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Recently, I came across a statement: “ADC sampling is the conversion of continuous analog signals that change over time into time-discrete analog signals.” I noticed that some colleagues said this statement was incorrect, and that it should be the conversion of continuous analog signals into time-discrete digital signals. I thought about it and did not refute it; it is actually just a matter of perspective.
First, let’s take a look at the complete conversion process of ADC:
From the above process, we can see that ADC sampling (Sampling) is the first step in the analog-to-digital conversion (ADC) process, not the entire ADC process. It focuses on the discretization in the time domain. Therefore, the phrase “continuous analog signals that change over time” refers to analog signals that are continuous in both time and amplitude (i.e., the signal is continuous in both time and amplitude). After sampling, the signal becomes time-discrete analog signals, meaning the signal is captured only at specific time points, but the amplitude values are still continuous analog values, where the amplitude has not been quantized.
However, ADC includes not only sampling but also quantization and encoding. The overall output of the ADC is a digital signal, which is discrete in both time and amplitude. The “time-discrete analog signals” after sampling are merely an intermediate result, and then:
Quantization: Converts continuous amplitude into discrete amplitude (e.g., dividing into a finite number of levels).
Encoding: Converts the quantized values into binary digital codes (e.g., 16-bit numbers).
If we use “ADC sampling” to refer to the entire ADC process, this statement would be inaccurate because the complete output of the ADC is a digital quantity, not an “analog quantity.” However, here, “ADC sampling” clearly specifies the “sampling” part, so there is not much issue. It is just that in a less rigorous context, it can easily lead to misunderstandings.
Finally
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