Synthesis loss in receiving array antennas and transmission efficiency in the Fresnel region

Abstract

We address transmission between array antennas in the Fresnel region, where there is a difference between the theoretical and actual transmission efficiencies. In particular, we focus on the effect of synthesis loss in the receiving antenna's power combiner circuit caused by amplitude and phase differences among the signals received by the elements. We designed 24 GHz array antennas and investigated the effect of synthesis loss on transmission efficiency via simulation. The synthesis loss was found to increase for smaller transmitting antenna sizes and larger receiving antenna sizes. In addition, to clarify the origin of the discrepancy between the theoretical and actual efficiency values and accurately estimate the efficiency, we defined four other loss factors and calculated them via simulation. Based on the results obtained, we propose an approximate equation for transmission efficiency in terms of synthesis loss and aperture efficiency. Finally, we calculate the efficiency with the effect of the loss factors included and confirm that the calculated and measured efficiencies are almost identical.