In this letter, a triple-layer wideband transmitarray operating at 12 GHz is designed. The unit cell has three metal layers, which are etched on three dielectric substrates. On the top and bottom layers, cross slots are etched, while a double square ring is etched on the intermediate layer. The simulation is carried out by Ansys HFSS. The designed element generates nearly perfect parallel sets of phase curves over a large frequency range, so the wideband transmitarray can be realized. To validate the wideband characteristic, a 233-element transmitarray prototype is fabricated and tested. Its measured 1-dB gain bandwidth is 16.8% (11.5-13.6 GHz), and its measured maximum gain is 25.8 dBi at 12.4 GHz, leading to 46.5% aperture efficiency.

In this letter, a wideband high-efficiency 1-bit 16 × 16 reconfigurable reflectarray antenna (RRA) is proposed. First, a wideband and low loss 1-bit RRA element is designed. It consists of double-layer patches printed on two dielectric substrates, respectively, forming a multiresonant behavior to expand the bandwidth.Due to the relatively thin thickness of the double-layer dielectric substrate (0.05 λ ₀ ), the element has low reflection loss. Therefore, the high efficiency and wide bandwidth performances can be obtained simultaneously. The phase difference between the two states of the RRA element is stable within 180 ± 20° in the frequency range of 12.9–16.5 GHz. Based on the broadband RRA element, a 16 × 16 RRA was fabricated and measured. Tested results show that the proposed RRA achieves 22.5% of 1 dB gain bandwidth and 25% of maximum aperture efficiency.

A reflectarray for generating wideband circularly polarized (CP) orbital angular momentum (OAM) vortex wave in X band is proposed. First, a dual-linearly-polarized element consisting of two rhombus-shaped metal patches etched on two dielectric substrates is designed. The element has high isolations between two polarizations and preferable linear phase responses in wide frequency band. Then, the phase distribution of the reflectarray carrying the OAM vortex wave with mode l=1 is designed, and dimensions of the elements are determined by their reflective phases. The far-field radiation patterns and near-field phase distributions are simulated to verify the proposed design. Finally, prototype of a 313-element reflectarray with a linearly polarized (LP) Vivaldi feed, which converts an incident LP wave into a reflective CP wave, is fabricated and measured. The results of measurement indicate that the reflectarray can generate CP OAM vortex wave with mode l=1 in 9-11 GHz band (a fractional bandwidth of 20%). The reflectarray also achieves 20% 1-dB gain bandwidth, and its peak gain is 19.9 dB at 11 GHz. Except for a very narrow band (10.9-11.1 GHz), its measured 3-dB axial ratio (AR) bandwidth is about 40%.

A novel compact ring monopole antenna with double meander lines is proposed for wireless local area networks (WLAN) applications in IEEE 802.11b/g/a systems. The designed antenna, fed by a 50 Ω microstrip transmission line, is only 32 mm in height and 16 mm in width. By introducing a horizontal and a vertical branched strips to a closed rectangular strip ring, the proposed antenna can generate two separate impedance bandwidths. Prototypes of the proposed antenna have been constructed and tested. The obtained impedance bandwidths reach about 12% for the 2.4 GHz band and 45.3% for the 5 GHz band, which meet the required bandwidth specification of 2.4/5 GHz WLAN standard. Also, good radiation performance and antenna gain over the two frequency ranges have been obtained.

This communication presents a wideband high-efficiency circularly polarized (CP) folded reflectarray antenna (FRA) based on the CP selective surface (CPSS). The proposed CPFRA is comprised of a simple CPSS on the top layer, a wideband reflectarray plane on the bottom layer, and a wideband planar CP antenna as the primary source. First, the simple CPSS based on the traditional Pierrot structure is designed. The CPSS can reflect one CP wave, while it can transmit its orthogonal CP wave. Then, a subwavelength element is used to design the wideband reflectarray, and a wideband planar CP microstrip patch array is selected as the feed. According to the ray tracing principle, the distance between the upper CPSS and the bottom planar reflectarray is reduced to half of the distance between the planar reflectarray and the imaginary feed approximately. At last, we design a wideband high-efficiency CPFRA. Measured results of the fabricated prototype reveal that its maximum gain at 10 GHz is 27.8 dBic, its 3 dB gain bandwidth is 15%, its 3 dB axial-ratio (AR) bandwidth is 23%, and its maximum aperture efficiency is about 45.4%. Good broadband and low-profile characteristics make the proposed CPFRA have potential value in some wireless communication system.

In this letter, a broadband 1 bit reconfigurable transmitarray antenna (RTA) based on polarization rotation element is proposed. The transmitarray element is composed of two split circular rings connected by two narrow strips and sandwiched by two orthogonal polarizers. As phase shift and polarization conversion structure, the two patches are separated by the air layer, and the p-i-n diodes are soldered in the center of the narrow strips. The polarizer grids are used as dc bias lines to conduct p-i-n diodes. By controlling the p-i-n diodes in the on and off states, the polarization orientation of the wave emitted by the RTA element is changed. Then, the outgoing waves in the two states physically form a broadband 180° phase difference, which broadens the operating bandwidth of the RTA effectively. By utilizing the novel unit cell, a 16 × 16 elements RTA is designed, fabricated, and measured. The measured results show that the 3 dB and 1 dB gain bandwidths are 45% and 17%, respectively. The peak gain is 16.8 dBi with aperture efficiency of 18.4%. Furthermore, the proposed RTA has good beam scanning performance with 2-D scanning range of ±40°.