This year has seen all kinds of impressive sensor advances, whether they involve the applications they serve, the processes that make them, or even their packaging. Combined with wireless technology, sensors have become powerful tools. What does it all mean? It means a narrowing of the gap between our world of analog variables and the digital power of the computer, giving us a better understanding of our surroundings.
Many of these sensors take advantage of microelectromechanical systems (MEMS). Traditionally, MEMS have been found in the automotive world triggering air bags and measuring engine manifold absolute pressure (MAP). But their roles are expanding into, for instance, tire-pressure monitoring systems (TPMSs).
SENSORS HIT THE STREETS These advances aren't just in the hardware, though. Cambridge Consultants developed a sensor software platform for advanced pedestrian safety that fuses anti-collision automotive radar with video sensors (Fig. 1). This object classification software alerts drivers to pedestrians in real time. It also enables low-cost implementation of active radar-plus-video capability.
More recently, Micron Technology introduced an automotive image sensor to promote safer and smarter driving. Automotive manufacturers can use it to design-in camera functionality for side-view mirror replacement and assistance. It also can be used in a reversing camera so that drivers can clearly see what's happening next to, or behind, their car.
Sensors are a-sizzle in the consumer electronics arena, too. Low-cost MEMS sensors with dual-axis and tri-axis capabilities can be found in cell phones, audio and video recorders, laptop computers, notebooks, PDAs, MP3 players, and electronic games to detect free falls, acceleration, shock, and vibration. They're also spreading into other applications like inclinometers and golf clubs (Fig. 2).
More fertile ground for MEMS sensors and technology lies in homeland security and fuel-cell technology. MEMS-based sensing platforms are under development for detecting biological and chemical threats. Exciting fuel-cell systems have been demonstrated with MEMS technology, promising more efficient automotive power sources.
MEMS technology is receiving a boost in packaging as well. A research team at the University of Arkansas has received a grant from the National Science Foundation (NSF) and wiSpry Inc., a private company, to develop novel MEMS packaging technologies for products used in telecommunications, homeland security, biomedical devices, automotive and aerospace sensors, and fuel cells. The academic researchers will collaborate with researchers at wiSpry and at Sandia National Laboratories on this project. They will investigate the packaging of MEMS wafers measuring 4 to 12 in. in diameter. The wafers will be developed by using silicon, polymer, or low-temperature co-fired ceramic materials. And, imaging sensors are the rage in medical applications. Combined with wireless sensing capability, they let physicians non-invasively observe a patient's internal organs. Given Imaging produced a pill that contains a video camera sensor and a complete transceiver. Gastrointestinologists can use it to observe a patient's colon condition from the comfort of a nearby workstation receiving the pill's transmissions.
CMOS image sensors are making great strides in performance, challenging CCD image sensors for applications. Toshiba and OmniVision released 3.2-Mpixel image sensors for high-end cell phone uses. Both operate at 15 frames/s and incorporate an analog-to-digital converter (ADC).
WIRELESS SENSING EVERYWHERE Wireless sensing technology comprising self-reliant, battery-powered nodes is pushing sensing to the extreme. Sensor modules, motes, and ICs all have had a huge impact on the industry as parts of wide-ranging wireless sensor networks."Wireless dust" networks represent one of the hottest trends in this field. For example, Dust Networks announced a major upgrade to its SmartMesh-XR network. Previously available technologies simply are unable to reach its performance level.
We're just at the beginning stages of the wireless sensor revolution, with an exceptionally bright future in store for wireless sensor networks. Continued innovations in sensor, transceiver, and battery technologies are sure to increase the utility of wireless sensing.
For instance, RF Monolithics offers a surface-mountable, 433.92-MHz surface-acoustic-wave (SAW) resonator. This low-power quartz resonator IC measures just 3 by 3 mm (Fig. 3). It's designed for automotive TPMSs, remote keyless entry/access, security systems, and active RFID tags.
Quartz has held out against silicon-circuitry integration— until now. SiTime is about to deliver the industry's smallest programmable CMOS MEMS device. Its resonator will have a much higher and more stable frequency. On top of that, its cost will run substantially less than traditional quartz-based crystal oscillators.