Synthesis and Design of Highly Selective Multi-Mode Dual-Band Bandstop Filter

Abstract

This paper presents the synthesis and design of the multi-mode dual-band bandstop filter (MM-DBBSF). A highly selective multi-mode dual-band bandstop response is obtained using a quarter wavelength coupled line structure. It has been shown that by increasing the coupled line's order, the selectivity and the transmission zeros are increased in the desired stopband. Moreover, a step impedance resonator (SIR) is used between two coupled lines to achieve more transmission poles for better out of band selectivity. The paper show a detailed theoretical synthesis of the coupled line and SIR structure. In order to validate the theoretical model, ideal and microstrip topologies are designed and simulated. Furthermore, a high-frequency substrate is used to fabricate four prototypes. The simulated and measured results show good concurrence.

Broadband dual‐band bandstop filters based on step‐impedance stubs and transmission‐line networks

“…As shown in Figure 8, the ideal frequency responses of Filter B are simulated based on Equations ( 1), (2), and ( 9)- (16). Two TZs can be observed in each stopband, and nine TPs are shown in the passbands, with a return loss better than 18 dB in the passbands on both sides of the stopband, and better than 51 dB in the passband within the stopband.…”

“…More and more DBSFs have been proposed. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The filter proposed in Reference [1] adds a passband within the stopband to form a basic dual-band bandstop filter, but each stopband has only one transmission zero (TZ), and there are no extra transmission poles (TPs) next to the stopband to form sharp selectivity. And the 3-dB fractional bandwidths (FBWs) of the stopbands are very narrow.…”

“…They are very innovative, yet their 3-dB FBWs of the stopbands are too narrow as well. In order to improve the performance in all aspects, the filters proposed in References [14][15][16][17][18] show multiple TPs to form sharp selectivity and wide bandwidths of the stopbands, excellent passband, with deep stopband suppression. However, their structures are too complex in order to achieve dual-frequency, which is inconvenient for debugging and manufacturing.…”

“…The bandstop filter plays an important role in filtering noise and harmonics in front‐end RF devices, while the dual‐band bandstop filter (DBSF) can filter out more spurious signals more accurately with a smaller size. More and more DBSFs have been proposed 1‐18 1] adds a passband within the stopband to form a basic dual‐band bandstop filter, but each stopband has only one transmission zero (TZ), and there are no extra transmission poles (TPs) next to the stopband to form sharp selectivity.…”

Design and Implementation of Microwave Dual-Band Pass Interdigital Filter Using an Analytical Approach

“…Therefore, in order to incorporate two or more desired communication bands in a single hardware unit, or to reject unwanted interfering frequencies, multi band filters are needed. Multi-band filters are attracting more and more interest in modern microwave filters design [2]- [8].…”