A compact dual-wideband bandpass filter using an asymmetrical resonator is presented. The proposed resonator consists of three uniform microstrip lines of different lengths, and provides not only three transmission poles but also two transmission zeros for each passband. Thus, the bandpass filter has wide bandwidths and sharp cutoff responses. Theory as well as experimential results are given to validate this design concept.
Abstract-This paper presents two full differential bandpass filters with small occupied areas. Both filters are designed with the same basic structure which consists of two double coupled resonators with magnetic coupling. The resonators are stacked up and have the advantage of high coupling efficiency, reducing the area. Nevertheless, in the basic structure, the insertion loss in the high stopband is above −10 dB and therefore does not meet the requirement for bandpass filter design. Thus, two solutions are introduced to form the proposed filters. The first one integrates the ground plane, while the second one makes the use of an extra transmission zero. With the help of these solutions, two types of full differential bandpass filters are implemented on an FR4 using the embedded passive device technology, with the additional purpose of being designed for SiP applications. The passband of the filters conforms to the WLAN IEEE 802.11a (5 GHz) standard. Most importantly, the occupied areas of the two proposed bandpass filters are only 6 mm × 6.7 mm and 6.6 mm × 8.3 mm respectively. Compared with previous research, area reductions of up to 98.05% and 97.76% can be achieved.
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