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

Abstract

A 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

A broadband low profile microstrip filter-antenna with an omni-directional pattern

“…Details of the filterantenna design and the simulated results are given. The results show that the filter-antenna has broadband, low profile configuration, an omni-directional pattern and high suppression in the stopband [11].…”

“…Two square open-loop resonators and an impedance transformation line are printed on the circuit board. In this case, the design integrates filterantenna into the communication system circuit board [11]. The resonance characteristics of the antenna are adjusted by changing the impedance transformation line, then the antenna can be used as the filter last resonator.…”

“…This has been caused by the invention of many wireless products and services such as wireless local area network, mobile phone, etc [11]. Monopole antennas are attractive for present wireless communication systems because they can provide uniform radiation fields across all azimuth planes [2][3].…”

Compact Dual-Band Inverted-F Filtering Antenna Using Dual-Mode Resonators

“…Inspired by the mainstream design method for filtering antenna in [7][8][9] which replaces the last stage of the filter with a quarter-wavelength coupled line and a radiator, the last stage of the filter in Figure 2 is modified. This modification makes the second SLR act as a dual-band admittance inverter.…”

“…Several efforts have been made to replace the last stage of the filter with a radiator [7][8][9] without the need of extra circuit area. These works integrate the antennas and filters successfully which can realize good impedance matching and steep band-edge selectivity.…”