With the rapid development of smart phones, smart bracelets, TVs, computers and other consumer electronic products in the direction of thin, portable, intelligent, etc., their display screens also undergo rapid evolution and iteration of "spherical screen - flat screen - flexible screen". In the era of spherical screens, CRT is the only choice; in the era of flat screen, LCD has become the deserved king; in the future era of flexible screen, OLED has simple structure, ultra-thin, high color saturation and contrast, low power consumption and easy The realization of flexible display and other advantages has become the focus of investment and research in industry and academia.
Flexible OLED panels will grow rapidly in the next 5 yearsIn recent years, products such as smart phones, smart bracelets, smart watches, and televisions that use OLEDs as screens have shown rapid growth. In the main battlefield of smart phones, more and more high-end machines use OLED displays, especially flexible OLED screens. According to statistics, China's vivo, Meizu, OPPO and other brands began to adopt large-scale OLED screens. In 2016, the penetration rate of OLED screens in these brands of smartphones reached more than 12%. As Apple plans to upgrade its LCD screen to OLED screen in 2017~2018, both domestic and international industry chains are actively carrying out relevant industrial layouts, and the entire OLED market is booming. Flexible OLED display panels will maintain rapid growth in the next five years, with a compound annual growth rate of more than 30%, and its market size will reach more than 40 billion US dollars by 2020. The penetration rate of OLED screens in the smart phone market will be More than 50%.
Faced with huge market demand and bright market prospects, China's BOE, Tianma, Visionox, Hehui Optoelectronics, Huaxing Optoelectronics, and Xinli have invested heavily in building a number of G4.5-G6 OLED production lines in recent years. In 2016, glass-based OLED displays have begun to gain small-scale applications in smartphones. However, due to China's lack of mature technology and investment in OLED products, the full release of production capacity will need to be around 2018. At present, Korean companies are in an absolute market monopoly position, of which Samsung accounts for more than 95% of the small and medium-sized OLED panel market share, and LG monopolizes the entire large-size OLED TV panel market.
There are two kinds of mainstream OLED production technology routes.From the technical point of view, the mainstream OLED production technology route can be divided into two types: low temperature polysilicon thin film transistor (LTPS-TFT) driving red green blue (RGB) OLED luminescent pixels, and oxide thin film transistor (Oxide-TFT) driving white OLED pixels The RGB pixels are obtained by illuminating and filtering through a Color Filter. The former is mainly used for small-size display, and the representative company is Samsung; the latter is mainly used for large-size display, representing LG.
Samsung adopts LTPS technology, mainly focusing on the small-size OLED screen technology used in smart phones. From Galaxy S to Galaxy S7, the screen resolution has been increased from 218ppi to 2K (577ppi). It is expected that the resolution of OLED mobile phones may reach in the future. Around 800ppi.
The advantages of LTPS technology are high mobility and low power consumption, which is beneficial to mobile terminal devices such as smart phones that are powered by batteries. However, LTPS itself has a polycrystalline structure with poor uniformity and must be laser annealed and ion implanted. The cost-effective process results in high product costs and is difficult to apply to large-size panel production.
LG adopts Oxide technology, mainly because Oxide is amorphous structure, easy to realize large-area, low-cost preparation, and can be used in large-size OLED TV field; however, the mobility of IGZO (Oxide material) technology TFT backplane adopted by LG is biased. Low (~10cm2/Vs) leads to higher power consumption. If the mobility of Oxide TFT can be greatly improved, it can reverse the disadvantage of high power consumption and is expected to gain a competitive advantage in small-sized markets such as smart phones. Especially in the field of flexible OLED display, LTPS production temperature is above 450 °C, which is a severe test for flexible substrate materials and manufacturing processes, and the cost is high; while Oxide's production temperature can be as low as 350 ° C or less, the process Simple, low cost, and the demand for raw materials is greatly reduced, which is conducive to expanding the localization rate of raw materials and key equipment. It is an effective way to achieve catch-up in China.
Packaging and bending resistance reliability issues need to be addressedIn the field of high mobility Oxide TFT technology, some universities/scientific research institutions (South China University of Technology, Shanghai University, Fudan University, Peking University, Suzhou Institute of Nanoscience, etc.) and enterprises in China are actively exploring. Guangzhou Xinshijie Optoelectronics Technology Co., Ltd. (hereinafter referred to as “New Visionâ€) is committed to breaking through the limitations of foreign IGZO Oxide materials, and is committed to the development of new Oxide semiconductor materials based on lanthanide rare earth doped In-Zn-O (Ln-IZO). Combined with the independently developed Nano-Barrier BCE structural process route (5 lithography, compatible with s-Si TFT production line), high mobility Oxide TFT technology with electron mobility close to 40cm2/Vs can be realized, which can effectively reduce OLED display Overall power consumption. At present, New Vision is actively cooperating with domestic panel manufacturers to explore the possibility of large-scale application of high mobility Ln-IZO TFT technology in small-sized OLED display fields such as smart phones.
In the future development of the flexible OLED display industry, in addition to the need to consider the low-cost alternative of TFT technology, it is also necessary to consider packaging, bending resistance and reliability issues.
From the perspective of packaging of flexible OLED devices, organic materials and electrodes in OLED devices are sensitive to moisture and oxygen in the environment. Therefore, after the OLED device is fabricated, it must be packaged in situ to achieve the effect of blocking water and oxygen, packaging film. The water vapor barrier capacity needs to reach 10-6g/m2/day to ensure the life of the device. At present, the more effective packaging method is to use thin film packaging technology. The so-called thin film package is not a film for packaging beforehand, and is attached to the OLED device, but needs to be grown on the OLED electrode in situ under vacuum conditions by PECVD, ALD, etc. after the OLED electrode is fabricated. The nano-scale film with water-oxygen barrier properties is used for packaging purposes and has very high technical requirements. Especially for flexible OLEDs, because of the need to face multiple free bends, more stringent requirements are imposed on the package performance.
From the point of view of the flexural resistance of the flexible OLED display, the flexible OLEDs on the market are all fixed surfaces, and the user cannot bend freely according to their own preferences, mainly because the flexible OLED display bends or bends. If the radius of curvature exceeds a certain limit, the device will be aging, resulting in a decrease in brightness, black spots, dark lines, etc., and a rapid decline in service life. This needs to be continuously solved through systematic research from the perspective of "materials - film - device - process".
In short, the flexible OLED display industry is in a period of rapid development, and the industry prospects are bright. However, China's industrial development still faces problems such as insufficient technology accumulation, late start of production line construction, and dependence on imports of equipment and materials. This requires close collaboration between domestic upstream and downstream industries, and strives to take the initiative in the new round of flexible OLED industry competition.
- 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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