Wideband Dual-Mode Patch Antenna With Compact CPW Feeding Network for Pattern Diversity Application

A wideband microstrip patch antenna is proposed in this communication for pattern diversity application. Broadside and omnidirectional radiation patterns are generated by the odd and even modes of a single circular patch. A compact feeding network based on coplanar waveguide is designed to provide in-phase and out-of-phase excitations, which can excite the two modes in wide bandwidth. The size of the feeding network is only 35 × 14.5 mm². A prototype of the proposed antenna is fabricated and tested. The measured overlapped bandwidth (|S₁₁| <; -10 dB and |S₂₂| <; -10 dB) achieves 775 MHz (2.165-2.94 GHz) or 31% corresponding to the center frequency. The Port isolation is below -28 dB in the entire bandwidth.

I. Introduction

A microstrip patch antenna has been extensively applied in modern wireless communication and radar systems due to its merits of low fabrication cost, low profile, and easy integration with circuits [1]. But the bandwidth of the patch antenna is narrow, given its high -factor. The enhancement of bandwidth attracts considerable research interests because the demand for wide bandwidth grows rapidly. Increasing antenna profile is useful to decrease the -factor of patch. However, the feeding network needs to be carefully designed to excite the potential bandwidth as wide as possible. Complex feeding techniques, such as aperture coupling [2], [3], proximity probe coupling [4], [5], and meandering probe feeding [6], [7], have been well researched. But the size of these feeding networks is large. The complexity will further increase if balanced or multiple-Port feeding is required.