The relative movement of a receiver and transmitter in a communications
system is used to advantage by electronically synthesizing a larger
apparent antenna aperture, thereby increasing signal-to-noise ratio. The
approach may be used regardless of whether the transmitter is fixed and
the user or vehicle is moving, or the user or vehicle is fixed and the
transmitter is moving. According to the method, the apparent angle between
the receiver and transmitter is determined relative to the direction of
movement and used to produce time-delayed replicas of the received
signaling stream which are coherently added to synthesize the increased
apparent receiver antenna aperture. Since only the receiver is modified
according to the invention, existing transmitters and infrastructures can
be used without modification. Although some data buffering is required,
only a few number of beams need to be synthesized, in contrast to more
complex military SAR configurations.
