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This article proposes a planar monopole antenna with two frequency‐tunable bands for wireless devices used in the WiMAX system. The antenna has two radiating branches acting as monopoles and resonating at around 2.4 GHz (lower band) and 3.4 GHz (higher band). By using two varactors on the radiating branches with novel designs of DC‐biasing circuits, the two operating bands can be continuously tuned using the corresponding DC‐bias voltages. The lower band can be tuned to cover the frequency bands of 2.3–2.4 GHz and 2.5–2.69 GHz, and the higher band can cover the frequency bands of 3.3–3.4 GHz, 3.4–3.6 GHz, and 3.6–3.8 GHz for the WiMAX system. The antenna has a small overall size of 40 × 35 × 0.8 mm³ with a compact radiator of only 14.5 × 8.2 mm². The antenna performance in terms of tuning, reflection coefficient, radiation pattern, efficiency, and peak gain are studied using computer …