Multifunctional Cell-Phone Chip
Wireless receiver can access ultrawide range of radio frequencies
SOURCE: “An 800MHz to 5GHz Software-Defined Radio Receiver in 90nm CMOS” R. Bagheri et al.
Paper presented at the International Solid-State Circuits Conference, February 5-9, San Francisco, CA
RESULTS: At the University of California, Los Angeles, Asad Abidi and colleagues have built a low-power receiver for a wireless chip that can receive radio signals over a range from 800 megahertz to five gigahertz and tune in to the band a particular application requires.
WHY IT MATTERS: Handheld devices are offering more wireless capabilities, including Wi-Fi and GPS. For each new function, engineers need to add a chip that is tuned to a specific radio frequency. A mobile device that allows users to surf the Internet using a Wi-Fi connection requires at least two chips, one for cell-phone service and one for Wi-Fi. Abidi’s wideband receiver could make it possible to tune in all frequencies with a single, universal chip. Such a chip could allow a single handheld device to access any wireless service: it could receive radio and Wi-Fi signals, provide cellular service all over the world, even open a car door.
METHODS: Abidi and his team based their research on software-defined radio (SDR), a concept first proposed in the 1990s. Typically, an SDR device converts incoming analog radio signals to digital signals and then uses software to sort through the frequency bands. That requires hundreds of watts of power, however. To save power, the team modified SDR technology by using an electronic component called a wideband anti-aliasing device, previously used only in physics research. This device can access a wide range of the radio spectrum and emphasize a single band, so that only that band is converted to a digital signal. The method requires just milliwatts of power.
NEXT STEPS: The researchers have met half the challenge of building a universal cell-phone chip, but a truly universal chip would not only receive but transmit across a wide range of frequencies. Abidi’s team is now working to develop components for a transmitter that operates over the same range of the spectrum as its wideband receiver.
Antenna used in RFID tags powers tiny computers
SOURCE: “A Wirelessly Powered Platform for Sensing and Computation” Josh Smith
Paper accepted for the Eighth International Conference of Ubiquitous Computing, September 17-21, Orange County, CA
RESULTS: Using the same approach that makes passive RFID tags come to life when scanned, Josh Smith, an Intel researcher, has built a sensor that can collect environmental information and transmit it without a battery.
WHY IT MATTERS: Sensors that collect and transmit information are useful in many applications, such as tracking the temperature of food shipments. But most sensors require batteries; often, when the battery dies, the sensor needs to be replaced. Battery-free sensors could last much longer.
METHODS: The sensor uses an antenna similar to those found in battery-free RFID tags. When the sensor comes within range of an external device called an RFID reader, which emits radio waves, the antenna and circuitry harvest power from the radio signal to turn the sensor on. As long as the reader is within the antenna’s range, the sensor collects and processes environmental information. The brain of the device is a microcontroller, requiring less than a milliwatt of power, that contains a 16-bit processor, eight kilobytes of flash memory, and 256 bytes of random-access memory.
NEXT STEPS: Currently, the sensing device must be within a meter of the reader to work, but Smith says that with minor changes to the way the microcontroller processes the data, the range can be extended to three meters or more. He and his team are also looking into integrating the micorcontroller and antenna into a single chip to shrink the device.
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