New-Tech Europe | July 2018

July 2018

16 Designing a

Broadband, Highly Efficient, Gallium Nitride, RF Power Amplifier (RFPA) Using NI AWR Design Environment Software Platform 22 The future is optical 26 Security and Reliability Are Key in Wireless Networks for Industrial IoT 30 Optimizing Device Lifecycle Management Of Remote, IoT Connected, LPWA Devices

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July 2018

About New-Tech Magazines Group Read To Lead ‘New-Tech Magazines’ A world leader in publishing high-tech and electronics, producing top quality publications read by tens of thousands professionals from all over the world especially from Europe, innovative electronics, IoT, microwave, homeland security, aerospace, automotive and technological industries. Our specialized target audiences prefer New-Tech Europe because they know that our publications are a reliable source of the latest information in their respective fields. Our multidimensional editorials, news items, interviews and feature articles provide them with a full, well-rounded picture of the markets in which they operate - an essential asset for every technological leader striving to stay ahead, make the right decisions, and generate the next global innovation. Moreover, as an attractive platform for advertisers from around the world, New-Tech Europe has become a hub for bustling international commercial activity. Here, through ads and other promotional materials, Israeli readers obtain crucial information about developers and manufacturers worldwide, finding the tools, instruments, systems and components they need to facilitate their innovative endeavors. Targeting the needs of both the global and european industries and global advertisers, New-Tech Magazines Group constantly expands and upgrades its services. Over the years, the company has been able to formulate a remarkably effective, multi-medium mix of offerings, combining magazine publications with useful online activities, newsletters and special events and exhibitions.

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8 l New-Tech Magazine Europe

Contents

10 LATEST NEWS

16

Designing a Broadband, Highly Efficient, Gallium Nitride, RF Power Amplifier (RFPA) Using NI AWR Design Environment Software Platform

16

22 The future is optical 26 Security and Reliability Are Key in Wireless Networks for Industrial IoT 30 Optimizing Device Lifecycle Management Of Remote, IoT Connected, LPWA Devices

36 OUT OF THE BOX 38 NEW PRODUCTS 46 INDEX

22

26

30

www. new- t echeurope . com

New-Tech Magazine Europe l 9

Latest News

Premier Farnell Signs Contract for State-of-the-art Order Fulfilment Solution for New Leeds Distribution Centre

Premier Farnell, theDevelopment Distributor, has signed a contract with SSI Schaefer, one of the global market leaders and innovators in the intralogistics sector, to equip the company’s new Leeds Distribution Centre with a state-of-the-art order fulfilment solution. Construction work commenced on the high-quality 361,000

been designed to consider the nature of the product and the current regulations governing its handling and storage. Nick Wilkins, Chief Supply Chain Officer said, “This contract with SSI Schaefer is a key milestone in the delivery of a modern warehouse for the Premier Farnell group, positioning the business for future growth. Our

sq ft distribution unit at Muse Developments’ flagship Logic Leeds site on 29 March. The distribution centre project, which will be the largest ever warehouse development in Leeds, is scheduled to be completed by the end of the year. The main contractor is Derbyshire-based Bowmer and Kirkland and the site is expected to be fully operational by late 2019/early 2020. At the heart of the fully integrated solution to be provided by SSI Schaefer is the highly efficient Navette Matrix System, which operates alongside vertical lift storage machines and conveyors backed up by conventional shelving and pallet storage. All elements of the solution will be controlled by SSI Schaefer’s WAMAS warehouse management system and processes have

success is based on fulfilling market leading delivery promises. In partnering with SSI Schaefer we will continue to provide that service, supply our network of eight other warehouses across the globe, and develop core value-adding services for our customers right from our warehouse operations. We are very pleased to be working with SSI Schaefer.” SSI Schaefer’s Managing Director, Jaap Vos stated, “We are delighted to be working in partnership with Premier Farnell. Delivering an advanced system to enhance and support their operation creates the opportunity to continue to develop solutions ahead of anticipated future requirements.”

Outstanding sales performance, strong leadership, and technical excellence are highlighted in annual distribution awards

Avnet Abacus, one of Europe’s leading interconnect, passive, electro-mechanical and power distributors and a regional business unit of Avnet (NYSE: AVT), is the recipient of TDK Corporation’s 2017 European Senten Manten Gold award. This recognition comes as a result of the consistently strong operational and sales

The annual awards are based on TDK’s annual Senten Manten distributor performance evaluation programme. The Japanese term, Senten Manten, stands for the perfect result, with a maximum of 1000 points available. Distributors are assessed on performance and collaboration with TDK in four categories: business performance, inventory management, contractual terms, and operational

Picture: Members of the collaborative team at Avnet Abacus and TDK Europe

performance achieved by Avnet Abacus, with 17.6% sales growth year on year gained across the TDK product range.

excellence. Avnet Abacus was awarded the top score

10 l New-Tech Magazine Europe

Latest News of 830 points across the categories.

