Triple-band Slot Antenna Array for Energy Harvesting for Wireless Sensor Networks

An energy harvesting antenna array for wireless sensor applications is presented in this paper. The microstrip line feeding network excites four slots to achieve wireless local-area-network (WLAN) 2.4/5.2/5.8 (2.4-2.484/5.15-5.325/5.725-5.825 GHz) bands. The design is printed on a flame retardant 4 (FR4) substrate with thickness of 1.6 mm, permittivity of 4.4, and loss tangent of 0.0245. The overall size of the antenna array is only 60 x 60 x 1.6 mm(3) and, with dual-ports, consists of two antenna arrays; port 1 is designed for a WLAN 2.4 GHz band and port 2 is designed for a WLAN 5.2/5.8 GHz band. The feeding network (electric length = lambda(g)/4) was used to connect the array network and antenna, and for the purpose of in phase excitation, we used microstrip lines (electric length = lambda(g)/2) to adjust the phase difference of these two antenna elements to 180 degrees. Finally, 8 mm above the antenna array, we placed a metal reflector the same size as the antenna to adjust the radiation patterns to the -y direction and to enhance the radiation directivity and gains.