The development of 5G millimeter wave will bring many new concepts, from signal characteristics, component design to testing, etc., will bring different challenges from the past, but these challenges also contain more new business opportunities. With the investment, the price of millimeter wave components will become cheaper and closer to the sweet spot acceptable to the market.
Wireless communication is moving towards higher speed and greater bandwidth. However, the frequency spectrum used in the low and middle frequency bands below 6GHz has been very crowded. Therefore, the application of millimeter wave above 30GHz has become the focus of future wireless communication technology. The next generation of Wi-Fi 802.11ad/ Both WiGig and the fifth-generation mobile communication (5G) technology will use high-frequency millimeter wave technology. 5G will use this to increase the transmission rate to a maximum of 20Gbps. By then, a Blu-ray movie can be downloaded in only 20 seconds while running high-definition There is no problem with quality live broadcast or VR videos. 
However, the technical shortcomings of millimeter wave technology due to the high-frequency characteristics have yet to be overcome, including high-frequency path loss (Path Loss), transmission loss (Propagation Loss), wall penetration (Wall Penetration), etc.; in addition, high-frequency components The materials, performance, and power consumption of the company also need to be broken. Therefore, this event invites research units and technology leaders to serve as lecturers to analyze how to overcome high-frequency millimeter wave technology bottlenecks, technology development status and application trends, test verification architecture and development prospects. 

Fig. 1 Dr. Shuhan Liao from the Institute of Information Technology stated that the fifth generation of mobile communications covers more than ever before, which can be said to be the driving force leading the development of high-tech industries in the next 10 to 20 years.
3GPP leads the development of 5G technology 
Beginning in 1998, 3GPP, composed of major countries and telecommunications and communications manufacturers, has become the most important organization for formulating international authorized frequency band wireless technology standards. The next 5G will also gradually develop formal technical specifications under its promotion. The scope of the fifth generation mobile communications is even greater than before. It can be said to be the driving force leading the development of high-tech industries in the next 10 to 20 years. PCG) and Technical Specification Group (TSG). The TSG responsible for technical formulation is subdivided into four: responsible for EDGE radio access network (GERAN), radio access network (RAN), system and business aspects (SA), core Net and Terminal (CT). 

The formulation of 5G standards has officially confirmed the three major development goals at the 3GPP Workshop on 5G in Phoenix, USA in September 2015. The standard formulation work will begin, and Taiwan will also actively participate in early this time, hoping to play a more important role in the 5G era . Liao Shuhan pointed out that 3GPP has a rigorous process for formulating standards. In addition to grouping according to technical characteristics, the technical architecture will be passed through the study item before the general standard is formulated, so that relevant members can understand the value and necessity of the technology. After confirmation Only then entered the working stage of substantive formulation (Working Item). 

In addition, 3GPP also categorizes the technical content and related documents in detail and opens up queries from all walks of life. All concerned professionals can inquire about the published technical specifications and standard results. In the formulation of the 5G New Radio technology, which is most directly related to the future transmission rate, the functional requirements that will affect the first layer (L1) of the communication protocol have been completed in March 2017. Under the independent and non-independent new radio architecture, the first layer of the communication protocol (Layer 1, L1) and the second layer (Layer 2, L2) of the communication protocol should complete the design of the third stage (Stage 3) of the common basic technology. Among them, the completion time of the common third stage design target is December 2017. The completion time of the design target of the third phase of the components or standards related to the independent NR architecture is March 2018, and the completion target of the independent NR architecture is June 2018. 

Figure 2 is Keysight's senior project manager Zhang Shixian explained that the low- and mid-range frequency bands below 6GHz are already full of various applications, and it is very difficult to find continuously idle frequency bands.
Millimeter wave technology is challenging 
Due to the gradual maturity of technology, many wireless communication technologies have invariably developed in the application of high-frequency millimeter waves in recent years. From the perspective of the physical characteristics of millimeter waves, Zhang Shixian, senior project manager of Keysight (Figure 2), explained that the low and medium frequency bands below 6GHz are already full of various applications. It is very difficult to find continuous idle frequency bands, so go higher. Frequency band development has become the future trend. 

