A novel approach to suppress mutual coupling (MC) between two patch antennas is presented in this letter. A parasitic isolator, which is printed between the two patches, controls the polarization of the coupling field to reduce the antenna coupling. Furthermore, a defected ground structure is employed to suppress the cross-polarization (XP) level. There exists a tradeoff between the MC reduction and XP improvement in this approach. As an example, a two-element patch array with an optimized isolator is fabricated and measured. The measured results show that, at the resonant frequency, the achieved isolation enhancement and XP level are 19.6 dB and -13.2 dB, respectively.

A wide-angle scanning planar phased array with magnetic current elements is proposed. A pattern reconfigurable technique is used to design the element that enhances scanning gain and decreases the sidelobe level throughout the entire scanning range. The array is comprised of eight elements in a 2×4 arrangement with uniform spacing. The proposed phased array operates at 5.8 GHz and can scan with 3 dB beamwidth the entire upper ground elevation plane from -90° to +90° enabled by a two-step pattern reconfigurability mechanism consisting of: 1) coarse-angle scanning and 2) line-angle scanning. Significant outcomes also include the reduced sidelobe level (less than 7.8 dB) and the particularly small fluctuation (±0.75 dB) of the gain during scanning over a scanning range of 150° (from 75° to +75° in the elevation plane). With the absence of any structure above the ground level, the high efficiency, and the coverage of the entire upper half-space, this proposed antenna array is very attractive for a variety of phased array applications, particularly those that require a Hush-mounted structure.

A wide-angle scanning planar phased array with pattern-reconfigurable windmill-shaped loop elements has been designed. Each element has a four-port windmill-shaped structure over a high-impedance surface, and it can steer the main beam in four different space quadrants by exciting one port at a time. A 16-element planar (4 × 4) array is fabricated and measured to demonstrate the wide-angle scanning performance of the array. The results show that the fabricated array is able to scan its main beam up to 72° and supports a 3-dB scanning coverage up to 92° in each quadrant. In addition, input amplitudes and phases for the array are optimized with a hybrid particle swarm optimization algorithm to enhance the array scanning performance.

This letter presents a novel two-dimensional planar-phased array with wide-angle scanning performance. A parasitic pixel layer-based antenna is used as the array element. The antenna optimized with a multiobjective genetic algorithm has wide beamwidth in both xoz- and yoz-planes. A 64-element planar (8 × 8) array is fabricated and measured to validate its scanning performance. With the uniform and optimized inputs, respectively, applied to the high- and low-elevation areas, the measured results show that the phased array is able to scan its main beam from -75° to +75° in both xoz- and yoz-planes, and it supports 3-dB beam coverages from -85° to +85° in the xoz-plane and from -85° to +80° in the yoz-plane.

A novel linear phased array design for wide-angle scanning applications is presented in this letter. Eight patternreconfigurable antennas (PRAs), capable of switching their patterns from quasi-broadside to monopole-like radiation with the help of p-i-n diodes, are used as the basic elements. By combining the scans of the PRAs working at two symmetrical modes in two subspaces, the phased array is able to scan its beam from -81° to +81° in the E-plane with a gain fluctuation less than 3 dB. The proposed array is simulated, fabricated, and measured. The simulated and measured results show that the performance of the phased array is superior to that of the former designed arrays using PRAs due to its less reconfigurable modes, simpler biasing network, and wider beam-scanning coverage.

A method based on the microstrip patch mode and reconfiguration technique is analyzed, studied, and applied to wide-angle scanning phased arrays. First, a summative evaluation of microstrip patch modes available for wide-angle scanning or near endfire has been made. Second, to validate this new method, a multilayer microstrip patch element is established and its resonant modes TM01 and TM20 are excited. Third, a reconfigurable technique is used to reconfigure the above resonant modes and a wide joint 3-dB beam coverage is obtained. Fourth, a prototype of 1 × 4 uniform linear phased array with the above reconfigurable elements is proposed. The prototype operates at 5.8 GHz and its main-beam direction can scan from -75° to +75° in the elevation plane with a gain fluctuation less than ±1 dB. Finally, in order to reduce the sidelobe levels, a hybrid particle swarm optimization algorithm is used to optimize the excitation amplitudes and phases. The measured results show an excellent wide-angle scanning performance, which validates the effectiveness of the proposed method.