An A/D Scheme Of Stepped Signal Superimposition Based On Oversampling Theory

With the continuous development of science and technology, digitization and the accuracy of the product play more and more important roles in many systems. Many products need to be measured based on analog to digital converter (ADC), which aims to transfer the analog signal which needs to be detecting into a digital signal, in order to facilitate better transmission and processing. And with the development of human cognition, and more and more fields (such as astronomy, biology medicine, seismology and other areas) need to be explored, and the detection of weak signals (such as: weakening Magnetic signal, low light, micro-vibration, small displacement detection of ECG, EEG, etc.) have been the key factor to explore uncharted territory. However, when we are detecting of weak signals, due to the limited performance of general detection devices and A/D converters and other device, the test results often cannot meet the need to probe the unknown. When using high-precision A/D converter, testing costs will be high. In many cases, before performing detection, amplifying and filtering the input signal could make the small amplitude of the signal enter the recognition range of the A/D converter, and then use the normal precision of the A/D converter for sampling, quantization, and then realize the detection of signal. But this will add the complex amplifier, and makes the system becomes complicated, and not conducive to reduce costs.In order to improve the A/D converter’s ability to identify signals, and to increase the effective number of bits of A/D conversion, the concept of oversampling has been proposed. Over-sampling technique is a common method for ADC to increase resolution, the method by increasing the sampling frequency could reduce the noise power which is mixed in the pass band of the input signals, thereby improving the signal to noise ratio, thus increasing the effective bit number of ADC. Due to the wide range of applications of oversampling, it rapidly becomes a widely used method in the A/D converter field. Based on the theory of oversampling, experts made a lot of approaches to improve ADC’s accuracy, further enriching the oversampling theory. Among numerous scenarios, Δ-Σ modulation and triangular wave modulation has a relatively wide range of applications.In this paper, the idea comes from the mean gradient theory. In the mean gradient scheme, a stepped signal was added to the input signal, the total amplitude of stepped signal is 1LSB, and the amplitude of each ladder is 1/2m LSB, after applying the mean gradient scheme, resolution of A/D system turns into 2m times over the original one. Although the mean gradient theory’s effect on improving the A/D resolution is obvious, but because of the volatility of the value ladder program is too small, it is difficult to be widely promoted in the application.Inspired by the mean gradient theory, based on oversampling theory, this paper presents a method named ladder wave superposition based on oversampling. This method aims to overcome the detection problem of low A/D deficiency, using the low-resolution A/D device, on the basis of saving testing costs, to realize high-precision measurements. This method is not only applicable to the general A/D detection system, and it elevates the input signal level by adding the stepped sign also that weak signals can enter the identification range of the ordinary A/D converter, then enables detection of weak signals. Step wave superposition method based on oversampling provides a new approach for weak signal detection, it has a good prospect in weak signal detection area.Finally, the paper offers the simulation experiments of step wave superposition scheme based on oversampling in weak signal detection, the simulation results shows that the method achieves the goal to improve the resolution and demonstrate the effectiveness of this method.