A wideband dual-polarized aperture array design is presented based on elements formed by a triangular configuration of octagonal rings. The octagonal ring elements are linked by capacitors and placed a defined distance from a groundplane. A broader frequency bandwidth has been achieved by placing a further layer of conductive rings above the element rings forming a metamaterial superstrate layer. Low dielectric constant material can be used to fill the space between the array rings and the groundplane, and between the elements and the superstrate layer. A dual-polarized finite ORA array has been fabricated and measured. The octagonal ring antenna array inherently exhibits a broad scan range with a stable cross polarization performance, however in practice the cross polarization depends on the feeding arrangements. Two feeding methods are discussed with a stripline feed showing best performance.

Propagation measurements using a large array are used to study the angle of arrival (AOA) across the ultrawideband (UWB) frequency range of 3.1 to 10.6 GHz. A two-dimensional Unitary ESPRIT algorithm is employed to give a high resolution estimation of AOA including both the azimuth and elevation angles of multipath components. The frequency dependence of AOA is investigated over the UWB frequency band. The multipath rays form clusters in both angular and temporal domains. Within a cluster the azimuth and elevation AOAs are determined to follow Laplacian and Gaussian distributions respectively. In the indoor environment considered, a typical cluster extends over an angular sector of approximately 14 degrees in azimuth and 9 degrees in elevation, with up to 5 clusters observed. We note that these propagation characteristics will allow UWB systems to utilise smart antennas or MIMO structures to improve overall throughput.

This article comprehensively reviews recent developments and research on deep learning-based (DL-based) techniques for integrated sensing and communication (ISAC) systems. ISAC, which combines sensing and communication functionalities, is regarded as a key enabler for 6G and beyond networks, as many emerging applications, such as vehicular networks and industrial robotics, necessitate both sensing and communication capabilities for effective operation. A unified platform that provides both functions can reduce hardware complexity, alleviate frequency spectrum congestion, and improve energy efficiency. However, integrating these functionalities on the same hardware requires highly optimized signal processing and system design, introducing significant computational complexity when relying on conventional iterative or optimization-based techniques. As an alternative to conventional techniques, DL-based techniques offer efficient and near-optimal solutions with reduced computational complexity. Hence, such techniques are well-suited for operating under limited computational resources and low latency requirements in real-time systems. DL-based techniques can swiftly and effectively yield near-optimal solutions for a wide range of sophisticated ISAC-related tasks, including waveform design, channel estimation, sensing signal processing, data demodulation, and interference mitigation. Therefore, motivated by these advantages, recent studies have proposed various DL-based approaches for ISAC system design. After briefly introducing DL architectures and ISAC fundamentals, this survey presents a comprehensive and categorized review of state-of-the-art DL-based techniques for ISAC, highlights their key advantages and major challenges, and outlines potential directions for future research.

A bunny ear shaped combline element for dual-polarized compact aperture arrays is presented which provides relatively low noise temperature and low level cross polarization over a wide bandwidth and wide scanning angles. The element is corrugated along the outer edges between the elements to control the complex mutual coupling at high scan angles. This produces nearly linear polarized waves in the principle planes and lower than -10 dB cross polarization in the intercardinal plane. To achieve a low noise temperature, only metal conductors are used, which also results in a low cost of manufacture. Dual linear polarization or circular polarization can be realized by adopting two different arrangements of the orthogonal elements. The performances for both mechanical arrangements are investigated. The robustness of the new design over the conventional Vivaldi-type antennas is highlighted.

Multi-user massive multiple-input-multiple-output (massive MIMO) will play a key role in future wireless communication networks. Since spatial channel diversity is the fundamental merit of this technique, high channel correlation may significantly restrict its abilities. This study investigates the impact of channel correlation on a prototyped massive MIMO network with the objective to identify an antenna array geometry which has reduced mutual coupling and channel correlation. To this end, a highly-efficient directional wideband single antenna element was designed for the antenna arrays and the user equipments (UEs). The designed array geometry is tested in an experimental indoor wideband massive MIMO setup. Important system parameters, such as channel correlation, power delay profile, and average received power from the UEs, are studied by analyzing the measured channel data. Furthermore, system-level simulations and network capacity calculations are performed based on the measured channel data to evaluate the performance of the prototyped antenna arrays. A regular array was also fabricated and used for benchmarking comparison. Moreover, a power control algorithm is introduced for the uplink, which was shown to improve the network capacity by up to 3 dB. The results demonstrate that the introduced antenna array outperforms the uniform antenna array in terms of mutual coupling and channel capacity.

The transition to clean and low-carbon energy is an irresistible trend globally that drives the scale of trade in the global LNG market to grow continuously. The paper reviews the global LNG trade in 2020 and forecasts the future LNG supply and demand. On this basis, the costs in segments of a LNG project are analysed from the perspective of the LNG industry chain. The feasibility of export from LNG projects and the preferred target markets are determined by calculating the economic index of projects. It is concluded that the possibility of future rebound in oil prices and the demand growth in the incremental market in emerging Asian countries are most likely to determine the capacity scales of new LNG projects around the world and contribute to a dynamic balance in the LNG market in the medium- and longterm. The costs in different segments of the LNG industry chain vary greatly with the availability of resources and markets. The economics of LNG export depend on the demand for LNG imports in end markets, the cost plus in different segments of the industrial chain, and the affordability of end consumers. Through the cost and economic analysis on typical LNG Projects, Qatar is found still the most economical and highly profitable country in the global LNG export market nowadays. Unsatisfactory economic performance is a common reason for delayed investments in many large LNG projects in Australia and other countries.