Design of Single Feed Dual Band Dual Polarized Microstrip Antenna With Defected Ground Structure for Aeronautical and Radio Navigation Applications

A single feed proximity coupled dual frequency dual polarized microstrip antenna is presented in this paper. A simple back-to-back structure with a common ground plane is used to get dual frequency and directivity at opposite directions. By incorporation of the spiral shape defected ground structure (DGS) in the common ground plane, the realization of circular polarization at lower band is achieved. A dumbbell shape DGS is also incorporated in the common ground plane to reduce lower patch size by 10.4% and to improve impedance matching. The proposed antenna radiates right hand circular polarization at the lower band (1.59-1.61 GHz), which covers aeronautical and radio navigation and satellite application spectrum, and linear polarization at the upper band (2.45-2.52 GHz), which covers fixed mobile radio location and radio determination applications spectrum allocated in India. At boresight, the 3 dB axial ratio bandwidth of 20 MHz at the lower band and a gain of 5.1 dB at the lower resonant frequency and a gain of 6.7 dB at the upper frequency band are achieved. The advantages of using DGS in designing the proposed antenna and comparison of proposed antenna with earlier reported single feed dual band dual polarized antennas are also presented. A laboratory prototype of proposed antenna has been fabricated to cross verify the simulation results. The measured results are in agreements with the simulated ones.