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A compact microstrip dual-band bandpass filter with multiple transmission zeros is proposed. This filter is composed of input/output (I/O) coupling structure with source-load cross-coupling and two pairs of short-ended resonators resonating at 2.4 and 5.8 GHz, respectively. By proper arrangement of the I/O coupling structure with source-load cross-coupling, multiple transmission zeros are introduced. In this way, high selectivity of both passbands and good out-band rejection level better than 20 dB up to 9 GHz are achieved. Good agreement can be found between the full-wave electromagnetic simulations and measured results, which verifies the proposed design concept. [ABSTRACT FROM AUTHOR]

Two dual-band bandpass filters featuring flexible frequency choice and compact size are proposed using two kinds of resonators.One is based on two pairs of different dimensional slotted ground resonators; another is based on a pair of slotted ground resonators and a microstrip-stepped impedance resonator. Unlike traditional filters, the harmonics of slotted ground resonators forming the lower passband are tuned to higher frequencies; the resonators forming the lower and upper passband lie at the two sides of signal line, the two passbands can be adjusted to the desired values with expected bandwidth by changing the sizes of the resonators independently. The interactions between them are minor. The proposed filters do not need extra impedance matching network unlike traditional dual-band filters and with the ground plane efficiently used, they are more compact in structure. Both filters are optimized with jumping genes evolutionary algorithms for multiobjectives, such as low-insertion loss, suitable bandwidth, and good stopbands. Two optimized bandpass filters were also implemented. Simulation and measurement results are performed to verify their good characteristics. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26028 [ABSTRACT FROM AUTHOR]

A new dual-band bandpass filter featuring flexible frequency choice is proposed.It consists of two resonators out of the two sides of the signal line with different sizes forming two passbands with desired frequency responses and bandwidths. For the resonator forming the lower passband, a shunt resistor is added at the center to make the even mode responses disappear. A wide stopband is obtained between the fundamental and higher odd mode response. So when a smaller resonator is put in the other side of signal line to produce the upper passband, a flexible frequency ratio of two passband can be gotten. The proposed filter is fabricated and measured. Good agreements are obtained between the simulations and measurements. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26030 [ABSTRACT FROM AUTHOR]