Synthetic-aperture communications receivers

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. Significant cost potentials can be realized via economy of scale, due to relatively simple FFT processing. Although some data buffering is required, only a few number of beams need to be synthesized, in contract to more complex military SAR configurations. Use of the inventive technology lowers antenna side lobes, resulting in a higher signal to noise ratio, which, in turn, may provide for better reception, more users at a given time, and enhanced services such as image/video capabilities, which are currently problematic to implement.