A stacked multi-layer substrate integrated waveguide (SIW) microstrip patch antenna with broadband operating bandwidth and low cross-polarization radiation is provided. A complete study on the propagating element bandwidth and cross polarization level is presented to demonstrate the importance of the design. The proposed antenna includes three stacked printed circuit board (PCB) layers, including one layer for the radiating 2 × 2 rectangular patch elements and two SIW PCB layers for the feeding network. There are two common methods for excitation in cavity-backed patch antennas: probe feeding (PF) and aperture coupling (AC). PF can be used to increase the bandwidth of the antenna. Although this method increases the antenna’s bandwidth, it produces a strong cross-polarized field. The AC method can be used to suppress cross-polarized fields in microstrip patch antennas. As microstrip patch antennas are inherently narrowband, the AC method has little effect on their bandwidth. This paper proposes an antenna that is simultaneously fed by AC and PF. As a result of this innovation, the operating bandwidth of the antenna has increased, and cross-polarization has been reduced. Actually, the combination of probe feeding and aperture coupling schemes leads to achieving a broadband operating bandwidth. The arrangement of radiator elements and cavities implements a mirrored excitation technique while maintaining a low cross-polarization level. In both numerical and experimental solutions, a less than −30 dB cross-polarization level has been achieved for all of the main directions. A fractional impedance bandwidth of 29.8% (10.55–14.25 GHz) for ${\mathrm{S}}_{11}$ < −10-dB is measured for the proposed array. Simulated and measured results illustrate good agreement. Having features like low cost, light weight, compactness, broadband, integration capabilities, and low cross-polarization level makes the designed antenna suitable for remote-sensing and satellite applications.

Millions of passengers use high-speed trains (HSTs) daily, in the world. The roofs of HSTs can be equipped with a variety of transmitting and receiving antennas to accommodate high-data-rate Internet services with reliable radio access for passengers. The design of commercial antenna systems is a compromise between cost, size, manufacturability, and performance. This article proposes a new, compact, and low-cost two-port millimeter-wave diplexing directive end-fire antenna, which is designed, fabricated, and tested. The proposed antenna is made of a tapered slot antenna and a diplexing structure based on transitions in stacked printed circuit boards (PCBs). The ports of the antenna cover the frequency band 25.9–32.4 GHz (6.5 GHz) and 34.6–37.1 GHz (2.5 GHz). In all operating frequency bands, measured isolation between input ports exceeds 24 dB. Furthermore, symmetric directive end-fire radiation patterns are obtained experimentally, with low sidelobe level and low front-to-back ratio. All these features make the proposed diplexing antenna suitable for high-speed railway wireless networks.

In this study, an efficient model of the channel matrix is developed for a $2\times $ 2 wireless body area network multiple input output (WBAN-MIMO) system based on deep learning algorithms. The model is composed of three deep-learning algorithms. Moreover, the model simultaneously predicts channel matrix $H$ in an underground mine and identifies the position of the collected data in both line-of-sight (LoS) and non-line-of-sight (NLoS) scenarios. The model was trained and evaluated using the magnitude and phase of the collected data in an underground mine environment within a frequency range of 2.3 GHz – 2.5 GHz. These measurements, conducted with different antenna configurations in the LoS and NLoS scenarios, constitute an input to the model. The latest predicts the channel matrix ${H}$ with position and identifies whether the channel is a LoS or NLoS. Finally, the path loss and channel impulse response models were compared with measurement-based models. The modeled channel prediction exhibited a lower root mean square error (RMSE) for channel prediction and high classification accuracy for LoS-NLoS and position identification, respectively. The numerical results reveal that deep learning WBAN-MIMO modeling offers a powerful solution for future wireless systems in underground mine environments.

This paper proposes a robust approach for developing a new class of electrically reconfigurable phase shifter. This design employs via posts on SIW technology in conjunction with surface mount PIN diodes. To ensure optimal performance over the intended frequency band in a space-efficient manner, the transmission line is based on a substrate integrated waveguide (SIW) which offers superior low-loss properties. Additionally, PIN diodes are integrated into the SIW line using transverse coplanar waveguide (CPW) stubs. The efficiency of the proposed design method and the practicality of incorporating an innovative biasing circuit on a single layer without requiring additional wire bonding layers is demonstrated in the experimental prototypes outlined in this paper. This approach facilitates a scalable and modular device design. The principle of achieving such high-quality circuits is detailed and is also confirmed by experimental and theoretical results which are in good agreement up to at least 6 GHz, validating the design procedure and demonstrating that complex circuit functions can be achieved with relatively inexpensive compact structures. The proposed structure has potential applications in time-varying systems, communication receiving sections, and beamforming networks.

This letter proposes a bilayer transmissive Huygens metasurface with an independent phase response for two orthogonal polarizations to generate two distinct modes of Orbital Angular Momentum (OAM) beams. The performance of the proposed unit cell is comprehensively investigated, and its efficiency in the near field is verified through an analytical approach. Then, the necessary theories for realizing converged OAM beams by merging the lens and OAM phase distributions are inclusively elaborated. Moreover, a Dual-polarized Quad-ridged Open-ended Waveguide (DQOW) antenna is designed to illuminate the metasurface. Ultimately, two scenarios are explored through the designed surface. The first strategy generates the second ( $l_{x}=2$ ) and third ( $l_{y}=3$ ) modes of the OAM beams in the x- and y-polarizations, respectively, while the second strategy produces modes $l_{x}=0$ and $l_{y}=2$ in two orthogonal polarizations. It appears that the suggested configuration managed to obtain a respectable level of agreement between simulation and measurement results.

In this paper, the use of circularly polarized multiple-input-multiple-output (MIMO) antenna systems is proposed as a new solution for future body-to-body (B2B) applications. Four B2B channels have been characterized inside a mine. The statistical parameters of the B2B channels using co-positioned (CP) and 90 degrees rotated (90R) antennas have been determined. Path loss (PL) exponent values varied between 2.33 and 1.26. The time dispersion parameters and channel capacities are computed for both CP and 90R scenarios. Moreover, channel correlation matrices and the Rician K-factor have been determined and discussed in terms of their effect on capacity and Root mean Square (RMS) delay spread. Overall, the circularly polarized setup exhibits the best performance in terms of PL, RMS delay spread and channel capacity. The NLOS situation caused a significant drop in channel capacity due to the significant increase in PL, and an increase in the RMS delay spread due to the multipath richness. The MIMO-NLOS scenario exhibits the highest throughput gain of 1.752 (at an SNR of 20 dB), due to its low branch correlation. A model of the B2B impulse response has been created based on a statistical-empirical approach, to determine the optimal path amplitudes and time of arrival.