What is nonlinear distortion?

Question 1: The difference between linear distortion and nonlinear distortion is 1) for different reasons. Linear distortion is due to the existence of linear components in the circuit, whose impedance varies with frequency, resulting in different amplification and delay times of signal components with different frequencies in such a large electrical appliance. However, nonlinear distortion is caused by introducing nonlinear components or entering nonlinear regions. 2) With different results, linear distortion may change the magnitude and relative time relationship of signal components with different frequencies, but it will never produce new frequency components that the input signal does not have. The main feature of nonlinear distortion is that it produces new frequency components that the input signal does not have.

Question 2: What is distortion? Distortion, what is distortion?

According to the different situations of waveform distortion, it can be divided into amplitude distortion, frequency distortion and phase distortion. Amplitude distortion is called amplification of signals with different amplitudes. Amplification of signals with different frequencies is called frequency distortion. For signals with different frequencies, the difference of time delay after amplification is called phase distortion (or time delay distortion).

Distortion is a phenomenon that the amplitude proportional relationship, phase relationship and waveform shape of input signal and output signal change. Distortion of audio power amplifier can be divided into two categories: electrical distortion and acoustic distortion. Electrical distortion is caused by the circuit, while acoustic distortion is caused by the speaker of the sound reproduction device. The types of electrical distortion are harmonic distortion, intermodulation distortion and transient distortion. Acoustic loss * * * If the AC interface is deformed. According to the nature, there are nonlinear distortion and linear distortion.

Linear distortion refers to the change of amplitude and phase relationship between signal frequency components, and only the amplitude and phase distortion of waveform appears, which is characterized by not producing new frequency components.

Nonlinear distortion refers to the distortion of signal waveform and new frequency components. The main points of distortion produced by audio power amplifier are as follows:

I. Harmonic distortion

This distortion is caused by nonlinear elements in the circuit. After the signal passes through these components, it will produce new frequency components (harmonics) and interfere with the original signal. This distortion is characterized by the inconsistency between the waveform of the input signal and the waveform of the output signal, that is, waveform distortion. The main ways to reduce harmonic distortion are: 1, and appropriate negative feedback is applied. 2. Choose an amplifier with high characteristic frequency, low noise figure and good linearity. 3. Improve the power reserve and filter performance of the power supply.

Second, intermodulation distortion.

Two or more signals with different frequencies generate beat frequencies through amplifiers or speakers, forming new frequency components. This distortion is usually caused by active devices in the circuit, such as transistors and electron tubes. The amplitude of distortion is related to the output power. Because these newly generated frequency components are not similar to the original signal, less intermodulation distortion is easy to be detected by human ears.

Methods to reduce intermodulation distortion: 1. Electronic frequency division is used to limit the working bandwidth of amplifier circuit or speaker, thus reducing the occurrence of beat. 2. Choose a pipeline or circuit structure with good linearity.

Question 3: What is "nonlinear distortion"? Nonlinear distortion: When the input speaker is a single-frequency signal, the output sound signal of the speaker contains its frequency doubling component. This distortion phenomenon is called nonlinear distortion.

Question 4: What does the nonlinear distortion of transistor mean? The current characteristic of transistor (collector) has a saturation region, that is, Ic will not increase after Ib increases to a certain extent.

This will distort the user's signal. If it is a sine wave, the top is cut off.

This is an extreme example. In fact, as long as Ic and Ib can't keep a linear relationship, the waveform will go out of shape. This distortion is nonlinear.

Question 5: What is the cause of nonlinear distortion of transistor amplifier circuit? Many factors. Actually, there is no absolute linear region. Affected by temperature and so on. The ideal view is:

Mainly the value of the transistor is the current amplification factor. The so-called parameters are all extended with this. The emitter voltage is less than a certain value and has not been turned on, so it is nonlinear at this time. When it is greater than this value, it is in normal working state, and it is linear at this time. Collector current = emitter current X. This value is that when this value continues to increase, the collector current cannot increase indefinitely. Beta will drop sharply. Then it is nonlinear. So we want it to work in a linear region. The whole circuit will appear nonlinear distortion.

Question 6: What is the nonlinear distortion of an amplifier? One of the reasons is that the triode in the amplifier circuit is a nonlinear element. When its working current changes, its amplification factor and input resistance will change. For sinusoidal signals with the same frequency, the amplification factor will be different when the input signal amplitude is different. The second reason is that the inductive elements (including transformers) and capacitive elements in the amplifier circuit will produce different impedances and phase shifts for signals with different frequencies. When the input signal is non-sinusoidal, it can be decomposed into several sinusoidal signals with different frequencies. When these signals pass through a circuit containing inductance and capacitance, the circuit will reflect these frequencies differently. After they are synthesized by the amplifier circuit, they will have great changes with the waveform of the original signal.

