Ultrathin and Flexible Ultrawideband Antenna Array Based on Integrated Impedance Matching Line

In this letter, we propose a method to realize an ultrathin and flexible ultrawideband (UWB) antenna array. The array element integrates an UWB impedance matching line into the antenna radiation patch to replace the conventional vertical feed structure of the UWB antenna array, enabling the entire antenna radiation layer to be ultrathin and flexible. A stretchable honeycomb layer with a low dielectric constant is used to support the radiation layer and make it easy to be conformal. In addition, the antenna adopts an ultrathin bendable dielectric substrate to achieve UWB directional radiation properties. In the substrate structure, a high-pass frequency selective surface is designed to improve the radiation efficiency, particularly at the low-frequency band. Finally, the overall UWB antenna array structure can be made ultrathin, flexible, and bendable by using multilayer lamination. To verify this method, a 6 x 6 array antenna prototype was fabricated and measured. The measured results confirm that the proposed method achieves a bandwidth of 2-18 GHz with active voltage standing wave ratio (VSWR) < 2.5 and the profile of the entire antenna is only 0.047 lambda(L), where lambda(L) denotes the free-space wavelength at the lowest operating frequency. After flexible conforming, the antenna can still maintain stable electrical properties.