A multi-frequency circularly polarized metasurface antenna array based on quarter-mode substrate integrated waveguide for sub-6 applications

A miniaturized multi-frequency circularly polarized array is designed in this paper. The antenna array is composed of three independent sub-arrays employing modified quarter-mode substrate ntegrated aveguide (QMSIW) to achieve three circularly polarized frequency bands. By introducing strip-slot, the impedance bandwidth of the antenna array is broadened while the dimension is decreased by 75% to realize miniaturization. Meanwhile, metasurface causes the impedance bandwidth of the sub-array to be further enhanced. Moreover, the metal vias are employed in the antenna array design to further achieve miniaturization. The antenna array is manufactured and measured to verify the design. Both the measured and simulated results display that the array achieves the impedance bandwidths of 10%, 11.7%, and 14.8% and axial ratio bandwidths of 8.8%, 8.0%, and 8.5% at 2.5, 3.5, and 4.8 GHz, respectively. The gain is stable in the operating band within an uncertainty of 0.7 dBi. The whole dimension is 0.92λ×0.63λ×0.04λ, where λ₀ is the wavelength at the lowest resonant frequency. Furthermore, the simple structure and miniaturization provides great convenience in sub-6 applications.