Analysis of millimeter wave terminal technology and test solutions

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Analysis of millimeter wave terminal technology and test solutions [Copy link]

This article first introduces the global millimeter wave spectrum allocation, and then summarizes the technical challenges that millimeter wave terminals will face by analyzing the characteristics of millimeter wave. It focuses on the research progress of large-scale antenna technology on the terminal side and millimeter wave RF front-end technology, and analyzes its test scheme based on the characteristics of millimeter wave terminals. Finally, the possible commercial plans of domestic millimeter wave terminals are analyzed. 1. Introduction With the rapid development of mobile communications, the development of low-frequency spectrum resources has become very mature. The remaining low-frequency spectrum resources can no longer meet the peak rate requirements of 10Gbps in the 5G era. Therefore, future 5G systems need to find available spectrum resources in the millimeter wave band. As one of the key technologies of 5G, millimeter wave technology has become the focus of research and discussion by current standard organizations and all parties in the industry chain. Millimeter wave will bring many technical challenges to the realization of future 5G terminals, and the test scheme of millimeter wave terminals will also be different from that of current terminals. This article will introduce and analyze the current status of millimeter wave spectrum division, challenges in implementing millimeter wave terminal technology, and test solutions. 2. Millimeter wave spectrum division In 2015, ITU-R WP5D released a research report on IMT.ABOVE 6GHz, which detailed the attenuation characteristics of radio waves in different frequency bands. At the World Radiocommunication Conference (WRC-15) of the same year, multiple 5G candidate millimeter wave frequency bands were proposed, and the final determination of 5G millimeter wave spectrum will be completed at WRC-19. After years of research and discussion, countries and regions have made progress in the division of millimeter wave spectrum resources. The following will focus on the current status of millimeter wave frequency band division in China, the United States, and Europe. China: In June 2017, the Ministry of Industry and Information Technology widely solicited opinions from the public on the use of 24.75-27.5 GHz, 37-42.5 GHz or other millimeter wave frequency bands for 5G systems, and included the millimeter wave frequency bands in the scope of 5G trials, with the intention of promoting 5G millimeter wave research and millimeter wave product R&D trials. United States: As early as 2014, the FCC (Federal Communications Commission) started the allocation of 5G millimeter wave frequency bands. In July 2016, it was determined that 27.5-28.35 GHz, 37-38.6 GHz, and 38.6-40 GHz would be allocated as licensed spectrum for 5G, and 64-71 GHz would be allocated as unlicensed spectrum for 5G. Europe: In November 2016, RSPG (Radio Spectrum Policy Group of the European Commission) released the EU 5G spectrum strategy, which determined that 24.25-27.5 GHz would be the first frequency band for 5G in Europe, and 31.8-33.4 GHz and 40.5-43.5 GHz would be the potential frequency bands for 5G. 3. Implementation of millimeter wave terminal technology The high frequency and large bandwidth of the millimeter wave band will bring many challenges to the implementation of future 5G terminals. The impact of millimeter waves on terminals is mainly on antennas and RF front-end devices. 3.1 Large-scale antenna arrays on the terminal side Due to the limitation of antenna size, large-scale antenna arrays can only be used on the base station side in low-frequency bands. However, as the frequency increases, in the millimeter wave band, the size of a single antenna can be shortened to the millimeter level, making it possible to deploy more antennas on the terminal side. As shown in Figure 1 below, currently most LTE terminals have only two antennas deployed, but in the future, the number of antennas in 5G millimeter wave terminals can reach 16 or even more, and all antennas will be integrated into a millimeter wave antenna module. Since the free space path loss of millimeter waves is greater, and the characteristics such as air attenuation and rain attenuation are not as good as those of low-frequency bands, the coverage of millimeter waves will be seriously affected. Using large-scale antenna arrays on the terminal side can obtain more diversity gain, improve the reception and transmission performance of millimeter wave terminals, and make up for the shortcomings of insufficient millimeter wave coverage to a certain extent. Large-scale antenna arrays on the terminal side will be one of the key factors for the commercialization of millimeter waves.

