Compact, Copolarized, and High-Isolation Two-Port Patch Antenna for MIMO Applications

An effective decoupling structure is presented for compact, copolarized, and high-isolation two-port multiple-input-multiple-output (MIMO) patch antenna. The proposed decoupling structure is composed of chip capacitors and metallic vias, essentially behaving as an inductor-capacitor (LC) series band-stop filter. Specifically, the LC decoupling structure is periodically positioned along the center of the patch, effectively blocking the radiating current when it resonates with half of the patch. Furthermore, the proposed antenna can be treated as a pair of back-to-back TM1/2,0-mode printed inverted-F antennas with zero edge spacing but high isolation. As a validation of the concept, the measured results of a fabricated prototype consist well with the simulated ones, demonstrating good isolation better than 24 dB over the whole impedance bandwidth of 2.41-2.53 GHz. With a compact size of 0.26λ0× 0.25λ0 × 0.03λ0 (λ0 is the free-space wavelength at the center frequency), the peak isolation reaches 38 dB at 2.46 GHz. The proposed structure holds significant promise in MIMO antenna applications due to its merits of compact size, high isolation, and identical broadside radiation property.