14 May 2015

TowerJazz and UCSD demo first 256-element 60GHz silicon wafer-scale 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) have demonstrated what is claimed to be the first 256-element (16 x 16) wafer-scale phased-array transmitter with integrated high-efficiency antennas operating in the 56-65GHz frequency range. First-time success was achieved for the wafer-scale RFIC using TowerJazz's own proprietary models, kit and the millimetre-wave capabilities of its SBC18H3 0.18µm SiGe BiCMOS process. 

TowerJazz says that, in addition, its proprietary methods allowed for very large chip area with an extremely high level of integration. The phased-array system-on-a-chip (SoC) targets the emerging 5G high-performance wireless standard, which will aim for greater than 10Gbps peak data-rate communication. The array has beam-forming capabilities that include independent amplitude and phase control for all 256 different antenna elements. By developing this wafer-scale chip, UCSD and TowerJazz have demonstrated highly scalable RFIC transmitters for 5G phased-array applications. The collaboration on the chip was partially funded by the Diverse Accessible Heterogeneous Integration (DAHI) program of the US Defense Advanced Research Projects Agency (DARPA) under the direction of Dr Daniel Green.

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 much more compact and much faster than mechanically steered arrays. Also, phased arrays allow the creation of deep nulls in the radiation pattern to mitigate strong interference signals from several different directions. They have been in use since the 1950s in defense applications and have seen limited use in commercial systems due to their relatively high cost. UCSD's design and utilization of TowerJazz's wafer processes are aimed at greatly reducing the cost of phased arrays, especially at millimeter-wave frequencies for 5G communication systems. 

"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 foundry process, which enables lower-cost phased arrays through integration of multiple circuit functions and high-efficiency antennas on the same silicon chip," says Dr Gabriel M. Rebeiz, Distinguished Professor of Electrical Engineering at UCSD (the lead professor on the chip development). 

"The results achieved by UCSD's 5G 60GHz phased-array transmitter again demonstrate the remarkable teamwork between TowerJazz, UCSD and DARPA, to provide novel capabilities and technologies to both the aerospace and defense community as well as commercial markets," comments Dr David Howard, TowerJazz's executive director and fellow & co-principal investigator for the DAHI program.  

UCSD's phased-array SoC

The wafer-scale 256-element SiGe BiCMOS SoC phased-array is 42mm x 42mm and combines the 60GHz source, amplifiers, distribution network, phase shifters, voltage-controlled amplifiers and high-efficiency on-chip antennas (16 x 16 elements), allowing record performance for a new generation of high-performance phased arrays for the 60GHz band (56-65GHz), says TowerJazz. Such an advance better serves the needs of the greater-than-$500m emerging market for 5G 60GHz base-stations with beam-forming capabilities and Gbps data rates, it is reckoned. The antennas are integrated on-chip, removing the expensive and lossy transitions and distribution network between the phased array and the off-chip antennas.

The wafer-scale phased array with 256 radiating elements, together with all the necessary CMOS control circuits such as dual SPI control (serial parallel interface), is capable of electronic beam scanning to +/-50° in all planes – the most of any mm-wave phased-array antenna to date, it is reckoned. A measured EIRP (equivalent isotropically radiated power) of 45dBm at 60GHz was achieved from the wafer-scale array at an operating temperature of 95-100°C, congruent with base-station temperatures, and within the FCC's EIRP power limits for the 60GHz band. The architecture could be scaled to 512 (16x32) or 1024 (32x32) elements due to on-chip antenna integration and the wafer-scale integration of multiple reticles on a single chip.  

TowerJazz's SBC18H3 BiCMOS process

The phased-array chip was developed using TowerJazz's SBC18H3 BiCMOS, which offers both high-performance 0.18µm SiGe bipolar and high-quality passive elements, combined with high-density 0.18µm CMOS, to enable high-speed networking and millimetre-wave applications. The process offers SiGe transistors with peak fmax of 280GHz and peak fT of 240GHz, suitable for low-power, high-performance millimetre-wave circuits, replacing the need for more expensive gallium arsenide chips, it is claimed.

The SBC18H3 process 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. TowerJazz also manufactures the faster, lower-noise process SBC18H4, which has an fmax of 340GHz.

The chip was designed and tested by Samet Zihir and Ozan Gurbuz of UCSD's Electrical and Computer Engineering Department under the supervision of professor Rebeiz, with help from TowerJazz's Dr Arjun Karroy. 

The SBC18H3 process is available through the TowerJazz multi-project wafer (MPW) system. The chip is available from UCSD (e-mail rebeiz@ece.ucsd.edu).

TowerJazz is exhibiting in booth #736 at the IEEE MTT-S International Microwave Symposium (IMS 2015) in Phoenix (19-21 May), where Rebeiz is presenting the paper 'A 60 GHz 64-element Wafer-Scale Phased-Array with Full-Reticle Design' (20 May, 1:50–2:10pm in Room 125AB).

See related items:

TowerJazz and UCI demo integrated 94GHz imaging transceiver with record performance in silicon

Phasor launching phased array transceiver using TowerJazz's SiGe BiCMOS for satcoms on the move

Tags: TowerJazz SiGe BiCMOS

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