Active phased array antenna based on DDS

The use of active phased-array antenna in communication system can bring about not only improved system performance, but also extended functions, so it has found its ever-broadly applications in communication system. This paper introduces an active phased-array antenna system that has eight antenna elements without RF phase shifters. The antenna system consists of planar array, digital T/R modules, receiving DBF; system control /analysis software, etc. Its basic theory is that in transmitting channel, the traditional RFphase shifter and attenuator are replaced by direct digital synthesizer (DDS). As the operating frequency of DDS available is not sufficiently high, the upper frequency converter is used to convert the frequency to required system operating frequency (2.0 GHz). In transmitting mode, through controlling DDS, the amplitude and phase weights needed for transmit beam formation and the LO signals needed for upper frequency conversion are produced. In receiving mode, through controlling DDS, the LO signals is needed for down frequency conversion for the received signal are produced. The resultant digital I/Q signals are used to form the receive beam. This paper introduces in detail the ways and results of an experiment on an active phased array antenna based on DDS. Through the research on the eight-element active phased array antenna based on DDS, the notable virtues of DDS technology in phased array antenna, and the potential applications of the phased array antenna in communications are proven.