Kneeling for DMT coding modulation principle

Is there any more information about DMT?

A digital signal is generated by sampling, quantifying and encoding a continuously changing analog signal, which is called PCM (Pulse Code Moshulation). The digital signal of this electricity is called the digital baseband signal and is generated by the PCM power terminal. Simply put, it's analog-to-digital conversion.

Pulse modulation is to convert a time-continuous, value-continuous analog signal into a time-discrete, value-discrete digital signal and then transmit it in the channel, pulse coding modulation is the process of sampling the analog signal, then quantifying the amplitude of the sample value, and encoding.

If you control the switch, simply put, you can achieve it through the programming of the microcontroller, which is a square wave generator, set the output pulse width duty cycle to control the stop frequency of the switch, and that's it.

DMT (DiscreteMultitone), in which DMT modulation technology is adopted by the national standard developed by the ANSI standardization group. However, due to the fact that this standard has not been available for a long time, there are still a considerable number of ADSL products that use QAM or CAP modulation technology.

This analog signal is changed by a frequency division multiplexer, so that multiple analog signals can be transmitted on the line at the same time, and when it reaches the receiving end, it is restored to the analog signal of the original frequency range through a de-frequency process, and then the analog signal is converted into a sound signal by the receiver's first machine.

Modulation is to use baseband pulses to control a certain parameter of the carrier waveform to form a signal suitable for line transmission.

Demodulation means that when the modulated signal reaches the receiving end, the analog signal converted by the modulator removes the carrier and returns to the original baseband digital signal.

The use of a modem can also convert audio signals to higher frequency signals and higher frequency signals to audio signals. Therefore, another purpose of modulation is to facilitate the reuse of lines, so as to improve the utilization rate of lines.

Based on the three main parameters of the carrier signal, modulation methods can be divided into three types: amplitude modulation, frequency modulation, and phase modulation. The English word for modem is modem, and its role is to act as a "translator" of analog and digital signals.

There are two types of electronic signals, one is"Analog signals", one is"Digital signals"。The ** line we use transmits analog signals, while the PCs transmit digital signals between them. So when you want to connect your computer to the Internet through a ** cable, you have to use a modem"Translation"Two different signals.

Transfer mode. Modem was originally only used for data transfer. However, with the continuous growth of user demand and the fierce competition between manufacturers, there are more and more "two-in-one" and "three-in-one" modems in the market. In addition to data transmission, these modems also have fax and voice transmission functions.

1.Fax modem

In addition to saving the cost of a dedicated fax, faxing through modem has many advantages: you can fax documents from the computer directly to the other party's computer or fax machine without having to print out the documents first; Incoming faxes can be easily saved or; It can overcome the problem of gradual fading of handwriting due to the use of thermal paper in ordinary fax machines.

2.Voice modem

Modulation is to multiply the carrier signal and the binary signal, want to dry demodulation through the bandpass filter, and then multiply with the carrier, pass through the low-pass, and then come out is the demodulation signal.

What details should be paid attention to when making an ASK modulator and demodulator, if there is an actual circuit diagram and principle, the TDA5255 is a low-power, monolithic FSK ASK transceiver suitable for 433 MHz 435 MHz half-duplex low data.

How 2-ask modulation works:

In 2-ask modulation, there are only two states of change in the amplitude of the carrier wave, that is, a continuous carrier wave is keyed by using a baseband rectangular pulse of digital information "0" or "1", so that the carrier output is intermittent. "1" is indicated when there is a carrier output, and "0" is transmitted when there is no carrier output.

When the modulated signal is a binary digital signal, this modulation is called binary digital modulation.

Is it that 0 has no waveform 1 has a waveform and that amplitude modulation?

Can you send me a copy?