In this work, a new dual-band dual-polarized transmitarray antenna element based on multilayer frequency selective surfaces is introduced. This novel configuration has been successfully tested for K/Ka SatCom frequency bands and is composed of a single low-profile printed circuit board incorporating 5 metal layers without any vertical transitional elements. In contrast to existing solutions, this proposal eliminates the need for vertical interconnections, air gaps, or spacers between the metal layers, resulting in a cost-effective board with an overall thickness of 0.24λ ₀ at 30 GHz. The proposed unit cell operates at 20 and 30 GHz exploiting an interleaved lattice configuration. It affords independent control of the transmitted field phase within a range of 300 degrees, at both frequency bands, while maintaining a transmission loss not exceeding 3.5 dB. To substantiate the proposed design, an 87×87mm ² transmitarray has been prototyped and experimentally validated. The measured results indicate a peak gain of 20.6 and 22.8 dBi at 20 and 30 GHz, respectively. Furthermore, the -1dB gain bandwidth has been found to be 5% in the first band and 4.5% in the second band.

The application of radar technology in indoor people monitoring has opened up new avenues, such as localization and tracking, vital signs monitoring, and fall detection. Nevertheless, one of the significant challenges facing radar systems is the issue of indoor multipath propagation, which results in radar ghosts that can diminish the detection accuracy or even compromise the monitoring process entirely. This study delves into the utilization of reconfigurable intelligent surfaces (RISs) in radar-based indoor people localization. Thanks to the use of RIS, targets can be tracked from multiple orientations, achieving a more precise estimation of the propagation channel and in turn mitigating the effects of indoor multipath propagation. As a result, the detection performance of the radar system can be improved without increasing the radar's complexity. Empirical evidence gathered from experiments conducted in a laboratory environment has demonstrated the feasibility of the proposed approach in accurately locating multiple subjects in a two-dimensional (2-D) space while being able to reject radar ghosts. Practical implications of this novel approach include the development of smart building systems, Internet of Things (IoT), telemedicine, Hospital 4.0, automated nurse call solutions, ambient assisted living, firefighter tracking, and security applications.

This letter introduces a new design for a 2-D electronically steerable parasitic array radiator (ESPAR) based on a 3×3 microstrip patch array. The proposed configuration enables conical beam steering by using nine radiating elements, one active U-slot patch antenna and eight parasitic elements. To validate the proposed design, a prototype was manufactured and experimentally validated. The reported results show a continuous steering range of 75 degrees on E-plane (ϕ = 0°), ranging from -45° to +30°, 74 degrees on H-plane (ϕ = 90°) from -37° to +37°, and 60 degrees on D-plane (ϕ = 51°), from -36° to +25°. The operational bandwidth is about 1.8 %, including the band reduction due to beam scanning. The measured aperture efficiency is equal to 38% with a maximum gain of 8.2 dB.

A quad-band linear-to-circular polarization converter with low insertion loss is presented for satellite communication (Satcom) applications. Addressing the well-known challenges in designing metasurfaces capable of multi-band operation, a generalized circuit-based synthesis approach, based on classical filter theory, is proposed. The method enables the design of N-band polarization converters by implementing a pair of second-order band-stop frequency-selective surface (FSS) filters for each band. Cascading multiple such layers yields the desired multi-band response. Equivalent circuit parameters are derived from high-level system specifications, such as target center frequencies, and are then mapped to physical dimensions. Full-wave simulations and experimental measurements confirm that the proposed converter achieves polarization conversion across both uplink and downlink sub-bands of the Ku and Ka bands, with right-hand and left-hand circular polarizations (RHCP and LHCP), respectively. These results are achieved while maintaining low levels of insertion loss across all operating bands.

This letter presents a wideband substrate-integrated waveguide (SIW) crossover employing back-to-back SIW-to-grounded coplanar waveguide (GCPW) transitions. The design is based on a spatially confined CPW-like mode at the intersection of orthogonal paths to minimize cross-coupling. A scalable topology is demonstrated, allowing architecture to support multiple crossing paths (e.g., 1×1, 1×3, 2×2) without degrading bandwidth. Experimental results for a $1 \times 1$ prototype demonstrate an 83% fractional bandwidth (6.7–16.9GHz) with isolation>25dB and return loss >12dB. A comparative analysis confirms the design achieves a superior figure of merit (FoM) in terms of bandwidth, isolation, and loss relative to the state of the art.

A packaged transmit array (TA) antenna is designed for automotive radar applications operating at 77 GHz. The compact dimensions of the proposed configuration make it compatible with standard quad flat no-lead package (QFN) technology. The TA placed inside the package cover is used to focus the field radiated by a feed placed in the same package. The unit cell of the array is composed of two pairs of stacked patches separated by a central ground plane. A planar patch antenna surrounded by a mushroom-type EBG (Electromagnetic Band Gap) structure is used as the primary feed. An analytical approach is employed to evaluate the primary parameters of the suggested TA, including its directivity, gain and spillover efficiency. The final design has been refined using comprehensive full-wave simulations. The simulated gain is 14.2 dBi at 77 GHz, with a half-power beamwidth of 22°. This proposed setup is a strong contender for highly integrated mid-gain applications in the automotive sector.