Mixed-Domain Signal Processing

We argue that mixing domains within circuits and systems can result in new possibilities. We have presented several examples of mixed-domain systems. Internally time-varying (but externally time-invariant) circuits can be designed to consume only the minimum power needed for each task at hand. Several techniques have been presented for making this possible, while avoiding output transients. Internally nonlinear (but externally linear) digital filters make possible 1) keeping internal signal strength large, even for small-strength inputs and 2) maximizing signal-to-error ratio for a large range of input signals. Continuous-time DSP may offer certain advantages of digital technology without its drawbacks: 1) fully digital (noise immunity, programmability), 2) no sampling; thus no signal aliasing, 3) smaller in-band quantization error, and 4) power goes down with decreasing input activity. All of the principles discussed are at the early research stage; none has reached commercial feasibility. Thorough experimental validation and application of some of the principles presented are being pursued