What Is a Carrier Wave?

Carrier or carrier frequency (carrier frequency) is a physical concept. It is a radio wave of a specific frequency. The unit is Hz. It is an electromagnetic wave that is modulated in frequency, amplitude modulation, or phase to transmit speech, music, images, or other signals.

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Carrier or carrier frequency (carrier frequency) is a physical concept, a radio wave of a specific frequency, the unit

In communication technology, a carrier wave (carrier wave, carrier signal or carrier) is an electric wave generated by an oscillator and transmitted on a communication channel, which is modulated to transmit voice or other information. The carrier frequency is usually higher than the frequency of the input signal. It belongs to a high-frequency signal. The input signal is modulated onto a high-frequency carrier, just like riding a high-speed train or an airplane, and then being transmitted and received. Carrier is the physical foundation and carrying tool for transmitting information (voice and data).

The unmodulated periodic oscillating signal is called a carrier. The carrier can be a sine wave or a non-sine wave (such as a periodic pulse sequence). After the carrier is modulated, it is called a modulated signal, which contains the full-wave characteristics of the modulated signal. Generally, the frequency of the sine carrier is much higher than the bandwidth of the modulated signal, otherwise aliasing will occur and the transmitted signal will be distorted.

It can be understood in this way that the frequency of the data that we generally need to send is low frequency. If it is transmitted according to the frequency of its own data, it is not conducive to reception and synchronization. With carrier transmission, we can load data signals onto the carrier signal. The receiver receives the data signal according to the frequency of the carrier. The amplitude of the meaningful signal wave is different from the amplitude of the meaningless signal. Extract these signals. Come out is the data signal we need.

Channel is a logical concept, a channel for users to pass information, and is artificially defined. A channel in FDMA is a radio wave of a specific frequency. Each user uses a pair of frequencies to carry information when receiving and transmitting information. In order to improve frequency utilization and increase user capacity, 2G has begun to use TDMA. In TDMA, a channel is a certain period of time on a radio frequency of a specific frequency (in this time segment, the user has the right to use this radio wave, can receive information, and can send information). The unit of a channel in a TDMA system is a composite unit. It is necessary to specify both the frequency (Hz) in which the channel is located and the time in which the channel is located. Visually speaking, the channel is like the train number. In FDMA, different train numbers are different frequencies (this is the easiest to understand). But if the user has few goods to send, wouldn't it be cost-effective to occupy a train? Therefore, train utilization must be improved. So everyone thinks of a way: use a physical train, but stipulate that different users use this train in different time periods, during this time segment the train belongs to the user to unload, load, and transport, regardless of whether the goods have not been sent, As soon as this time period ends, the user stops working and another user uses the train. In this way, this train provides transportation services for different users in different time periods. This is the TDMA system. Conceptually, the train + the time the user uses the train constitutes a logical channel, that is, a time slot.

A carrier is a continuous signal that operates at a predefined single frequency. Changing the carrier so that it can represent data in a form suitable for transmission is what we often call Modulation. The modem can be understood as a large and fast ship that can sail in the vast ocean. Any boat can be carried on this ship and reach the other side of the ocean. If the boat goes straight to the sea, its ability to resist wind, waves, bumps and reefs is too weak, and it is likely to be a disaster waiting for him.

There is no difference in principle between the power carrier communication and the telecommunication system wired carrier communication, but the power line is used instead of the communication line. However, multiplexing communication on the power line is not as simple as the communication line. Not only does it ensure the safety of personal equipment, but also to obtain the best carrier signal transmission efficiency, this must be processed to solve the problem Connection problem.