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Fujikura Technical Review

No.51 February, 2022

ISSN 2436-9268
ISSN 0388-225X
Published by :
Fujikura Ltd.
1-5-1, Kiba, Koto-ku, Tokyo 135-8512, Japan


Expected Application Spaces and Supporting Technologies in 5G

Fifth generation (5G) mobile network services have finally started and many applications as well as new services are expected to be introduced into our life and work. As a next-generation infrastructure, 5G networks have been aimed at significantly increasing speed and capacity from 3G/4G wireless communications. Also 5G will provide drastically evolved communication networks connecting a massive number of devices to the internet and providing high reliability and low latency. This paper overviews requirements that 5G will meet and also discusses its underlying technologies, especially from the perspective of development of millimeter-wave technology.


Wiring Board Material Technology for Millimeter Wave Application

In the field of mobile communication networks, commercial services of 5th generaation networks have started, and millimeter waves (mmWaves) with frequencies over 30 GHz have been started to be used in electronic devices. Since millimeter waves cover wide frequency bands, high-speed, large-capacity network systems are becoming available. However, there is a problem that mmWave signals cannot be handled efficiently in conventional electronic wiring boards due to high transmission loss in those boards. To solve the problem, wiring board technologies optimized for mmWave application are indispensable. This paper reviews the technologies specifically focusing on wiring board materials.


Narrow-Band and Low-Loss Bandpass Filter for Quasi Millimeter-wave 5G Application

A 28-GHz bandpass filter (BPF) with a 2-GHz bandwidth (7% fractional bandwidth) built of silica-based post-wall waveguide (PWW) is presented for 5G-applications. The filter is composed of 5 cylindrical resonators. The dielectric loss-tangent of the substrate is as low as 0.00036 at 44 GHz. The dimensions of the BPF is 11×10 mm2. The insertion loss of the BPF, not including I/O interfaces for probing measurement, is less than 0.8 dB. Design of I/O interfaces for the BPF is also presented.


A High-gain Array Antenna Available for One-dimensional Beamforming at V-band

We propose an array antenna using liquid crystal polymer (LCP). The antenna works between 57 and 71 GHz. In order to achieve a wide beamforming range in the horizontal direction and a relatively high gain for each antenna element, a sub-array antenna consisting of four patches arranged in a row is used. Each sub-array antenna is fed from the center in order to prevent the radiation direction from changing with frequency. The layer structure consists of wiring layer, ground, antenna layer, and parasitic antenna layer from the bottom. S11 is less about -10 dB and the gain is higher than 9 dBi from 57 to 71 GHz.


28 GHz Bandpass Filter using Liquid Crystal Polymer (LCP)

We present three types of bandpass filters operating at 28 GHz with 5th-order Chebyshev, 4th-order canonical and 6th-order canonical stages. All of them are made of liquid crystal polymer (LCP) with solder bump input and output transition to printed circuit board (PCB) and are optimized to have very compact size. First, the characteristics of the filters are estimated by the coupling matrix. Then they are designed by electromagnetic simulation and are fabricated by PCB process. Measurement demonstrates that peak of │S21│ is 3.1 dB for the fifth-order Chebyshev, 2.2 dB for the fourth-order canonical, and 2.8 dB for the sixth-order canonical filters. 1-dB bandwidth is 2.9 GHz for the fifth-order Chebyshev, 2.45 GHz for the fourth-order canonical and 2.45 GHz for the sixth-order canonical. 25-dB bandwidth is 5.52 GHz for the fifth-order Chebyshev, 5.79 GHz for the fourth-order canonical, and 4.61 GHz for the sixth-order canonical.


Millimeter-Wave RFIC Technologies For 5G Systems

This paper describes semiconductor technologies for millimeter-wave radio frequency integrated circuits (RFICs) used in the fifth generation mobile communication systems (5G). Specifically, this paper explains bulk complementary metal oxide semiconductor (CMOS) technology, the mainstream semiconductor fabrication process, silicon on insulator (SOI) CMOS technology that improves the high-frequency characteristics of bulk CMOS, and silicon germanium (SiGe) bipolar-CMOS (BiCMOS) technology that enhances the high-frequency characteristics based on bipolar technology. This paper also discusses millimeter-wave RFICs developed using each technology.


