Author
Abstract
This paper proposes hybrid architecture of feedforward/feedback second order
single-loop modulator for high resolution analog-to-digital converter (ADC)
applications. Different techniques for oversampling modulator are discussed. The
proposed architecture consists of three stages. The first stage is 2nd order single
loop oversampling ADC with novel feedforward/feedback architecture. In the
second stage, an error cancellation circuit (ECC) is proposed at the output of the
modulator to noise shaping of quantization noise. In addition, the third stage is a
decimation filter in order to reduce the oversampling ratio (OSR) which is suitable
for broadband applications. With low OSR=24, the signal-to-noise ratio (SNR) is
improved about 55 dB if compared with traditional architecture (feedback singleloop
high order topology). The achieved resolution or the effective number of bits
(ENOB) is (22-bit). With high OSR=256, the net improvement in quantization
noise reduction is 64 dB if compared with feedforward architecture (single-loop
high order) and the ENOB=28. Finally a 1-bit quantizer is used in the proposed
architecture which greatly decreases the circuit implementation complexity and
power consumption. Simulation results show the superiority performance of
proposed hybrid architecture as compared with traditional modulator topologies
(feedforward and feedback).
Keywords
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