The physical characteristics of high-frequency millimeter waves are different from those of radio waves below 6GHz. Zhang Shixian said that the functional and technical characteristics of millimeter waves include: Broad Bandwidth, Uncluttered Spectrum, and High Resolution ), Small Antenna Size, Highly Integrated SoC (Compact Integrated mmWave SoC), Massive MIMO/Beamforming, High Directivity, and Advantageous Use of Atmospheric Properties) etc. 

These features partly help to provide better use experience of high-frequency bandwidth and 5G, and some bring many technical bottlenecks and challenges, such as high-frequency path loss, less experience in millimeter wave applications, low control of characteristics, and easy refraction and scattering (Reflection and Scattering). Diffusion), body shielding and grip blocking signals, smaller and more fragile cables/adapters and accessories, high cost, millimeter wave antenna and front-end integration, millimeter wave beamforming calibration (mmWave Calibration for Beamformining), etc. 

Figure 3 SGS Global OTA Technology Director Liao Zhaoxiang believes that the massive MIMO antenna forms a directional beam through an array to overcome the problem of millimeter wave signal attenuation.
Massive MIMO is one of the key technologies 
Due to the characteristics of high millimeter wave frequency, short wavelength, short transmission distance and signal susceptibility to interference, many new technologies and designs must be adopted to overcome them, and provide a stable high-speed transmission rate. Among them, Massive MIMO antennas It is the most frequently mentioned one. Liao Zhaoxiang, SGS's global OTA technology director (Figure 3), believes that MIMO is a fairly common antenna transmission technology in recent years. The number of massive MIMO antennas is more than 64. Through the array method, directivity is formed. Beam to overcome the problem of millimeter wave signal attenuation. 

The main purpose of Massive MIMO is to enhance the signal rate and strength through the transmission and reception of multi-antenna signals. In the future, the array antenna design of 5G base stations will change from 4G 2D antennas to 3D, cone-shaped, cylindrical, etc. Different array antennas will generate different signal beams, and the cost will increase. However, because the Massive MIMO antenna has a high degree of directivity, beamforming technology can concentrate the energy on the terminal equipment, which can effectively improve energy efficiency. 

The future 5G system will use both the low and medium frequency bands below 6GHz and the high frequency millimeter wave frequency bands. Liao Zhaoxiang pointed out that receiving, transmitting and encoding Massive MIMO data is a major challenge, that is, how to transmit the channel state data from the receiver to the Transmitter to complete the encoding in advance. Therefore, through the following methods: flexible Software Defined Radio (SDR) can capture and transmit radio frequency signals; accurate time and frequency synchronization can be achieved between radio stations; high-output precision buses can be migrated and transmitted. Consolidate a large amount of data; excellent processing performance can be used for physical layer and MAC execution to meet real-time performance requirements. 

Fig. 4 Xu Mingren, deputy manager of Rod Schwarz’s technology development department, further said that the larger the product volume of far-field measurement, the higher the frequency, and the longer the measurement distance required.
High-frequency millimeter wave signal testing is challenging 
Because of the high frequency of millimeter wave, the distance between each antenna is greatly shortened with the frequency. The distance between the antennas is one-half wavelength, and the area and distance of the antennas are greatly reduced. Massive MIMO and small base stations as mentioned above can be realized. But know whether the antenna design is appropriate? The test and verification of the antenna signal becomes very important. Generally speaking, the distance required for far-field measurement is proportional to the volume and frequency of the product. Therefore, the larger the product volume, the higher the frequency, and the longer the measurement distance required. , The average measurement laboratory cannot build such a large measurement environment. 

Mr. Xu Mingren, Deputy Manager of the Technical Development Department of Rod Schwarz (R&S) (Figure 4) further explained that in the past, a 900MHz mobile phone only needed about 6 cm to measure the distance, and to a V-band above 60GHz, it would require a test distance of 4 meters. If the object to be measured is large, such as a base station transceiver system, it used to have a distance of 6 meters at 900MHz, and it would take 400 meters to reach the 60GHz frequency band, which is almost two mountains. The test method is divided into outdoor far-field (Outdoor Far-Field), the environment is better to build, but it is susceptible to interference; Indoor Far-Field (Indoor Far-Field), can build an environment without interference, but high-frequency products It is difficult to test, so some people use Compact Range to greatly reduce the distance of the far-field test through signal reflection. There is also a Near-Field test method, which can convert the test result through a formula. 

