Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Asynchronous analog-to-digital converter based on level-crossing sampling scheme | Kafashan et al. EURASIP Journal on Advances in Signal Processing 2011 2011 109 http content 2011 1 109 o EURASIP Journal on Advances in Signal Processing a SpringerOpen Journal RESEARCH Open Access Asynchronous analog-to-digital converter based on level-crossing sampling scheme Mohammadmehdi Kafashan Sajjad Beygi and Farrokh Marvasti Abstract In this paper a new iterative algorithm is used to convert analog signals to digital A D using an asynchronous A D converter. It is a realtime system which encodes the amplitude information of the analog signal into a time sequence. In particular using asynchronous systems for data conversion is an effective technique in order to reduce power consumption. The decoder should recover original signal from irregular samples. If a more intelligent reconstruction technique is used for decoding signals with higher bandwidth can be digitized. In this work we employ delta- and sigma-delta level-crossing sampling schemes. These asynchronous A D converters are simple to implement and have very good performance with lower power consumption. Keywords signal reconstruction analog-to-digital converter level-crossing sampling iterative algorithm 1 Introduction Analog-to-digital converters have many applications in digital signal processing and communication systems. Conventional A D converters consist of two steps sampling operation followed by digital quantization. The noise introduced by signal distortion due to quantization decreases the A D performance. In the literature the performance of A D converters is measured by the number of bits per sample and signal-to-noise ratio SNR 1 2 . Uniform sampling is used for synchronous implementation where a common clock is operated in order to convert analog signals to digital values. In the sigmadelta modulator the original signal is highly oversampled and the internal clock operates at a much higher rate than the bandwidth of the signal however the oversampled signal .
