Ultra Low Power Electronics

Systems such as the next generation wireless sensor systems for monitoring remote assets in both military and industrial/commercial applications need to operate on limited battery or environmentally scavenged power for months or years. These systems can have complex power envelopes that vary widely as the system moves through its operating modes. Maximizing the sensor capabilities within the available energy supply requires a careful analysis of the sensor energy requirements as it moves through its operating modes, and demands the use of dynamic power management techniques based on the state of the system.

Operation of CMOS digital logic at ultra low power supply voltages including the subthreshold regime (where power supply voltage is below the threshold voltages of the MOS transistors) has proven to be very beneficial for energy constrained systems as it enables minimum energy consumption in logic circuits during active computation and reduces leakage currents in components that must be continuously powered. There are two primary penalties for ultra low voltage operation. The first is a 10-100x loss in throughput,  and the second is the exponential variation of subthreshold current with both transistor threshold voltage (Vth) and supply voltage (Vdd) variations. In subthreshold operation, device-to-device transistor drive current variations, and thus logic gate switching times increase by10x or greater compared to operation at superthreshold voltages. In deep sub-micron technologies, even a static CMOS logic style does not guarantee functionality in subthreshold as random process variations cause degraded logic gate noise margins, large on-die variations in gate delay, and other design challenges.

Camgian’s NULL Convention Logic™ (NCL) design methodology addresses the issues of subthreshold operation and provides an elegant solution to power management. Circuits designed with NCL are effectively delay insensitive. They are very robust to changes in process, temperature and voltage that will break the functionality of a convention design and have been shown to operate well in subthreshold. Furthermore an NCL circuit can autonomously change the power supply voltage from subthreshold to superthreshold in response to the processing throughput requirements of the system. Thus balancing system performance with minimizing energy consumption.

Low power Digital Signal Processor

To provide a programmable low power processor as a platform for wireless sensor systems Camgian is developing an asynchronous digital signal processor (DSP) based on the use of NCL technology. Results from modeling and simulation under a Defense Research Projects Agency (DARPA ) program have shown that a factor of approximately 20X reduction in power consumption can be achieved in NCL circuitry by exploiting subthreshold operation and dynamically controlling the power supply voltage to the minimum needed to support the data rate requirements in an example unattended ground sensor application. This asynchronous DSP is being developed with support from DARPA and the Department of Defense (DoD).

RF Circuits

Camgian’s unattended ground sensor architecture is based around a radar sensor with a software programmable architecture specifically designed for this type of application. The radar architecture itself provides significant power reduction and when combined with aggressive power management techniques, a commercial off-the-shelf (COTS) version of the sensor system has been successfully demonstrated to a DoD customer and is now in low rate initial production.  To maximize the utility of the system and address a broad range of applications a major reduction in size, weight and power (SWAP) is now being pursued. In a DARPA SBIR program Camgian demonstrated that with a custom ASIC design using a combination of architectural optimization and power management techniques a power reduction of 50-600X is possible. Camgian is currently developing a programmable radar-on-chip (P-ROC) with DARPA and DoD support.

Power Scavenging

To support the introduction of revolutionary new intelligent, adaptable micro-systems Camgian is developing a general purpose micro-power source based on energy scavenging that can be used to supply supplemental power to battery operated remote sensor nodes and under best circumstances to completely power the node. The micro-power source will integrate state-of-the-art energy harvesting, such a solar and thermoelectric technologies with efficient boost circuits to convert low voltages generated by the energy harvesters to the levels required to drive the electronics and ultra low voltage/energy electronics based on NCL capability for sub-threshold operation.  This work is being supported by a DoD program.