A 60 GHz retrodirective array system with efficient power management for wireless multimedia sensor server applications

A 60 GHz retrodirective array system with efficient power management for wireless multimedia sensor server applications is proposed. The system consists of three sections: a retrodirective array, a local oscillator (LO) and a power management system. The proposed system is able to efficiently control battery power by turning off when it is not in use. In particular, the power management circuit controls the power of the LO by a rectenna for efficient battery operation. Although there is no interrogating signal, the system is in a sleeping mode where extremely low power consumption occurs. When the system is interrogated by an RF signal, the system is awaken and starts consuming full power. When the received power density is larger than 0.013 mW/cm ^{, the system turns on and starts working as a retrodirective array. Furthermore, the proposed system can avoid the use of an expensive LO by employing a fourth subharmonic mixer. Experimental data are used to verify the proposed idea.}