A wide-beam antenna and a planar phased array with wide-angle scanning performance based on image theory are proposed. To solve the wide-angle scanning problem, a summative evaluation of basic types of carrier-based antennas is given and the antenna types available for wide-angle scanning arrays or end-fire arrays are pointed out. Afterward, a wide-angle scanning array with an artificial magnetic conductor (AMC) ground is proposed. The main beam direction of the array can scan from -89° to 90° in the H-plane with a gain fluctuation less than 3 dB and the scanning 3-dB beamwidth can cover a range from -105° to 105°. An excellent wide-angle scanning performance from the broadside direction to the end-fire direction can be obtained by the proposed method, which can be used to guide the design of wide-angle scanning arrays.

In order to extend the scanning range of a phased array and maintain the scanning gain flatness, a novel millimeter-wave phased array with four linearly-arranged pattern reconfigurable elements is presented in this communication. The phased array has been designed, fabricated, measured and analyzed. The active patterns of each reconfigurable element are measured at different reconfigurable modes and the pattern scanning performance of the phased array is synthesized by using these active patterns. Furthermore, a genetic algorithm is used to lower the level of side lobes of the proposed phased array. The results show that the phased array can scan its main lobe from -75° to +75° in the elevation plane with a gain fluctuation less than 3 dB.

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.

This communication presents a novel compact broadband circularly polarized (CP) implantable patch antenna for biomedical applications in 2.4 GHz Industrial, Scientific, and Medical (ISM) band. By employing slots on the patch plane and shorting method, the whole size (including the superstrate) of the designed antenna can be enormously reduced to 9.8×9.8×1.27 mm3, which is equivalent to 0.0784λ0 × 0.0784λ0 × 0.0102λ0 (λ0 is the free-space wavelength at 2.4 GHz). Under the premise of keeping a slotless ground, not only a good size-reduction is realized, but also the impedance bandwidth and the axial ratio (AR) bandwidth are greatly improved. A simulated -10 dB impedance bandwidth of 21.5% with a 3 dB AR bandwidth of 15.8% is acquired in a skin phantom. The antenna also exhibits good robustness to different thicknesses of biocompatible coating. The influence of different body phantoms is discussed to evaluate the sensitivity of the proposed antenna. The experiments are carried out in both skin-mimicking gel and pork, and the respective measured impedance bandwidths are 25.9% and 25.7%. The CP purity is experimentally validated by comparing the communication link levels in two orthogonal polarization directions. The maximum specific absorption rate (SAR) value satisfies the IEEE standard safety guidelines.

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.

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.