Dual‐band bandpass filter using two simple coupled microstrip rings

Abstract

A new dual‐band bandpass filter (BPF) using two very simple coupled microstrip rings is proposed in this paper. The two identical 3λg/2 microstrip rings are coupled each other with λg/2 coupled length, resulting in the generation of dual frequency bands with multiple transmission zeros (TZs). Theoretical deduction is presented to verify the proposed structure. The center frequencies and bandwidths of the two passbands can be tuned by controlling the impedance parameters of the microstrip rings. For demonstration, a prototype example of this dual‐band BPF is fabricated and characterized. The measured results show that it has high selectivity and great return losses of passbands with multiple TZs at the stopband.

A low-cost dual bandpass planar filter for WiMAX and mobile communications

“…Band pass filters are used in a wide range of wireless communication systems, particularly microwave systems with limited space for microwave components and circuits [19]− [23]. The following requirements must be met by this type of filter in order to work with contemporary communication systems: insertion loss reduction in the band, high selectivity, size compactness, and harmonics suppression [24]− [26].…”

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.…”

“…Compact DBBPF topologies can be obtained by using a modified SIR [ 11 ] or stepped impedance loaded by stubs [ 12 ]. Another approach for obtaining DBBPFs is by the use of coupled lines [ 13 ], or by using coupled microstrip rings [ 14 ] or parallel-coupled SIR-based dual-band bandpass filters [ 15 ]. Other techniques include broadside-coupled-based DBBPF [ 16 ] or signal interference/interaction techniques [ 17 , 18 ].…”