IBM claims to have achieved a milestone in creating a phased-array transceiver that contains all of the millimeter-wave components necessary for both high data-rate communications and advanced-resolution radar imaging applications. The newly demonstrated integrated circuits tackle data bottleneck issues for mobile communications applications and allow radar-imaging technology to be scaled down to the size of a computer laptop.
Advanced radio-frequency integration has been a key driver in the growth of mobile device capability and sophistication, says IBM. Millimeter-wave bandwidth has the ability to support Gb/s wireless communications, dramatically expanding opportunities for mobile backhaul, small-cell infrastructure, and data-center overlay network deployment.
The frequency range of the ICs is well suited to high-resolution radar imaging applications due to its short wavelength, relatively low atmospheric attenuation, and ability to penetrate debris. The ICs enable radar technology to be scaled down, giving pilots the ability to penetrate fog, dust and other vision-impairing obstructions.
“This transceiver presents the highest level of integration achieved so far in a silicon-based solution for millimeter-wave frequency applications,” says Dr Alberto Valdes-Garcia, IBM Research, Communications and Computation Subsystem Group. “It is a key step toward phased-array systems of the future that are scalable, low-volume, light-weight, and low-cost.”
IC and scalable array assembly technology
The packaged transceiver operates at frequencies of 90-94GHz and is implemented as a unit tile, integrating four phased-array ICs and 64 dual-polarized antennas. By tiling packages next toeach other on a circuit board, scalable phased arrays of large aperture can be created while maintaining uniform antenna element spacing. The beam-forming capabilities enabled by hundreds of antenna elements will allow for communications and radar imaging applications that will extend over a range of kilometers, says IBM.
Each of the four phased-array ICs in a tile integrates 32 receive and 16 transmit elements with dual outputs to support 16 dual-polarized antennas. Multiple operating modes are supported, including the simultaneous reception of horizontal and vertical polarizations. Fabricated using an IBM silicon germanium (SiGe) semiconductor process, the ICs also integrate frequency synthesis and conversion as well as digital control functions.
The complete scalable solution (including antennas, packaging and transceiver ICs) transforms signals between millimeter-wave and baseband, all in a form factor smaller than an American nickel coin.
Mobile back-haul technology
Mobile service providers have started to alleviate backhaul congestion issues by using E-band wireless links. E-band spectrum, allocated by the US Federal Communications Commission (FCC) for point-to-point communications, covers frequencies of 71-76GHz, 81-86GHz and 92-95GHz, and enables wireless data transfer at very high rates. The atmospheric attenuation in this band is relatively low, making it well suited to supporting long-range communications links.
Existing E-band solutions consist of multi-chip modules and bulky mechanically aligned antennas. The newly developed compact scalable phased array solution provides electronic beam steering and the bandwidth to support Gb/s wireless communications.
Millimeter-wave radar and imaging capabilities
The millimeter-wave range spans 30-300GHz on the electromagnetic spectrum (10-100 times higher than the frequencies used for mobile phones and Wi-Fi). Frequencies of 90-94GHz are well suited for short- and long-range, high-resolution radar imaging.
Weather, debris and other vision-impairing obstructions often leave aircraft pilots helpless, but 94GHz radar imaging technology could alleviate this problem, says IBM. Moreover, the design’s support for two antenna polarizations — with minimal increase in footprint — provides a further advantage while navigating through fog and rain.
IBM debuted the phased-array transceiver design at the IEEE Radio Frequency Integrated Circuit Symposium (RFIC 2013) in Seattle, WA, USA on 4 June. The work was partially funded by the Defense Advanced Research Projects Agency (DARPA) Strategic Technology Office (STO).
