Design of a Vertically Polarized Patch Antenna With Switchable Near-Endfire Beam Using Characteristic Mode Analysis

In this letter, a vertically polarized patch antenna with switchable endfire beam is proposed. The basic structure of the antenna is an array of three square patches where three shorting pins are vertically placed along the midlines of each one. The philosophy behind this is coupling two distinctive modes such that their respective radiation away from one end of antenna are doubled and are canceled out from the other. Here, characteristic mode analysis is given and has provided useful guidelines to the best choices of modes and optimal coupling from perspectives of gain and sidelobe level. With a compact size, the patch antenna can generate vertically polarized near-endfire pattern with gain up to 5.19 dBi and sidelobe levels (SLL) down to -15 dB around 2.17 GHz. Furthermore, the beam can be converted to its mirrored one as the single feed is switched between two symmetrical ports.