An Extremely Small-Footprint Dual-Wideband Stacked Antenna Based on Quarter-Mode Substrate Integrated Waveguide

A dual-wideband quarter-mode substrate integrated waveguide (QMSIW) antenna, which has an extremely small footprint, is proposed in this letter. Unlike conventional stacked patch structures that hardly get band expansion at a profile lower than 0.02λ_L (λ_L refers to the vacuum wavelength at the lowest frequency), the proposed design achieves dual-wideband under a profile of just 0.019λ_L, based on a double-layer QMSIW and a specific coupling control method. The driven QMSIW and parasitic QMSIW each generate a quarter-TE₁₀₁ mode, forming the first band that can cover part of the N78 band (3.38 GHz to 3.60 GHz). Furthermore, the two QMSIWs also introduce two quarter-TE₃₀₁ modes, forming the second band that covers part of the N79 band (4.80 GHz to 5.00 GHz). The first and second bands use the right and left slots to regulate the coupling degree, respectively. These two frequency bands can meet the commercial needs of Chinese communication operators. To validate the principle and design method, a prototype was designed, fabricated, and measured. The proposed antenna exhibits a remarkably small footprint of 34.3 mm × 12.1 mm × 1.726 mm (0.386λ_L × 0.136λ_L × 0.019λ_L) and demonstrates an impedance matching bandwidth of 8.1% at 3.46 GHz and 4.9% at 4.87 GHz.