Figure 1: LTE terminal and millimeter wave terminal antenna concept

Deploying more antennas on the terminal means an increase in the difficulty of terminal design. Unlike the deployment of large-scale antenna arrays on the base station side, the large-scale antenna arrays on the terminal side are restricted by the size of the terminal and the power consumption of the terminal, and the difficulty of implementation will be greatly increased. Currently, the deployment of large-scale antenna arrays can only be realized on fixed terminals. The design of large-scale antenna arrays for mobile terminals faces many challenges, including antenna array calibration, mutual coupling between antenna units, and power consumption control. 3.2 Millimeter-wave RF front-end devices RF front-end devices include power amplifiers, switches, filters, duplexers, low-noise amplifiers, etc. Among them, the power amplifier is the most core device, and its performance directly determines the communication distance, signal quality and standby time of the terminal. At present, the materials used to manufacture RF front-end devices that support low frequency bands are mostly gallium arsenide, CMOS and silicon germanium. However, due to the large difference between the millimeter wave band and the low frequency band, the physical properties of the manufacturing materials of low-frequency RF front-end devices will be difficult to meet the requirements of millimeter wave RF front-end devices. Taking the power amplifier as an example, the current mainstream power amplifier manufacturing material is gallium arsenide, but in the millimeter wave band, the manufacturing process of gallium nitride and InP is stronger than gallium arsenide in terms of performance indicators. The following table shows the development direction of the main RF front-end device manufacturing process from low frequency to millimeter wave band.

In addition, the large bandwidth of the millimeter wave frequency band puts forward higher requirements on RF front-end devices. The RF front-end devices of future millimeter wave terminals may need to support continuous bandwidths above 1GHz. Although gallium nitride is considered to be the mainstream manufacturing process for future millimeter wave terminal RF, due to factors such as cost and production capacity, high-performance RF front-end devices based on gallium nitride technology are mostly used in special scenarios such as military industry and base stations. The development of millimeter wave RF front-end technology will become the key to the realization of millimeter wave terminals. It is expected that after 2020, the technology and cost of millimeter wave mobile terminal RF devices may meet the requirements of large-scale commercial use. 4.Analysis of millimeter wave terminal test solutions Currently, laboratory tests of LTE terminals mainly use conduction connections, using RF feeders to connect the device under test and the test instrument. This test solution has low requirements for the site and is less affected by external interference. However, with the use of large-scale antenna arrays on the millimeter wave terminal side, the terminal's wireless transceiver will be integrated into the antenna to form an antenna module. In the future, millimeter wave terminals may not have RF test ports, and factors such as high insertion loss caused by coupling at high frequencies make traditional conduction connection test solutions even more unfeasible. Therefore, OTA (Over The Air) testing will become the mainstream solution for millimeter wave terminal testing. OTA testing can directly test the overall radiation performance of the device, can test the overall performance of the device, and can more truly reflect the actual performance of the device, but the test needs to be carried out in a microwave darkroom, the test site requirements are relatively strict, and the test cost is expensive.

