Computationally Efficient Conversion from Pulse-Code Modulation to Naturally Sampled Pulse-Width Modulation
This paper describes two new algorithms to convert a uniformly sampled sequence into a naturally sampled pulse-width modulation (NPWM) signal. They are suitable for both single- and double-edge NPWM. Single-edge algorithm A requires nine additions and seven multiplications per output sample and achieves a total harmonic distortion (THD) of -88.48 dB when the input signal is a 6.66-kHz tone upsampled 8 times. Single-edge algorithm B requires 14 additions, 11 multiplications, and one comparison per output sample and yields -113.07 dB of THD under the same conditions. Intermodulation distortion is very low for both algorithms. Polynomial interpolation methods with the same degree of accuracy are computationally more expensive. The algorithms have enabled the implementation of digital audio amplifiers performing efficient real-time digital signal processing.:
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