Miniaturized Dual-Polarized, High-Gain, and Wideband Dielectric Resonator Antenna for Low Band Massive MIMO Applications

A new dual-polarized compact crossed-notched dielectric resonator antenna (DRA) with high-gain and wideband perfor-mance is proposed for low-band massive multiple-input multiple-output (MIMO) applications at the 700 MHz band of 5G new radio (5G NR) technology. The DRA element consists of three dielectric layers with relatively high relative permittivity constants (ϵ_r1 = 15 for the bottom and top layers and ϵ_r2 = 23 for the middle one) for a compact antenna. Characteristic mode analysis (CMA) of a rectangular DRA reveals that two pairs of degenerate modes, namely M2/M3 and M4/M5, resonating at 0.4 and 0.6 GHz respectively can be used to achieve dual polarizations with a proper feeding strategy. By jointly reshaping the conventional DRA along with adding a notch into the middle dielectric layer, the two pairs of degenerate modes are merged to produce a broad bandwidth with a compact size of 0.2λ_max × 0.2λ_max (λ_max being the wavelength at low-frequency point). The measured results show an impedance bandwidth of 13.15% (710 MHz–810 MHz) and an isolation of less than −17 dB. Furthermore, the antenna exhibits a good radiation pattern over the working band with a high gain of 7 dB. Finally, the proposed element is tested in a massive MIMO system of 3 ×4. The results exhibit a wideband of 17.7% and high isolation of more than 12 dB along with a stable gain of 5 dBi within the operating band.