Recent progress in microstrip antennas has improved their size and efficiency, particularly in mobile, satellite, and Wi-Max technologies. These enhancements are crucial for advancing wireless communication systems, benefiting applications like telemedicine and GPS technology. The chapter introduces a dual-band unit cell of frequency selective surface (FSS) resonating at 4 GHz and 5.5 GHz, using a combination of I-shaped and modified I-shaped metal strips for dual-band filtering. The research focuses on individual shape analyses and aims to contribute to the development of compact and efficient dual-band FSS designs. The research introduces a dual-band FSS unit cell resonating at 4 GHz and 5.5 GHz, combining I-shaped, H shaped, and modified I-shaped and H shaped metal strips for dual-band filtering. The proposed FSS design, with a 10x10 mm2 unit cell dimension and FR-4 dielectric, exhibits broad frequency band characteristics, aligning well with simulated and measured results.
Top1. Introduction
In the 19th century, the significant discovery of electromagnetic waves, predicted by James Clark Maxwell, paved the way for the development of radio communication. Heinrich Hertz demonstrated radio communication in 1888, leading to the success of commercial radio in the 20th century (Dadgarpour et al., 2014). Antennas have since become an indispensable technology in various aspects of human life. The IEEE standard defines an antenna as a crucial component in wireless communication systems, serving as a link between guiding media and free space. Researchers have introduced various antenna types to accommodate the evolving wireless communication system, with the microstrip patch antenna being widely recognized. Known for its cost-effectiveness, lightweight, compact size, and planar structure, it has gained popularity due to advancements in VLSI and semiconductor technology (Dhouibi et al., 2012).
Antennas play a crucial role in various applications, including satellite systems and telecommunications, by transmitting and receiving radio waves. Instead of relying on a single large antenna, arrays of smaller antennas are often organized to enhance directivity and gain (Dhouibi et al., 2012).
The study of frequency selective surfaces dates back to the early 1960s, with similar structures patented by Marconi in 1919. The term “frequency selective surface” was later patented by Yee in 1993, with clear definitions and discussions provided by Munk (Foroozesh & Shafai, 2006). In satellite platforms like Voyager, Galileo, and Cassini, the integration of FSS sub-reflectors with dual-reflector antennas has proven effective, enabling the allocation of the main reflector among various frequency bands (Sabban, 2014). The growing demand for multifunctional antennas in communication systems has led to the development of FSS with multiband features.
In specific applications, signal filtering is critical for extracting necessary signals from space. FSS plays a vital role in this context by reducing interference between signals and acting as a filter (Foroozesh & Shafai, 2006).
1.1 Frequency Selective Surface
Filters are pivotal in nearly all electronic or RF circuits, serving to control frequency signals by diminishing noise and undesirable interference once integrated into a design. They are classified as—low-pass, band-pass, and high-pass filters—based on their function. For instance, a low-pass filter permits lower frequencies to pass while obstructing higher frequencies. Complementary to filters in transmission lines are frequency selective surface (FSS) or dichroic configurations for space waves. Acting as a spatial filter when exposed to electromagnetic radiation, an FSS transmits specific frequency bands while reflecting others (Foroozesh & Shafai, 2006).
To grasp the idea of spatial filtering more comprehensively, envision a wave impinging on a metal surface. This concept falls into two main categories: absorbing energy or redirecting the energy. From a dynamic perspective, these represent the two possible outcomes for power in those frequencies – either absorption or redirection.
Figure 1.
FSS mechanism (Foroozesh & Shafai, 2006)
An FSS can serve as a concealment for communication facilities, marking one of its initial applications. These structures, known as radomes, operate as band-pass filters to reduce Radar Cross Section (RCS) (Foroozesh & Shafai, 2006).