Figure 2: Darkroom for OTA testing

At present, the research on LTE OTA and MIMO OTA has been quite in-depth, but the research on millimeter wave OTA is still in its infancy. The standard project for millimeter wave OTA testing has begun to be discussed in CCSA. Figure 3 below is a schematic diagram of the LTE OTA test system. The scheme for future millimeter wave terminal OTA testing is expected to refer to the system of LTE OTA testing, but due to the application of millimeter wave operating frequency and active antenna array technology, the future millimeter wave OTA testing will make some technical improvements. As a necessary solution for millimeter wave terminal testing, OTA testing will face the following challenges: 1) New millimeter wave absorbing materials. Because traditional soft sponge absorbing materials have defects in physical and electrical properties, they cannot fully meet the requirements of 5G millimeter wave measurement. Therefore, researching and developing absorbing materials that are more suitable for millimeter wave darkrooms will be the key to millimeter wave OTA testing. 2) OTA test far-field measurement conditions. OTA testing can be divided into near-field and far-field testing according to the test field type. Usually, for the test of antenna radiation performance, the test receiving antenna is generally placed in the far field. At this time, the electromagnetic radiation belongs to a plane wave, and the relative angular distribution of the field is independent of the distance from the antenna. The size is inversely proportional to the distance from the antenna. The main lobe, side lobe and zero point of the antenna pattern have all been formed. In the near field, the receiving antenna may interfere with the transmitting antenna due to the coupling of capacitance and inductance, resulting in erroneous results. The condition for determining the far field is that the distance between the device under test and the measuring antenna must be greater than 2D2/λ, where D is the diameter of the measuring antenna and λ is the wavelength. Since the wavelength of the millimeter wave band is very short, the distance of the antenna far field is relatively large. Taking the 30GHz frequency band as an example, the measuring antenna diameter is 0.2m, and the distance of the far field will reach 80m. It is difficult for the darkroom to reach such a large size. In addition, the increase in the test distance will also increase the path loss between the terminal under test and the measuring antenna, which will further reduce the sensitivity and accuracy of the test system. To solve the problem of millimeter wave far field conditions, we can shorten the measurement distance by using the compact field method, or use the mid-field measurement method instead of the far field measurement. Compact field method: It usually uses a parabolic metal reflector to reflect the spherical wave sent by the measuring antenna through the reflecting surface to form a plane wave, forming a good quiet zone at a certain distance. The antenna is placed in the quiet zone to measure the far field characteristics of the antenna. It is similar to the far field measurement, but the measurement distance is shortened to facilitate measurement in an ideal far field environment (darkroom). The compact field antenna measurement system can simulate the far-field plane wave electromagnetic environment in a smaller microwave darkroom, and use conventional far-field test equipment and methods to test the radiation performance of the antenna. Mid-field method: The distance calculation method of the mid-field (Fresnel zone) is

Also taking the 30GHz frequency band, the measurement antenna diameter is 0.2m as an example, the distance of the mid-field is only 1.26m, and the size of an ordinary darkroom can also meet the requirements. Therefore, at the system level, new mid-field measurement theories and field source reconstruction methods can be studied, and the mid-field can be used to replace the far field for OTA testing.

