Abstract
In this letter, a compact wideband bandpass filter (BPF) with a wide stopband is proposed based on the substrate integrated defected ground structure (SIDGS) and folded stepped-impedance resonator (FSIR). Such a SIDGS resonator can not only allocate a specific resonance with compact size but also introduce the different harmonic positions compared with a traditional microstrip line resonator. Meanwhile, due to the discrepant harmonic positions of proposed SIDGS and FSIR, a wide stopband response can be achieved using a compact stacked-coupled scheme. To verify the mechanism, a miniaturized wideband BPF operating at 1.69 GHz (i.e., f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) is implemented and fabricated. A measured wide stopband up to 11.8 f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> with a 20-dB rejection level is achieved.
Highlights
W ITH the development of the modern wireless system, the demands for the wide-stopband bandpass filters (BPFs) are increasing for rejecting interference from other systems
To achieve the wide stopband response, the corrugated microstrip lines [1], predefined upper stopband characteristics [2], defected ground structures (DGSs) [3], and loaded triangular stub resonator [4] have been developed in BPF design
A compact wideband BPF with a wide stopband is proposed based on substrate integrated DGS (SIDGS) and folded stepped-impedance resonator (FSIR)
Summary
W ITH the development of the modern wireless system, the demands for the wide-stopband bandpass filters (BPFs) are increasing for rejecting interference from other systems. To implement wideband BPF with wide stopband response, the low-pass filter [5], electromagnetic bandgaps (EBG) [6], [7], dispersive coupling [8], spiral resonators [9], coupled line with stubs [10], [11], DGS [12], stepped-impedance resonator (SIR) [13]–[17], and coplanar waveguide (CPW) structure with loaded stubs [18] are introduced. The design of wideband BPF with merits of low insertion, wide upper stopband, and compact size remains a great challenge. A compact wideband BPF with a wide stopband is proposed based on substrate integrated DGS (SIDGS) and folded stepped-impedance resonator (FSIR). The measured results show that the BPF has the merits of low insertion loss, wide stopband with high rejection level, and compact size
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