Baseband digital offset correction

摘要

A signal processing system includes a main digital-to-analog converter (DAC) for receiving a digital baseband signal and converting the digital signal into an analog signal. Also included in the system is a connection circuit for receiving the analog signal, and output terminal, and an analog filter coupled between the connection circuit and the output terminal for filtering the analog signal. The system includes a calibration circuit coupled between the connection circuit and the output terminal for setting an offset voltage level. The calibration circuit includes (a) an approximation circuit coupled to the output terminal and operable during a calibration mode to determine the offset voltage level and store the offset voltage level as a digital offset signal and (b) an offset DAC coupled between the connection circuit and the approximation circuit for converting the digital offset signal into the offset voltage level. The connection circuit, which is a node, subtracts the offset voltage level from the analog signal.