We propose a coupling-grounded patch antenna pair for sharing the same radiator with the high isolation performance, where the two feeding ports are connected through such shared radiator with very close distance of 0.1λ0. More specifically, two coupling pins grounded on the symmetry plane of the radiator are shown to be capable of tuning the common mode (CM) impedance to be the same as the differential mode (DM) impedance, thus a very high isolation of such patch antenna pair is obtained. Both simulation and measurement results demonstrate that the isolation of the patch antenna pair could be greatly improved from the original 3 dB to approximately 25-50 dB in the N79 band (4.8-4.9 GHz). Furthermore, the extension to four-port antennas is also investigated. The proposed patch antenna pair with less occupied area provides significant promising application values for the multiple-input multiple-output (MIMO) systems, especially for the sophisticated fifth-generation (5G) mobile terminals.

We propose a series of closely spaced self-multipath decoupled antenna pairs that is capable of realizing self-decoupling performance from a single band to four bands for 5G mobile terminals. Firstly, we propose a self-multipath counteraction method by building multiple coupling paths on the radiating branch of one of the antennas, where the coupling energy passing through the multiple coupling paths could be counteracted at the feeding ports. Based on this principle, two types of single-band self-multipath decoupled antenna pairs are constructed with the shorted-end and the open-end without using any additional decoupling structures. Then, a dual-band and wideband self-multipath decoupled antenna pair is designed by combining the multipath of such two types of single-band self-multipath decoupled antenna pairs. Finally, a four-band and wideband self-multipath decoupled antenna pair is constructed to further widen the decoupling bandwidth based on the dual-band self-multipath decoupled antenna pair. Both simulated and measured results show that the four-band antenna pair can be self-decoupled at four bands with the isolation more than 20 dB over entire N77, N78 and N79 bands, demonstrating excellent multi-band and wideband self-decoupling performance. The proposed self-multipath counteraction method, with the merits of simple antenna structure and wideband self-decoupling performance, should provide significant application values for the very compact and wideband multiple-input multiple-output systems.

We propose the metasurface-based cavities for splitting a linearly polarized (LP) electromagnetic wave into two symmetric circularly polarized (CP) beams with opposite helicities. More specifically, periodic strip slits and rectangular C-slits etched on substrate integrated waveguide cavities are shown to be capable of perfectly coupling the LP wave into the cavities from the strip slit array, and then releasing them with specific polarization directions according to the orientations of the C-slits. Such metasurface-based cavities with gradient oriented C-slit array would further create the opposite equivalent phase gradients for the right-hand and left-hand CP transmitting waves that are decomposed from the released LP wave with anomalous birefractions and polarization conversion simultaneously.

We propose a compactly placed high-isolated antenna pair through the decoupling of the transmission line for the application of mobile terminals. Especially, the transmission line, loaded with a decoupling branch and a phase-shift circuit, is employed to create two transmission paths, where the coupling powers through such two paths are capable of being counteracted perfectly. By adjusting the decoupling branch and the phase-shift circuit, the decoupling amplitude and phase could be controlled independently, thus realizing a very high isolation of such antenna pair. Both measured and simulated results show that the isolation of the antenna pair, with compact distance from 1/40λ ₀ to 1/8λ ₀ , is better than 25 dB in Wi-Fi 2.4G/Bluetooth band with a peak value of over than 40 dB. Furthermore, the decoupling technique is extended to multi-element and dual-band operations. Our proposed design, with independent control of decoupling amplitude and phase, should provide promising values for the application of multiple-input multiple-output and diversity systems.

We demonstrate the frequency scanning performances from a linearly tapered rectangular waveguide slot array antenna using the spatial angular filtering meta-surface. To be more specifics, the meta-surface at the narrow side of the waveguide is shown to be capable of releasing different wavelength energies when under the illuminations from different incident angles, while the tapered waveguide is proposed to mimic the oblique incidence and thus functions as the excitation of the antenna. Such frequency scanning radiations can also be extended for both orthogonally polarized electromagnetic fields when integrated with another polarization selective surface properly behind the meta-surface. Finally, we carry out the experiments to verify our proposed designs and demonstrate the excellent beam scanning performances when the frequency is changing.

We introduce a meta-surface cavity into the waveguide slot array design and demonstrate the perfect generation of dual-circularly polarized (CP) dual-beams, where the cavity consists of meta-surface coated dielectric substrate surrounded by metallic vias and metal walls. When integrated with the rectangular waveguide, the meta-surface cavity functions as the leaky wave passage, capable of coupling the linearly polarized incidence from the feed into the cavity and releasing the resonant mode with birefringent radiations of right-hand and left-hand CP waves. Our design, performing the beam splitting and polarization conversion simultaneously as a waveguide slot array, should pave the way for building up more advanced meta-surface-based architectures for the manipulations of electromagnetic fields in the transmission regime.