Design and performance analysis of a Polyimide film substrate-based flexible microstrip antenna with different thicknesses for 2.45 GHz ISM band applications

This paper presents the design and fabrication of a compact, low-profile flexible microstrip patch antenna using polyimide film with a dielectric constant (ε
r
) of 3.5 and a loss tangent (tan δ) of 0.002. The polyimide is chosen for its lightweight, flexibility, thermal stability, mechanical toughness, and chemical resistance. The study emphasizes the critical role of substrate thickness in influencing antenna parameters, comparing the impact of varying thicknesses (0.1mm, 0.5mm, 1mm, 1.5mm, and 2mm) on the performance of a rectangular microstrip patch antenna. The microstrip-inset feed method is employed for impedance matching and feeding. The paper evaluates performance parameters such as resonant frequency, reflection coefficient, bandwidth, gain, directivity, as well as the influence of substrate thickness on design parameters. The antenna with a 0.1mm polyimide film thickness has been fabricated. It exhibits a return loss of - 19.33 dB (simulated) at 2.45GHz and -23.69dB (measured) at 2.46 GHz. The experimental results are in good agreement with the simulated outcomes. A bending test with a curved surface of radius 70 mm was also carried out to check flexibility of antenna. The antenna is operated at the resonant frequency of 2.45GHz in the ISM band, making it suitable for wireless communication, IoT, and flexible electronics applications, particularly in harsh and high-temperature environments. The design and simulation were carried out using High-Frequency Structure Simulation (HFSS) software.