Digitally Tunable Capacitors Make Possible Antenna Tuning

Nov 18, 2008 12:15 PM, MD&D News Staff

The DuNE Technology from Peregrine Semiconductor Corp. has enabled a single-die tunable capacitor circuit—a Digitally Tunable Capacitor (DTC)—that meets the performance demands for antenna tuning in leading-edge cellular and mobile applications. The devices offer excellent power handling and linearity, low power consumption, and high integration in a small form factor.

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Antenna tuning is desirable in the latest cellular and mobile systems because it can recover some of the performance lost to new features, functionality, and industrial design requirements. These factors reduce the space available for antennas. Antenna tuning uses dynamic impedance tuning to optimize the antenna performance for both the frequency of operation and the environmental conditions.

Because Peregrine’s UltraCMOS technology allows the monolithic integration of RF, analog, and digital circuitry, a single-die DuNE DTC can integrate high-Q tunable capacitors with a built-in low-voltage serial interface in a chip-scale package with a footprint five times smaller than competing technologies, according to the company.

In cellular applications, the result is a Q of 40 to 80 at 1 to 2 GHz, typical capacitances of 0.5 to 10 pF, and typical tuning ranges of 3:1 to 6:1 with five-bit (32-state) resolution. Power handling is greater than +38 dBm into 50 Ω. Linearity (IP3) is better than +65 dBm, and switching speed is better than 5 μs.

In mobile TV applications, the DuNE Technology provides a Q of 40 to 70 at 470 to 862 MHz for a 1.36 to 6.3 pF (4.6:1) tunable capacitor. Current consumption is only 11 μA at 2.75 V, while power-handling capability is +28 dBm and IIP3 is greater than +62 dBm.

Peregrine plans to release individual DTC devices during 2009, beginning with DTCs for mobile TV, which will be offered in 2- by 2-mm, eight-pin dual flat no-lead (DFN) packages.