Nigel Ward, president of Avnet Abacus, commented: “This is a great accolade that exemplifies the strength of our long-term engagement with TDK. TDK continues to be a key technology partner working in collaboration with our technical teams to deliver the very best product solutions to customers across Europe.” Dietmar Jaeger, head of the TDK’s distribution business in Europe and Vice President of the Global Sales Distribution, added: “We have an excellent relationship with Avnet Abacus on all management levels. This award fully endorses the successful efforts of their teams, which have resulted in high-class technical support to customers across our product range.” Leti demonstrates new waveform for 5g low-power wide-area internet of things networks

physical layers to take advantage of the low power consumption of the transmission mode. Under more severe transmission conditions, the system switches to more resilient high-performance orthogonal frequency division multiplexing (OFDM). When both very long- range transmission and power efficiency are required, the system selects Turbo-FSK, which combines an orthogonal modulation with a parallel

Leti, a research institute of CEA Tech, today announced that field trials of its new Low Power Wide Area (LPWA) technology, a waveform tailored for Internet of Things (IoT) applications, showed significant performance gains in coverage, data-rate flexibility and power consumption compared to leading LPWA technologies. Leti’s LPWA approach includes its patented Turbo-FSK waveform, a flexible

Image: Performance chart comparison

concatenation of convolutional codes and makes the waveform suitable to turbo processing. The selection is made automatically via a medium access control (MAC) approach optimized for IoT applications. “Leti’s Turbo-FSK receiver performs close to the Shannon limit, which is the maximum rate that data can be transmitted over a given noisy channel without error, and is geared for low spectral efficiency,” said Vincent Berg, head of Leti’s Smart Object Communication Laboratory. “Moreover, the waveform exhibits a constant envelope, i.e. it has a peak-to-average-power ratio (PAPR) equal to 0dB, which is especially beneficial for power consumption. Turbo-FSK is therefore well adapted to future LPWA systems, especially in 5G cellular systems.” In the new system, the MAC layer exploits the advantages of the different waveforms and is designed to self-adapt to context, i.e. the usage scenario and application. It optimally selects the most appropriate configuration according to the application requirements, such as device mobility, high data rate, energy efficiency or when the network becomes crowded, and is coupled with a decision module that adapts the communication depending on the radio environment. The optimization of the application transmission requirements is realized by the dynamic adaptation of the MAC protocol, and the decision module controls link quality.

approach to the physical layer. It also relies on channel bonding, the ability to aggregate non-contiguous communication channels to increase coverage and data rates. The field trials confirmed the benefits of Leti’s LPWA approach in comparison to LoRaTM and NB-IoT, two leading LPWA technologies that enable wide-area communications at low cost and long battery life. The results indicate the new technology is especially suitable for long-range massive machine-type communication (mMTC) systems. These systems, in which tens of billions of machine-type terminals communicate wirelessly, are expected to proliferate after 5G networks are deployed, beginning in 2020. Cellular systems designed for humans do not adequately transmit the very short data packets that define mMTC systems. Designed to demonstrate the performance and flexibility of the new waveform, the field-trial results stem primarily from the system’s flexible approach of the physical layer. The flexibility allows data- rate scaling from 3Mbit/s down to 4kbit/s, when transmission conditions are not particularly favorable and/or a long transmission range is required. Under favorable transmission conditions, e.g. a shorter range and line of sight, the Leti system can select high data rates using widely deployed single-carrier frequency-division multiplexing (SC-FDM)

New-Tech Magazine Europe l 11

Latest News

Baidu to Integrate Mobileye’s Responsibility Sensitive Safety Model into Apollo Program

Baidu announced that it plans to work with Mobileye to integrate and commercially deployMobileye’s Responsibility Sensitive Safety (RSS) model in both the open source Project Apollo and commercial Apollo Pilot programs. Baidu also announced plans to adopt Mobileye’s Surround Computer Vision Kit as the visual perception solution; it will be integrated as part of Baidu’s proposition to the Chinese OEM market. The safety collaboration between Mobileye, an Intel Company, and Baidu is a significant strategic success for Mobileye’s RSS model, which was published last year, and will help deliver a safe driving solution for autonomous vehicles (AV) on China’s challenging roadways. “Our team recognizes the value and critical role that Mobileye’s RSS model plays in safely deploying autonomous driving. Project Apollo will integrate RSS to successfully enable safe driving today, and drive further autonomous research on China’s roadways.” – Weihao Gu, general manager of Baidu’s Intelligent Driving Unit What It Is: Apollo is designed to be “an open, secure and reliable self-driving ecosystem” that can help members of the autonomous driving industry quickly build their own complete autonomous vehicle systems. It has enlisted 116 global partners since its launch a year ago. RSS is an open and transparent formal model that provides safety assurance of AV decision-making. RSS does this by formalizing common sense human-centered concepts of what it means to drive safely. Examples: always maintain a safe following distance and right-of-way is given but not taken. The Mobileye Surround View Camera kit includes 12 cameras positioned around the vehicle plus Mobileye’s computer vision (CV) hardware and software, which leverages the cameras combined view into a unified and comprehensive CV solution for autonomous cars. Why It’s Important: The decision-making systems in

