4GHz continuous-time bandpass delta-sigma modulator for directly high IF A/D conversion

ABSTRACT

We present in this article a fourth-order integrated LC bandpass Delta-Sigma modulator for direct conversion of high intermediate frequencies. It is designed in a 0.25 μm BiCMOS SiGe:C process from STMicroelectronics. The modulator is able to direct digitize a 1GHz IF signal in a 20MHz bandwidth. The continuous-time loop filter employs two integrated LC resonators with active Q?enhancement circuits. A multi-feedback architecture is used to achieve higher order noise-shaping, while maintaining the modulator stability. A multibit quantizer was implemented to reduce quantization noise and improve stability.

REFERENCES

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INDEX TERMS

Primary Classification:
  B. Hardware
  B.7 INTEGRATED CIRCUITS
      B.7.1 Types and Design Styles
          Subjects: VLSI (very large scale integration)

General Terms:
Design

Keywords:
A/D conversion, bandpass delta-sigma modulator, continuous-time delta-sigma modulator, high order noise-shaping, high-IF sampling, multi-feedback architecture