Requirements for the control of noise voltage by communication power supply equipment

Modern telecommunication systems have high requirements on the quality of the DC power supply voltage. The voltage is not allowed to be interrupted instantaneously, and its fluctuation, transient and noise voltage should be less than the allowable range. The noise voltage refers to the pulsation in the output voltage of the rectifier equipment and DC converter Components, this pulsating component is composed of AC voltages of various frequencies. There are several types of noise voltage:

1. The phone weighs heavily. Due to the different response of human ears and headphones to various frequencies, after the noise voltage of various frequencies in the 25Hz ~ 5KHz frequency band is equivalent to the voltage value of 800HZ, take the root mean square value. Phone-weighted noise is also called phone-weighted noise.

2. Peak-peak noise. Refers to the needle pulse voltage with the largest amplitude generated in the rectifier circuit, superimposed on the DC output, which can make the logic circuit malfunction.

3. Broadband noise. Refers to the root mean square value of the effective value of the noise voltage at different frequencies.

4. Discrete frequency noise. Refers to the noise voltage of any frequency in the 3.4KHz ~ 30MHz frequency band. It is usually radio interference noise, or radio frequency noise.

5. Transient noise. Refers to non-fixed external random instantaneous noise, including external random electromagnetic interference, equipment malfunction caused by malfunction of the machine or ground wire interference. The shorter the pulse duration of transient noise, the higher the allowable value. For example, when the pulse is 1us, 135V is allowed; when 1000us, 0.17V is allowed.

Because modern telecommunications equipment uses a large number of integrated circuits, they are very sensitive to interference of various frequencies. When telecommunications power equipment is produced, it is necessary to take filtering measures for the pulsating components in the DC output voltage of the rectifier equipment and output the DC power distribution equipment in the telecommunications room The noise voltage index measured at the terminals is strictly regulated to meet the electromagnetic compatibility requirements of telecommunication equipment. The noise voltage index of the basic DC power supply specified in the "General Technical Requirements for the Power System of the Communication Bureau (Station)" within the range of its rated voltage allowable fluctuation is shown in Table 1 below:

Table 1 The noise voltage index of the basic power supply

Among all types of noise voltages, foreign standards mainly set the weight and wideband noise indicators. For discrete noises, there are no provisions in the standards of the United States and Europe. Our standards refer to Belgium introduced by Shanghai Bell Company. The standard of the switch (1240) puts forward, the origin of these regulations and what effect they will actually have in communications, has not been clearly explained so far, and there is generally no problem in the test, but it is gradually ignored by people. The categories of noise voltage indicators are specified, but in the actual test, the main concern is the telephone weighing noise voltage, because it is the most harmful, causing varying degrees of impact and interference on the communication system.

The DC voltage on the subscriber line in a fixed telephone is usually provided by the rectifier equipment in the communication room. The telephone counterweight noise carried on it is transmitted through the telephone circuit and sent to the telephone user's headset, which will produce a buzzing noise. , Affecting call quality. In the error-free transmission circuit of information (in the field of data transmission), the purity of the DC power supply is particularly important. When the additional AC voltage (mainly telephone weighing noise) exceeds the specified value, the transmission quality will be reduced and the bit error rate of the signal Increased, resulting in errors.

According to the ITU recommendation, the telephone weighting (weighted) noise is based on the 800Hz noise voltage. The response strength of the noise frequency at other frequencies is expressed by the equivalent noise coefficient. Table 2 gives the ITU-T recommendation O.41 (Blue Book Volume IV.4O Series Recommendations) The data of telephone counterweight noise (weighted by noise meter) is reflected in the graph curve as shown in Figure 1.

Table 2 Weighting coefficients and limits of telephone weighing noise (weighted by ITU noise meter)

The test point for the weight-bearing noise of the DC power supply system of the telecommunications power supply is strictly selected at the output terminal of the DC power distribution equipment. Because the measured values ​​are different at the output of the battery and the input of the telecommunications room, it is difficult to evaluate the quality of the equipment.

With the development of society and the improvement of people's living standards, ordinary people not only require communication services to be convenient and fast, but also have higher and higher requirements for communication quality. Especially after joining the WTO, Chinese telecommunications companies are facing more severe competition. Improving the quality of communication networks is becoming an urgent task for telecommunications operators, and strictly controlling the power source of communication equipment-rectifier equipment and DC converters The noise component of the output DC voltage should become a very important measure to improve the quality of network communication.

Figure 1 Weighted curve of phone weight

About Copper Accessories

   Copper Accessories includes Plastic Spool, insulating paint and cable wire, plastic has colorful choose for you .insulating paint has two kinds of packages (200 kg and 1000 kg). cable wire is very flexible .House wiring cables and feeder cables.

  

Copper Accessories

Copper Accessories,Low Oxygen Copper Rod,Upcast Process Copper Rod,Copper Round Bar

HENAN HUAYANG ELECTRICAL TECHNOLOGY GROUP CO.,LTD , https://www.huaonwire.com