Solid state device replaces long electrical delay lines in phased array radars

The device is said to take advantage of the difference in speed between light and sound, according to research engineer Ryan Westafer. Acoustic technology is used to produce a type of signal delay that's essential to phased array performance. "Most true time delay equipment currently uses long, meandering electromagnetic delay lines – comparable to coaxial cable – that take up a lot of space," said Westafer. "While there are some time delay designs that use photonic technology, they also have size and functionality drawbacks." Georgia Tech's delay device uses acoustic delay lines embedded within thin film materials. The component can, says Westafer, be made thousands of times smaller than an electrical delay line design and can be readily integrated on top of semiconductor substrates. Traditional phased array systems use 30cm of electrical delay line to create a delay of 1ns. By contrast, Georgia Tech's design is just 40µm square. In operation, an electromagnetic wave is transmitted through an electrical line to the delay device. A piezoelectric transducer then converts electromagnetic waves to acoustic waves and, over the distance of a few microns, the waves are slowed by several orders of magnitude. Once the required delay is achieved, acoustic waves are transduced back to electromagnetic waves, delivered into another electrical line and transmitted by an antenna. A similar sequence, but in reverse, takes place when the radar beam bounces back from its target and is received by the antenna. To date, the Georgia Tech team has demonstrated that its device can deliver a 10ns delay at full radar signal bandwidth.