Abstract: Embodiments provide radio-frequency systems that can automatically detect, focus-on, and track objects in the environment without the need for expensive electronic scanning and phase-shifting components. Some embodiments are directed to retrodirective systems including: (1) quiescently broadcast pseudorandom-modulated radiation, such as pseudorandom bit sequences, in the absence of a target, over a field-of-view comparable to the beam solid angle of a single element in the transmit array; (2) a receive antenna element or array, in a desired spatial relationship with respect to the transmit antenna array, that receives reflected pseudorandom radiation from a target; and (3) an electronic signal-processing and feedback channel between the receive and transmit arrays that carries out cross-correlation between the received radiation and the transmitted pseudorandom signals and computes complex correlation coefficients to form a re-transmitted beam.

Abstract: Embodiments provide radio-frequency systems that can automatically detect, focus-on, and track objects in the environment without the need for expensive electronic scanning and phase-shifting components. Some embodiments are directed to retrodirective systems including: (1) quiescently broadcast pseudorandom-modulated radiation, such as pseudorandom bit sequences, in the absence of a target, over a field-of-view comparable to the beam solid angle of a single element in the transmit array; (2) a receive antenna element or array, in a desired spatial relationship with respect to the transmit antenna array, that receives reflected pseudorandom radiation from a target; and (3) an electronic signal-processing and feedback channel between the receive and transmit arrays that carries out cross-correlation between the received radiation and the transmitted pseudorandom signals and computes complex correlation coefficients to form a re-transmitted beam.