Automatic antenna tuning for RF transmitter IC applying high Q antenna

Automatic antenna tuning circuitry is presented for high Q printed antennas. It is applied in a general purpose 0.6 /spl mu/m BiCMOS transmitter chip devoted to short range applications in the ISM bands (315, 434, 868 and 915 MHz). The circuitry maintains maximum output power without the application of external matching circuit and/or costly tuning procedures usually required to counter technological spreading. Real time compensation of environmental variations such as "hand effect" is also possible. As the efficiency of the driver stage is close to maximum with high Q antennas, the power consumption is reduced at the targeted output power ranges (-20...+10 dBm).

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