A 5GHz all-passive negative feedback network for RF front-end self-steering beam-forming with zero DC power consumption

This paper presents an all-passive negative feedback network to perform autonomous RF front-end beam-forming towards the direction of the incident RF beam. The beam-forming front-end block consists of a passive network for RF signal processing, voltage rectifiers, and voltage-controlled phase shifters, all of which are passive components and consume zero DC power. A proof-of-concept 4-element self-steering beam-forming block at 5GHz is implemented in a standard 130nm CMOS process and occupies an area of 4.1mm2. The measurements demonstrate that a high-quality 4-element array factor is successfully synthesized for the input progressive phase shift from -120° to +120°. At an input power Pin of -17dBm/element, the normalized array factor is -4.3dB/-3.2dB at +90°/-90° input progressive phase shift in the closed-loop operation, out-performing reported active self-steering beam-formers. To the best of our knowledge, this is the first demonstration of an all-passive network for front-end self-steering beam-forming with zero DC power.