A novel dual-band patch antenna operating at 28/38 GHz is proposed for multiple-input multiple-output (MIMO) communication systems in this paper. The antenna utilizes substrate integrated waveguide (SIW) transmission line as the feed by means of a coupling slot on the SIW. A square patch antenna functions as the radiator for 28 GHz. The inductive loading, which presents as a pair of shorting pins in this design, achieves the impedance matching for 28 GHz-band. Etched on the square patch, the proposed H-shaped slot makes the radiator to performance as an antenna containing two radiating arms and thus introduces another resonant frequency at 38 GHz. Directions of the surface current on the paired arms are identical and produce a reasonable radiation pattern for 38 GH-band. Simulated results declare that the antenna achieves an S 11 <; -10 dB bandwidth of 27.6 - 28.5 GHz (relative bandwidth of 3.2%) and 36.9 - 38.9 GHz (relative bandwidth of 5.3%), while simulated gain is 9.0 dBi at 28 GHz and 5.9 dBi at 38 GHz, respectively. Measured results have verified the feasibility and correctness of the proposed dualband antenna, which indicate that the antenna is a promising candidate for MIMO communication systems at millimeter-wave (mmW) band.

In this paper, a new class of shielded half-mode substrate integrated waveguide (SD-HMSIW) and shielded quarter-mode substrate integrated waveguide (SD-QMSIW) filtering power dividers (FPDs) have been presented. The proposed prototypes are capable of splitting/combining power and selecting frequency simultaneously. The SD-HMSIW and SD-QMSIW resonant cavities combine the features of compact size, high quality factor and low loss. To the best of author’s knowledge, it is the first time employing the shielded SIW structure for FPD designs. Six prototype circuits with pure or hybrid SD-HMSIW/SD-QMSIW resonators are designed and fabricated to validate the proposed concept. Multilayered structures are implemented to minimize the dimensions of the FPDs further. Transmission zeros distributing near the operating passband are introduced by cross coupling mechanism. Both measured and simulated results indicate that the proposed FPDs with shielded SIW structures exhibit not only filtering performance, but also good magnitude and phase imbalance characteristics in the operating frequency band.

In this letter, a metasurface (MS)-based multi-layer wideband circularly polarized (CP) 4 × 4 truncated corner patch antenna array is proposed for Q-band applications. The patch array consists of four 2 × 2 patch subarrays, a metasurface structure, and an H-shaped substrate integrated waveguide (SIW) power divider. Each 2 × 2 patch subarray acts as the CP radiating element, which is fed by a compact parallel-fed microstrip power divider using sequential rotation (SR) technology. The metasurface structure has 4 × 4 square plates covering over each patch to improve $\rm \vert S_{11}\vert$ , AR and gain performances. The antenna was fabricated and measured to verify the practical feasibility. -10-dB $\rm \vert S_{11}\vert$ bandwidth of 32% (37.4-52.2 GHz), 3-dB AR bandwidth of 25.8% (39.2-51.5 GHz), 3-dB gain bandwidth of 27.6% and the peak gain of 18.2 dBic are achieved in the vicinity of 45 GHz.

A wideband millimeter-wave (mmW) tapered slot antenna (TSA) array operating in the Q-band is reported, aiming at the upcoming fifth generation wireless communications. The antenna element is comprised by a TSA with two arrays of comb-shaped slits symmetrically cut on the edges of the two fins, respectively, which enables a degree of miniaturization for the radiator. Importantly, the geometrical structures of adjacent elements are flipped such that the fins of two neighboring TSAs are electrically connected. A miniaturized T-shaped eight-way power divider based on substrate integrated waveguide (SIW) technology is used to feed the linear array, where adjacent output channels are out-of-phase. In order to compensate the phase errors caused by the conventional compact T-shaped eight-way power divider, a well-tuned matching circuit composed of two consecutive inductive windows embedded inside the SIW are employed behind each TSA element, resulting in an enhanced gain and a low side lobe level over a wide bandwidth. A prototype of the proposed antenna is fabricated using standard printed circuit board process and characterized, showing a good agreement between measured results and simulation predictions. The fabricated antenna experimentally achieves an S11 < -10 dB bandwidth of 13.0% (38.97-44.45 GHz), within which the gain is higher than 13.4 dBi and the side lobe level is below -14.6 dB. Its directive end-fire radiation patterns and wideband operation make it a suitable candidate for various mmW wireless communication systems.

A novel cylindrical Luneburg lens operating at 26 GHz-band using hole drilling technology are reported, aiming at proper radiation patterns. The cylindrical Luneburg lens antenna converge microwaves in the plane perpendicular to the generatrix of the cylinder. An E-plane-focused cylindrical Luneburg lens antenna with the thickness of 20 mm and diameter of 88.2 mm is proposed for working at 26 GHz. Feed of the lens antenna is a conventional rectangular waveguide. Furthermore, in order to compensate the phase of the microwave in the non-converging plane (H-plane in this case), a pair of printed circuit boards (PCBs) etched with particular metal grids is attached to the side faces of the lens. With optimized design for the grids, a narrower beam is obtained in the H-plane while the side lobe level (SLL) of the cylindrical Luneburg lens could be drastically reduced compared with lens antenna without the special metal grids. Measured results of the fabricated lens antennas are in a good agreement with the simulation, proving its effectiveness and practicability that the designed grids benefit the radiation pattern performances. With an appropriate pattern for the H-plane achieved, proposed cylindrical Luneburg lens operating at millimeter-wave (mmW) band is a suitable candidate for multibeam communication systems.

In this paper, we propose TransConvNet, a hybrid model combining Convolutional Neural Networks (CNNs), self-attention mechanisms, and transfer learning for wireless signal recognition under challenging conditions. The model effectively addresses challenges such as low signal-to-noise ratio (SNR), low sampling rates, and limited labeled data. The CNN module extracts local features and suppresses noise, while the self-attention mechanism within the Transformer encoder captures long-range dependencies in the signal. To enhance performance with limited data, we incorporate transfer learning by leveraging pre-trained models, ensuring faster convergence and improved generalization. Extensive experiments were conducted on a six-class wireless signal dataset, downsampled to 1 MSPS to simulate real-world constraints. The proposed TransConvNet achieved 92.1% accuracy, outperforming baseline models such as LSTM, CNN, and RNN across multiple evaluation metrics, including RMSE and $R^2$. The model demonstrated strong robustness under varying SNR conditions and exhibited superior discriminative ability, as confirmed by Precision–Recall and ROC curves. These results validate the effectiveness and robustness of the TransConvNet model for wireless signal recognition, particularly in resource-constrained and noisy environments.