Delta-Sigma .DELTA.-.SIGMA. modulator having a dynamically tunable continuous time Gm-C architecture
US5729230A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 17, 1996 |
| Grant date | Mar 17, 1998 |
| Priority date | — |
| Expiry date | Jan 17, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M3/454
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A continuous-time tunable Gm-C architecture for a .DELTA..SIGMA. modulator includes a tunable resonator and a low bit rate, high sample rate quantizer connected in a feedback loop. The resonator shapes the quantization noise spectrum so that the bulk of the quantization noise occurs outside the signal spectrum. A tunable Gm cell tunes the resonator's resonant frequency to maximize the modulator's SNR. The tunable Gm cell includes a fixed Gm cell having transconductance G.sub.f, a current divider and a recombination circuit that together effectively multiply G.sub.f by a factor .alpha., where -1<=.alpha.<=1, without effecting the cell's common mode current I.sub.cm. A positive current source supplies I.sub.cm, while maintaining a common mode resistance of R/2 and a theoretically infinite differential mode resistance. Thus, the resonator's resonant frequency can be varied from DC to approximately 1 Ghz while maintaining a stable common mode operating point and improving the modulator's quality factor.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.