Choosing an instrument and meter is practical and economical for the factory. Because the factory is not a laboratory, the requirements for measuring instruments are: under the premise of meeting the production and process error parameters of measurement parameters, in a limited investment range. The internal selection accuracy can meet the requirements and the performance is stable. It is an instrument produced by a regular manufacturer, which is the most ideal.
For some high-demand customers, we have to say that we want to use high-quality products, and use the best materials. Of course, this is welcomed by manufacturers. Such customers do not need cost, only reliable quality. Here, remind users not to blindly pursue high-quality instruments from abroad, the key is to take into account their actual use, equipment input costs, after-sales service, etc., so as not to cause excessive investment, in case of problems, they should not get Some services.
We know that the degree of reflection error is called accuracy. The instrument with high accuracy has a small measurement error, and the instrument with low accuracy has a corresponding measurement error. Measuring the "accuracy" of instruments at the production site is: under the premise that the accuracy of the instrument can meet the requirements, it is important to choose products with long-term stability. Because the instruments used in the field do not have standard environmental conditions at all, the errors of the instruments operating in the field should also include additional errors caused by ambient temperature, humidity, vibration, electromagnetic interference, power supply fluctuations, etc., that is, comprehensive errors.
To see the quality of an instrument, you can't just look at the accuracy. It is important to consider the effects of parameters such as ambient temperature, humidity vibration, electromagnetic interference, and power fluctuations. For the occasions with high measurement requirements, of course, the comprehensive error requirement for the instrument is as small as possible. At this time, it is better to pass the test for additional error of the instrument for selection and optimization.
The requirements and dependence of automation on industrial production are getting higher and higher. To be efficient and stable, it is necessary to have stable and reliable control instruments. To ensure stable and reliable control, the premise is that the reliability and stability of on-site measurement parameters are Basic. Therefore, higher requirements are imposed on the instruments used in the field, which requires long-term stability and high reliability. This is the most concerned issue for users. Therefore, under the premise that the measurement accuracy meets the requirements of use, long-term stability and high reliability are selected. Instrumentation is the most important criterion.
When considering the long-term stability of the instrument, it is not necessary to unilaterally pursue high indicators. It should be combined with the comprehensive comparison and comprehensive analysis of the local environmental factors to find the most suitable instrumentation products. As the saying goes, choose the right one. Not expensive.
- The Description of 3G 4G LTE/5G Antenna
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2G base station: GSM: 900/1800MHz; CDMA: 800 MHZ;
3G base station: CDMA2000&WCDMA: 2100MHz; Td-scdma: 1880-1920201 0 0-2025232-2370 MHZ;
4G base station: TDD-LTE: 2320-2370,2570-2620MHz; -
This paper discusses the key technologies in 3G/4G/5G (third generation/fourth generation/fifth generation) communication systems, and then discusses the differences in the antenna technologies adopted by them. After reading and studying a large number of papers on the key technologies of 3G/4G/5G communication system, here I make some analysis and summary of my own. With the rapid development of science and technology, mobile communication technology has undergone profound changes, from 1G to 2G, to 3G, and then to 4G and 5G. On December 4, 2013, the fourth generation of mobile communication 4G technology was officially operated in the Chinese market, which means that China's mobile communication industry has entered the 4G era. At this time, research institutes in various countries and world-renowned enterprises engaged in communication technology research have entered the research and development of the new generation of mobile communications, namely 5G (fifth generation mobile communication system). No matter which generation of communication system, the research technology is to analyze the characteristics of wireless communication channel to overcome the noise interference. A lot of researchers are now looking at Massive MIMO technology. How is it different from the antenna technology used in 3G/4G communication systems? Will it become the core technology of the next generation of wireless communications? 1 Key technologies of 3G/4G/5G Communication System 1.1 Key technologies of 3G Communication System Since the early 1990s, the mobile communication industry began to actively study the standards and technologies of the third generation of mobile communication. In January 2009, China's Ministry of Industry and Information Technology issued 3G licenses to China Mobile, China Telecom and China Unicom, indicating that China entered the ERA of 3G mobile communications. The third generation mobile communication system mainly includes WCDMA, CD-MA2000 and TD-SCDMA. Its key technologies include: A. Rake receiving technology; B. Channel coding and decoding technology; C. Power control technology; D. Multi-user detection technology; E. Smart antenna; F. Software radio. 1.2 Key technologies of 4G Communication System In December 2013, China officially entered the era of 4G (fourth generation mobile communication system) communication network. In 4G mobile communication system, OFDM(Orthogonal frequency Division multiplexing) technology is adopted. OFDM technology is due to its spectrum utilization
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It is widely regarded as high rate of 2 and good anti-multipath fading performance. In the future, RESEARCH related to OFDM technology will also be carried out in 5G communication networks. The main key technologies of 4G communication system include: a. OFDM technology; B. MIMO technology; C. Multi-user detection technology; D. Software radio; E. Smart antenna technology; F. IPv6 technology. China's Ministry of Industry and Information Technology has just issued 4G licenses to the three major operators, and they are still deploying their networks on a large scale with a small number of users. At this time, China Mobile said it will start the RESEARCH and development of 5G communication system. Analysts pointed out that the three major operators are participating in THE RESEARCH and development of 5G, one is to keep up with the changes of The Times, and the other is that the demand is faster than the technology development. Li Zhengmao, vice-president of China Mobile, said at the 2014 MWC in Barcelona: "China Mobile will fully support the development of 5G projects, hoping to lead the industry in THE development of 5G technology and the setting of technical standards." With the deepening of mobile communication technology research, the key support technologies of 5G will be gradually defined and enter the substantive standardization research and formulation stage in the next few years. The jury is still out on what core technologies will be used in the future. However, I have compiled a list of nine key technologies that have been the focus of discussion in various high-end mobile forums. A. Large-scale MIMO technology; B. Filter bank based multi-carrier technology; C. Full duplex technology; D. Ultra-dense heterogeneous network technology; E. Self-organizing network technology; F. Use of high frequency band; G. Software-defined wireless networks; H. Wireless access technology: (1) BDMA (Beam Split multiple Access technology)
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3 (2) NOMA (Non-orthogonal multiple Access technology) i. D2D (device-to-device) communication. Figure 1 is the layout of Massive MIMO antennas in 5G communication networks. I am studying Massive MIMO technology in my lab. Figure 1 shows users communicating with each other centered on a large-scale antenna. The performance of wireless communication systems is mainly restricted by mobile wireless channels. Wireless channel is very complex, and its modeling has always been a difficult point in system design. Generally, statistics are made according to the measured values of communication systems in specific frequency bands. Wireless fading channel is divided into large scale fading channel model and small scale fading channel model. The so-called large-scale fading model describes the field intensity variation over a long distance (hundreds or thousands of meters) between the transmitter and receiver, and reflects the rule that the received signal power changes with the distance caused by path loss and shadow effect. A small scale fading model describes the rapid fluctuations of the received field intensity over a short distance or time. The large scale fading channel model is caused by the influence of the surface contour (such as mountains, forests, buildings, etc.) between the receiver and the source. The small-scale fading channel model is caused by the multipath effect and doppler effect. If there are a large number of reflected paths but no LOS (direct signal) signal component, the small-scale fading is called Rayleigh fading, and the envelope of the received signal is described statistically by the Rayleigh probability density function. If LOS is present, the envelope is subject to Rician distribution. Multipath effect phenomena cause flat fading and frequency selective fading.
The Picture of 3G 4G LTE/5G Antenna
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