Question 7: Correlation analysis of nonlinear distortion The amplitude of output signal voltage of amplifier circuit is limited by saturation region and cutoff region. Under the condition of given circuit parameters, the amplitude of output voltage without obvious distortion is called the maximum output amplitude, which is usually expressed by peak value or peak-to-peak value. Limited by the saturation region, the maximum output voltage can only reach (UCEQ -UCES), and limited by the cutoff region, the maximum output voltage can only reach IC. Therefore, the maximum amplitude of the actual output voltage can only be twice the smaller value in (UCEQ-UCES) and IC (peak-to-peak). The setting of static working point has great influence on the maximum output amplitude. In order to obtain a larger output amplitude, the Q point should be set near the midpoint of the AC load line. The distortion caused by transistor working in nonlinear region is called nonlinear distortion. The causes of nonlinear distortion come from two aspects: one is the nonlinearity of transistor characteristics; Second, the Q-point setting is inappropriate or the input signal is too large. It is explained that the distortion caused by the high or low selection of Q point makes the transistor enter the saturation region or the cutoff region in part of the time of the input signal, which is called saturation distortion and cutoff distortion respectively. In order to avoid the cutoff distortion caused by the instantaneous working point entering the cutoff zone, we should make IC≥ICm +ICEO GS02 18. In order to avoid the saturation distortion caused by the instantaneous working point entering the saturation region, we should take the multimedia service of UCE≥Uom+ UCES GS02 1 as one of its future development directions, and the multimedia service needs high-speed data transmission to support it, so broadband transmission is wireless communication. Orthogonal frequency division multiplexing (OFDM) technology can effectively resist the interference between signal waveforms, has excellent anti-noise performance and anti-multipath fading ability, and has high spectrum utilization rate, and is suitable for high-speed data transmission in wireless mobile channels with multipath propagation and Doppler frequency shift. With its inherent ability of resisting delay spread and high spectrum utilization, OFDM technology has quickly become a research hotspot and the core technology of the next generation wireless communication. As we all know, OFDM signals have high peak-to-average power ratio, which requires high linearity of high power amplifier (HPA). Otherwise, nonlinear distortion will occur, which will lead to spectrum expansion and in-band signal distortion and worsen system performance. Therefore, it is necessary to suppress the nonlinear distortion of the system. In this paper, a distortion compensation technique combining PTS(Partial trans * * * lt sequence) and RLS (recursive least square method) is proposed, which can effectively reduce the nonlinear distortion of high power amplifier. 2. 1 Partial transmission sequence Partial transmission sequence (PTS) First, each OFDM symbol is divided into V sub-blocks, each sub-block is multiplied by a phase factor, and then X ′ (k) is IFFT-operated to obtain X ′ (n). The phase factor bi should be selected to make the peak-to-average power ratio of x ′ (n) the lowest. 2.2 adaptive compensation therefore, the amplitude predistortion is realized by inverting the AM/AM characteristic curve of HPA, and the phase predistortion is realized by subtracting the AM/PM response of HPA from the phase of the original signal. Considering the OFDM system with the number of subcarriers N=256, the subcarriers are modulated by 16QAM, the number of PTS blocks is V=4, and the OFDM time domain signal is generated by adjacency method, δ = 0.004, λ=l, ωA(O)=0, ωP(0)=0. In communication systems, the predistortion performance is usually independent of multipath fading, so it is assumed that the channel is an ideal additive white Gaussian noise channel, there is no intersymbol interference, and the clocks of the transmitter and receiver are accurately synchronized. Where Pmax represents the maximum output power of the amplifier and po represents the average power of the output signal of the amplifier. Fig. 2 shows signal constellations of receivers with and without predistortion under different output power compensation conditions. It can be seen that the predistortion can effectively compensate the nonlinear distortion caused by the power amplifier (Figure 2(a) and (b)). At the same time, it can be seen that with the decrease of output power back-off, the high power amplifier enters the limit region. At this time, even pre-distortion can not completely eliminate the nonlinear distortion introduced by the power amplifier (Figure 2(c) and (d)). When obo = 4.5 db, the error rate curve of the system with or without predistortion is shown in Figure 3. Make it higher ... >>

Question 8: What is the cause of nonlinear distortion of transistor amplifier circuit? The nonlinear distortion of triode amplifier circuit can be divided into saturation distortion and cutoff distortion, which is related to the static operating point you choose. If the static operating point you choose is very low, it is easy to have saturation distortion, and if it is too high, it will have cutoff distortion. In addition, as an amplifier, the voltage or current frequency of the transistor must be within the normal working frequency of the transistor, which is what we call the passband. Distortion also occurs when the operating frequency is below or above this passband.

Question 9: What is the nonlinear distortion of the amplifier circuit? Refers to the distortion caused by improper static working point and components with poor linearity.