We propose two types of ladder antennas, each having loops and rungs. The antennas are analyzed using the method of moments. First, a ladder antenna whose loops have stubs is investigated, and dual operation is demonstrated. Second, the other ladder antenna without stubs is analyzed. The analysis reveals that we can obtain circularly polarized radiation by shifting the loops with respect to the rungs. Finally, we design a circularly polarized array of ladder antennas without stubs, showing an enlarged-band dual operation that is twice as wide as that of an array of ladder antennas with stubs.
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