What is channel equalization, what is clock recovery, and what is carrier recovery???

Channel equalization is used to resist ISI, i.e., anti-intersymbol crosstalk. Clock recovery must be done in the digital system to ensure that the 01 received by the receiver is received in the order in which it was transmitted. Carrier recovery is used in demodulation, where the transmitter modulates the signal to a certain frequency band (the band where the carrier is located), and the receiver moves the signal from this frequency band, in the simplest case, by multiplying the received signal with the carrier at that frequency.

Channel equalization refers to an anti-fading measure taken to improve the transmission performance of the communication system in the fading channel. It is mainly designed to eliminate or reduce the inter-symbol crosstalk (ISI) problem caused by multipath delay in broadband communication.

The mechanism is to compensate for the characteristics of the channel or the entire transmission system, and there are various structural methods for the constant parameter or variable parameter characteristics of the channel, the data rate is different, and the equalization has a variety of structural methods. It is broadly divided into two categories: linear and nonlinear equilibrium.

It is difficult to equalize the band channel, and it is generally balanced in the baseband after the receiver is demodulated, so the baseband balancing technology is widely used. In practice, adaptive filters are generally added to achieve channel equalization.

Clock recovery is becoming more and more widely used as a core function that must be possessed by high-speed serial communication, and clock recovery modules are available in Ethernet, PCI-Express, and Aurora. In contrast, the traditional parallel transmission mode of simultaneous clock and data transmission cannot achieve a bandwidth of more than 1 GBS.

Carrier recovery is the process of recovering the original carrier from a modulated signal.

In the 8-bit and 10-bit encoding methods, there is a clock recovery method, which is the same as the one mentioned above, but I think your purpose is to extract the clock and use the clock to sample the digital signal, if this is the case, you can use a clock that is more than 4 times larger than the digital signal to collect the digital signal and recover the digital signal by judgment. For specific methods, please refer to the communication method between FPGA and serial port, the serial port signal is a low-frequency signal, but there is no follow-up clock, and the FPGA needs to generate a relatively high-frequency clock to collect, and then judge and recover. If it's a high-frequency signal, the best thing to do is to output the clock that generated the digital signal and directly give it to you for the next level of sampling, which is the "source synchronization" design.

Clock Data Recovery should also be a data recovery software. However, if you want to recover lost data from your phone, the operation is relatively simple, after rooting your phone first, find a data recovery app in the app market, such as DiskDigiger, Data Recovery Master, Gecko Data Recovery, etc.

Component parameters cannot be guaranteed to be error-free, and the system is inevitably subject to various interferences.

Classmate, what's your name?

The basic principle for a database to be recoverable is "redundancy," i.e., duplicate storage of data.

Database recovery implementation:

1) Data dump (also known as "dump") Dump is the process by which DBA copies the entire database to tape or another disk for storage. These alternate data texts are referred to as backup copies or backup copies. In the event of a momentary failure, you can remount the backup copy.

2) Create a "logging" file. A log file is a file that records the update operation of a transaction to a database. For each insertion, deletion, or modification of the database, note the value before and after the change and write it to the "Log" file so that it can be documented.

System Restore is.

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in a component. With it, you can revert back to your previous state in the event of a computer failure without losing your personal data files (eg.

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Word documents, browser history, drawings, favorites, or emails). System Restore monitors changes to your system and certain application files and automatically creates easy-to-identify restore points. These restore points allow you to restore your system to its previous state.

Restore points are created every day or during major system events, such as installing applications or drivers. You can also create and name your own restore points at any time.

System recovery is generally the recovery function that comes with the system, or the system disk is activated and restored with the system disk.

Repairing damaged system files means that the corrupted system files are intact, and if the repair is successful, the system will be the same as before you repaired, and all installed software programs and records will be kept intact.

Restore your computer's original system settings. But the software is not removed.

Equalizer A component in a communication system that corrects the amplitude frequency characteristics and phase frequency characteristics of a transmission channel. When a sine wave with frequency f is fed into the transmission channel, the amplitude ratio of the output voltage to the input voltage varies with f is called the amplitude-frequency characteristic, which is referred to as the amplitude-frequency characteristic. The characteristic that the phase difference between the output voltage and the input voltage varies with f is called the phase frequency characteristic, or phase frequency characteristic for short. The signals transmitted by various transmission channels are generally composed of some components of different frequencies.

In the range of the signal frequency field roll, if the amplitude-frequency characteristic of the channel is constant; The phase characteristic that varies with f is a straight line and can be written.

f)=2 ft+, t is constant; called cut) is equal to n, n=0, 2, 4、......Then the signal waveform will not produce shouting distortion after transmission. The condition makes the components of different frequencies have the same output-to-input amplitude ratio after transmission, and the condition makes them have the same time delay. However, the actual channel often does not meet the above conditions, so the signal is distorted.

If the distortion exceeds the allowable amount, the channel characteristics should be corrected with an equalizer.

The requirement for equalization is related to the nature of the signal. Since the human ear is not sensitive to phase, only the amplitude and frequency characteristics of the channel are required when transmitting analog signals. When transmitting TV signals, there are requirements for the amplitude and phase frequency characteristics of the channel, otherwise the image will be distorted.

When the baseband transmission of digital signals is carried out, the amplitude and phase frequency characteristics are required, because the waveform distortion will produce inter-symbol interference and increase the bit error rate. When the digital signal carrier is transmitted, the phase interception in the phase frequency characteristics of the channel is not required, because the phase reference is not required when receiving the digital FM signal, and the phase reference can be solved by the carrier recovery circuit when receiving the digital modulation signal. In this way, only the amplitude-frequency characteristics and delay frequency characteristics are required for carrier transmission.