29 March 2012

TowerJazz and UCSD demo first silicon wafer-scale 110GHz phased-array transmitter

Specialty foundry TowerJazz (which has fabrication plants at Tower Semiconductor Ltd in Migdal Haemek, Israel, and at its subsidiaries Jazz Semiconductor Inc in Newport Beach, CA, USA and TowerJazz Japan Ltd) and The University of California, San Diego (UCSD), which provides a program in microwave, millimeter-wave and mixed-signal RFICs, have collaborated to demonstrate what is claimed to be the first wafer-scale phased array with 16 different antenna elements operating at 110GHz frequency range.

First-time success was achieved for the RFIC using TowerJazz’s proprietary models, kit and the mm-wave capabilities of its SBC18H3 0.18-micron silicon-germanium (SiGe) BiCMOS process. The device targets applications for automotive radar, aerospace & defense, passive imaging, security, and mm-wave imaging. The collaboration on the phased-array chip was partly funded by the US Defense Advanced Research Projects Agency (DARPA).

Phased arrays allow the electronic steering of an antenna beam in any direction and with high antenna gain by controlling the phase at each antenna element. The radiation beam can be ‘moved in space’ using entirely electronic means through control of the phase and amplitude at each antenna element used to generate the beam. This beam steering technique is more compact and much faster than mechanically steered arrays. Phased arrays also allow the creation of deep nulls in the radiation pattern to mitigate strong interference signals from several different directions. They have been in use in defense applications since the 1950s and have seen limited use in commercial system due to their relatively high cost. UCSD’s design and use of TowerJazz’s existing wafer processes are targeted at greatly reducing the cost of phased arrays, especially at millimeter-wave frequencies.

The wafer-scale SiGe BiCMOS chip measures 6.5mm x 6.0mm and combines the 110GHz source, amplifiers, distribution network, phase shifters and high-efficiency on-chip antennas, allowing a new generation of miniature and low-cost phased arrays for W-band (75-110GHz) applications. TowerJazz says that such an advance better serves the needs of the greater-than-$100m emerging markets of auto radar and passive imaging (security). The antennas are integrated on-chip, eliminating the expensive and lossy transitions and distribution network between the phased array and the off-chip elements. TowerJazz says that the wafer-scale phased array with 16 radiating elements, together with all the necessary CMOS control circuits, is capable of electronic beam scanning to +/-40 degrees in all planes. The architecture could be scaled to 64 elements (8x8) or 256 elements (16x16) due to on-chip antenna integration and the single-chip integration of multiple elements.

By developing the wafer-scale chip, UCSD has demonstrated independent amplitude and phase control at 106-114GHz for all 16 different antenna elements, and provides commercial availability of highly scalable (from 16 elements to 256 elements) RF-IC transmitters for W-band and D-band phased-array applications. The chip was designed and tested by Woorim Shin, Ozgur Inac and Bonhyun Ku, all of UCSD’s Electrical and Computer Engineering Department under the supervision of professor Gabriel M. Rebeiz, and was partially sponsored by the DARPA program GRATE (Gratings of Regular Arrays and Trim Exposures) under the direction of Dr Carl McCants. The work was performed under a subcontract to UCSD from TowerJazz.

The phased array chip was developed using TowerJazz's SBC18H3 BiCMOS, which offers both high-performance 0.18-micron SiGe bipolar and high-quality passive elements combined with high-density 0.18-micron CMOS, to enable high-speed networking and mm-wave applications. The process offers SiGe transistors with a peak Fmax of 280GHz and a peak Ft of 240GHz, suiting low-power, high-performance mm-wave circuits, while replacing the need for more expensive gallium arsenide (GaAs) chips, TowerJazz says. SBC18H3 comes standard with 1.8V and 3.3V CMOS (dual-gate), deep trench isolation, lateral and vertical PNP transistors, MIM capacitors, high-performance varactors, polysilicon as well as metal and N-well resistors, p-i-n and Schottky diodes, high-Q inductors, triple-well isolation, and six layers of metal.

“We have a track record of successful collaboration with TowerJazz, and the ability to bring this innovative design from UCSD to market depends strongly on TowerJazz’s SiGe BiCMOS process, which enables lower-cost phased arrays by integrating many functions and high-efficiency antennas on the same silicon chip,” comments Electrical Engineering professor Gabriel M. Rebeiz (the lead professor on the chip).

The SBC18H3 process is available through the TowerJazz multi-project wafer (MPW) system. The chip is available via professor Rebeiz at rebeiz@ece.ucsd.edu.

Tags: TowerJazz SiGe BiCMOS

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