Based on the conventional design method of bandstop filter
, the design procedures of the proposed DBBSF are outlined as following:
By using Ansoft's commercial software high-frequency structure simulator (HFSS10), the properties of the proposed bandstop filter
have been simulated.
The photograph of the fabricated bandstop filter
(BSF) with multiple rejection zeros is shown in Figure 6(a), the open-end stub between the two spiral inductors is replaced by a step impedance resonator (SIR) for the consideration of compact size.
For bandstop filter
, the transmission zeros are also exhibited at the stop-band to improve selectivity.
Defected microstrip structure (DMS) can be created by etching patterned structure on the signal strip and has been widely used in the applications of microwave devices [16-22], especially for the compact bandstop filter
design due to its obvious stopband characteristic and slow-wave effect [19, 20].
A dual-band bandstop filter
is presented, as shown in Fig.
have been widely used in RF devices in several applications and technologies to prevent interferences with other applications and users since decades ago to nowadays [1-4].
Figure 3 shows the configuration of our dual-band bandstop filter
with center band frequencies at 1.8-2.8 GHz on alumina substrate with a relative dielectric constant of 9.5, loss tangent of 0.0004, and dielectric substrate thickness of 0.76 mm.
The structures of applying a defected ground plane to stub-type three-pole bandpass filters  or using quarter-wavelength shorted stubs inserting the bandstop filters
to substitute for redundant connecting lines  were proposed and demonstrated to provide widened bandwidth and stopband.
[16.] Cakir, G., "Design of a compact and wideband microstrip bandstop filter
," Microwave Opt.
The detail of the proposed wideband bandstop filter
is shown in Figure 2.
Inspired by [10-15], a novel Hilbert-shaped CELC (H-CELC) is proposed for a more compact sub-wavelength particle in Section 3, followed by a popularization of it in a bandstop filter