autonomous vehicles today are based on artificial intelligence (AI) – meaning they operate probabilistically and can make mistakes. When it comes to safety and the lives of passengers, a probabilistic model is not enough. That’s why Mobileye recommends adding a separate, deterministic layer on top of AI-based decision-making solutions in autonomous vehicles today. Baidu and Mobileye will collaborate on the verification of RSS’s formal model to the unique driving styles and road situations of the China market, and will jointly publish updates to the RSS model as this work results in new discoveries. “At Mobileye, safety assurance of automated vehicles is one of the most important issues facing the AV industry, and we are pleased Baidu has agreed to join us in this effort to deliver verifiable safety of AV decision-making into the China market,” said Jack Weast, chief systems architect for Intel’s Autonomous Driving Program. Why It’s Different: RSS was first proposed in 2017 by Mobileye CEO and CTO Professor Amnon Shashua and is an open, transparent and technology-neutral starting point for the industry to align on what it means for an AV to drive safely. To put it simply: While planning gets you from point “A” to point “B,” RSS helps keep you safe along the way. How It Works: RSS formalizes human notions of safe driving into a verifiable model with logically provable rules, defines appropriate responses, and ensures that only safe decisions are made by the automated vehicle and that the automated vehicle will do everything it can to avoid being involved in unsafe situations initiated by others. Mobileye’s RSS formulas will be integrated into the existing safety model (known as “DPS”) of Baidu’s Apollo Pilot. Apollo Pilot is Baidu’s deployment version of Project Apollo and is being developed for multiple Chinese OEMs.

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Latest News

Hyundai Motor Company Partners with Autotalks to Develop Connectivity Technology for Increased Road Safety

Hyundai Motor announced its strategic partnership with Autotalks, a leading technology company specialized in the manufacturing of Vehicle to Everything (V2X) communication chipsets.

In autonomous vehicles, V2X complements existing sensors, allowing them to make more informed decisions as well as easing their interaction with other road users. “Connectivity is one of the core technologies that can be applied to smart city business models, as well as autonomous driving and infotainment,” said Yunseong Hwang, director of open innovation business group at Hyundai

Hyundai Motor forms a strategic partnership with Autotalks through a direct investment to accelerate the development and deployment of the next generation chipset for connected cars.

Top Image: Hagai Zyss, Autotalks CEO.

Motor Company. He added, “Hyundai will continue to invest in disruptive technologies that are in line with Hyundai’s current and future strategic pillars.” Hagai Zyss, CEO of Autotalks, commented, “Having a top global car manufacturer such as Hyundai invest directly in Autotalks is not only a vote of confidence in the company but a testament to the growing V2X market. Hyundai’s pursuit of cutting-edge communication and safety technologies is a perfect match with Autotalks’ leading V2X capabilities. The funding from Hyundai will fuel Autotalks’ technology roadmap as well as support our customers and partners all over the globe.” Prior to the current investment by Hyundai, Autotalks completed four funding rounds with a total of more than $80 million in investments. now expanding our collaboration to IoT as we seek to integrate new, low-power NB-IoT functionality into end-devices based on our combined expertise with global brands and device manufacturers,” said Luca Orsini, Head of Networks, Ericsson North East Asia. “As we look for new ways to connect end users and expand the potential of the Internet of Things, collaborations like this confirms our commitment to delivering global Massive IoT solutions for enabling new capabilities and facilitating the support of new IoT use cases and applications.” “Ericsson is a pioneer in mobile technology and a global leader in mobile networks infrastructure,” said Jerry Yu, Corporate Vice President and General Manager of Intelligent

