What is the main hardware used in the digital audio sampling and quantization process?

The main hardware is an analog signal to digital signal converter (A/D converter). A/D converter, also called analog-to-digital converter, refers to an electronic component that converts analog signals into digital signals. The function of A/D conversion is to convert analog quantities that are continuous in time and continuous in amplitude into digital signals that are discrete in time and discrete in amplitude. Therefore, A/D conversion generally goes through four processes: sampling, holding, quantization, and encoding. .

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

The main hardware analog-to-digital converter used in the digital audio sampling and quantization process is the analog signal to digital signal converter (A/D converter).

The circuit that converts analog signals into digital signals is called an analog-to-digital converter, or an analog-to-digital converter, referred to as an A/D converter (or ADC). The function of the A/D conversion is Convert analog quantities that are continuous in time and continuous in amplitude into digital signals that are discrete in time and discrete in amplitude. Therefore, A/D conversion generally goes through four processes: sampling, holding, quantization, and encoding. In actual circuits, some of these processes are combined. For example, sampling and holding, quantization and encoding are often implemented simultaneously during the conversion process.

Basic Principle

The basic principle of this converter is to sample the input analog signal at specified time intervals and compare it with a series of standard digital signals , the digital signal gradually converges until the two signals are equal. Then the binary number representing this signal is displayed. There are many types of analog-to-digital converters, such as direct, indirect, high-speed and high-precision, ultra-high-speed, etc. Each has many forms. The opposite function of the analog-to-digital converter is called a "digital-to-analog converter", also known as a "decoder". It is a device that converts digital quantities into continuously changing analog quantities. There are many types and forms.

Steps of analog-to-digital conversion

Analog-to-digital conversion generally goes through the steps of sampling, quantization and encoding.

Sampling refers to replacing the original time-continuous signal with a sequence of signal samples at certain intervals, that is, discretizing the analog signal in time.

Quantization is to use a limited number of amplitude values ​​to approximate the original continuously changing amplitude value, and change the continuous amplitude of the analog signal into a limited number of discrete values ​​with certain intervals.

Encoding follows certain rules to represent the quantized value as a binary number, and then converts it into a binary or multi-valued digital signal stream. The digital signals obtained in this way can be transmitted through digital lines such as cables, microwave trunk lines, and satellite channels.

Classification

There are many types of analog-to-digital converters, depending on their working principles. , can be divided into indirect ADC and direct ADC.

Indirect ADC first converts the input analog voltage into time or frequency, and then converts these intermediate quantities into digital quantities. Commonly used are double-integral ADCs whose intermediate quantities are time.

Parallel comparison type ADC: Since the parallel comparison type ADC adopts simultaneous parallel comparison of various magnitudes, each output code is also generated in parallel at the same time, so the fast conversion speed is its outstanding advantage. At the same time, the conversion speed is closely related to the output code bit. It doesn't matter how much. The disadvantages of the parallel comparison ADC are high cost and high power consumption. Therefore, this ADC is suitable for applications requiring high speed and low resolution.

Successive approximation ADC: Successive approximation ADC is another direct ADC. It also generates a series of comparison voltages VR, but unlike the parallel comparison ADC, it generates comparison voltages one by one, which are successively related to the input voltage. Compare respectively, and perform analog-to-digital conversion in a gradual approximation manner. Each conversion of the successive approximation ADC requires bit-by-bit comparison and requires (n 1) beat pulses to complete, so its conversion speed is slower than the parallel comparison ADC, much faster than the double integral ADC, and is medium speed ADC devices. In addition, when there are many digits, it requires much fewer components than the parallel comparison type, so it is the most widely used integrated ADC.

Double integrating ADC: It is an indirect ADC. It first integrates the input sampling voltage and the reference voltage twice to obtain a time interval that is proportional to the average value of the sampling voltage. At the same time, within this time interval, Use a counter to count standard clock pulses (CP), and the counting result output by the counter is the corresponding digital quantity. The advantages of the dual-integral ADC are strong anti-interference ability; good stability; and can achieve high-precision analog-to-digital conversion. The main disadvantage is the low conversion speed, so this kind of converter is mostly used in instruments that require high accuracy but low conversion speed, such as multi-digit high-precision digital DC voltmeters.

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