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系统设计的CMOS开关电流带通Σ - Δ调制器的数字通信芯片
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The current explosion of interest in the realization of mixed-signal systems on
chip using VLSI technologies has motivated the use of oversampling Sigma-Delta
Analog-to-Digital Converters (ADCs) to implement the front-end of such systems.
This type of ADCs, composed of a low-resolution quantizer embedded in a
feedback loop, uses oversampling (a sampling frequency much larger than the
Nyquist frequency) to reduce the quantization noise and modulation [Inos62] to
push this noise out of the signal band. The combined use of redundant temporal data (oversampling) and filtering modulation) results in high-resolution, robust
ADCs, which have lower sensitivity to circuitry imperfections and are more suitable than traditional Nyquist-rate ADCs for the implementation of Analog-to-Digital(A/D) interfaces in a standard CMOS technology.
The efficiency of ADCs has been demonstrated in a large number of ADC
Integrated Circuits (ICs) for digitizing lowpass signals with diverse bandwidths and applications [Nors97][Mede99]. Recently, the principle of modulation has been
extended to bandpass signals, leading to a new type of ADCs, named BandPass
ADC [Schr89], which are especially suited to convert bandpass
signals with a narrow bandwidth. This has an obvious application at the front-end of modern wireless communication systems such as mobile phones, digital radio
receivers, etc.
have much in common with their lowpass counterparts – whose
basic properties and limitations have been described elsewhere [Nors97][Mede99].
However, there are some issues which are peculiar to This chapter is devoted to the description of these issues. In Section 1.2, digital radio receivers are
described, pointing out the need for an ADC at the IF location. Section 1.3 and Section 1.4 give an overview of ADCs. Section 1.5, Section 1.6 and Section 1.7explain the basic concepts and architectural issues of , Finally, Section 1.8 summarizes the performance of state-of-the-art.
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