Hyundai is expanding partnerships in the connectivity field to further strengthen connectivity technology vital to autonomous driving and explore new business opportunities within smart city infrastructure. V2X technology allows vehicles to communicate with one another, with other road users and road infrastructure, enhancing road safety and mobility. The main focus of any V2X solution is safety. As a reliable non-line-of-sight sensor working in all environments and weather conditions, it helps prevent road collisions and avoid dangerous situations. In manned vehicles, V2X systems convey important information to the driver in the form of alerts and notifications and can also actuate the vehicle in dangerous situations. At the Ericsson booth at Mobile World Congress Shanghai, Ericsson and MediaTek demonstrated end to end integration of NB-IoT use cases with commercial end devices that are based on 3GPP Release 13, and the demo cases includes security guaranteed smart NB-IoT door-locker, NB-IoT based wearable health band and safety watch for kids. The two companies plan to further cooperate to test technology enhancements based on 3GPP Release 14, such as enhanced data transmission features, which improve throughput data rates up to 4 times the speed of R13. “MediaTek and Ericsson have been in close collaboration to drive ecosystem development since the start of 3G, and we are

Ericsson and MediaTek collaborate to accelerate and expand NB-IoT device ecosystem

New-Tech Magazine Europe l 13

Latest News

Devices Business Group of MediaTek, “As we work to deploy and validate our NB- IoT solutions, this collaboration will accelerate the commercial development and enable new functionalities for the rapidly growing and evolving Internet of Things marketplace.” As a result of testing end-

device manufacturers and wide- ranging products like bike share companies, fitness tracking devices, connected wearable devices, smart locker, smart meters and more. Likewise, MediaTek customers can rely on state of the art end- to-end compatibility with leading IoT network technology that

to-end use cases based on 3GPP Release 13 and verifying Release 14 feature compatibility, Ericsson customers can leverage MediaTek’s deep and diverse customer base of

support exciting 3GPP R14 NB-IoT functionalities that provide higher throughputs and capacity and can be used in a wide range of use cases.

Otaniemi to host a unique smart energy testing platform Business Finland has

granted funding worth almost EUR 5 million for the development of a smart and flexible energy system testing platform in Otaniemi, Espoo. The testing platform will be built around Nokia’s 5G network, utilising the opportunities it brings for the fast transfer of data.

Developing and taking innovations to the market requires networking and opportunities for experimentation As one of the companies involved in the project, Nokia aims to create new opportunities for cooperation

between telecom and energy sector operators and to develop ways of combining telecommunication, digital platform and consumer services. “In Nokia’s vision, 5G and automation can help to boost many industrial processes. One of these areas is smart electricity grids and the Smart Otaniemi project offers an excellent framework for developing innovations in cooperation with the top actors in the field. Our aim is to work even more closely with the energy sector in building new smart energy systems in Finland and on a global scale. This is also an excellent opportunity for Nokia to find new cooperation partners in a sector where the company has not operated extensively before,” says Lauri Oksanen, VP Research and Technology, Nokia Bell Labs. GreenEnergy Finland (GEF) is also one of the companies that is developing its solutions in Otaniemi. “Otaniemi is an excellent platform for testing the

The funding granted by Business Finland is divided among 11 companies and three research organisations. In addition, more than 20 companies will participate in the development of the testing platform with their own funds. Smart Otaniemi will be developed into an innovation ecosystem that brings together experts, companies, technologies and pilot projects, combining all the elements for the future of smart energy. “The energy sector ecosystem now being built in Otaniemi will attract internationally interest. At Business Finland we believe that testing platforms like these will help to create opportunities for Finnish companies to grow and internationalise. We will also attract foreign operators to Finland,” says Pekka Soini, Director General, Business Finland.

14 l New-Tech Magazine Europe

Latest News

development work through possible thesis topics. “Research plays on important role in this changing world. We also need bold experiments alongside strategic cooperation between the different actors. VTT wants to bring the actors together to find new business solutions for global opportunities. Smart Otaniemi is a good indication of a new kind of cooperation in Finland,” says Antti Vasara, CEO, VTT. Otaniemi’s smart energy testing platform is part of Business Finland’s Smart Energy program which accelerates the know-how and competitiveness of Finnish companies in the international markets with the help of testing platforms that are created in different parts of Finland.

commercial electricity market integration and smart electricity networks of properties as we create, together with competent partners, a working vision for a smart city of the future and develop solutions for everything from demand flexibility to energy digitalization,” says Miko Huomo, Executive Partner, GreenEnergy Finland. Involving consumers in testing newenergy solutions VTT Technical Research Center of Finland is coordinating the testing environment and building it in close cooperation with the network of actors formed by the universities and companies. The first experiments will already begin in 2018. The aim is to collect information and experiences on utilising the 5G and IoT platform, improving the energy efficiency of buildings, more flexible electricity markets, and the possibilities for charging electric vehicles. Students from Aalto University’s campus area will also be involved in testing the solutions. Students can also get involved in the

“By actively involving consumers in testing and developing the solutions, we can ensure the development of new types of user-friendly energy services,” says Pia Salokoski, Manager of the Smart Energy program. CUI Partners with SnapEDA to Offer Free PCB Footprint Files

“This partnership with SnapEDA is a continuation of CUI’s mission to equip our customers with necessary design tools and resources at every stage of the product development cycle,” said Jeff Schnabel, CUI’s VP of Global Marketing. “The addition of these PCB footprint

CUI announced that it has teamed up with SnapEDA, the market-leading parts library for circuit board design, to provide designers with a catalog of free, ready-to-download PCB footprints and symbols for CUI’s range of board mount electromechanical components.

