In this paper, a new self-decoupling method, namely weak-field-based decoupling technique, is proposed and validated based on inset-fed patch antenna arrays. The self-decoupling effect is realized by taking advantage of the inherent weak-field area created by the feeding structure and proposed inset-fed patch. By strategically arranging the array element in the weak-field area of the adjacent antenna element, the coupling strength between adjacent elements can be controlled under a very low level without the need of any additional decoupling circuitry or structures. A two-element patch antenna array was first developed and analyzed, achieving a peak isolation level of 61 dB. Afterwards, a fourelement linear patch antenna array was designed, fabricated and measured to further validate the proposed technique. With the distinct advantages of simple structure and effective isolation enhancement, the proposed self-decoupling method is very promising for MIMO applications.

In this article, a new low-profile decoupling structure originated from the phase shift concept for the patch antenna array is proposed. To clearly illustrate the operation principle, the phase of the signal transmitted from Patch 1 to Patch 2 has been initially studied and the decoupling condition for two closely spaced patch antennas in H-plane has also been obtained. Afterward, the decoupling element concisely composed of a half-wave microstrip line and a shorting pin is developed. Attributing to the introduction of additional signal path by the new decoupling structure, mutual coupling between two adjacent patches is effectively suppressed. To verify the feasibility of the proposed design scheme, demonstrators of two-element patch antennas with and without decoupling structure are, respectively, implemented and analyzed. Results indicate that compared with the coupled array, the isolation between two patch elements is enhanced from 7 to 18 dB at the center frequency of 3.16 GHz under the edge-to-edge separation of only 0.027 $\lambda _{0}$ . Besides, owing to the single layer layout, the profile of the whole antenna structure is as low as 0.02 $\lambda _{0}$ . Ultimately, the proposed decoupling scheme has been applied to the three-element counterpart, so as to demonstrate and validate its effeteness of isolation enhancement for multielement patch array.

This paper presents a patch and SIW cavity hybrid antenna with wide bandwidth and high-selectivity filtering response. The proposed antenna is a compact single layer structure with a height of 0.037 free-space wavelength and composed of one circular patch resonator, one square SIW cavity, and nine metallic pins. The circular patch is internally embedded in the square SIW cavity with a surrounded ring slot and the feeding probe is located in the SIW cavity. Here, the dominant resonant mode of the circular patch resonator (TM11) and first two modes of the SIW cavity (TE11 and TE21) are employed to achieve effective radiation from the ring slot under these three resonances. Among them, TM11 and TE21 both have broadside radiation performances and thus be used to achieve wide bandwidth, while TE11 is utilized to generate a radiation null in the lower stopband. Meanwhile, the mixed coupling occurs between these two distinct resonators can introduce another radiation null in the upper stopband. Besides, nine metallic pins can further enhance the frequency selectivity in the lower stopband. For demonstration, a prototype antenna is designed, fabricated, and measured. All the expected and simulated results have been satisfactorily confirmed in experiment.

A differentially driven dual-polarized high-gain stacked patch antenna is presented in this letter. Two-layer stacked patches are adopted to increase the impedance bandwidth of the antenna. Each of the two stacked patches is inserted with four shorting posts for enhancing the antenna gain. To validate the proposed design, a prototype was meticulously fabricated and tested. The simulated and measured results of the antenna show fractional impedance bandwidths of greater than 19% for differential reflection coefficients less than -10 dB and a high isolation level between the two polarizations (|S _dd21 | larger than 35 dB). The antenna gain of up to 11 dBi was also measured for the two ports. Furthermore, a good agreement of radiation patterns between simulation and measurement with the cross-polarization levels lower than -16 dB over the whole operating frequency band is achieved.

A low-cost 1 × 4 phased array incorporating continuously tunable substrate integrated waveguide (SIW) phase shifters is presented in this paper. Through seamless integration between antenna elements, phase shifters, and a SIW feeding network, the proposed phased array is assembled in a multilayered monolithic structure. To obtain a wide phase variation range, the electronically controllable phase shifter is constructed by introducing varactor diodes into a reflection-type architecture, which can also offer a simple solution to constitute the biasing circuit of the diodes. Due to the merits of adequate bandwidth and good radiation performance, an aperture-coupled patch antenna with multi-resonance characteristic is selected as the array element. Accordingly, a prototype of the proposed phased array was fabricated by applying standard printed circuit board (PCB) facilities. Measured results demonstrate that a continuous beam scanning range from -45° to 45° covering the whole operating band of 5.09-5.98 GHz is obtained. Meanwhile, a gain of up to 11 dBi and an impedance bandwidth of 16.1% are achieved. Owing to the features of continuous wide-angle steerable beam, easy fabrication and integration, the proposed phased-array antenna is attractive for 5G Wi-Fi applications.