Broadside subwavelength microstrip antennas partially loaded with metamaterials

A new designing for solving zero radiation problem of subwavelength microstrip antenna at broadside loaded with double-positive material and double-negative metamaterials is presented. The subwavelength rectangular microstrip antenna does not radiate efficiently at broadside because of the radiation from the two radiating edges cancels each other. So, the new structure of subwavelength microstrip antenna array made of two identical subwavelength rectangular microstrip antenna partially filled with metamaterials is proposed and studied. Due to the phase compensation properties of double-negative metamaterials, arbitrarily low resonant frequency can be also obtained for a fixed dimension for the proposed antenna array. And, two elements for the new antenna array are aligned regularly along the coordinates and the phase difference between the excitation sources of two-element subwavelength antenna array is set to a special value π. With this scheme, the radiation of antenna array at broadside in the direction normal to the radiator and the ground plane is clearly enhanced by comparing radiation patterns between the subwavelength microstrip antenna and the subwavelength antenna array.