In the measurement error part, millimeter waves are more prone to errors than low-frequency signals. Xu Mingren said that the main reason is that the high-frequency signal pairing is not easy to do. Once the instrument is paired with the object under test, the test result will appear. There are two ways to solve the error. One is to add an attenuator to the path, and the other is Frequency Response Correction, which can effectively reduce the measurement error. 

Figure 5 Chen Mingbang, Technical Director of Nokia, pointed out that the future 5G network will be a highly application-driven architecture, so the concept of Network Slicing is very important.
2018 5G standards appear as scheduled 
5G is an important trend in the development of the technology industry in the next few years. In addition to the transmission rate, 5G can also achieve more functions that were not possible in the past. For example, Chen Mingbang (Figure 5), Technical Director of Nokia (Remote Surgery) Guaranteed Surgery, A Touchy-feely Internet, Self-driving Cars, Drones, Virtual Reality, Guaranteed Awesomeness ), Home Broadband. 

In the 3GPP plan, the first version of 5G will be officially launched in Release 15, which will be divided into non-standalone specifications to be completed by the end of 2017, and standalone specifications will be in June 2018 Completed, together is the first complete 5G technical architecture. Chen Mingbang explained that the difference between non-standalone and standalone New Radio (NR) is whether there is a core network and base station compatible with 4G. Non-standalone NR will use the LTE core network EPC and base station. At the same time, the control command (Control Plane) and the data (User Plane) are separated for processing. 

The future 5G network is a highly application-driven architecture, so the concept of network slicing is very important, providing different transmission rates and network delays in response to different needs. Chen Mingbang explained that 5G modulation should continue 4G LTE adopts OFDM and fully supports beamforming. The spectrum application ranges from 400MHz to 90GHz. The bandwidth of each channel below 6GHz is 100MHz, and the frequency band above 6GHz can reach 400MHz. It also supports networks. Slicing and cloud operations. 

Figure 6 Chen Wenjiang, deputy technical team leader of the Institute of Information Technology of the Industrial Technology Research Institute, said that before 2014, the industry had many doubts about the development of millimeter wave industrial applications, including signal loss and high cost.
Undoubtedly the development potential of millimeter wave 
The application of high-frequency millimeter waves is now a definite trend. The time invested by the Industrial Technology Research Institute was in 2014. Chen Wenjiang (Figure 6), deputy technical team leader of the Institute of Information Technology, said that when the industry was promoting the industrial application of millimeter waves, There are still a lot of noise and doubts, including the loss of millimeter waves and the high cost. However, such doubts have gradually decreased in 2015. Fortunately, compared with the development of many wireless technologies in the past, Taiwan’s investment is not too late. . 

The 5G network architecture is based on a simple concept, Chen Wenjiang described, it means to open a lot of roads in cities and large roads in the countryside. The low- and mid-range frequencies below 6GHz are like cities. There are more flexible network configurations through heterogeneous networks to make networking more convenient and reliable. High-frequency millimeter waves are rural areas. In the past, the area was sparsely populated, so large frequency bands were used to provide high transmission. rate. In the recent application of the millimeter wave frequency band, there is a consensus that 28GHz, about 850MHz available frequency band, and the 38GHz frequency band, the available frequency band is about 3GHz. 

5G will definitely apply large-scale array antennas, while using beamforming technology. Take 38GHz array antennas as an example. The size of each antenna is about 0.38 cm. The size of 64 8×8 array antennas is about 3.2×3.2 cm², with a small area. , But the more antennas, the more concentrated the signal, so each beam will be smaller. How to align the signal to the terminal requires the addition of Beam Tracking technology, which allows transmission and connection through fast scanning and phase conversion Will not be interrupted by the movement of the terminal. 

Looking at the future development trend of 5G millimeter wave, Chen Wenjiang explained that millimeter wave related technologies and components are highly integrated (Tightly Integration); in addition, all RF front-end ICs are systematic, including antennas, power amplifiers and RF ICs And so on, even the design is difficult to separate; lower power amplifier (PA) output, and higher antenna array gain; beam scanning beam tracking; intelligent beamforming; linearization (Linearization) power amplifier and model Modular Phased Antenna Array (Modular Phased Antenna Array). 

