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The secret of supersampling: Why are high frequencies so critical to digital conversion?
In the field of digital signal processing, supersampling technology is quietly changing our audio and video experience. Especially in the application of digital-to-analog converters (ADC) and analog-to-digital converters (DAC), this technology not only improves the quality of digital signals, but also improves the efficiency of transmission. In this rapidly changing technological environment, it is crucial to understand the underlying mechanisms of how this technology works.
The essence of supersampling technology is to convert low-bit-depth digital signals into high-quality digital signals at an extremely high sampling rate.
Challenges of digital conversion
In the digital conversion process, a fundamental challenge lies in how to correctly characterize the various characteristics of analog signals. Typically, digitizing an analog signal directly transfers all noise from the system and transmission into the digital signal, which degrades the sound quality over time. To solve this problem, engineers had to find better digital methods, such as Nyquist rate ADCs. This method is designed at a sampling frequency higher than twice the highest frequency of the signal, but faces the requirement and complexity of highly precise components.
Advantages of supersampling
Compared with the Nyquist method, the oversampling strategy is to obtain lower bit depth results at a higher sampling frequency. Such a design can bring multiple benefits, including:
Noise shaping technology can shift noise to high-frequency areas above the signal response, and then easily filter out this part of the noise using a low-pass filter.
The trade-off between frequency and resolution
Another important consideration is the trade-off between frequency and resolution. By installing a drop filter after the modulator, not only can the noise in the signal be filtered, but the sampling rate can also be reduced, thereby increasing the representable frequency range and sample resolution. This process is similar to a time averaging operation, allowing the rapidly sampled data stream to be integrated.
Improvement and change
In the history of digital conversion, a highly influential improvement was the supersampling technique combined with subfeedback, which was first proposed by De Jager in 1952 and introduced by Enos and his colleagues in 1962. The team elaborates further.
High-order modulators and multi-bit quantizers
For users, high-order modulators not only further shape noise, but also effectively reduce quantization noise in the baseband frequency. As sampling rates increase, gamma shaping becomes increasingly important. This process allows us to achieve more accurate sound quality in the digital conversion.
Even if it is a unit-bit modulation, its pulse density modulation (PDM) appropriately exhibits the characteristics of high sampling frequency.
Future Outlook
Today, supersampling technology is not only widely used in digital audio, but is also rapidly penetrating into digital video and other fields. Through powerful digital circuits, this technology continues to improve our digital media experience and paves the way for future new technology applications.
With the advancement of technology, can we imagine that there will be a more extreme digital conversion experience in the future, even beyond our imagination, creating new sensory enjoyment for users?
