# A Miniaturized RHCP Slot Antenna for Wideband Applications Including Sub-6 GHz 5G
Such techniques could be integrated with the proposed wide-slot structure to achieve further performance enhancement while significantly reducing the antenna size [43; 44; 45]. Notably, metasurface-based CP antennas have emerged as a promising solution to achieve a wide bandwidth with compact geometries [46; 47]. Meanwhile, the integration of artificial intelligence and machine learning techniques has begun to influence antenna design, enabling data-driven optimization of CP performance metrics [48]. In recent years, numerous wideband CP antennas have been proposed utilizing techniques such as fractal geometries [49] and reconfigurable structures [50]. While these designs often achieve excellent performance, they typically involve complicated configurations, and they require external biasing circuits. In contrast, the antenna proposed in this study offers a simple and cost-effective solution while maintaining competitive performance within the targeted frequency band. The choice of wideband circular polarization ensures consistent performance across multiple potential operating bands within the sub-6 GHz spectrum, which is crucial for modern systems that require frequency agility and interoperability with different 5G and IoT standards. In addition, it offers significant advantages, especially in scenarios involving mobility, multipath environments, and polarization mismatch, such as user terminals or indoor to outdoor links. A multi-band antenna, for example, a tri-band antenna, would limit the operation to fixed frequencies, which is less flexible and might lead to poor performance in between bands. Therefore, a wideband circular polarization antenna can better address the dynamic requirements of sub-6 GHz 5G and related wireless applications, making it more suitable for current and future deployment scenarios. In 5G systems, the receiver plays a vital role in capturing and processing incoming radio frequency signals to extract the transmitted data. A typical 5G receiver architecture consists of a radio frequency front-end that performs signal filtering and low-noise amplification, and they are followed by a frequency down-conversion stage that shifts the RF signal to an intermediate frequency or directly to baseband. The key challenges for 5G receivers include supporting wide bandwidths, operating at high frequencies while maintaining a low noise figure, and achieving high energy efficiency. The performance of the receiving system is highly dependent on antenna characteristics such as the polarization, gain, and bandwidth, which directly affect the signal-capturing quality and system reliability in a dynamic wireless 5G environment. This paper presents a new and compact wide-slot antenna that is fed by a 50 \(\Omega\) microstrip feedline. By adding three strips to the tuning stub and modifying the slot of the ground plane by attaching a rectangular stub and parasitic patch, a wideband impedance BW and ARBW are obtained. For validation, the proposed antenna is fabricated, and its performance is assessed by a laboratorial test. The simulated and measured results show the good coverage of the antenna BW and a broadside ARBW along a wide range of frequencies that are applicable for various wireless communication applications. It is found that the measured \(-\)10 dB impedance BW is 78% (2.65 GHz, 2.08-4.73 GHz), while the broadside 3 dB ARBW is 71.6% along the range (2.31 GHz, 2.07-4.38 GHz). This work has been compared with other well-known wide-slot antennas, and the comparison shows that the proposed design makes a compromise between the size reduction and the gain value so that it is superior to the other designs.