A high selectivity dual‐band bandpass filter using quadruple‐mode multi‐stub loaded ring resonator (SLRR)

Abstract

A high selectivity dual-band filter is proposed based on the quadruple-mode multi-stub loaded ring resonator. The ring resonator can utmostly avoid bending the electromagnetic wave. Two external open stubs are employed to generate four transmission poles where the odd-and even-mode is utilized to analyze the resonant frequencies of the BPF. The internal stub effectively reduces the insert loss (IL) by improving the external quality factor Q e of the second passband. In addition, five transmission zeros are generated due to the multipath and self-resonance modes to improve the out-of-band selectivity of the proposed filter. The proposed filter centered at 2.65 and 4.84 GHz is designed, fabricated and measured. The simulated results agree well with the measured results.

Compact quad‐channel diplexer design using dual‐band bandpass filters with multiple transmission zeros

“…As the key components in the quad‐channel diplexer design, many DB‐BPFs have been reported, but they still suffer from poor passband flatness or selectivity as in References 2, 12, 13. The DB‐BPF in Sun et al 14 has good selectivity but its stopband is too narrow. A very good selectivity has also been achieved in Deng et al, 15 but it has too high insertion loss.…”

Dual-Band and Wideband Bandpass Filters Using Coupled Lines and Tri-Stepped Impedance Stubs

“…Bandpass filters are mainly transmission line-based passive devices that are used in many RF/microwave circuits and wireless communication and radar systems. They are essential front-end components that can pass signals within a certain frequency range and reject unwanted out-of-band signals [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. There are many parameters to be considered in the design and implementation of a bandpass filter, such as the design structure, size, passband frequency bandwidth, insertion loss, selectivity, roll-off rate, isolation, and stopband rejection.…”

“…Many technical solutions have been proposed to increase the filter’s frequency bandwidth, including the adoption of multiple frequency bands (dual, triple, quadruple, etc.) [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. This type of filter is excellent for multiple frequency systems such as carrier aggregation or wireless local area network (WLAN) bands.…”

“…A DBBPF with a center frequency ratio of 1.15 was demonstrated using a stub-loaded resonator and two shorted lines coupled to a stub-loaded resonator in [ 7 ]. Apart from the above stub loading techniques, modified open/short-circuited stub-loaded resonators [ 8 ], quint-mode resonators [ 9 ], and ring resonators loaded with multi-stubs [ 10 ] have been employed to realize DBBPFs with good selectivity. Even though some of the DBBPFs based on the stub-loaded theory have a center frequency ratio of less than two, they have a narrow bandwidth.…”