Figure 3: Schematic diagram of LTE and millimeter wave test system

5. Analysis of domestic millimeter wave terminal commercialization plan Domestic research and testing related to 5G are in full swing, but compared with Europe and the United States, my country still has more available spectrum resources in the low frequency band below 6GHz, including 3.3-3.6 GHz, 4.8-5 GHz and some re-cultivated spectrum, so my country's demand for millimeter waves is not very urgent. Judging from the roadmaps of all parties in the industry chain, the first frequency band of domestic 5G should be the low frequency band below 6GHz. At present, research related to millimeter waves is still in its infancy, and the division of 5G millimeter wave spectrum needs to be further determined. It is expected that the official 5G millimeter wave terminal will appear in 2020. In the early stage of 5G commercialization, low-frequency base stations below 6GHz will be the main focus. It is expected that large-scale commercial use of 5G millimeter wave terminals in China will take a long time to achieve. 6. Conclusion This paper introduces the global division of millimeter waves and summarizes the challenges and difficulties that millimeter wave terminals will encounter in technical implementation. Millimeter wave terminals will be equipped with more antennas to form antenna modules. At the same time, in the RF front-end manufacturing process, materials with better high-frequency characteristics will be developed and applied. Finally, the OTA test of millimeter wave terminals and the commercialization of millimeter wave terminals are analyzed. As one of the key technologies of 5G, millimeter wave technology will surely be reused in the upcoming 5G era. The research and testing work related to millimeter wave terminals will also continue to accelerate, laying the foundation for the commercialization of millimeter waves. About the author Zhan Wenhao: He graduated with a master's degree from the Hong Kong University of Science and Technology and is currently working at the Guangzhou Research Institute of China Telecom Co., Ltd. His main research directions are 5G technology research and terminal new technology research. Dai Guohua: Graduated with a master's degree from South China University of Technology, currently works at Guangzhou Research Institute of China Telecom Co., Ltd. His main research directions are mobile communication application development, terminal new technology research, etc.Conclusion This paper introduces the global millimeter wave division and summarizes the challenges and difficulties that millimeter wave terminals will encounter in technical implementation. Millimeter wave terminals will be equipped with more antennas to form antenna modules. At the same time, in the RF front-end manufacturing process, materials with better high-frequency characteristics will be developed and applied. Finally, the OTA test of millimeter wave terminals and the commercialization of millimeter wave terminals are analyzed. As one of the key technologies of 5G, millimeter wave technology will surely be reused in the upcoming 5G era. The research and testing work related to millimeter wave terminals will also continue to accelerate, laying the foundation for the commercialization of millimeter waves. About the Author Zhan Wenhao: Graduated with a master's degree from the Hong Kong University of Science and Technology, currently working at the Guangzhou Research Institute of China Telecom Co., Ltd., his main research directions are 5G technology research, terminal new technology research, etc. Dai Guohua: Graduated with a master's degree from South China University of Technology, currently working at the Guangzhou Research Institute of China Telecom Co., Ltd., his main research directions are mobile communication application development, terminal new technology research, etc.Conclusion This paper introduces the global millimeter wave division and summarizes the challenges and difficulties that millimeter wave terminals will encounter in technical implementation. Millimeter wave terminals will be equipped with more antennas to form antenna modules. At the same time, in the RF front-end manufacturing process, materials with better high-frequency characteristics will be developed and applied. Finally, the OTA test of millimeter wave terminals and the commercialization of millimeter wave terminals are analyzed. As one of the key technologies of 5G, millimeter wave technology will surely be reused in the upcoming 5G era. The research and testing work related to millimeter wave terminals will also continue to accelerate, laying the foundation for the commercialization of millimeter waves. About the Author Zhan Wenhao: Graduated with a master's degree from the Hong Kong University of Science and Technology, currently working at the Guangzhou Research Institute of China Telecom Co., Ltd., his main research directions are 5G technology research, terminal new technology research, etc. Dai Guohua: Graduated with a master's degree from South China University of Technology, currently working at the Guangzhou Research Institute of China Telecom Co., Ltd., his main research directions are mobile communication application development, terminal new technology research, etc.Taking 2m as an example, the far field distance will reach 80m. It is difficult for the darkroom to reach such a large size. In addition, the increase in test distance will increase the path loss between the terminal under test and the measurement antenna, which will further reduce the sensitivity and accuracy of the test system. To solve the problem of millimeter wave far field conditions, we can shorten the measurement distance by using the compact field method, or use the mid-field measurement method instead of far field measurement. Compact field method: It usually uses a parabolic metal reflector to reflect the spherical wave sent by the measurement antenna through the reflection surface to form a plane wave, forming a good quiet zone at a certain distance. The antenna is placed in the quiet zone to measure the far field characteristics of the antenna. It is similar to the far field measurement, but the measurement distance is shortened to facilitate measurement in an ideal far field environment (darkroom). The compact field antenna measurement system can simulate the far field plane wave electromagnetic environment in a smaller microwave darkroom, and use conventional far field test equipment and methods to test the radiation performance of the antenna. Middle field method: The distance calculation method of the middle field (Fresnel zone) is

Also taking the 30GHz frequency band and the measurement antenna diameter of 0.2m as an example, the distance of the middle field is only 1.26m, and the size of an ordinary darkroom can also meet the requirements. Therefore, at the system level, we can study new middle field measurement theories and field source reconstruction methods, and use the middle field instead of the far field for OTA testing.