A 60 GHz Wide-Band Communication Module that also Supports the New 5G Band

We have developed a 60 GHz wide-band communication module that covers the entire 60 GHz band including the new 5G band for FWA, wireless back-haul, enterprise, and V2X applications. We also have evaluated the module in indoor and outdoor environments and it has satisfied requirements for above applications.


Optical Connector for 5G Base Station

In recent years, mobile communication systems are shifting from the 4th generation, which mainly focuses on mobile phone services, to the 5th generation mobile communication system (5G), which enables high-speed, low-latency and high-capacity with multiple connections of various devices. The 5G offers improved services at autonomous vehicles, industrial equipment, security and medical care. The 5G deployment has begun in each country, and a lot of base stations start building. In this paper, we report on the development of a filed-assembly optical connector that can realize 5G optical fiber network wiring with high quality and less capital investment.


Methods for Promoting AI and Technological Developments for the Realization

While many applications of Artificial Intelligence (AI), mainly deep learning have been progressing, they often get stuck at Proof of Concept (PoC) step in manufacturing processes. To efficiently introduce AI into the manufacturing process, we have defined our AI roadmap. Based on this, we are studying, developing, implementing, and operating AI systems at our company. This paper will explain how we are putting effort into AI, details of specific projects, and the technologies we have developed to implement them. We will also discuss a direction of AI system architecture based on new technology movements such as 5G.


Low-attenuation Large-Aeff Optical Fiber for Long-Haul Transmission

Digital coherent technology, which enables large-capacity transmission, has been put to practical use especially in long-haul systems. Accordingly, G.654.E category1) is recommended by ITU-T as an optical fiber that can improve the optical signal-to-noise ratio (OSNR) required for systems using digital coherent technology. We have developed FutureGuide®-HSC-110 (hereafter HSC-110) and FutureGuide®-HSC-125 (hereafter HSC-125) compliant with ITU-T G.654.E. Both products have low attenuation and large Aeff. HSC-110 can be used in a cable with high density while HSC-125 has a high figure of merit (FOM). Both optical fibers suffer low macro- and micro-bending losses, so they can be used in cables with various structures.


The Fujikura Group's High-power Semiconductor Laser Technologies

The Fujikura Group has accumulated in-depth technology and know-how to develop products such as high-power semiconductor lasers and laser modules. In addition, we also have expertise to grow high-quality III-V compound semiconductor crystals, enhance power and efficiency of laser diodes by optimizing the structure, multiplex beams, mount parts on substrates, and dissipate heat. This paper introduces the technologies and performance of high-power semiconductor lasers developed by the Fujikura Group.


Over 150 kW Class CHAdeMO Liquid-Cooled Charging Cable and Connector

In recent years, there has been a strong demand for shortening battery charging time for EVs because the capacity of batteries installed in EVs is increasing. Consequently, there is a growing need to introduce DC high-power EV chargers to the market. To meet the need, a charging cable and connector for DC high-power EV chargers have to be developed. The optimal solution is to apply liquid cooling technology for forced cooling by circulating a coolant to the charging cable and connector.  Therefore, we have developed a liquid-cooled charging cable and connector for over 150 kW class DC high-power EV chargers conforming to the CHAdeMO specification ver. 2.0. This paper mainly describes the applied liquid cooling technology and the evaluation results of cooling performance for the developed charging cable and connector, which has achieved the target cooling performance.


Fine-pitch Flexible Printed Circuit Board for Particle Physics Experiment

The recent progress of the flexible printed circuit board (FPC) technologies has significantly contributed to the high performance and minimization of the various electric devices, typified by smartphones and wearable devices. Based on the technologies cultivated in producing these products, we have engaged in developing FPC boards for academic applications, which require more complicated designs than our current design standard for mass-produced products. This paper presents the results of development of FPC boards with fine-pitch, high-density circuits in a particle detector used in J-PARC muon g-2/EDM experiments.