An advanced low profile microstrip antenna using hybrid structure for bandwidth enhancement

Abstract

Microstrip antennas offer many benefits to high-frequency systems, including ease of integration with other RF/microwave components. Unfortunately, microstrip antennas have also been plagued by inherently narrow bandwidths, limiting their use in some applications. A number of approaches have been proposed to increase the operating bandwidths of these antennas, including increasing the substrate thickness, using different impedance-matching and feeding techniques, and using multiple resonators and slot antenna geometries. However, these methods tend to add to an antenna’s weight and volume, and can increase the fabrication cost. A low-profile microstrip antenna with strip-slot hybrid structure is proposed to enhance the bandwidth up to 41% within a height of 0.06λ0 (λ0 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., TM10 mode and antiphase TM20 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 0.067λ0.