Circuit board design has historically been a time-consuming and challenging process due to the variety of product configurations and standards. With this partnership, users will be able to prevent footprint errors and design smarter, thanks to a library of verified PCB footprints and symbols readily available in all major CAD formats, including: Altium, Eagle, KiCad, OrCAD/Allegro, PADS/DxDesigner, and PCB123. The files are free to download from CUI’s CAD model library and product pages, or via the SnapEDA website, where they can then be placed directly into a product’s design.

files bolsters CUI’s already extensive catalog of ready-made 3D models, further streamlining the design process for engineers,” Schnabel concluded. “We are committed to building the industry’s largest, verified library of component models. Adding CUI and their broad portfolio of board level components to our catalog supplies yet another source from which engineers can gather PCB files for seamless integration into their designs,” stated Natasha Baker, CEO of SnapEDA.

New-Tech Magazine Europe l 15

Designing a Broadband, Highly Efficient, Gallium Nitride, RF Power Amplifier (RFPA) Using NI AWR Design Environment Software Platform

J. Brunning, and R. Rayit, SARAS Technology

Introduction Demand for linear RF power amplifiers (RFPAs) covering the frequency range 1.5 – 2.8 GHz is driving new design methods for broadband, linear, and highly efficient RFPAs operating in output back-off mode (OBO). Improving efficiency in power amplifiers has long been a challenge for designers, in part due to poor control of harmonic loading impedances. The difficulty of measuring waveforms at microwave frequencies makes it hard to determine if optimum waveshaping has been achieved. Broadband design adds an additional challenge when a harmonic of a lower operating frequency lies in the intended operating band. These inherent difficulties can be compounded by imprecise design techniques, leading to multiple time- consuming and expensive iterations.

In this article, a first-pass design flow is described that uses NI AWR Design Environment, specifically Microwave Office circuit design software, as well as a measurement technique for the input and output impedances of the matching networks prior to RFPA “turn-on.” Several approaches to the problems inherent in PA design are presented with an aim of minimizing uncertainty and achieving first-time success. The effectiveness of this approach is demonstrated using a commercially available discrete 10 W gallium nitride (GaN) on silicon (SiC) packaged high- electron-mobility transistor (HEMT) using a 0.25 µm process (Qorvo T2G6000528) and a 20 mil RO4350B printed circuit board (PCB) dielectric. The fabricated RFPA achieved a peak power of >+40 dBm and a peak drain efficiency of >54 percent over its operating bandwidth. In back

off-mode the RFPA achieved an un- corrected linearity of 30 dBc and drain efficiency ≥34 percent when driven with a coded orthogonal frequency- division multiplexing (COFDM) 2.5 MHz, 9.5 dB peak-to-average power ratio (PAPR) modulated signal in the 2.0 – 2.5 GHz band. RFPA Design Flow Device Selection The initial design of the RFPA began with a thorough device/ technology selection process, the purpose of which was to select a best candidate device against a specific set of criteria prior to the time-consuming tasks of load/ source pull and network synthesis. Several candidate devices seemed acceptable on the basis of claimed frequency and power. In addition to the more common parameters such as Vds, gain, operating frequency

16 l New-Tech Magazine Europe

range, and power rating, other more detailed device data such as Cds, Cgs, and transformation ratio were also carefully considered. Optimal Load Impedance Extraction Once a device was selected and a nonlinear model obtained, the optimal source and load impedances were determined. The required load impedances necessary to achieve maximum power, maximum efficiency, gain, or an acceptable trade-off between these performance metrics are frequency dependent and vary substantially over the operating bandwidth of a broadband design. To determine the correct load impedance, a combination of load- pull plotting at the fundamental and harmonic frequencies, waveform engineering, or circuit design techniques based on shaping the transistor voltage and current waveforms, were performed in Microwave Office. It should be noted that using waveform engineering in determining any optimal impedance relies on having access to the intrinsic device nodes, in other words, across the intrinsic current generator of the device plane rather than at the package reference plane. Assuming the nonlinear model provides these nodes, then a waveform engineering approach enables the visual observation of voltage and current swing, clipping, and class of operation of the amplifier. For this example, the load pull simulation was run at Vds = +28V, Idq = 90 mA across the operating band and the optimal power and efficiency impedances were extracted with the mid-band results shown in Figure 1. A target load region based on the overlap between the Pmax -1 dB and drain efficiency max (effmax) – 5 percent contours was defined. Clearly, the larger this target area is, the easier the matching problem becomes. In

