DIGITAL BASEBAND RECEIVER IN A MULTI-CARRIER POWER AMPLIFIER

摘要

A power amplifier system and method for locating carrier frequencies across a frequency band, identifying the modulation format of each carrier, and locating and suppressing undesired intermodulation distortion (IMD) products generated by the power amplifier. The system includes an amplifier (138) for amplifying RF carrier signals in a main signal path (102), a variable phase shifter (122) and variable attenuator (120) on a feed forward path (104), and a tunable receiver (144) that digitizes a portion of the frequency band to baseband. The tunable receiver (144) includes a tunable voltage controlled oscillator (212) which provides an oscillating frequency to a mixer (204) and is phase-locked to a highly stable reference oscillator (208). The mixer (204) downconverts a desired RF based on the oscillating frequency to IF. A filter (220) passes only a selected portion of the IF signals, and the filter (220) has a passband sufficient to discern both narrowband and wideband carriers and their associated IMD products. Based on the locations of the carrier frequencies, a processing unit (240) determines the IMD locations of the carrier frequencies, determines the IMD locations, and adjusts the variable phase shifter (122) and variable attenuator (120) on the feed forward path (104) until the IMD products in the main signal path (103) are suppressed below a desired threshold.