Clock distribution circuit for active aperture antenna array

A system is described for communicating a time reference or clock signal to a plurality of processors over substantial distances where propagation time between units is significant compared to the processing time. The timing signal is in the form of two continuous sinusoidal waves of different frequency but equal amplitude, which are added to give equal contributions in the resultant composite, two frequency, sum signal. The resulting waveform has sharply defined nulls occurring at the difference which are used as a precise time reference.