Zero-position coding with separated baseband in low-power class-D audio amplifiers for mobile communications

A digital real-time implementation of a binary zero-position coding concept with separated baseband is presented. This coding concept applies to highly power-efficient class-D amplification for use in low-power mobile audio equipment. With its separated baseband - which by theory is free of distortion - this concept enables the design of ultra-linear class-D power amplifiers. The implemented coding system has a dynamic range of 70 dB and a separated baseband extending from 0 to 42 kHz with a resulting switching rate of only 97.6 kHz. Theory, implementation considerations, and measurement results are discussed.