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An improved low distortion sigma-delta ADC(analog-to-digital converter) for wireless local area network standards is presented.A feed-forward MASH 2-2 multi-bit cascaded sigma-delta ADC is adopted;however,this work shows a much better performance than the ADCs which have been presented to date by adding a feedback factor in the second stage to improve the performance of the in-band SNDR(signal to noise and distortion ratio),using 4-bit ADCs in both stages to minimize the quantization noise.Data weighted averaging technology is therefore used to decrease the mismatch noise induced by the 4-bit DACs,which improves the SFDR(spurious free dynamic range) of the ADC. The modulator has been implemented by a 0.18μm CMOS process and operates at a single 1.8 V supply voltage. Experimental results show that for a 1.25 MHz @-6 dBFS input signal at 160 MHz sampling frequency,the improved ADC with all non-idealities considered achieves a peak SNDR of 80.9 dB and an SFDR of 87 dB,and the effective number of bits is 13.15 bits.
An improved low distortion sigma-delta ADC (analog-to-digital converter) for wireless local area network standards is presented. A feed-forward MASH 2-2 multi-bit cascaded sigma-delta ADC much better performance than the ADCs which have been presented to date by adding a feedback factor in the second stage to improve the performance of the in-band SNDR (signal to noise and distortion ratio), using 4-bit ADCs in both stages to minimize the quantization noise. Data weighted averaging technology is therefore used to decrease the mismatch noise induced by the 4-bit DACs, which improves the SFDR (spurious free dynamic range) of the ADC. The modulator has been implemented by a 0.18 μm CMOS process and operates at a single 1.8 V supply voltage. Experimental results show that for a 1.25 MHz @ -6 dBFS input signal at 160 MHz sampling frequency, the improved ADC with all non-idealities can achieve a peak SNDR of 80.9 dB and an SFDR of 87 dB, and the effective n umber of bits is 13.15 bits.