A Compact Triple-Fed High-Isolation SIW-Based Self-Triplexing Antenna

A novel and compact all planer-fed self-triplexing patch antenna is designed and demonstrated for triple-band operation simultaneously. The model is comprised of one substrate-integrated waveguide (SIW) cavity, three planar ports, and one modified I-shaped slot. The proposed antenna is designed in a simple three-step method to achieve improved self-triplexing property. In the first step, a rectangular slot is created and its position is altered to obtain initial isolation (>20 dB) between any two ports. Secondly, the same slot is modified to an I-shape, which creates three patches facing three different ports and radiates at three different frequencies (4.14, 6.1, and 8.32 GHz) with minimum isolations above 28.4 dB. In the third step, one input-port is off-centered to obtain port isolation tradeoff so that isolation between any two ports is better than 30.8 dB. Importantly, the proposed design also supports easy individual frequency tuning using single variable. For demonstration purpose, the antenna is fabricated and characterized. The proposed planar antenna is very simple, compact, and feasible for handheld microwave devices.