Focal Distance Reduction of Transmit-Array Antennas Using Multiple Feeds

The reduction of the focal distance of transmit-array antennas using multiple feeds is investigated theoretically and through full-wave simulations. A theoretical model of multiple-feed transmit arrays is derived using analytic formulas; it shows that the focal distance can be divided by a factor of two using a quadruple-feed configuration. The theoretical results are validated through full-wave simulations for two transmit arrays operating in the 60-GHz band.