High Side Of Passband Research Articles

Co-design of low profile single-fed circularly polarized filtering antenna with high out-of-band rejection

A co-design of circularly polarized (CP) filtering antenna is proposed in this paper. The filtering antenna system consists of two λ/2 open-loop resonators which improve the selectivity of passband and a corner-truncated patch which works as both a radiating element and the last stage resonator of filtering network to form an extra minima/pole. Furthermore, an attenuation on the high side of passband is introduced through cross coupling between the first open-loop resonator and CP antenna. By vertically and seamlessly integrating the patch with open-loop resonators, a third-order filtering response is obtained while transition loss is removed. Additionally, the ground plane is shared by the patch and the filtering network to reduce size occupation. An antenna prototype has been fabricated and measured, good agreement is achieved between measurements and simulations. In conclusion, proposed antenna reaches a more compact structure due to multiple functions realized by the patch, a better frequency selectivity and high rejection due to the extra attenuation pole introduced through cross coupling between patch and the first resonator.

Quasi quarter SIW‐mode resonator and its application to sierpinski fractal filter design

ABSTRACTIn this letter, a new kind of quasi quarter SIW resonator (QQSIWR) using Sierpinski fractal defected structure is presented first. Comparing with SIW resonator, this novel resonator has lower resonant frequency (f0) and acceptable unloaded quality (Qu) value, while maintaining almost unchanged electromagnetic fields distributions. The frequency characteristics and Qu of this resonator is investigated under different fractal sizes. To validate the properties of QQSIWR, a miniature cross‐coupled bandpass filter (BPF) with a size reduction over 88% is proposed and optimized using Sierpinski fractal structure and cross coupling technology. It can produce asymmetrical frequency response by generating a transmission zero (TZ) on the high side of passband. A prototype of the filter is fabricated and measured, and the measured results are in good agreement well with the simulated ones. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1176–1179, 2016