Compact Microstrip Dual-Mode Dual-Band Bandpass Filters Using Stubs Loaded Coupled Line

Abstract

Abstract-This paper presents two novel dual-mode dual-band bandpass filters (BPFs) by using stubs loaded coupled line. The analytical equations of their transmission poles and transmission zeros are given by the classical even-/odd-mode method. Design rules for two dual-band BPFs are also given, which show the easily tuned passband frequency locations and in-band performance. As examples, two dualmode dual-band BPFs, dual-band filter A with central frequencies (CFs) at 3.5/6.8 GHz and −3 dB fractional bandwidth (FBW) of 14%/10%, while dual-band filter B with CFs at 2.4/6.8 GHz and −3 dB FBW of 43%/16% are designed, fabricated and measured. Good agreement can be observed between the simulations and measurements. These two filters exhibit simple design procedures, simple physical topology, low insertion losses, good return losses, high isolation and compact sizes.

Dual-Band Filter for Wimax and Wlan With Improved Upper Stop Band Performance

“…However, in this SIR configuration, designer does not have the flexibility of selecting the desired second resonant pass band. This is in contrast to coupled line resonator using multi-stub loaded resonator based dual band pass filter where designer has the choice to choose the desired first and second pass bands, but suffers from high insertion loss [2]. Another approach proposed in [9] uses defected ground structures (DGS) to achieve dual pass band filter characteristics.…”

“…In practice, dual-band filters are often employed in applications as mobile and satellite systems where application flexibility, size and weight are important constraint parameters [1][2][3]. Being one of the key components in communication systems, as the filters improve the performance and incorporate additional features, demand for dual band filters increases [1][2][3].…”

“…In particular, the commonly used approach is to use planar structures to achieve dual-band filter characteristics. The advantages of using planar dual-band filter structures are its small size, low weight and conformal nature [1][2][3]. Moreover, there are various methods such as meandering line and metamaterial geometry which have been reported to decrease the effective geometrical area [6,7].…”

“…Due to the demand for application flexibility and high date rate communication systems, lot of research is being done in the field of dual-band passive filters [1,2]. In practice, dual-band filters are often employed in applications as mobile and satellite systems where application flexibility, size and weight are important constraint parameters [1][2][3].…”

“…In [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19], several techniques relating to planar dual-band filter design have been proposed. In particular, the commonly used approach is to use planar structures to achieve dual-band filter characteristics.…”