2013 International CES, the big consumer electronics show in Las Vegas, is just getting started and already mobile device integration is a popular theme across the show. According to CNN:

If the show sets the tone for the year’s technology, 2013 will be about watching TV on your 5-inch smartphone while your self-driving car ferries you to work. Companies will continue to try to connect everything to the Internet—lights, power outlets, cars, cameras, kitchen appliances—and allow you to control them from a mobile device.

“Consumers are increasingly interested in buying four different types of products: tablets, smartphones, high-definition televisions, and traditional PCs and laptops,” writes Parmy Olson at Forbes.com. According to researchers at Accenture, consumers want all-in-one capabilities in various sizes, when it comes to computer hardware. As a result, there is intense pressure for electronics manufacturers to product multi-function devices: web, video, communications.

The more functions stuffed into portable devices, the tougher the challenge for design engineers. Sensitive electronics must be protected, such as displays and batteries. Getting molded enclosures and hardware to fit as planned is difficult, especially in mobile devices. Rogers’ high performance foams , including PORON® cushioning and sealing materials, absorb and distribute impact energy, shielding mechanical components and electronics, preventing unwanted damage, such as cracks in cell phone screens.

Automotive Advances

Auto companies are also out in force at CES this year. CNN reports:

Ford, Toyota, Hyundai, Audi and others [are] showing off technology to make cars smarter. There will be self-driving and assisted-driving cars, which use a combination of mounted cameras, sensors and GPS to can take the wheel completely or just help a driver into a tight parking spot.

Vehicles are connecting to the Internet to improve navigation, better monitor a car’s performance and alert the driver to maintenance needs. They are also taking a cue from (and synching with) smartphones. Cars will continue to integrate apps, voice control and entertainment into the dash, some even running on the Android operating system.

Many of the auto innovations are based on microwave and millimeter-wave systems that provide more stable performance under all weather conditions. Basic printed circuit board (PCB) material requirements include relative dielectric constant that is low and consistent with changes in temperature, tight tolerance of the dielectric constant, good phase stability, a low dissipation factor (for low dielectric-related loss), and low conductor loss. Rogers’ high frequency laminates provide low dielectric loss and excellent mechanical properties vs temperature for reliable multilayer circuit board construction.

For more details on automotive design and high frequency electronics, see

PCB Advances Drive Automotive Applications

Low-Loss PCBs Enable MM-Wave Auto Electronics 

 

This post authored by John Coonrod originally appeared on the ROG Blog hosted by Microwave Journal. You can find The Role of PCB Materials in Impedance Matching, Part 1 here.

Successful high-frequency circuit design requires achieving an impedance match among a wide range of transmission-line features, circuit elements, and active and passive components. High-frequency circuits typically operate at a characteristic impedance of 50 Ω, and matching the different parts of the circuit and its components to that impedance helps maximize the transfer of power from a source to a load, such as from a transmitter to an antenna. In the previous blog, some of the challenges in achieving good impedance match at RF/microwave frequencies were detailed, including the importance of a printed-circuit-board (PCB) material with stable and consistent effective dielectric constant. To further explore the impact of a circuit substrate on high-frequency impedance matching, two popular PCB materials from Rogers Corp. – RO3010™ and RO3035™ circuit materials – will serve as examples to show how circuit-material parameters can be translated into solutions for high-frequency impedance-matching issues.

Both RO3010 and RO3035 laminates are ceramic-filled PTFE-based circuit materials with consistent mechanical properties, although with different values of dielectric constant. Both are designed to provide stable dielectric constant versus temperature and frequency with a dielectric constant that does not vary across the width, length, and thickness of the materials. This consistency is instrumental in achieving a good impedance match for all parts of a circuit, without having to “customize” impedance tuners or quarter-wave transformers because of changes in the dielectric constant of the material.

The RO3010 laminate, suitable for microstrip and stripline circuits through 77 GHz, is defined by a “process” dielectric constant of 10.2 at 10 GHz, held to a tolerance of ±0.3 in the z-direction (thickness of the material). The material’s data sheet also lists a second value of dielectric constant of 11.2 in the z-direction, from 8 to 40 GHz. This is referred to as the “design” dielectric constant, recommended for use in commercial simulation software.

