Time-Quantized Frequency Modulation, Time-Domain Dither, Dispersive Codes, and Parametrically Controlled Noise Shaping in SDM
Time-domain quantization (TDQ) and noise shaping applied to linear frequency modulation (LFM) offers an alternative although unconventional means of generating uniformly sampled 1-bit code with characteristics similar to that generated by feedback sigma-delta modulation (SDM). Fundamental insight into the SDM process emerges by exploiting the relationship between uniform quantization and phase modulation. Linearity and output noise spectra are benchmarked against linear pulse-code modulation (LPCM) and error spectra derived by comparing 1-bit SDM against an identical feedback loop but without quantization. Sony FF class SDM is discussed and an example is shown to achieve almost noiseless performance from 0 Hz to 30 kHz by incorporating parametrically determined noise shaping stabilized by step-back in time closed-loop control.
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