A novel microstrip resonator with broadband filtering and narrowband radiating functions

This letter proposes a novel microstrip resonator that can perform filtering and radiating functions simultaneously.The proposed structure consists of outer ring, inner ring, circular patch, and three ports. The operating frequencies ( f 1 and f 2 ) for a filter and an antenna are different. At the lower band, in which the center frequency is f 1 , the proposed structure represents the characteristics of a wideband bandpass filter that has three transmission poles in a passband. Also, the proposed structure is operated as a radiating element at f 2 . The measured isolation between the filter and the antenna is less than −25 dB over the entire impedance bandwidth for the filter and the antenna. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:940–943, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25884