the complexity of the task increases beyond what is required for an average performing power amplifier design. However, in the case of a broadband amplifier, particularly one with high performance specifications, the realized network is required to control the impedance variation over a far larger fractional bandwidth. After defining optimal impedances and target areas, the load network was developed using a simplified real-frequency technique (SRFT) [3] to design the ideal lumped element network and then convert to distributed stepped impedance format [4] before performing electromagnetic (EM) simulation on the network. In this example, the EM results agreed closely with the predictions of circuit-based modelling, but for less conventional matching topologies this might not be the case. In general, EM simulation is seen as an important step in reducing uncertainty in the design flow. Onedesign technique is to represent the conjugate of the optimal impedance as that of a two-terminal generator (port 1), after which the matching network design can be viewed as a problem of reducing the mismatch loss that exists between this complex-valued load and a 50Ω termination over the amplifier’s operating bandwidth. This mismatch Figure 1: Fundamental load pull analysis from within Microwave Office showing contours at constant compression with Pmax ≥4 1dBm and Effmax ≥70 percent for min, mid, and max frequency points over the operating bandwidth. The boundary region is defined as the intersection of Pmax – 1 dB and Effmax – 5 percent, Zo reference = 50Ω

this case Pmax occurred on a tightly- packed, clockwise rotating locus over the operating bandwidth, which was helpful in the case of the broadband amplifier. Load pull was performed at the fundamental frequency due to the broadband nature of the RFPA and consequent difficulties in achieving the optimal harmonic terminations [1] without using TX zeros in the network [2]. Load pull at the second harmonic was also performed and a region of high efficiency identified [1] that could be controlled in the network synthesis. Network Synthesis Narrowband RFPAs have the advantage of showing little variation of the optimal load impedance over their operating bandwidth and hence the task of network design is somewhat less complex. This is not to say that a low fractional bandwidth match is always trivial. Indeed an investigation of source and load impedances will reveal that for very high performance, the network fundamental impedance must often be precisely controlled to a single gamma point with significant sub-optimal performance penalties if the network locus ‘misses’ its target load impedance. Morever, precise control of harmonic termination impedances for F and F-1 classes and

New-Tech Magazine Europe l 17

can, however, be evaluated at the 50Ω side (port 2) of the network as shown in Figure 2a. As a passive network, the output matching circuit had an operating power gain < 1, equal to its efficiency as determined by internal dissipative loss only. The necessarily smaller transducer gain was the product of this efficiency with the effect of loss due to reflection at the input. These quantities are presented as percentage efficiencies in Figure 2b. The transducer gain was evaluated for a generator whose impedance is the conjugate of the target load impedance to be seen by the device drain. Although the output was matched for compressed power and efficiency, not small reflection at the drain, the second factor was found to agree closely with the predicted reduction in compressed power due to imperfect realization of the target load impedance. Thus, the plotted transducer gain was a good measure of the overall quality of the output matching achieved. A further analysis (Figure 2b) of the load network using transducer power gain (GT) as a measure of load network mismatch loss between the transistor and the purely real 50Ω termination was also considered. An efficiency figure for the load network was calculated as 96.6 percent at 2800 MHz, with close correlation to the value calculated from the return loss at the same frequency. For comparative purposes the operational power gain (GP), which considers purely ohmic loss in the network, was also calculated to have an efficiency of 97.7 percent. Although this dissipation loss does not directly include reflection losses, its value does depend on the termination impedances as these affect the distribution of current and voltage within the network, and hence the copper and dielectric losses respectively.

Figure 2a: Load network loss and match as a function of frequency of the realized distributed load network.

Figure 2b: Transducer power gain (GT) as a function of frequency to express load network efficiency of the realized distributed load network. Operational power gain (GP) is shown for comparison.

Source Network Control of the source impedance variation over operating bandwidth was achieved through the use of a bandpass filter network, which also has the advantage of reducing low frequency gain, where the transistor’s inherent gain is very high. This particular source impedance matching network is also responsible for assisting with the amplifier’s low frequency stability. The impedance transformation ratio of about 15:1 needs a more elaborate network. In general, although not used here, matching networks with a deliberate

Achieving a broadband optimal match using this transistor was relatively straightforward for several reasons. Firstly, the transformation ratio is relatively low (about 2:1) over the operating bandwidth; secondly, the load impedance for optimal Pmax points were tightly packed, and thirdly, the optimal impedance varied with increasing frequency on a clockwise rotating locus. As commented above, the fairly low transformation ratio was a useful criterion favoring selection of this GaN device in a broadband RFPA application.

