Tunable Microstrip Antenna using Reactive Impedance Surface

Tunable microstrip antenna can be used in WLAN, satellite communication and mobile communication. Many solutions have been given to design a multilayer antenna which can operate over maximum two frequencies but no solution has been investigated to tune a single antenna over more than two frequencies. Hence this project work focuses on the design of multilayer Tunable microstrip antenna comprising of Reactive Impedance Surface (RIS). Therefore an active element like PIN diode is used to tune the MSA at different frequencies. The microstrip antenna is fabricated on glass epoxy substrate and suspended in air at a height of 1 mm from ground. This suspended MSA feeds 3 x 3 array of square parasitic patches. RIS has a Partially Reflecting Surface (PRS) consisting of an parasitic array fabricated on 1.6 mm FR4 dielectric superstrate and placed at about a half wavelength from ground plane. The printed Microstrip antenna is fed by a perfectly matched coaxial probe of impedance 50 Omega. Metallic short is used in simulation work for different combination of arrays to tune the MSA over 5.875 GHz to 5.3 GHz. The outcome of our evaluation test shows that the frequency shift of 575 MHz is achieved by shorting of combinations of elements out of 3x3 array of square parasitic patch. The novelty is brought in the given design by making it tunable at four different frequencies.