Figure 3: Schematic diagram of LTE and millimeter wave test system

5. Analysis of domestic millimeter wave terminal commercialization plan Domestic research and testing related to 5G are in full swing, but compared with Europe and the United States, my country still has more available spectrum resources in the low frequency band below 6GHz, including 3.3-3.6 GHz, 4.8-5 GHz and some re-cultivated spectrum, so my country's demand for millimeter waves is not very urgent. Judging from the roadmaps of all parties in the industry chain, the first frequency band of domestic 5G should be the low frequency band below 6GHz. At present, research related to millimeter waves is still in its infancy, and the division of 5G millimeter wave spectrum needs to be further determined. It is expected that the official 5G millimeter wave terminal will appear in 2020. In the early stage of 5G commercialization, low-frequency base stations below 6GHz will be the main focus. It is expected that large-scale commercial use of 5G millimeter wave terminals in China will take a long time to achieve. 6. Conclusion This paper introduces the division of millimeter waves around the world and summarizes the challenges and difficulties that millimeter wave terminals will encounter in technical implementation. Millimeter wave terminals will be equipped with more antennas to form antenna modules. At the same time, in the RF front-end manufacturing process, materials with better high-frequency characteristics will be developed and applied. Finally, the OTA test of millimeter wave terminals and the commercialization of millimeter wave terminals are analyzed. As one of the key technologies of 5G, millimeter wave technology will surely be reused in the upcoming 5G era. The research and testing work related to millimeter wave terminals will also continue to accelerate, laying the foundation for the commercialization of millimeter waves. About the author Zhan Wenhao: He graduated with a master's degree from the Hong Kong University of Science and Technology and is currently working at the Guangzhou Research Institute of China Telecom Co., Ltd. His main research directions are 5G technology research and terminal new technology research. Dai Guohua: Graduated with a master's degree from South China University of Technology, currently works at Guangzhou Research Institute of China Telecom Co., Ltd. His main research directions are mobile communication application development, terminal new technology research, etc.Taking 2m as an example, the far field distance will reach 80m. It is difficult for the darkroom to reach such a large size. In addition, the increase in test distance will increase the path loss between the terminal under test and the measurement antenna, which will further reduce the sensitivity and accuracy of the test system. To solve the problem of millimeter wave far field conditions, we can shorten the measurement distance by using the compact field method, or use the mid-field measurement method instead of far field measurement. Compact field method: It usually uses a parabolic metal reflector to reflect the spherical wave sent by the measurement antenna through the reflection surface to form a plane wave, forming a good quiet zone at a certain distance. The antenna is placed in the quiet zone to measure the far field characteristics of the antenna. It is similar to the far field measurement, but the measurement distance is shortened to facilitate measurement in an ideal far field environment (darkroom). The compact field antenna measurement system can simulate the far field plane wave electromagnetic environment in a smaller microwave darkroom, and use conventional far field test equipment and methods to test the radiation performance of the antenna. Middle field method: The distance calculation method of the middle field (Fresnel zone) is

Also taking the 30GHz frequency band and the measurement antenna diameter of 0.2m as an example, the distance of the middle field is only 1.26m, and the size of an ordinary darkroom can also meet the requirements. Therefore, at the system level, we can study new middle field measurement theories and field source reconstruction methods, and use the middle field instead of the far field for OTA testing.

Figure 3: Schematic diagram of LTE and millimeter wave test system

5. Analysis of domestic millimeter wave terminal commercialization plan Domestic research and testing related to 5G are in full swing, but compared with Europe and the United States, my country still has more available spectrum resources in the low frequency band below 6GHz, including 3.3-3.6 GHz, 4.8-5 GHz and some re-cultivated spectrum, so my country's demand for millimeter waves is not very urgent. Judging from the roadmaps of all parties in the industry chain, the first frequency band of domestic 5G should be the low frequency band below 6GHz. At present, research related to millimeter waves is still in its infancy, and the division of 5G millimeter wave spectrum needs to be further determined. It is expected that the official 5G millimeter wave terminal will appear in 2020. In the early stage of 5G commercialization, low-frequency base stations below 6GHz will be the main focus. It is expected that large-scale commercial use of 5G millimeter wave terminals in China will take a long time to achieve. 6. Conclusion This paper introduces the division of millimeter waves around the world and summarizes the challenges and difficulties that millimeter wave terminals will encounter in technical implementation. Millimeter wave terminals will be equipped with more antennas to form antenna modules. At the same time, in the RF front-end manufacturing process, materials with better high-frequency characteristics will be developed and applied. Finally, the OTA test of millimeter wave terminals and the commercialization of millimeter wave terminals are analyzed. As one of the key technologies of 5G, millimeter wave technology will surely be reused in the upcoming 5G era. The research and testing work related to millimeter wave terminals will also continue to accelerate, laying the foundation for the commercialization of millimeter waves. About the author Zhan Wenhao: He graduated with a master's degree from the Hong Kong University of Science and Technology and is currently working at the Guangzhou Research Institute of China Telecom Co., Ltd. His main research directions are 5G technology research and terminal new technology research. Dai Guohua: Graduated with a master's degree from South China University of Technology, currently works at Guangzhou Research Institute of China Telecom Co., Ltd. His main research directions are mobile communication application development, terminal new technology research, etc.

月下良缘

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alan000345

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