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.