A Low-Profile Wideband Dual-Sense Circularly Polarized MIMO Antenna for mmWave Applications

A wide band, dual-sense circularly polarized (CP) mmWave multiple-input-multiple-outputs (MIMO) antenna with a low profile is presented in this letter by using a tapered microstrip line, parasitic/meta-surface elements, and shared defected ground plane. The electrical footprint of the four-port MIMO antenna is 1.63 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda \times$</tex-math></inline-formula> 1.63 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda \times$</tex-math></inline-formula> 0.04 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula>, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> is the free space wavelength at the lower operating frequency, and has a single-layered prototype manufactured on the Rogers 5880 substrate. The wide operating frequency bandwidth (17.5-40GHz) is achieved by the installation of a special meander line structure and tapered microstrip line. The isolation and axial ratio (AR) bandwidth are enhanced with the help of parasitic meta-surface elements and connected ground plane with circular shape defected ground structure. A good diversity performance with channel capacity loss <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\leq$</tex-math></inline-formula> 0.25, mean effective gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\leq$</tex-math></inline-formula> 1.05dB, envelope correlation coefficient (ECC) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\leq$</tex-math></inline-formula> 0.025, diversity gain value <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\geq$</tex-math></inline-formula> 9.99dB, and total active reflection coefficient (TARC) values lower than -10dB are achieved. The axial ratio (AR) covers 5G bands of 24GHz, 28GHz, and 31GHz.