Excess loop delay compensation technique for tunable bandpass delta sigma modulators

Excess loop delay is one of the most critical problems in continuous-time delta-sigma modulators as it leads to SNR degradation and even system instability. This paper discusses the effect of excess loop delay on a tunable continuous-time bandpass modulator, both analytically and by simulations. Furthermore, it suggests a simple compensation technique for the excess loop delay that preserves the modulator stability with a delay of one period. It is shown that the compensation achieves almost the ideal SNR of the modulator.