A Miniaturized Differentially Fed Patch Antenna Based on Capacitive Slots

This letter presents a novel miniaturized differentially fed patch antenna. The antenna works in half-mode by loading shorting pins on one edge of the patch. Two shorted patches are separated by a slot with an interdigital structure and differentially fed by two probes on the opposite sides. Both the two feed probes are close to the short-circuit edge of the patch. Two parasitic shorted strips with pins are placed near the other two opposite sides of two patches for miniaturizing the antenna size. The odd–even mode theory is used to investigate the miniaturization mechanism of the capacitive slot and guide the design. In addition, the slow-wave effect of the interdigital structure can further miniaturize the antenna size. The simulated results show that the electrical size of the antenna is only 0.094 × 0.094 × 0.012 ${\rm{\lambda }}_{0}^{3}$ , which has about a 90.6% size reduction with respect to the conventional square patch antenna. An antenna at S-band is fabricated and measured to verify the feasibility of the design, which is suitable for narrowband Internet of Things applications.