A phased array is a group of antennas that are fed by relative signals that are varied in a way that makes the radiation pattern of the array reinforced in a particular direction and suppressed in all other directions. By manipulating the phase, the antennas’ beam can be steered electronically within nanoseconds. The width of the beam is controlled by the amplitude of the transmitted waves. , This is critical, for example, when one wants to send information from one satellite to another without the signal reaching any nearby satellites. With amplitude and phase control, deep nulls in the antenna pattern can be synthesized so as to greatly reduce the effect of interfering signals from neighboring transmitters. Phased arrays are common in warships of various navies as the basis for radar systems used for surface detection, air detection, tracking and missile uplink capabilities.
At the tiny size of just 3.2 by 2.6 square millimeters, the new 16 element phased array chip can transmit data at 30-50 GHz. This chip – the UCSD DARPA Smart Q-Band 4×4 Array Transmitter – is strictly a transmitter. Gabriel Rebeiz, Professor of Electrical engineering from the UCSD Jacobs School of Engineering, who led the project, says the team are currently working on a chip that will be able to transmit and receive data.
“This compact beam-forming chip will enable a breakthrough in size, weight, performance, and cost in next-generation phased arrays for millimeter-wave military sensor and communication systems” wrote DARPA officials in a statement. The chip contains all the digital circuits necessary for complete digital control of the phased array and reduces complexity.
While phased arrays have been around for more than half a century, many units of communication equipment based on the technology are larger than highway billboards. The main obstacle to using such high-end satellite communication devices for any purpose besides military/governmental applications is that the most powerful phased arrays can cost hundreds of millions of dollars. Engineers are now working to miniaturize these devices and fully integrate the technology into silicon-based electronic systems for both military and commercial applications.
Although the chip that the scientists are developing is designed for use at the defense satellite communications frequency known as the Q Band (40-50 GHz), it can be moved to the 24 or 60 GHz range for commercial communications. The integrated chip is expected to enable wireless rapid transmission of hundreds of gigabytes of information without adhering to the requirements of wireless optical data transfer. Prof. Rebeiz estimates this kind of system could be available in as little as three years from now.
For more information about the UCSD DARPA Smart Q-Band 4×4 Array Transmitter see the USCD website.