LONDON — Fujitsu Laboratories Ltd. has said it has developed a millimeter-waveband power amplifier (PA) using a standard 90-nm CMOS process technology.
Fujitsu Labs (Tokyo, Japan) applied CMOS modeling technology and design techniques to minimize high-frequency signal loss and get the extreme operational frequencies out of the process technologies, the company said. Fujitsu claimes the circuit is the first CMOS-based PA that operates at 77GHz. The technology realizes CMOS radio frequency front-end circuitry that includes a power amplifier, thereby enabling integration with baseband circuitry on a single chip, for use in millimeter-wave automotive radar systems.
A paper is due to presented on the circuit at the International Solid-State Circuits Conference (ISSCC) 2008 to be held in San Francisco from February 3 to 7.
The application of standard CMOS technology in millimeter-wave circuitry has been problematic due to signal loss. In order to boost the gain in an amplifier, a number of factors that are not evident on a circuit diagram, such as parasitic capacitance, need to be accurately reflected. In addition, signal loss in a matching circuit needs to be suppressed to enable maximum amplification performance.
Fujitsu Labs developed two technologies that make it possible to apply standard CMOS technology to millimeter-wave amplifiers.
Fujitsu Labs established a transistor model that shows the operating characteristics at millimeter-waveband and developed parameter-extraction method technology. To keep the circuitry compact, Fujitsu Labs developed a "short stub" matching circuit and integrated it with the power-supply circuitry in a way that would further reduce signal losses. This reduced the amount of chip space required by the matching circuit to one-tenth previous levels, and also reduced signal loss to 0.4-dB.
The resulting CMOS PA operates at 77 GHz with 8.5-dB gain and 6.3 decibel milliwatts (6.3dBm) saturated output power. Furthermore, a separate PA operating at 60GHz was developed and achieved 8.3 dB of gain and 10.6 dBm saturated output power.
Fujitsu Labs' new technology makes it possible to implement 77GHz automotive radars using inexpensive standard CMOS technologies. These developments could also be used to extend the transmission range of wireless communications systems in the 60GHz band.
Furthermore, by combining baseband circuitry with RF front-end circuitry on one chip, millimeter-waveband transceiver chips — which had been expensive to produce in the past — can now be made considerably smaller. As a result, widespread application of millimeter-waveband technologies in both automotive radar systems and wireless communications systems is anticipated in the future.
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