Broadband and Low-Profile Microstrip Antenna Using Strip-Slot Hybrid Structure

Abstract

In this letter, a low-profile microstrip antenna with strip-slot hybrid structure is proposed to enhance the bandwidth up to 41% within a height of $0.06\,\lambda _{{\rm{0}}}$ ( $\lambda _{{\rm{0}}}$ is the center operating wavelength in free space). The proposed antenna consists of four strips, which are separated by three narrow slots. By controlling the dimensions of the strips and the slots, dual modes, i.e., ${\rm{TM}}_{{\rm{10}}}$ mode and antiphase ${\rm{TM}}_{{\rm{20}}}$ mode, are excited and coupled to increase the operating bandwidth. The strip-slot hybrid structure can be excited with optimized impedance matching using an aperture-coupled Y-shaped feeding microstrip line. A prototype of the proposed antenna is constructed and tested. Experimental results show an impedance bandwidth of 41% for the reflection coefficient less than −10 dB, achieving an obvious improvement of operating bandwidth with a low profile of $0.06\,\lambda _{{\rm{0}}}$ .