TOKYO Toshiba Corp. has fabricated a 60-GHz receiver CMOS chip which it claims can drastically lower the cost of devices for emerging millimeter-wave communication applications.
The advance was presented Friday (June 15) at the 2007 Symposia on VLSI Circuits in Kyoto, Japan.
The test chip measures 2.4 by 1.1 mm, and all required receiver function blocks were integrated, including an antenna, low-noise amplifier, mixer (down converter) and a phase-lock loop (PLL) synthesizer, using a 90-nm CMOS process. "We integrated a PLL synthesizer on chip and believe that it's the first chip that operates alone as a receiver," said Toshiya Mitomo, a researcher at Toshiba Mobile Communication Laboratory.
Millimeter-wave communication chips operating at 60 GHz have previously been fabricated with gallium arsenide. GaAs modules required the integration of an antenna and a synthesizer separately using bonding wire. The result is a bulky, expensive device.
By contrast, Toshiba's CMOS device promises to lower fabrication costs to one-tenth the cost of a GaAs module, claimed Koji Ogura, Laboratory leader of Toshiba Mobile Communication Laboratory.
When CMOS process technology is applied at high frequencies like a 60-GHz receiver, however, silicon substrates easily leak signals. Parasitic elements are generated at wiring interconnects on the substrate in blocks such as the amplifier and the mixer. The fab problems make chip operation unpredictable.
To solve them, Toshiba engineers used a fully differential structure, including a differential on-chip dipole antenna. The differential structure is already being used in devices like mobile phones, but is relatively rare in 60-GHz devices, said Mitomo.
By adding noise and parasitic elements in opposite phases as a way to cancel them, the structure drastically suppressed their influence, Mitomo added.
Toshiba's test chip operated in the 61.5-GHz range with power gain of 22 dB.
Next, the Toshiba researchers plan to develop a high-power amplifier needed for a transmitter IC. They will then seek to find an application for their single-chip millimeter-wave CMOS transceiver.