A Compact Wide Stopband and Wide Passband Bandpass Filter Fabricated Using an SIR Technique

The demand for modern multiband and wideband communication systems is increasing. Bandpass filter architecture is widely used, and its reorganization and innovation can produce a new wideband filter. In this paper, two low-impedance stepped impedance resonators (SIRs) are strongly coupled to form an equivalent capacitor. This paper also presents a circuit that can become an inductor, a capacitor, and an inductive series resonant wide stopband bandpass filter. The center frequency of the bandpass filter is 2.3 GHz. The wide stopband frequency of the band is as high as 8.05 GHz. The center frequency can be controlled by a low-impedance capacitor when the same SIR is used in a set of architectures. In this paper, the center frequency is controlled by a 4.1 GHz series-resonant wide-stopband bandpass filter that is connected to the lower half of the transmission line. The overall circuit function becomes a wideband bandpass filter. This wideband circuit can filter up and down for a 3-dB cutoff frequency ranging from 1.9 to 4.5 GHz. The filter bandwidth is 2.6 GHz. The center frequency is 3.2 GHz.