Compact Dual-band Microstrip Bandpass Filter Research Articles

Design of ultra compact dual-band bandpass filter using L-shaped resonator

A compact dual-band microstrip bandpass filter (BPF) is presented for application at the frequencies 2.4 and 5.84 GHz. The proposed main resonator consists of two L-shaped resonators. To improve the upper-stopband of the proposed filter, modified U-Shaped resonators are accepted. The operation mechanism of the filter is investigated based on proffered equivalent-circuit model and transformation function. The sketched dual-band BPF attends the insertion loss less than 0.1 and 0.4 dB Also the return loss is 26 and 28 dB at 2.4 and 5.84, respectively. This proffered filter structure is proper for Bluetooth and wireless local area networks and other wireless communication systems. An overall good agreement between measured and simulated results is observed.

COMPACT DUAL-BAND MICROSTRIP BPF WITH MULTIPLE TRANSMISSION ZEROS FOR WIDEBAND AND WLAN APPLICATIONS

In this letter, a novel compact dual-band microstrip bandpass filter (BPF) with multiple transmission zeros is proposed using the third-order interdigital structure and dual-mode short stub center-loaded resonator (DSLR) for wideband and WLAN applications. The high impedance feedline for the filter with the folded DSLR can function as the quarter-wavelength resonator (QWR) for the third-order interdigital filter. Meanwhile, the folded DSLR can be adopted without an evident increase of the size of the compact interdigital filter. Three transmission zeros between two passbands and in the lower- and upper-stopbands can be created due to the cross coupling between two high impedance feedlines as well as between the input and output, and the intrinsic characteristic of the DSLR. Further, two inverse QWR coupling short stubs with different size loaded in the 50 Ω feedlines can generate four transmission zeros to improve the isolation and deepen the stopband. Finally, a compact dual-band BPF prototype is designed, and good agreement can be obtained between measured and simulated results.

Compact dual-band microstrip bandpass filter without external feeds

A compact dual-band microstrip bandpass filter is proposed and designed to operate at 2.4 and 5.2GHz without needing any external impedance-matching block. The modified half-wavelength stepped-impedance resonator with sinuous configuration is constructed to simultaneously excite the dual resonances at these two specified frequencies with miniaturized overall size. The parallel-coupled microstrip line is properly characterized to minimize the return losses within both dual passbands. The optimized results exhibit the good dual-band filtering performances with return losses higher than 20dB as well being confirmed by experimentation with a fabricated filter circuit.