Multiband slot-ring antenna with single- and dual-capacitive coupled patch for wireless local area network/worldwide interoperability for microwave access operation

A compact size slot-ring antenna design with a dual operating band that satisfies both wireless local area network and worldwide interoperability for microwave access operation is proposed. To achieve optimum impedance matching for both lower and upper operating bands, an inner circular radiating patch is capacitively coupled with the open end of a coplanar waveguide feed line, thereby demonstrating wideband characteristics from 1.97 to 4.25 GHz with a voltage standing wave ratio (VSWR) of 2:1 for the lower band, whereas the broad upper band which is excited owing to a pair of protruding stubs from the feed line can cover between 4.92 and 5.93 GHz. Further investigation on the method for a dual-capacitive coupled patch design is performed, whereby the inner circular patch is divided into two halves that are coupled with each other. The design process and initial characteristics of the two proposed antennas will be discussed in detail via simulated, and experimental results with satisfactory performance are observed within all bands of interest.