Performance comparison of near-field focused and conventional phased antenna arrays at 140 GHz

The future high frequency systems require very high antenna gains to cope with the large channel losses. In order to obtain large gain and flexible beamforming, large antenna arrays are often considered. With hundreds or thousands of antenna elements, transmit energy is highly concentrated on the target. However, large numbers of antenna elements make the antennas very large compared with the wavelength. Therefore, it is likely for the user to be in the near field of the array. In this region, the maximum antenna gain is obtained by focusing the energy on the desired locations. The downside is a need to know the exact locations of the radios. This paper focuses on analysis of the traditional linear phase beam steering and near field focusing beam steering and the impact of the user location uncertainty on the achievable antenna gain. The uncertainty in the user location can arise, for instance, due to user mobility. The results show that the near field focusing gives superior gain in the near field of the antenna array, but is more sensitive to the user location information than the linear phase beam steering.