Wide-bandwidth, high-dynamic-range linear amplifier for a CDMA transmitter in a wireless base station

摘要

A CDMA base station transmitter employing the Kahn envelope-elimination-and-restoration technique includes a switching amplifier adapted to linearly amplify the low-level baseband signal derived from the digital amplitude information portion of the digital CDMA signal to be transmitted downlink. In order to achieve the wide bandwidth and high dynamic range needed to linearly amplify the low-level baseband signal derived from the digital amplitude portion of the CDMA signal, a truncating circuit truncates a predetermined number of the least significant bits of each word of the digital amplitude portion before the amplitude portion is converted to a low-level baseband signal and is amplified by the switching amplifier. High resolution is restored to the amplified output by a power-dissipating post regulator at the output of the switching amplifier, which dissipates the switching amplifier's high level, low resolution output power in accordance with an error signal produced in a high-gain feedback loop from the difference between the output of the regulator and the baseband signal derived from the all the bits in each word of the amplitude portion, thereby driving the error signal to zero and imparting the desired high resolution to the regulator output.