Cascaded feedforward sigma-delta modulator for wide bandwidth applications

Abstract

In this paper, we propose a cascaded feedforward sigma-delta modulator for wide bandwidth applications. In our proposed approach, we use a 1.5-bit quantizer as feedback in the multi-bit sigma-delta modulator. The 1.5-bit feedback may cause coarse quantization errors, however the error can be canceled in the digital part. Here an adaptive filter with least mean square algorithm is used to reduce the nonlinear effect. The simulation results show that the SNDR of this architecture is very close to that of the ideal feedforward summation sigma-delta modulator with multi-bit DAC and can be used for the wide bandwidth application.