Why two different values for dielectric constant? And what is the significance of having two difference values of dielectric constant to impedance matching with this material? For the case of RO3010 material, and in fact for many circuit laminates, values of dielectric constant are determined by standardized test methods. The “process” value is the result of a clamped stripline test method in which a stripline resonator is formed using two sheets of RO3010 laminate and a clamping fixture with a thin resonator circuit. The frequency of the resonator is measured and used to determine the dielectric constant. A potential problem with this method is any air entrapped between the two sheets. As noted in the last blog, air has a dielectric constant of 1.0. If it is mixed in with materials being evaluated, and if electromagnetic (EM) waves propagate through the air, the determination of dielectric constant can be altered.

The clamped stripline test method is also sensitive to the anisotropic nature of most PCB materials—that is, the dielectric constant is typically different in the x and y directions than in the z direction. The stripline resonator method can be more sensitive to the influence of the material’s dielectric constant in the x and y directions than in the z direction.

The “design” dielectric constant value for RO3010 laminate results from the differential phase-length method, which is based on measurements using microstrip transmission lines. In this method, two microstrip circuits of different lengths are fabricated on a material under test and phase angle differences are evaluated using the same connectors or test fixture and an appropriate test instrument, such as a vector network analyzer (VNA). From the lengths of the circuits and their differences in phase angles, the influence of the PCB material on the wave propagation of the two circuits can be used to determine the dielectric constant of the material at a specific frequency. This method is relatively accurate in gauging the dielectric constant in a material’s z-direction and is less affected by a material’s anisotropic effects. But it is relatively slow and not well suited for high-volume production.

A simple example may help to understand the importance of the “design” dielectric constant, or Design Dk as it is known, to impedance matching. This example consists of a circuit application at 2 GHz, using 25-mil-thick RO3010 laminate, and it requires a main line impedance of 50 Ω and a load with 30-Ω resistance and -40-Ω reactance. If the process Dk of 10.2 is used to calculate the circuit dimensions, a quarter-wavelength transformer section would have a length of 0.542 in., a width of 0.055 in., and would be placed 0.271 in. from the load. If the same transformer width is assumed, and the same laminate, but the circuit dimensions are now based on a Design Dk value of 11.2, the quarter-wavelength transformer section would have a length of 0.518 in. and would be placed 0.259 in. from the load. The two different Dk values yield quite different results in terms of transformer length and location from the load.

The RO3035 circuit material also features very consistent electrical properties but with much lower dielectric constant values, with a “process” dielectric constant of 3.50 ± 0.05 in the z-direction at 10 GHz, measured by the clamped stripline method, and 3.6 in the z-direction from 8 to 40 GHz as measured by the differential phase length method. It also exhibits stable dielectric constant with frequency and temperature to minimize performance variations when pursuing impedance-matched circuits. Because a number of material properties contribute to impedance and impedance matching, including dielectric thickness and conductor thickness, the RO3010 and RO3035 materials are available with a number of different dielectric thicknesses and electrodeposited copper foil thicknesses, allowing designers to select the mechanical parameters that can best suit their efforts to control impedance.

Impedance matching of RF/microwave circuits can be challenging enough without dealing with unexpected variations in material parameters, such as inconsistent copper cladding and dielectric thickness. The key parameters for the RO3010 and RO3035 circuit laminates are tightly controlled to help make impedance matching more straightforward and based on the expected impedances of circuit dimensions for a specific effective dielectric constant. In general, material properties that are critical to impedance matching and maintaining a desired impedance include tight control of the dielectric constant, control of conductor thickness, and control of dielectric thickness. For example, for achieving impedance-matched circuits, dielectric materials maintained to thickness tolerance of ±10% or better can help achieve impedance matches that are consistent and predictable.

The next blog will take a close look at designing RF/microwave bandpass filters, and why RT/duroid® 6010 PCB material provides the right features for filters.

Do you have a design or fabrication question? John Coonrod and Joe Davis are available to help. Log in to the Rogers Technology Support Hub and “Ask an Engineer” today.

 

The first battery in the form of an electrochemical cell was developed by Alessandro Volta in 1800 and later refined in the Daniell cell in 1836. While these power sources are now commonplace, they often lag the technology they power – from cell phones to electric vehicles. Recent developments are promising, as shown in the following research updates.

•            How Improved Batteries Will Make Electric Vehicles Competitive. It will likely take a decade, but improvements to lithium-ion batteries could lead to much cheaper EVs.