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the only simple option was to monitor waveforms at the package plane, which clearly has limitations due to the package parasitic effects. (Negation of the parasitic network was feasible, but only if topology and component values are known and their electrical impact removed through de-embedding during simulation). Although care had been taken to control the second harmonic load impedance, analysis of the waveforms, as shown in Figure 3, showed that third harmonic impedance was very favorable without further optimization. These waveforms showed a peak voltage of <60 V and a peak current of <1500 mA at 1500 MHz, which were well within device ratings. What was more instructive in terms of the efficiency performance was the near-ideal Class F operation with the half-wave rectified current waveform exactly 180 ̊ out of phase with the voltage waveform and very little voltage/current overlap. Using a DLL (dynamic load line) analysis, the waveform was defined as three regions; Region A where Vmin and Imax, Region B where Vmax and Imin, and the transition region. Using this technique, the waveform was controlled successfully. Calculating over one period, it was found that the waveform remained in Region A or B for 63.8 percent of the time and the transition occupied only 36.2 percent. RFPA Validation To validate the approach and its accuracy, the RFPA was fabricated on Rogers 4350B 20 mil dielectric (εr = 3.48). The circuit was mounted on a jig consisting of 3 pieces containing: the source network (INMAT), load network (OUTMAT), and a copper center section to mount the device which was required to have its

Figure 3a: DLL using intrinsic V and I nodes at 1500 MHz CW stimulus. Regions A, B, and transition defined.

Figure 3b: Intrinsic V and I waveforms using the same nodes with corresponding regions defined in shaded area. Power output is 10W

Waveform Engineering Waveform engineering [5] was also used to analyze the RFPA, using both the load-pull tuner and, more critically, the realized load network. Recent device models giving access to the voltage and current nodes at the intrinsic current generator plane allow accurate observation of both the V and I waveforms, as well as the dynamic load line (DLL), for analysis of clipping and the RFPA mode of operation, as well as the peak voltages and currents generated. Prior to these nodes being available,

positive slope, or equalization, can conveniently be introduced in the source matching circuit. Stability of the RFPA was achieved using a shunt connected series R – C pair adjacent to the input port followed by a series R. Although this was quite a severe approach, analysis showed the transistor to be potentially unstable in the operating band and therefore some gain was sacrificed in order to obtain unconditional stability from 1 MHz to >6 GHz where the transistor ceased to have gain (Fmax).

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source soldered down as shown in Fig. 4 (a). Passive Measurements Prior to assembling the complete RFPA the impedances of the INMAT and OUTMAT circuits, as presented to the transistor tabs, were measured to correlate modelled vs measured datasets. The measured data shows an excellent agreement between modelled impedance and measured impedance over an extended bandwidth of 1000 – 3000MHz with no tuning, as shown in Fig. 4 (b). An additional measurement of the INMAT and OUTMAT was performed from 20MHz to 10GHz and still showed very good agreement between modelled and measured datasets as shown in Fig. 5. With the aid of such a demountable jig, the impedances seen by the device can be measured directly and accurately without using mechanically awkward probes that also introduce electrical parasitics, notably stray inductance at the attachment point. The jig is not the production version of the amplifier, but its use is seen as an important stage of the design flow which conforms to the theme of eliminating uncertainties at every possible stage of the design. Small Signal Measurements Initial small signal gain measurements were carried out using a drain bias of Vds = +28V and an Idq = 90mA. A high degree of correlation between measured and modelled gain and match was observed as shown in Fig. 6 with an input return loss of >7.5dB over the operating band. Additionally, the RFPA exhibited no instability under practical stability tests such as varying the drain rail voltage and using an external tuner to vary the source impedance seen by the device.

Figure 4: (a) Fabricated RFPA on jig showing individual INMAT and OUTMAT measurement jigs and copper center section, (b) Measured vs modelled INMAT and OUTMAT 1000 - 3000MHz. (a) (b)

Figure 5: Measured vs modelled INMAT and OUTMAT 1000- 10000MHz.

Large-Signal

Measurements

a maximum P3dB of 40.6 dBm, maximum drain efficiency of 59.1 percent, and a maximum gain of 15.7 dB. The results in Figure7 show a high degree of agreement between modelled and measured datasets. It should also be noted that the RFPA delivered ≥10 W down to 1300 MHz and up to 2900 MHz, extending its range to a fractional bandwidth (BW) of 76.2 percent. To evaluate the efficiency in output back-offmodeand the intermodulation sideband performance, a 2.5 MHz channel BW COFDM signal with 9.5 dB PAPR was used over the band 2.0 – 2.5 GHz. In single-ended form at +34.5 dBm output, the average efficiency was 34 – 35.9 percent, with a linearity of 30 dBc measured at fcenter +/-1.25 MHz as shown in Fig.8. Similar results were obtained

(Continuous Wave) The large signal measurements were carried out using a drain bias of Vds = +28V and an Idq = 90 mA. A continuous wave (CW) signal source was fed into a driver amplifier prior to being fed into the amplifier under test. The RF input and RF output power measurements were corrected for any compression occurring in the driver stage. The three performance parameters measured were power gain, drain efficiency and power delivered to the load. In order to provide a reference these were all evaluated at the 3dB compression point. Modelled results showed a P3dBmax of 40.99 dBm, maximum drain efficiency of 63.2 percent, and a maximum gain of 16.41 dB. Measured results showed

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Figure 7: Modelled vs measured large signal CW results.

