A wideband compact printed dipole antenna array with an element size of 0.16 λ ₀ × 0.34 λ ₀ is proposed for millimeter-wave (mmW) applications, particularly for 5G applications. The two patches of the dipole are printed on two different layers to achieve a wide bandwidth of 50% (24-40 GHz) for SWR < 2. Ground-signal-ground (GSG) transmission line construction with a height difference between the feeding via and the two shorting vias is employed to achieve a relatively symmetrical radiation pattern. An antenna array consisting of the proposed antenna and a 1 to 8 substrate-integrated coaxial line (SICL) feeding network is fabricated and measured. Simulations are also used to verify the beam scanning performance (up to ±50°). The proposed compact printed dipole antenna is a good contender for 5G mmW applications due to its wide band, compact size, and good beam scanning performance.

A multifunctional tri-band antenna combining transmitarray (TA) and reflectarray (RA) is presented in this communication. Five-layer patches etched on three dielectric substrates with two air gaps are used as the unit cell. Cross dipoles inserted in cross slots control transmission characteristics at Ku-band (14 GHz). Double square rings on the top and bottom layers control reflection characteristics at K (21 GHz) and Ka (30 GHz)-bands, respectively. The antenna has dual-polarized characteristics in each band. The phase shift range that can be obtained is 360° for 3 dB transmission magnitude at Ku-band and 0.15 dB reflection magnitude at K and Ka-bands. The tri-band dual-polarized TA/RA antenna is designed, manufactured, and measured to verify the performance. The simulated results keep consistent with the measured ones. The measured results show that the TA has a peak gain of 23.8 dBi with an aperture efficiency of 40% at 14.25 GHz and 1-dB gain bandwidth of 6.5%. The RA has a peak gain of 28 dBi with an aperture efficiency of 44% at 21 GHz and 1-dB gain bandwidth of 7.3%, and has a peak gain of 31.5 dBi with an aperture efficiency of 47% at 30.5 GHz and 1-dB gain bandwidth of 7.1%.

This letter presents a novel superstrate composed of multilayer metasurface (MM), which is characterized by wideband monostatic and bistatic radar cross section reduction (RCSR) for Fabry-Perot (FP) antenna with magnetoelectric (ME) dipole-fed. The proposed MM consists of four layers, the top three layers form a polarization-selective absorber (PSA), and the bottom layer is a polarization conversion metasurface (PCM). The copolarized incident waves are absorbed by the PSA, while the cross-polarized waves pass through with a low insertion loss. Then, it is reflected by the PCM with 90° polarization rotation and absorbed by the upper PSA. Additionally, the bottom layer of the PCM unit is an improved pattern instead of the ground plane. It is capable of polarization conversion and partial reflection. Therefore, the MM and ME dipole are respectively utilized as the partially reflecting surface (PRS) and the primary source to construct an FP antenna. Simulation and measurement results show that the bandwidth of monostatic RCSR is more than 80%. The FP antenna also achieves a high aperture efficiency of 51%, which is due to the benefit from the widebeam characteristics of the ME dipole.

In this letter, we propose a dual-circularly polarized reflect-transmit-array antenna (RTA) with independent beam control. It can transmit left-hand circularly polarized (LHCP) wave as transmitarray antenna and reflect right-hand circularly polarized (RHCP) wave as reflectarray antenna at 8.7–10.2 GHz. In addition, 360° phase shift for each circularly polarized wave can be achieved by rotating the top and bottom patches. A 20 × 20- unit cell RTA is designed, fabricated, and measured. For the LHCP radiation, the measured results show that the 3 dB gain bandwidth and axial ratio (AR) bandwidth are 13.7% (8.8–10.1 GHz) and 15.9% (8.7–10.2 GHz), respectively. For the RHCP radiation, the measured 3 dB gain bandwidth and AR bandwidth are 11.4% (9.1–10.2 GHz) and 12.6% (8.9–10.1 GHz). The peak aperture efficiencies for LHCP and RHCP radiations are 45.5% at 9.2 GHz and 41.8% at 9.6 GHz, respectively.

This communication presents a novel bifunctional metasurface (MS) combining the reflectarray (RA) and transmitarray (TA) with dual-band orthogonally polarized dual-beam characteristics. The proposed reflect-transmit-array (RTA) is capable of reflecting the $x$ -polarized incidence without changing its polarization state around 10 GHz while transmitting the $y$ -polarized incidence and converting it into the circularly polarized (CP) waves around 14 GHz. To completely cover the working frequency bands of both modes, an antipodal Vivaldi antenna (AVA) is introduced as the source feed due to its intrinsic ultrawideband characteristics. As a proof of concept demonstration, a prototype consisting of 20 $\times20$ elements is also designed, fabricated, and measured. We observe a good agreement between the measurement and simulation results that shows a peak gain of 26.2 dBi and 27.3 dBic, 1 dB gain bandwidth (BW) of 9.8–11.3 GHz (14.2%) and 12.8–14.2 GHz (10.4%), and peak aperture efficiency (AE) of 48.7% and 35.1% for the reflection and transmission modes, respectively.

A high-efficiency double-layer transmitarray (TA) operating at 14.25 GHz is proposed using low-loss dual-linearly polarized elements. Each element comprises only two layers of patches printed on a dielectric substrate and four vias. Cross dipoles and spiral dipoles with four L-shape patches are used as the first and second unit cells, respectively. L-shape patches are employed to increase the transmission magnitude. The phase shift range is 360° for a transmission magnitude of -1 dB. A square TA composed of 400 elements is designed, manufactured, and tested to verify the design. The simulated results are consistent with the experimental results. The experimental results show that the TA has a gain of 29.18 dBi at 14.25 GHz, an aperture efficiency of 60.3%, and a 1 dB gain bandwidth of 6.8%.