developments of the new generation of communication systems and the limited spectrum, the needs of bandpass filters with sharp roll-off responses increase rapidly in recent years. In this research, we propose an inter-digital defected ground structure (DGS) for planar microstrip bandpass filters. The bottom ground plane of the microstrip line is composed of two rectangular opening slots and each of them contains a finger-like high-low (Hi-Lo) impedance strip. The high and low impedance strips represent an individual parallel resonator with different resonant frequencies. In other words, one Hi-LO impedance strip accounts for two parallel resonators. The two separated Hi-Lo impedance strips are coupled by a capacitive gap of the top microstrip line to form a fifth-order bandpass response. For a compact DGS, the order of the proposed bandpass filters can be increased easily by adding more Hi-Lo impedance strips in inter-digital arrangements. A prototype was implemented with a FR-4 substrate and fabricated with a standard PCB lithography. The dimensions of the fabricated device and the DGS were 0.18 λ by 0.04 λ and 0.04 λ by 0.03 λ, respectively. The measured frequency response was centered at 2.13GHz with a fractional bandwidth of 38.6% and the roll-off was 0.03 dB/Hz.
Type
conference paper