A Low-Profile Dual-Band Coaperture Monopolar Antenna Based on Cross-Layer Folded Structure

A dual-band co-aperture monopolar antenna with a very low profile is investigated in this paper. A novel cross-layer folded structure is proposed to construct a single-band monopolar antenna in the lower band. It can provide enough space for another higher-band section to be integrated together without extra profile. Meanwhile, by adding a high frequency radiation element to the reserved space, a dual-band co-aperture antenna with independent frequency control is obtained. Moreover, by exciting TM₀₁ and TM₀₂ modes in both bands, the proposed antenna can achieve a relatively large impedance bandwidth of 10.9% in the lower band and 14.6% in the upper band with a thickness of 3.14 mm. Stable monopole-like radiation patterns are achieved within the two bands and the gains in the lower and upper bands are 5.2–5.8 and 3.7–5 dBi, respectively. Compared with other works, the proposed antenna features its low profile and independent band performance.