•            The search for clean and green energy requires a better and more efficient battery technology. A team of researchers from Argonne National Laboratory and the University of Chicago are working on titanium dioxide electrodes that improve their performance as they are used.

•            Researchers at Rice University have developed a technique in which a lithium-ion battery can be pained on virtually any surface.

•            The US DOE has awarded up to $120 million to a multi-partner team to establish a new Batteries and Energy Storage Hub, to be known as the Joint Center for Energy Storage Research (JCESR).

•            Beyond lithium ion: ARPA-E places bets on novel energy storage. The largest grant winner in energy storage hopes to make a rechargeable lithium sulfur battery.

•            New research shows lithium iron phosphate in nanoparticle form is useful for high power battery applications.

•            New graphene-based inks are designed for printed batteries, biochemical sensors.

Batteries need to be packaged to absorb internal impact energy. PORON Urethane and BISCO Silicone foams withstand collapse that can happen due to the stresses of compression and temperature in battery packs over time. This Compression Set Resistance (C-set) Resistance can help extend the life of the battery by continuing to seal and absorb shock. These unique foams from Rogers Corporation also have a unique ability to act as a spring by retaining a very consistent level of force across a range of compressions. This allows the designer more flexibility and reliability in packaging of the battery pack due to the ability to predict the cushioning material’s behavior across varied dimensional tolerances.

Find out more in “Megatrends Fuel Growth in Materials.”

 

 

The Connecticut Technology Council (CTC) has awarded Rogers Corporation (NYSE:ROG) the 2012 Innovation Excellence Award.  The annual award recognizes significant technology leadership and innovation by Connecticut-based technology companies.

Robert Daigle, Senior VP of R&D and CTO, Rogers Corporation, with CTC’s CEO, Matthew Nemerson

“Rogers is honored to receive this prestigious award that highlights our long history of innovation,” said Robert Daigle, Senior Vice President and CTO, Rogers Corp. “For over 180 years, innovation has been at the heart of what we do as a materials solutions company. Today, our team collaborates with the world’s leading developers of next-generation technology, helping them power, protect and connect the world.”

Rogers’ unique power electronic solutions help power module and traction motor designers to safely and reliably increase efficiency and manage the power generated by electrified vehicles, high-speed trains, solar energy and wind farms. The company’s high-performance cushioning and sealing materials protect everything from your tablet computer to the most sophisticated medical devices. And its high-frequency laminate materials for printed circuit boards enable the telecommunications industry to achieve the ever-increasing speeds and reliability consumers demand from the internet.

Rogers is the ninth company to receive the Innovation Excellence Award from CTC, Connecticut’s industry association for the technology sector. Previous winners include ATMI, Inc. of Danbury, Pitney Bowes of Stamford, FuelCell Energy of Danbury, Open Solutions Inc of Glastonbury, Sonalysts, Inc. of Waterford, United Technologies Corporation, ESPN of Bristol, and Tangoe, Inc. of Orange.

 

This post authored by John Coonrod originally appeared on the ROG Blog hosted by Microwave Journal.

Impedance matching is an aspect of RF/microwave design that has challenged even the best circuit designers from time to time. High-frequency circuit designers generally aim for a characteristic impedance of 50 Ω, unless they are working on cable-television (CATV) circuits, which typically operate at 75 Ω. The 50-Ω impedance is not by chance, since it represents a state that supports the most efficient transfer of RF/microwave signal power from a source to a load, with the least number of signal reflections. Of course, high-frequency power can be transferred from a source to a load when they are at different impedances, and few sources and loads are precisely at 50 Ω. But mismatched conditions can lead to reflections and standing waves in high-frequency transmission lines, which can blend with desired signals and result in amplitude and phase distortion. For the lowest phase distortion and flat amplitude response, most RF/microwave circuit designers start with ensuring that all of the possible impedance mismatch points, such as transmission-line junctions, connections to components, and terminations with connectors, are as close to 50 Ω as possible.

