Analog-to-digital converter survey and analysis
IEEE Journal on Selected Areas in Communications
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Many wireless and sensor receivers are pushing the analog to digital interface into the RF/IF region to reduce analog components, size and power, and to increase flexibility associated with more processing in the digital domain. This paper presents a flexible band pass ADC that supports A to D conversion at RF or IF with high resolution and relatively low sampling frequencies. The Band Pass ADC architecture incorporates sub-sampling, time interleaving, and delta sigma noise shaping. Time interleaving four low pass delta sigma modulator ADCs with sampling frequencies of fs facilitates a band pass ADC with a center frequency of fs or 3 fs. The quantization noise is reduced in a bandwidth fb near the center frequencies with an effective delta sigma over sampling ratio of fs/fb. MATLAB simulation results show that more than 8 bits of resolution are obtained for center frequencies in the 1.8 GHz to 3.0 GHz region with a bandwidth of 70 MHz using time interleaved first order delta sigma modulators operating with sampling frequencies of 600 MHz to 1.0 GHz. Resolution is increased for smaller bandwidths. Band Pass ADC center frequencies are changed by adjusting the modulator sampling frequency fs providing flexibility for a multichannel receiver.