Figure 7 Jiang Weiyuan, assistant professor of the Department of Electrical Engineering of Mingzhi University of Science and Technology, pointed out that in addition to the future 5G system, because of technological breakthroughs, high-frequency microwaves will have a wider application and development.
Millimeter wave has a wide range of applications 
Millimeter wave has attracted much attention because of the development of 5G. In fact, related technologies and applications have been developed in the aerospace and military fields for a long time. Mingzhi University of Science and Technology Assistant Professor Jiang Weiyuan (Figure 7) pointed out that in addition to the future 5G system, Because of technological breakthroughs, high-frequency microwaves will have broader applications in the future. 24GHz will be a frequency band that can be developed. 24~24.25GHz has been designated as the ISM band, because 24GHz is just 10 times the well-known 2.4GHz. Signal absorption is also 10 times faster, energy concentration is 100 times higher, and the theoretical value of efficiency absorption can reach 1,000 times. 

The development of millimeter waves is also closely related to semiconductor materials. From the bandgap perspective, the most common semiconductor material, silicon (Si), has an energy band gap of only 1.11 eV, so it is difficult to use gallium arsenide as a material for high-frequency components. It is also very difficult to produce millimeter-wave components with a band gap of 1.43eV. In recent years, silicon carbide (SiC), which has gradually matured, has a band gap of 3.26eV, but its material is stable and has low electron mobility, making it difficult to become a millimeter-wave component material. Gallium nitride (GaN), the most popular in recent years, has an energy band gap of 3.42eV and high electron mobility. It is an important material for realizing millimeter wave devices in the future. 

In addition, the millimeter-wave microwave source can be heated quickly through a microwave-like method. Jiang Weiyuan said that pest control is one direction. The 24GHz microwave can be used to heat up to 55 degrees in 5 seconds to kill rice insects and insects in the rice warehouse. Eggs, and will not cause damage to the rice, it takes 800 seconds to use 2.4GHz, if you use it to heat slowly, you may even suffer heat damage to the rice. Therefore, millimeter wave components have several characteristics, such as smaller size, higher integration, higher energy control ability, and thermal effects. 

Figure 8 Lian Junxian, Technical Manager of National Instruments Greater China and Southeast Asia, believes that millimeter wave still has many technical bottlenecks, but the most important market factor is cost.
Millimeter wave component design challenges remain high 
Even though millimeter wave has become the focus of the development of wireless communication technology, and the commercial application of millimeter wave has been promoted since about 20 years ago, so far, there are still many technical bottlenecks in millimeter wave. National Instruments (NI) Greater China and Southeast Asia regional technology Manager Lian Junxian (Figure 8) believes that the most important factor is cost. Unless there is a heavyweight industry player who proposes an application that consumers love, gains support from the industry chain and breaks through the technical bottleneck, the industry invests heavily in millimeter waves. Product costs are greatly reduced, otherwise it would take another 5-10 years for the commercial application of millimeter waves. 

There are still three major challenges in the design of high-frequency millimeter-wave circuits, which are Conductor Loss, Dielectric Loss, and Radiation Loss. These are mainly due to the many characteristics of high-frequency circuits and mid- and low-frequency circuits. Different, new materials, technologies, design methods, and manufacturing processes are needed to make breakthroughs. In addition, wavelength-based matching components, especially some transmission lines; components that were difficult to achieve at low frequencies in the past, such as waveguides, can also be realized in the future; millimeter wave components have reduced circuits, thinner circuits, and thinner circuit boards, so the signal accuracy It is also demanded higher and higher. 

In addition, the packaging effect avoids the high frequency impedance from becoming high, and the packaging must use higher-level technology; the connector also has some verification tools such as SOLT, TRL and test board design. The development of 5G will bring many new concepts. From the perspective of design and testing, both high frequency and high bandwidth will bring more new challenges. However, these challenges will also bring more new business opportunities. With the investment, the price of millimeter wave components will become cheaper and closer to the sweet spot acceptable to the market.