Abstract: A method and apparatus for providing input voltages to power amplifiers (PAs) is disclosed. For one embodiment, a multiple-mode device having a corresponding PA for each mode is provided with a voltage adjustment mechanism that adjusts the output voltage from the switcher based upon the PA that is currently in use. The voltage adjustment mechanism may be controlled by firmware or software of a digital processing system (DPS) of the host device. The voltage adjustment mechanism may include a digital potentiometer controlled by the host DPS.

Abstract: A cellular subscriber modem for receiving CCITT-type quadrature amplitude modulated (QAM) signals. The cellular modem includes a novel symbol detector that converts received symbol information to polar notation. The detector's constellation thresholds include a circular threshold having a radius greater than the magnitude of the innermost symbols, but less than the magnitude of the outermost symbols, and radially spaced thresholds, which further discriminate between the outermost symbols. As a result, special cellular-compatible modem equipment need not be connected between the public-access switched telephone network and the computer equipment at the other end, which means that a CCITT-compatible cellular subscriber modem can then be treated as any other type of CCITT-modem. The detector may be implemented in the software of a standard modem processor, or as several analog comparator circuits.