A phase-angle circuit (24) processes the outputs of an antenna array (12) to apply to a compressive receiver (20) an ensemble of signals having components whose spatial frequencies are proportional to the bearing angle of the electromagnetic plane waves that give rise to them. A signal whose phase angle is equal to twice the bearing angle is generated by interconnecting the antenna elements as two quadrupoles offset by 45.degree.. The output of one of the quadrupoles is shifted in phase by 90.degree. and added to the output of the other quadrupole to generate the desired signal, which is applied as an input to the compressive receiver. Other inputs to the compressive receiver are generated in similar ways. The position of the compressive-receiver output port (22) at which a maximum occurs indicates the bearing angle of the electromagnetic plane wave that gave rise to the maximum.