Low power wireless sensor networks provide a new monitoring and control capability for civil and military applications in transportation, manufacturing, biomedical technology, environmental management, and safety and security systems. Low power integrated CMOS systems are being developed for microsensors, signal processors, microcontrollers, communication transceivers and network access control. This paper covers recent advances in CMOS-based microsensor systems, low power signal processing and RF communication circuits. Communication circuits include the demonstration of a 20 /spl mu/A supply current, 860 MHz, low phase noise CMOS local oscillator.