Low‐cost microstrip filter antenna with a monopole‐like radiation pattern for RF front end

Abstract

AbstractA low‐cost microstrip filter antenna with a monopole‐like radiation pattern suitable to be embedded inside a RF front end of wireless communication systems is presented. The filter antenna comprises two square open‐loop resonators, a coupled line, and a microstrip antenna with an impedance transformation line. The microstrip antenna is excited by the coupled line, which is treated as the admittance inverter in filter design. The microstrip antenna performs as not only a radiator but also the last resonator of the bandpass filter. Therefore, the transmission loss between the filter and the antenna is reduced. The patch of the microstrip antenna is stacked above the system circuit board of the RF front end. In this case, the design can fully integrate the circuit board of the RF front end into an internal filter‐antenna solution. The design procedure of the filter antenna follows the circuit approach—synthesis of bandpass filters. The measured results show good agreement with the simulated ones. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1810–1814, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26932