A phased array antenna system with controllable electrical tilt generates two signals V2a and V2b with variable relative delay therebetween. The signals are converted into antenna element drive signals by a power distribution network. The network splits each of the two signals V2a and V2b into three signal components. Pairs of components of different signals are input respective hybrid coupling devices (hybrids), which provide vector sums and differences of their inputs and act as phase-to-power converters. Their outputs are distributed between further hybrids, which act as power-to-phase converters and provide antenna element drive signals with phase varying both with element array position and also with the variable relative delay between the two signals V2a and V2b. Antenna electrical tilt is therefore controllable by altering a single relative delay.