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Miniaturized RF passive components like filters, inductors and capacitors required for future 5G and IoT requirements

The RF design consists of passive as well as active components. The inductors, capacitors, and resistors are one of the three passive elements that are the foundations of all electronics. The discrete and passive components are an integral part of the design; from front-end antenna matching to tight-tolerance mixers, oscillators, transformers, modulators, filters, switches, diplexers, and so on.  For example, filters are always needed to discriminate against out-of-band signals and attenuate them down to very low levels while preserving full power in the bands of interest.



With the introduction of services like 5G  having multiple bands as well as desired compatibility with earlier bands  is driving  demand of smartphones, tablets, and other mobile devices that must support more RF bands than ever order to offer worldwide coverage and meet marketplace demand. Despite the fact that their RF circuits are becoming more complex, these devices must remain as compact—if not more compact—with each new model.


Another trend in wireless design is moving towards higher frequencies like milllimeter waves whose one of the benefits is that components can get smaller. Specifically, antennas and inductors can shrink to surface-mount and PCB sizes. Integrated circuits, too, can contribute and have contributed to this shrink-fest as process geometries allow the integration of complete RF sections that seamlessly blend digital functionality with the analog realm of RF modulation, demodulation, antenna matching, and wave propagation.


With connected devices and the Internet of Things poised to become a multi-trillion dollar enterprise by the mid-2020s, Next-generation communications, energy storage, and sensing technologies could be smaller, lighter, and faster than ever. The emerging  Internet of Things revolution which  are generally consist of  nodes which are resource  scarce in computation, memory and energy require miniaturization of some key components and systems that will allow designers of next-generation wireless links to provide smaller and more efficient radios and radio subsystems.


As well as applications in sensors and energy transfer, inductors are key to the RFICs and RFIDs used in the Internet of Things. Radio frequency (RF) electronic components use a lot of passive components, like capacitors and inductors, until recently inductor could not be miniaturized as fast as transistors and digital electronics circuits.


The passive components that integrate several discrete parts into smaller, surface-mount versions, saving space and cost and improving performance are useful with modern, highly integrated standard radio link transceiver chips that already offer small-size solutions. Since these established standards are on their third or fourth generation, integrated passives are highly optimized and include miniature front ends, filters, baluns, and other assorted parts that can serve single-standard solutions like Wi-Fi, or multistandard protocols like Wi-Fi Bluetooth combinations.


While simple filters can be made of a few very small resistors, capacitors, and inductors, more stages and poles can be achieved using more complex structures. ICs do not make the best filters. The typical inductor Q that can be fabricated using CMOS process technology is less than 10. With copper and metallization techniques, this can be doubled to around 20. The problem is that to minimize insertion loss, Q values in the hundreds are needed. Presently, only discrete filters can do this.


Size, weight and power, as well as cost, (SWaP-C) considerations

When maximizing accuracy, range and speed are essential, large electronics that limit defense system design options are not acceptable. For this reason, size, weight and power, as well as cost, (SWaP-C) have always been a major consideration for aerospace and defense systems. Microelectronics includes a variety of electronics manufacturing processes capable of creating very small, dense components and systems assembled with high-precision. It starts with creating very dense circuits with narrow traces and spaces. With the right processes, systems can be partitioned differently, and capabilities previously delivered in three components can be integrated into one, saving space. At the next level up, microelectronics assembly involves placing very small components incredibly precisely, often within one micron tolerance or less. This capability is commonly used in photonics, defense and space applications.


Direct Printing of Passives

As electronic components have been miniaturized, so have the PCBs used to connect them. Developments in specialized system-on-chip (SoC) components, smaller passives, and higher transistor density in powerful processors have allowed more components to be placed in a smaller area. In addition, this has allowed newer devices to have greater functionality that would formerly have required multiple boards in a single package, or multiple devices connected together.


The structure of planar PCBs on rigid substrates is such that components are confined on one or two layers, ultimately limiting available board space. In addition, the manufacturing process for planar PCBs constrains the interconnect architecture that can be implemented to being purely orthogonal, making use of perpendicular vias and traces for layer transitions in multilayer PCBs. Other DFM guidelines for planar PCBs limit the allowed spacing between traces, pads, and vias, which inhibits components from being placed closer than would be allowed electrically.


With a 3D printing system, designers can break these traditional DFM rules and take full advantage of miniaturization of electronic components. There are some novel design choices layout engineers can easily implement when fabricating boards with an additive manufacturing system.


