The active phased-array antenna not only can improve the communication system performance

but also can extend its function

so it is used in communication system more and more widely.This paper introduces an active phased-array antenna system that has eight antenna elements without high frequency phase shifters.The system consists of planar array

digital T/R modules

receiving DBF and system control/analysis software etc.The basic theory is:in transmitting mode

the traditonal high frequency phase shifters and attenuator can be replaced by direct digital synthesis(DDS).Because the operation frequency of DDS is very low

the frequency must be converted to needed operation frequency(2.0GHz) by upper frequency conversion.In transmitting mode

through controlling DDS

it produces the amplitude and phase weights needed by transmitting beam

and the local oscillation signal needed by upper frequecy conversion.In receiving mode

through controlling DDS

it produces the local oscillation signal needed by down frequency conversion of the receiving signal.Then the DBF is used to form the receiving beam.This paper introduces in detail the ways and results of the experiment of the active phased array antenna based on DDS.Through the research of eight-element active phased array antenna based on DDS

the notable virtues of DDS technology in phased array antenna

and the potential application market of the phased array antenna in communication are proved.