The principle of mutual conversion between analog and digital signals

Analog-to-digital converters, ADCs, accurate to one decimal place, this kind of ADC accuracy is very low, very cheap, accuracy: 5, 6 digits is enough.

There are three basic processes for the digitization of analog signals:

The first process is "sampling", which is to extract the sample values of analog signals at equal intervals, so that continuous signals become discrete signals.

The second process is called "quantization", which is to transform the extracted sample value into the nearest numerical value, which indicates the size of the sampled value.

The third process is "encoding", which is to represent the quantized value as a set of binary numbers. The digitization of the analog signal can be done through these three processes, a method called "pulse coding".

After the digital signal is transmitted to the receiver, there needs to be a restoration process, that is, the received digital signal is converted back into an analog signal, which can be understood by the receiver. This process is called "digital-to-analog transformation" and reproduces it as a sound or image.

Summary. Analog and digital signals can be converted to each other. Analog signals are typically quantized using the PCM (Pulse Code Modulation) method and converted to a digital signal.

The PCM method is to make different binary values for different ranges of analog signals. For example, if we use 8 bits**, we can quantize the analog signal to 2 8 = 256 orders of magnitude. In practice, we often use 24-bit or 30-bit**.

Typically, a digital signal is converted to an analog signal by a carrier phase shift. Computers, LANs, and metro networks all use binary digital signals. At present, the actual transmission of the WAN has both binary digital signals and analog signals for digital signal conversion.

But due to its broader application prospects, digital signals are more commonly used. The ADC interface specified by the control board (e.g. micro:bit, Arduino) for analog-to-digital conversion.

The potentiometer and photocell use analog signals. They realize that digital signal conversion through the ADC port is too. So, it is very convenient to handle.

What is the conversion between digital and analog signals?

Analog and digital signals can be converted to each other. Analog signals are typically quantized using the PCM (Pulse Code Modulation) method and converted to a digital signal. The PCM method is to make different binary values for different ranges of analog signals.

For example, if we use 8 bits**, we can quantize the analog signal to 2 8 = 256 orders of magnitude. In practice, we often use 24-bit or 30-bit**. Typically, a digital signal is converted to an analog signal by a carrier phase shift.

Computers, LANs, and metro networks all use binary digital signals. At present, the actual transmission of the WAN has both binary digital signals and analog signals for digital signal conversion. But due to its broader application prospects, digital signals are more commonly used.

The ADC interface specified by the control board (e.g. micro:bit, Arduino) for analog-to-digital conversion. The potentiometer and photocell use analog signals.

They realize that digital signal conversion through the ADC port is too. So, it is very convenient to handle.

Digital-to-analog conversion. Digital-to-analog conversion is the conversion of discrete digital quantities into analog quantities of connection changes. Corresponding to digital-to-analog conversion is analog-to-digital conversion, which is the inverse process of digital-to-analog conversion.

The basic principle of d a conversion is to multiply the number to be converted by the step voltage to obtain the output voltage value, and then output.

Converting an analog signal into a digital quantity is called an analog-to-digital converter (AD converter); The conversion of digital quantities into analog quantities is called a digital-to-analog converter (DA converter). There are hundreds of monolithic integrated ADC and DAC chips on the market, and the technical indicators are becoming more and more advanced to meet the needs of different applications.

It goes through four steps: "sampling, holding, quantizing, and encoding";

The measurement of this analog signal at certain moments is calledSampling, quantify the influence of noise and receiver noise, and the sampling rate is generally fs=.

Usually the width of the sampling pulse, tw, is very short, so the sampling output is a narrow pulse with intermittent movements. In order to digitize a sampled output signal, it is necessary to maintain the instantaneous analog signal obtained from the sampled output for a period of time, which is the holdprocess

QuantifyIt is to convert the sampling signal of continuous amplitude into a digital signal with discrete time and discrete amplitude, and the main problem of quantization is the quantization error. Assuming that the noise signal is uniformly distributed in the quantization level, the mean square value of the quantized noise is related to the quantization interval and the input impedance value of the analog-to-digital converter.

