This paper proposes a compact zeroth-order resonant (ZOR) antenna with improved gain and efficiency. The proposed CRLH unit cell is based on the coplanar waveguide (CPW) structure. The proposed ZOR antenna is designed for a 2.45 GHz frequency band, and it has the characteristic of monopolar radiation. Shunt inductance is implemented by microstrip short-circuit stubs, and a metal-isolator-metal (MIM) capacitator provides series capacitance, where a large capacitance can be achieved in a small footprint. The proposed antenna comprises two interleaving composite right-/left-handed CRLH unit cells, where the size of one unit cell is measured at only 0.12λ0 x 0.098λ0. Because the field is loosely confined within the CPW-based unit cell, a good antenna peak gain of 2.03 dBi, and a radiation efficiency of over 68% is achieved when fabricated on a thin substrate. The proposed antenna did not require an additional matching network, reducing the total antenna footprint. This paper presents antenna parameters such as the return loss, radiation pattern, antenna gain, and radiation efficiency to validate the proposed design, which achieved good simulation results.
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