Figure 6: Comparison of modelled vs measured small signal gain and input return loss.

in the band 1.805 – 1.88 GHz using a wideband code division multiple access (WCDMA) test signal with PAPR = 7.8 dB. A balanced version of this amplifier is under construction. Including imperfect hybrids, it was predicted to have performance that achieves +37 dBm with an average efficiency of ~34 percent and a linearity of 30 dBc at fcenter +/- 1.25 MHz. The linearity performance could be improved through linearization techniques such as digital pre- distortion or envelop tracking. It is interesting to note that achieving a high-efficiency class of operation at signal peaks enables operation at greater peak compression, so the amplifier is operated at higher relative power over the whole signal dynamic range. Hence the efficiency and/or linearity is improved even on high PAPR signals. Conclusion This paper has presented a design for a broadband, linear, and efficient output back-off mode RFPA, emphasizing the importance of minimizing design uncertainties wherever possible. Using this approach, excellent agreement between the modelled and measured datasets has been proven and a first- pass design achieved. The design methodology used four stages: device selection using

qualitative and quantitative analysis, optimization in Microwave Office of load and source impedance matching networks using load/source pull, passive network synthesis (including EM verification), and waveform engineering using intrinsic voltage and current nodes. Together these techniques have proved to provide a systematic approach to designing the entire RFPA. In addition, a measurement technique for fabricated source and load networks, enabling comparison of modelled and measured impedances at the transistor tabs, has been demonstrated using a three-piece jig. Passive network synthesis using an SRFT technique combined with analysis using mismatch loss and transducer power gain has produced a broadband match using relatively simple source and load impedance matching networks. The results indicate that this particular RFPA could be well suited to operate as a multipurpose driver or output stage. Acknowledgements The author would like to thank Andy Wallace of AWR Group, NI and Qorvo / Modelithics for the device model. References [1] D. T. Wu, F. Mkadem and S. Boumaiza. “Design of a broadband

and Highly Efficient 45W GaN Power Amplifer via Simplified Real Frequency Technique”, IEEE MTT-S Int. Microwave Symposium, pp 1091- 1092, May 2010.
 [2] R. A. Beltran. “Class-F and Inverse Class-F Power Amplifier Loading Networks Design Based upon Transmission Zeros”, IEEE MTT-S Int. Microwave Symposium, June 1-6 2014.
 [3] P. L. D. Abrie. Design of RF and Microwave Amplifiers and Oscillators, 1st edition, Artech House, 1999.
 [4] D. M. Pozar. Microwave Engineering, 2nd ed, Wiley, 1998.
 [5] S. C. Cripps. RF Power Amplifiers for Wireless Communications, 2nd edition, Artech House, 2006. Figure 8: Intermodulation sideband performance measured using modulated test signal.

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The future is optical!

Professor Piet Demeester, imec

The mainstream adoption of cloud computing applications and the projected, sevenfold increase in global mobile data traffic between 2016 and 2021 are just some of the recent trends that continue to boost the demand for high- speed broadband. To cater for that need, the international research community has increasingly been focusing on advancing optical communication systems, using light to transport huge amounts of data from one place to another. The need for (ever more) speed To transmit those light beams – and the data they carry – optical communication systems make

use of optical fibers; flexible, transparent (glass or plastic) fibers with a diameter slightly thicker than that of a human hair. Compared to legacy (copper) cables, they enable data to be transmitted over longer distances, considerably faster. At the September ’17 European Conference on Optical Communication (ECOC), for instance, Japanese researchers presented a massive breakthrough in terms of how much data can be transmitted through a single optical fiber – reaching a transmission speed of 10 petabits (10 million gigabits) per second; a landslide achievement that will undoubtedly revolutionize the way in which intercontinental fiber-optic communication networks

will be built and operated going forward.

In pursuit of these ever more powerful optical communication systems, increasingly faster and efficient optical transmitters and receivers at both ends of the optical fibers need to be developed. And exactly that is one of the key strengths of our researchers at IDLab, an imec research group at Ghent University. Breaking the barriers of fiber-optic communication Our research in this space aims at improving the performance of four technologies in particular: Short-reach datacenter

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