Abstract
A dual-wideband bandpass filter is proposed and analyzed, which is based on loaded open-/short-circuited stubs. The dual-band filter consists of a second-order bandpass filter and a third-order bandpass filter, which can be designed separately. The bandwidth of two passbands can be adjusted by tuning the impedance and the length of the stubs. A dual-band bandpass filter prototype operating at 2.4/5.2 GHz is designed for demonstration. It shows a low insertion loss of 0.3 dB and wide bandwidth of 51.9% at 2.4 GHz and 23.3% at 5.2 GHz. The filter structure is simple without narrow coupling gap between resonators, which is easy for fabrication.
Highlights
As an indispensable part of the communication systems, microwave filter shoulders the important mission of frequency selection and has been widely used in military and civil fields
With the rapid development of modern wireless communication system, frequency spectrum resource is becoming more and more crowded, and singleband bandpass filters can not satisfy the demands of precise spectrum division, so multi-band bandpass filters are increasingly becoming a hot spot of scientific researches and explorations
The most direct way to design a dual-band bandpass filter is combining two single-band filters with different passbands [4], while it suffers from large size
Summary
As an indispensable part of the communication systems, microwave filter shoulders the important mission of frequency selection and has been widely used in military and civil fields. A method to design a selectivity-enhanced SIR dual-band bandpass filter with two open-circuited stubs added at one node of the port coupled-line stages is illustrated in [12]. In [13], a dual-band differential bandpass filter is designed by coupling two identical stepped impedance square RLRs and its frequency selectivity is improved by utilizing a sourceloaded coupling structure. Weng et al [14] used a stepped impedance RLR to design a dual-band bandpass filter with a narrow first passband and a wide second passband and tapped rectangular stub loaded resonators on the input and output ports to obtain a wide stopband. Wang et al [18] used bridged-T coils to replace transmission line sections to design reduced-size dual-band bandpass filters with wide bandwidths. The simulated results show that the 3-dB bandwidths of the filter are 1.742.96 GHz at 2.4 GHz and 4.63-5.85 GHz at 5.2 GHz, which is confirmed powerfully by the measured results
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