Abstract-In this paper, a compact and high isolation microstrip diplexer is designed for broadband and wireless local area network (WLAN) application, simultaneously. The bandpass filter (BPF) for broadband channel is formed by three-coupled-line structure and two short stubs with different size loaded in 50 Ω feed lines, and the BPF for WLAN channel consists of two coupling quarter-wavelength resonators (QWR) and one open stub loaded in short parallel-coupling feed structure. Multiple transmission zeros can be generated due to their intrinsic characteristics, so the broadband BPF with sharp skirt and wide upper-stopband performance and the WLAN BPF with sharp roll-off and lower-stopband characteristic can be realized. The tapped stub not only can generate new transmission zeros to deepen the stopband, but also can connect other BPF as an its part without deterioration of in-band performance. Hence, a compact microstrip diplexer combines of two BPFs without the extra junction matching network. The mutual loading effect approximately equivalent to a coupled QWR can also generate new transmission zero at the passband edge to improve the isolation. A microstrip diplexer with the 3 dB fractional bandwidths (FBW) of 80% for broadband channel and 5% for WLAN channel is designed and fabricated. Good agreement between the simulated and measured results is observed.
A novel microstrip diplexer with low insertion loss, high selectivity and isolation performance is proposed through the combination of two compact filters composed of short-circuit centred stepped impedance resonators and, a side-coupled shorted microstrip line, which are designed for GPS and UWB application, respectively. Due to the intrinsic characteristics and mutual loading effect of the two filters, multiple transmission zeros can be created to improve the out-ofband rejection and isolation of the diplexer. More compact size is obtained without an extra junction matching networks. Simulated results of the fabricated diplexer agree well with measured ones.
In this article, a novel tri‐band wideband microstrip bandpass filter (BPF) with compact size and high selectivity is proposed using three sets of resonators, that is, λ/4 resonators, short‐stub loaded resonator, and λ/2 resonators.Each of the resonators can not only separately generate one passband, but also mainly control the passband performance. Due to the extended feed lines, parasitic coupling and intrinsic characteristics of the resonators, multiple transmission zeros can be created to improve the selectivity. A tri‐band wideband microstrip BPF centered at 2.0, 3.6, and 5.5 GHz is designed, and the predicted results are confirmed experimentally. The size is only 0.156 × 0.303 λg in which λg is the guided wavelength at 2.0 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:258–261, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27334
A tri‐band microstrip bandpass filter (BPF) with compact size and high selectivity is presented by using the stub‐loaded resonator (SLR) and quarter‐wavelength stepped‐impedance resonator (SIR). The quarter‐wavelength SIR is designed for the first and third passband and the SLR mainly controls second passband performance, so three passband frequencies can be flexibly tuned. Because of the intrinsic characteristics of the resonators and source‐load coupling, multiple transmission zeros can be created to improve the selectivity. Finally, a tri‐band BPF prototype located at 0.98 GHz (FRID application), 3.6 GHz (Wimax application), and 5.8 GHz (WLAN application) is designed. Measurement results agree well with the full‐wave EM simulated results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:212–215, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27247
In this letter, a novel compact and high selectivity dual‐mode dual‐band microstrip bandpass filter (BPF) with quarter‐wavelength resonator and stub‐loaded resonator is proposed using extended feed lines.Either of the SIRs cannot only separately generate one passband but also mainly control the passband performance. Due to the extended feed lines, parasitic coupling and intrinsic characteristics of the resonators, multiple transmission zeros can be created to improve the selectivity. Meanwhile, the BPF can obtain compact size due to the folded resonators and feed lines. A dual‐mode dual‐band BPF with the fractional bandwidth 15.6 and 6.4% is designed and fabricated. The simulated and measured results show a better agreement and validate the proposed theory. The size is only 0.185λg × 0.130λg in which λgis the guided wavelength at the first passband center frequency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 2702:2705, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27211
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