## 1 Introduction  
The development of fifth-generation (5G) wireless communication systems demands antennas that are compact and high-gain and capable of operating at millimeter-wave frequencies, particularly in the 28 GHz band. As global mobile data traffic continues to increase exponentially, 5G networks are required to deliver enhanced data rates, reduced latency, and reliable connectivity across dense urban locations. To meet these demands,the mm-wave spectrum offers significant bandwidth potential but also introduces new challenges in terms of propagation loss, antenna gain, and integration. In this context, microstrip patch antenna arrays have emerged as a promising solution due to their low profile, ease of fabrication, and compatibility with planar circuit integration. However, designing antennas that simultaneously achieve high gain and broad bandwidth in a compact form factor remains a significant challenge. This study proposes a compact 1 \(\times\) 6 linear series-fed microstrip patch antenna array optimized for 28 GHz operation. The design offers wide impedance bandwidth, high directional gain, and desirable radiation characteristics while also addressing critical performance factors such as impedance matching, beam shaping, and cross-polarization suppression. Its simple, single-layer structure makes it a strong candidate for integration into 5G base stations and user equipment. Recent studies have explored a variety of techniques to enhance mm-wave antenna performance, including array miniaturization, substrate optimization, feed network improvements, and beamforming strategies. For instance, [PERSON] et al. [1] achieved an 8.9 dBi gain using a multilayered patch array structure, but their approach involved complex layer alignment and fabrication procedures, increasing production time and cost. [PERSON] and [PERSON] [2] demonstrated a compact planar phased array capable of electronic beam steering; however, their design suffered from significant gain degradation beyond \(\pm\)45\({}^{\circ}\) scan angles. [PERSON] et al. [3] introduced a high-gain (10.2 dBi) corporate-fed array, but the system required a large footprint and intricate feed network, limiting its practicality for compact deployments. [PERSON] and [PERSON] [4] utilized slotting techniques to enhance bandwidth but experienced modest reductions in gain. In contrast, the proposed array provides a balanced trade-off between gain, compactness, and design simplicity. Compared to multilayer phased arrays, the single-layer implementation on a Rogers RO3003 substrate reduces fabrication complexity by approximately 30-40%, enabling faster prototyping and lowering manufacturing costs. Table 1 presents a detailed comparison of the proposed design with existing state-of-the-art mm-wave antenna arrays. Recent advancements in 5G communication technologies have necessitated the development of high-performance antenna arrays operating at millimeter-wave (mm-wave) frequencies, especially in the 28 GHz band. The literature presents diverse approaches to achieving compact form factors, high gain, broad bandwidth, and beam steering, which are essential for 5G wireless systems. Several studies have proposed compact microstrip antenna arrays for 5G. [PERSON], [PERSON] [5] introduced a 2 \(\times\) 2 patch antenna array with a gain of 10 dBi, fabricated on a high-frequency substrate and optimized for low mutual coupling and high isolation, showing its suitability for mobile terminals in dense environments. [PERSON], [PERSON]. [6] presented a wide-beam scanning patch antenna for 28 GHz, featuring a highly integrated design with compact structure and beam-switching capability, achieving over \(\pm\)40\({}^{\circ}\) beam coverage. [PERSON], [PERSON] [7] designed a low-cost, high-gain microstrip antenna for 28 GHz on an FR-4 substrate, attaining over 10 dBi gain with a simplified feed network, making it cost-effective for mass deployment. [PERSON] et al.