# A New Low-Cost Compact Antenna for the 2.45 and 5.8 GHz ISM Bands
## 1 Introduction
Their ability to operate across multiple frequency bands enhances their adaptability to fluctuating RF environments, where the available frequencies or signal intensities may vary over time or space, especially critical for mobile devices operating in dynamic settings [13]. The multiband functionality ensures greater robustness and efficiency, making these antennas suitable for both current and future wireless systems. Moreover, the dual capability of antennas to support both wireless information transmission and wireless energy transfer provides an added layer of efficiency. A single multiband antenna can replace multiple narrow-band antennas dedicated to individual functions, leading to reduced costs, simplified device architecture, and a smaller ecological footprint. This integrated approach aligns with the principles of sustainable design, emphasizing resource efficiency while meeting the demands of modern wireless communication and energy harvesting systems. The ISM (Industrial, Scientific, and Medical) bands refer to frequency ranges allocated globally for non-commercial purposes that do not require a license for operation. Spanning from a few megahertz (MHz) to several hundred gigahertz (GHz), these bands serve a diverse range of applications in various domains. Their flexibility and widespread availability make them particularly appealing for systems requiring cost-effective and accessible wireless communication. Originally designated for industrial heating, scientific research, and medical diagnostics, the ISM bands have since become a cornerstone for innovative technologies. Among these, the 2.45 GHz and 5.8 GHz bands hold particular significance due to their unique balance between propagation characteristics and bandwidth availability. The 2.45 GHz band, for instance, has become the foundation for biotelemetry systems, enabling real-time patient monitoring and data transmission in healthcare environments [14; 15]. Similarly, the 5.8 GHz band, with its higher frequency and broader bandwidth, supports advanced applications such as high-resolution passive radar systems and precise location tracking [16]. Both bands also play a vital role in wearable and body-centric communications, particularly in the textile industry, where lightweight, portable systems are required for off-body and on-body networks [17]. Designing and deploying a microstrip antenna that operates effectively within the 2.45 GHz and 5.8 GHz ISM frequency bands represents a pivotal step in advancing the mass adoption of miniaturized connected devices. These antennas, known for their compactness, lightweight structure, and ease of integration, are particularly well-suited for modern applications that demand both efficiency and scalability. By optimizing performance in these specific frequency ranges, microstrip antennas enable more reliable and energy-efficient wireless communication, which is crucial for the proliferation of the Internet of Things (IoT) and other interconnected ecosystems. Moreover, leveraging these bands helps maximize the use of globally available radio resources, addressing challenges such as spectral congestion and power efficiency. The dual-band functionality further enhances versatility, allowing seamless operation across a variety of applications, from wearable devices and biotelemetry to high-speed data transmission and radar systems. This dual-frequency approach also facilitates innovations in adaptive antenna designs, such as beam steering and frequency agility, which contribute to superior network performance and resilience. Microstrip antennas consist mainly of a radiating element, commonly called a patch, a substrate, and a ground plane. These antennas fall into two categories, depending on the shape of the radiating element, which influences the nature of the radiation. These are monopole patch antennas (wired radiating element) [18] and microstrip antennas with a large radiating surface [19]. Small patch antennas generally have low gain and reduced bandwidth.