EncodingIt is to encode the quantized signal into a binary ** output. Some of these processes are combined, e.g., sampling and holding are done continuously using a single circuit, and quantization and coding are also implemented simultaneously during the conversion process, and the time taken is part of the holding time.

A digital signal is a signal in which the independent variable is discrete and the dependent variable is also discrete, the independent variable of this signal is represented by an integer, and the dependent variable is represented by a number in a finite number.

In computers, the magnitude of a digital signal is often expressed as a binary number with limited bits;

For example, a binary number with a word length of 2 bits can represent 4 sizes of digital signals, which are and 11; If the signal varies in the range of -1 1, then these 4 binary numbers can represent 4 numeric ranges, i.e., [-1, 0), [0, and [, 1].

There are three basic processes for the digitization of analog signals: sampling, quantization, and coding.

Sampling refers to the substitution of a sequence of signal sample values at certain intervals for the original continuous signal in time, that is, the discretization of the analog signal in time.

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

Encoding is to represent the quantized value with binary digits according to a certain law, and then convert it into a binary or multi-value digital signal stream. The resulting digital signal can be transmitted through digital lines such as cables, microwave trunk lines, and satellite channels. At the receiving end, it is the opposite of the above-mentioned analog signal digitization process, and then returns to the original analog signal after post-filtering.

The process described above digitization is also known as pulse code modulation.

Sampling: The so-called sampling is to extract an instantaneous amplitude value (sampling value) of the voice signal at a certain time interval t, and a series of time-discrete sampling values obtained after sampling are called sample value sequences. The sampled sample value series is discrete in time, which can be multiplexed by time division, and each sampled value can be quantized and encoded into a binary digital signal.

Quantization: There are two ways of quantization, in the quantization method, only rounding is not rounded, that is, all input voltages between 0 1 volts are output 0 volts, and all input voltages between 1 2 volts are output 1 volts, etc. With this quantization, the input voltage is always greater than the output voltage, so the resulting quantization error is always positive, and the maximum quantization error is equal to the interval between the two adjacent quantization stages, δ.

Encoding: The simplest way to encode is binary encoding. Specifically, the n-bit binary code is used to represent the quantized sample values, and each binary number corresponds to a quantized value, and then they are arranged to obtain a digital information stream composed of binary pulses.

In addition to the natural binary code mentioned above, there are other forms of binary code, such as Gray code and folded binary code, etc.

Analog and digital signals can be converted to each other

Analog signals are generally quantized into digital signals by PCM pulse code modulation, that is, different amplitudes of analog signals correspond to different binary values, for example, 8-bit coding can quantize analog signals into 2 8=256 orders of magnitude, and 24-bit or 30-bit coding is often used in practice;

Digital signals are generally converted to analog signals by phase shifting the carrier. Binary digital signals are used in computers, computer LANs and metropolitan area networks, and in the 21st century, both binary digital signals and analog signals converted from digital signals are actually transmitted in computer WANs. But digital signals are more promising.

AD conversion. AD conversion is analog-to-digital conversion. As the name suggests, it is to convert the analog signal into a multi-file touch signal. It mainly includes integration type, successive approximation type, parallel comparison type, series parallel type, -modulation type, capacitor array successive comparison type and voltage frequency conversion type.

A D converter is used to convert analog quantities into digital quantities through certain circuits. Analog quantities can be electrical signals such as voltage and current, or non-electrical signals such as pressure, temperature, humidity, displacement, sound, etc. However, before the A D conversion, the input signal input to the A D converter must be converted into a voltage signal by various sensors.

Analog signals are generally quantified into digital signals by the PCM pulse code modulation method, that is, different amplitudes of analog signals correspond to different binary values, and digital signals are generally converted into analog signals by phase shift of the carrier.

The analog signal is sampled-quantified-encoded into a digital signal, and the digital signal is converted into an analog signal in the opposite direction.