# A New Low-Cost Compact Antenna for the 2.45 and 5.8 GHz ISM Bands
## 1 Introduction  
The rapid and continuous advancement of wireless communication technologies has resulted in the proliferation of numerous radio standards that must coexist within modern communication systems [1]. This has been driven by the growing prevalence of connected devices, including personal computers, smartphones, IoT sensors, Wi-Fi routers, and Bluetooth-enabled peripherals, which frequently incorporate multiple radio frequency (RF) technologies tailored for diverse applications and operating across distinct frequency bands [2]. Among the critical components of any wireless system, the antenna stands out as a fundamental and indispensable element, as it facilitates the transmission and reception of electromagnetic signals. However, the integration of antennas into compact and multifunctional devices poses several design challenges. Primarily, the physical dimensions of the antenna often impose substantial constraints on the overall design of the device. These constraints are exacerbated by the need to ensure adequate isolation of the antenna from other radiating elements within the system, as well as from components operating at baseband frequencies. This isolation is essential to minimize interference, maintain signal integrity, and ensure optimal performance across the various RF technologies present in the system. Moreover, in many communication systems, the antenna is one of the largest individual components, frequently occupying a significant proportion of the device's volume [3]. Consequently, these challenges highlight the critical need for innovative antenna design approaches, including the development of miniaturized, multi-band, and highly efficient antennas that can seamlessly integrate into increasingly constrained form factors without compromising performance. A wide variety of antenna types are suitable for embedded applications, including wire antennas [4], aperture antennas [5], metasurface reflectors [6], and microstrip patch antennas [7; 8]. Among these, microstrip patch antennas (often referred to as printed-on-substrate antennas) have garnered sustained attention from researchers over the past several decades. These planar antennas have been extensively studied due to their numerous advantages: compact size, lightweight construction, cost-effectiveness, and straightforward manufacturing processes. Additionally, their inherent planar structure facilitates seamless integration into compact electronic devices [9]. To address the evolving demands of modern wireless communications, significant advancements have been made in microstrip antenna technology. Miniaturization techniques have enabled these antennas to achieve highly compact designs without compromising performance [10]. Furthermore, innovative approaches have expanded their operational bandwidth, allowing them to function effectively across multiple frequency bands, thereby enhancing their versatility for diverse applications [11]. Consequently, microstrip patch antennas are an essential component of wireless communication systems, and their design and optimization provide solutions in terms of efficiency, reliability, and integration of wireless devices. Electromagnetic (EM) energy recovery devices have recently emerged as a promising area of research, drawing increasing attention from the scientific community. The pervasive presence of radiofrequency (RF) waves in modern environments offers an opportunity to repurpose these waves, without compromising their primary function of information transmission within standardized protocols, as an alternative energy source. Through RF-to-DC conversion, this harvested energy can be used to power low-energy devices, such as wireless sensors and IoT nodes [12]. This approach aligns well with the growing demand for sustainable and self-powered technologies in smart environments. In this context also, the size and frequency versatility of antennas play a pivotal role. Compact and multiband antennas, in particular, provide significant advantages.