Basic studies on the phased-array behaviors of two types of chain coupled microwave oscillator systems are presented.The first type is a unidirectionally coupled oscillator chain in which one end oscillator is different from the others in free-running oscillation frequency.The second type is a mutually coupled oscillator chain in which the free-running oscillation frequencys of both the end oscillators deviate oppositely from the others.It is analytically shown that after attaining synchronization,the systems can operate as active phased arrays which are controlled by the oscillation frequency difference.Experiments on both the systems using three Gunn oscillators agreed well with the analyses.