Carrier C/N and signal-to-noise ratio s/n

 

 

Signal-to-Noise Ratio and download ratio:

During the transmission of TV signals, noise and interference are the main factors affecting image quality. The impact of continuous random clutter generated internally on useful signals is called noise, expressed by the noise coefficient NF or F. We call it interference because of the intrusion of external signals and the influence of harmonic and clutter produced by active devices.

There are many types of external interference, which affect the quality of TV programs:

Interference with the race track-mains and power supply interference between 50Hz and several hundred Hz.

Mesh interference-several kHz ~ Dozens of MHz of medium and short wave signals, bpers, mobile phones, game consoles, and air radio signal interference.

Snowflake and horizontal line interference-produced by fluorescent lamps, engines, and high-frequency devices.

Signal-to-Noise Ratio: the relative strength of the video and audio signals and the noise power. It is an important indicator of the quality of constant audios and video signals. It is represented by S/N. S/N = ps/PN or (S/N) dB = 10 lgps/Pn = psdb-pndb

Carrier: indicates the relative strength of high-frequency carrier and noise. It is an important indicator of the transmission quality of constant RF signal channels and reflects the signal quality of audio and video signals after transmission and demodulation. It is represented by C/N. C/N = pc/PN or (C/N) dB = 10 lgpc/Pn = 20 lguc/UN pal (video with 5.75 MHz) the relationship between the carrier value of the transmission system and the signal-to-noise ratio after demodulation is: S/N = C/N + 6.4 dB carrier value of the cable TV system (C/N) it is related to the input level of the amplifier, the noise factor, and the series of the amplifier. Each time the input level of the amplifier is reduced by 1 dB, the load ratio degrades by 1 dB.

 

What is signal-to-noise ratio S/N, carrier C/N, and Eb/N0?

The signal-to-noise ratio (S/N) is the ratio of the average power of the transmission signal to the average power of the noise. A carrier (C/N) is the ratio of the average power of the modulated signal to the average power of the supplementary noise. They are usually calculated in logarithm mode, in dB.

The signal-to-noise ratio differs from that of the carrier. The signal-to-noise ratio includes the power of the transmitted signal and the power of the modulated carrier. The signal-to-noise ratio only includes the power of the transmitted signal, the difference is one carrier power. Of course, the carrier power is usually very small compared with the transmission signal power, so the carrier power is very close to the signal-to-noise ratio. For the modulation method of the suppression carrier, the two values are equal. The signal-to-noise ratio and the carrier-to-noise ratio can be measured directly at the receiving end.

In modulation transmission systems, carrier-level indicators are generally used, while in baseband transmission systems, signal-to-noise ratio indicators are generally used. The reliability of the actual digital communication system is often described by a carrier-to-error rate relationship curve. The horizontal coordinate of the curve is C/N, and the vertical coordinate is Ber, as shown in. For a C/N, the smaller the BER, the higher the reliability of the communication system. It can be seen that the anti-interference capability of system B is better than that of system. At this time, the efficiency of system A and system B cannot be compared. It is possible that system A is superior to system B, or system B is superior to system. If B is better than a, the overall performance of system B is better than. If a is better than B, it means that system B can improve anti-interference capability by sacrificing efficiency.