Digital PA Modulator with Phase Shifter for Phased Array Transmitters

This paper presents a modulator for fully digital transmitter chains which allows to realize time delays with ps accuracy between several transmitter branches, as needed for phased array antennas in beamforming networks. The proposed digital modulator absorbs all delay units of an analog signal beamforming network, thus significantly reducing form factor and enhancing flexibility. Furthermore, since the system is digital, there are no amplitude variations that influence the transmitted signal when varying frequency. Also the digital system shows no amplitude variations that influence the transmitted signal when varying frequency. Implementation details and measurement results for up to 6 GHz are presented. In addition, an experimental set-up with two digital power amplifiers (PA) modules at 900MHz has been realized to validate the approach.