The frequency spectrum of pulse width modulated signals
Signal Processing - Special section: Security of data hiding technologies
On the convergence of Volterra filter equalizers using a pth-orderinverse approach
IEEE Transactions on Signal Processing
| Hi-index | 0.08 |
This article demonstrates the feasibility of pulse-width-modulation (PWM) of discrete time signals in a digital audio amplifier without inducing the nonlinear distortion usually associated with straightforward PWM. This is achieved by prefiltering the signal prior to the PWM mapping in such a manner that the overall result is distortion-free. All processing is done in the discrete time domain and relies on the interpretation of PWM as a Volterra filter. Computer simulations on CD music signals were performed. With no upsampling the distortion due to PWM gave a signal-to-noise-ratio (SNR) of approximately 45-50dB. Using the prefiltering scheme developed in this work, dramatic improvements of the reconstructed signal quality was demonstrated. The 9th order prefilter gave an SNR of well above 90dB for the music signals tested. Experiments using the same signals upsampled with N=8 showed that a 3rd order prefilter was sufficient for removing PWM-induced distortion.