A miniaturized and zeroth-order resonant composite right/left-handed (CRLH) antenna based on dual-arm spiral structure is presented. The proposed dual-arm spiral unit cell is able to implement and tailor the CRLH lumped elements easily in a compact fashion. Particularly, the gap coupling between the spiral arms contributes to the series capacitance and the metallic via-hole at the end of one arm results in the shunt inductance . The resonant frequency and thus the miniaturization factor can be

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... imply engineered by the spiral parameters that determine the corresponding circuit elements. The proposed CRLH antenna is composed of two unit cells, each of which occupies only at the operating frequency. From the experimental results, this compact antenna exhibits the dipole-like radiation patterns and has a peak gain of 0.53 dBi. The measured and simulated results are provided, and good agreement is achieved. Index Terms-Composite right/left-handed (CRLH), dual-arm spiral, miniaturization, small antenna.