Active Integrated Antenna Based Rectenna using a New Probe-Fed U-Slot Antenna with Harmonic Rejection

Antenna array is an effective means to increase the receiving power for rectification. However, a tradeoff arises between the antenna size and the radiation gain. In this paper, an antenna that has a high radiation gain and yet is compact in size is proposed for the rectenna named c-shaped u-slot coaxial-fed microstrip antenna. The proposed antenna in comparison of the inset-fed square patch antenna, not only has physical dimensions 32% less than square patch antenna, but also it has a gain of 6.96 dBi, while the gain of the square patch one is 2.677 dBi. Hence, its characteristics are comparable to several element antenna array, but an extra feeding network is not required and the system is compact. Also, the concept of the active integrated antenna (AIA) is used to design an efficient rectenna. Under this concept the antenna can provide certain circuit functions such as resonating, filtering, duplexing and harmonic rejection, in addition to its original role as a radiating element. Our proposed antenna is a kind of AIA that has the harmonic rejection characteristic. Therefore the matching circuits and the band-pass filter (BPF) are not needed for the proposed design. Because a c-shaped u-slot antenna in the rectenna can suppress the 2nd and 3rd harmonics, the harmonic rejection BPF can be removed. Moreover the impedance of the rectifying circuit is matched to the input impedance of the c-shaped u-slot antenna using a coaxial feed and finding a proper point on the surface of the antenna without matching circuit