Planar antenna arrays with helical elements for terahertz rectenna
Implementation of rectennas is a prospective method for electromagnetic radiation to DC conversion in terahertz band and bands of higher frequencies. A signal obtained from a single antenna in practical conditions may not be enough to drive rectenna’s rectifier. That problem is most likely to occur if the rectenna is used as a power source. Therefore the problem of increasing voltage over rectenna’s rectifier is important. One can try to address this problem with the use of antenna arrays. As the operating frequency increases the finite conductance of metals becomes a significant limiting factor. This makes considering minimally spaced arrays a worthwhile task. Such spacing results in tight coupling between elements of the array. As a consequence an analytical study of such structure is very hard. The paper examines the option of planar antenna array’s design with closely spaced helical elements. The array’s characteristics are determined using computer simulation. The maximum absolute value of the electric field strength was calculated at the antenna output gap for each array in the case of a normal incidence of a circularly polarized plane electromagnetic wave. The obtained values of the operating frequencies and the width of the operating frequency bands for the designed arrays are presented, as well as the values of the reflection coefficient in the center of the operating frequency band. The array parameters are optimized to maintain the operating frequency while increasing the number of antenna elements. The possibility of increasing the voltage at the array’s output in proportion to the number of antenna elements is demonstrated.