## 1 Introduction
Beyond spectrum-related challenges, several critical aspects of communication networks, including power efficiency, computational resources, thermal management, and device packaging, also require strategic advancements to support the next generation of wireless technologies. Furthermore, the currently separate mobile and satellite networks must be seamlessly integrated, unifying terrestrial and air-space domains with the support of emerging technologies such as high-altitude platform stations and drones [19]. This integration is expected to enhance both quality of service (QoS) and quality of experience (QoE), ensuring uninterrupted communication coverage even in the most remote areas of the world, including oceans, skies, and rural regions. The development of a 3D network will be instrumental in achieving this goal by interconnecting multiple nodes, such as mobile network towers, HAPS, and satellites, creating new possibilities for communication pathways and data rates. An example of a smart city utilizing 3D integrated networks is shown in Figure 1, where diverse devices can be interconnected to enable seamless communication across various environments. This survey provides a comprehensive review of recent advancements in radio frequency (RF) hardware technologies, with particular emphasis on the physical layer infrastructure required to support next generation wireless networks. Compared to conventional 5G and 6G surveys, which often focus on system-level architectures or protocol design, this work highlights the enabling role of core hardware components. Specifically, it investigates sub-terahertz and millimeter wave systems for ultra-high throughput, line-of-sight communications, the evolution of multiple-input multiple-output (MIMO) systems operating at high frequencies, developments in phased-array antenna architectures, and emerging techniques in energy harvesting and RF front-end reconfigurability. Special attention is also given to analog, digital, and hybrid beamforming architectures, which are key to improving spectrum utilization, especially in dense network environments. The survey further discusses how technologies like reconfigurable intelligent surfaces and adaptable hardware platforms can make wireless systems more flexible and energy efficient. By focusing on these critical physical layer advancements, this work aims to support future research and development in the design of scalable and high-performance wireless communication hardware. The content of this article is organized as follows. In Section 2, the main challenges at the physical layer of future wireless communication systems are discussed, including spectrum scarcity, propagation losses at mmWave and THz frequencies, and hardware limitations. In Section 3, a range of emerging technologies is presented, such as reconfigurable intelligent surfaces (RIS), massive MIMO, advanced beamforming techniques, wireless power transfer, and reconfigurable RF front-end systems, along with the role of digital twins in optimizing network performance. In Section 4, a comprehensive classification and analysis of antenna and antenna related technologies is provided, covering designs for user devices, centralized and distributed systems, and edge computing applications. Finally, conclusions are drawn in Section 6. Figure 1: Example of a 3D integrated network in the 6G era.