This technology implements a two-dimensional CRLH metamaterial zeroth-order resonant antenna by capacitively coupling a mushroom ring, grounded via a shorting pin, to the periphery of a standard circular or rectangular microstrip patch. The series capacitance in the gap between the patch and the ring, combined with the shunt inductance of the shorting pin, is designed to ensure that the electric field across the entire structure maintains a uniform phase.
Conventional mushroom-structure zeroth-order resonant antennas faced size limitations because they required multiple unit cells arranged in a row to achieve series capacitance through inter-cell spacing. Even when implemented as a single cell, design flexibility was restricted by the need for a separate gap between the feed line and the patch.
By simply adding a ring to an existing half-wave patch antenna, this technology induces both zeroth-order and negative-first-order resonances. The zeroth-order mode enables a low-profile, planar stacked version of a bulky monopole, while the negative-first-order mode reduces the antenna size. The multi-layer planar structure offers high manufacturing efficiency and improved gain compared to compact monopoles. It is suitable for internal antennas in mobile devices and IoT modules, ensuring omnidirectional monopole-like radiation even in devices with limited height.
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