3D printing processes that allow simultaneous deposition of an insulating and conductive structure can be used to easily fabricate passive components on a board. Such processes include aerosol jetting and inkjet printing, which can be used to deposit capacitors, inductors, passive filters, RF amplifiers, and unique antennas directly in a 3-printed substrate. When these components are placed in an interior layer, this frees up space on a surface layer for other components that may be more bulky, such as large capacitors, transformers, or connectors.


As a broader range of advanced materials become available for use in commercial 3D printers, such as semiconducting polymers, a wider range of passive and active devices can be printed directly on a surface layer or an interior layer. This allows a range of unique devices to be 3D printed alongside the board and conductors in a single process. Because these structures can be directly printed a layer at a time, they can be easily embedded inside the board with no required finishing or assembly steps.


Capacitor Technologies

Advances in semiconductor technologies is one of the strong driver that enables fast IoT, wearables, energy harvesting development etc. However, its use in real applications would not be possible without development of enabling capacitor technologies.

Thin film capacitors are a powerful substitute for electrolytic capacitors because of their use in manufacturing high-frequency devices in simple, compact forms. Thin Film capacitors have a higher voltage resistance than electrolytic capacitors, the ESR (Equivalent Series Resistance), also known as internal resistance, is low, performance is stable, and they last longer.

They also have greater dielectric strength and processing features, and Physical Vapor Deposition (PVD) technology can be used to provide high-frequency capacitance in a reduced profile. Energy storage devices such as voltage converters are essential to managing power usage for electronics needing high efficiency, quick response, and small sizes.



Electronic Components Join Forces To Take Up 10 Times Less Space On Computer Chips

Electronic filters are part of the inner workings of our phones and other wireless devices. They eliminate or enhance specific input signals to achieve the desired output signals. They are essential, but take up space on the chips that researchers are on a constant quest to make smaller. A new study demonstrates the successful integration of the individual elements that make up electronic filters onto a single component, significantly reducing the amount of space taken up by the device.


Researchers at the University of Illinois, Urbana-Champaign have ditched the conventional 2D on-chip lumped or distributed filter network design – composed of separate inductors and capacitors – for a single, space-saving 3D rolled membrane that contains both independently designed elements. The results of the study, led by electrical and computer engineering professor Xiuling Li, are published in the journal Advanced Functional Materials.


“With the success that our team has had on rolled inductors and capacitors, it makes sense to take advantage of the 2D to 3D self-assembly nature of this fabrication process to integrate these different components onto a single self-rolling and space-saving device,” Li said. In the lab, the team uses a specialized etching and lithography process to pattern 2D circuitry onto very thin membranes. In the circuit, they join the capacitors and inductors together and with ground or signal lines, all in a single plane. The multilayer membrane can then be rolled into a thin tube and placed onto a chip, the researchers said.


The device-fabrication process includes the deposition of metals by electron-beam evaporation and lithography to define the metal pattern and etching process. The final etching step then triggers the self-rolling process of the stacked membrane. “The patterns, or masks, we use to form the circuitry on the 2D membrane layers can be tuned to achieve whatever kind of electrical interactions we need for a particular device,” said graduate student and co-author Mark Kraman. “Experimenting with different filter designs is relatively simple using this technique because we only need to modify that mask structure when we want to make changes.”


The team tested the performance of the rolled components and found that under the current design, the filters were suitable for applications in the 1-10 gigahertz frequency range, the researchers said. While the designs are targeted for use in radio frequency communications systems, the team posits that other frequencies, including in the megahertz range, are also possible based on their ability to achieve high power inductors in past research.


“We worked with several simple filter designs, but theoretically we can make any filter network combination using the same process steps,” said graduate student and lead author Mike Yang. “We took what was already out there to provide a new, easier platform to lump these components together closer than ever.” “Our way of integrating inductors and capacitors monolithically could bring passive electronic circuit integration to a whole new level,” Li said. “There is practically no limit to the complexity or configuration of circuits that can be made in this manner, all with one mask set.”


Professor Pingfeng Wang and postdoctoral researcher Zhuoyuan Zheng, of industrial and enterprise systems engineering; professors Yang Shao, Songbin Gong and student Jialiang Zhang, of electrical and computer engineering; and professor Wen Huang and graduate student Haojie Zhao, from Hefei University of Technology, China; also contributed to this study. The National Science Foundation and the Jiangsu Industrial Technology Research Institute, China, supported this research. Li is the interim director of the Holonyak Micro and Nanotechnology Laboratory and also is affiliated with mechanical science and engineering, the Materials Research Laboratory and the Beckman Institute for Advanced Science and Technology at the U. of I.



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