The conversion of an analog signal into a digital signal introduces noise in the signal, which is called quantization noise. A higher resolution implies lower quantization noise or a higher signal-to-noise ratio SNR. However, that is not the end of the story. A delta-sigma modulator behaves as a lowpass filter for the signal and a highpass filter for the quantization noise, thus pushing the noise to higher frequency regions, as shown in Figure 3.
This phenomenon is called quantization noise shaping, and is taken advantage of by employing digital decimation that effectively lowpass filters the modulator output and removes the quantization noise. The reduction of noise power in the frequency band of interest means a higher SNR or a greater dynamic range, as the noise floor has been significantly lowered.
This improvement in SNR due to oversampling can be seen in Equation 2, where F s is the sample rate, K is the oversample factor, and BW is the bandwidth of the input signal. Figure 3 illustrates quantization noise shaping, which is one of the key advantages of delta-sigma ADCs. This allows high-resolution measurements with maximum accuracy, due to noise shaping and filtering. These devices are commonly used for strain, load, and pressure measurements in structural testing applications.
The thermocouple module is used in a wide variety of applications with varying sizes, as well as high-channel-count data acquisition systems for applications, such as temperature chamber monitoring. Applications of these devices include audio signal analysis, acoustics, vibration and modal analysis, and essentially any application that requires simultaneous sampling, large dynamic range about dB , and wide alias-free bandwidth DC to about 0.
Unlike other converter technologies, delta-sigma ADCs are free-running, meaning the input signal to the ADC is continuously being sampled even before a trigger condition happens. Moreover, because of the digital decimation filtering process, there is a delay before the input signal is converted to a digital sample.
This delay is specified as the number of samples that the input signal acquired before the trigger was received. This delay may or may not have to be compensated for, depending on whether you are using a digital or analog trigger. Refer to device specific product documentation for more information. Delta-sigma ADCs implement oversampling, decimation filtering, and quantization noise shaping to achieve high resolution and excellent antialiasing filtering.
This paper explains the delta-sigma ADC architecture and the SC Express approach to automatically compensating for filter delays in software. Back to top. Oversampling Delta-sigma ADCs use sample rates that are a large multiple, for instance, times the sample rate sufficient for a given signal. Digital Decimation Filtering The bit stream from the delta-sigma modulator is output to a digital decimation filter that averages and downsamples, thus producing an n-bit sample at the desired sample rate, Fs.
Quantization Noise Shaping The conversion of an analog signal into a digital signal introduces noise in the signal, which is called quantization noise. Figure 3.
Oversampling results in quantization noise shaping. Compensation for Digital Filter Delay Unlike other converter technologies, delta-sigma ADCs are free-running, meaning the input signal to the ADC is continuously being sampled even before a trigger condition happens. Stamatios Manesis. PC Interfacing. Pei An. Automotive Radar Sensors in Silicon Technologies.
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