A study on modulation method for transmission system using phased array antennas

Transmission systems using phased array antennas have been proposed, which made it possible to confine the communication area by switching the phase distribution for every symbol. These are known as directional modulation (DM), and the values of the phase shifters are chosen so that the phase of the desired signals on the constellation map is equal to those of the far fields of the phased array antenna (PAA). However, because the radiation patterns of the traditional DM are distorted from those of the ordinary PAA, the time-average antenna gain of these systems becomes significantly low in the desired direction, which causes the extra power consumptions. In this paper, a novel modulation method is proposed to enlarge the transmission distance with almost the same communication area. The calculation and experimental results are presented to ensure the validity of the proposed method.