Circuits in which the characteristic impedance is well matched throughout will suffer minimal reflections and exhibit few standing waves. Standing waves cause the impedance to fluctuate as a function of distance from the load. Circuits with well matched impedances throughout will exhibit a measurably low voltage standing wave ratio (VSWR). A perfectly matched transmission line would have a VSWR of 1.0:1. Under such ideal conditions, full power would be transferred from a source to a load, with no reflected power. In contrast, a severely mismatched line would have a VSWR that tends towards infinity, or a VSWR of ∞:1. For example, a short circuit or an open circuit, in which no power is transferred from a source to a load, both have a VSWR of ∞:1. Realistically, a circuit with VSWR value of about 1.50:1 is considered to have well matched impedance.

Maintaining a 50-Ω impedance throughout an RF/microwave circuit is no simple task. High-frequency circuit designers use numerous transmission-line technologies, including microstrip and stripline, and each has its own set of guidelines for determining characteristic impedance. For microstrip, for example, the impedance of a transmission line is dependent on the width of the signal trace, the thickness of the metal conductor used for the trace, the dielectric constant of the printed-circuit-board (PCB) material, and the height between the signal trace and the reference or ground plane, which is essentially the thickness of the PCB material.

Stripline circuits, which are formed as a sandwich of a signal trace between dielectric layers, also exhibit transmission-line impedance as inversely proportional to the line width and directly proportional to the thickness of the dielectric material layers. One difference between stripline and microstrip is that the height of the signal trace above the ground plane for stripline has less of an impact on impedance than the height of a microstrip signal trace above the ground plane. The air above a microstrip circuit will actually contribute to the characteristic impedance of the circuit, whereas a stripline circuit is contained within a sandwich of dielectric material. Because air has an effective dielectric constant of 1, it will always serve to lower the effective dielectric constant of any PCB material used in a microstrip circuit.

Because of this, the effective dielectric constant of PCB materials used in a stripline circuit will be higher than those same dielectric materials used in a microstrip circuit. Because of the impact of the air above a microstrip circuit—lowering the effective dielectric constant of its PCB material—the dielectric material in a stripline circuit must be planned for differently. To achieve the same controlled impedance in a stripline circuit as in a microstrip circuit, the distance from the circuit trace to the ground plane must be greater in the stripline circuit—essentially requiring thicker dielectric material.

Matching impedances within an RF/microwave circuit can also require careful planning and tight control of circuit parameters, such as trace width. Over time, circuit designers have developed a broad range of creative solutions for maintaining a matched 50-Ω impedance within their circuits even when employing complex circuit junctions and making interconnections to chip components, active and passive packaged components, and various connectors. Impedance is affected by such factors as the thickness of the metal conductor layer used for the transmission lines, the width of the signal trances formed on that layer, the thickness of the dielectric substrate, and the effective dielectric constant of the substrate. For example, a straight microstrip transmission line at a particular trace width may exhibit a 50-Ω impedance, but with an sudden change in direction, such as a 90° bend, the impedance of the transmission line can change. Circuit designers rely on a variety of circuit structures, such as single-stub and double-stub impedance tuners and quarter-wave transformers, to form impedance matches, for example between a 50-Ω transmission line and a high-impedance (300-Ω) source. These impedance matches become more difficult when they must be achieved over broad operating frequency ranges.

Trusted tools for achieving matched impedance include the Smith chart, for visualizing shifts in impedance, and the RF/microwave vector network analyzer, for measuring a circuit’s scattering (S) parameters, which are defined for impedance-matched conditions. And, of course, modern computer-aided-engineering (CAE) software tools can provide excellent assistance in developing impedance-matched RF/microwave circuits. Such software tools allow users to define the essential parameters of a circuit’s PCB material, including dielectric constant, which can have a tremendous impact on achieving a matched 50-Ω impedance.

Although the dielectric constant of a circuit-board material plays such a key role in determining the characteristic impedance of an RF/microwave circuit, it is a numerical value that represents a very complex property of a PCB material. The dielectric constant may vary across the length and width of a circuit board, and it can also vary as a function of temperature or frequency. The dielectric constant of a circuit material can be determined by a number of different methods; the value for a material may depend on the method used.

RF/microwave circuit impedance matching is not a simple topic, and books have been devoted to it. But a good starting point in understanding how to achieve reliable matched impedance in high-frequency circuits is by better understanding the role of the PCB material in determining a circuit’s effective impedance. To help with that understanding, the next Blog in this series will feature Part 2 to this impedance-matching discussion, focusing on two particular PCB materials–RO3010™ and RO3035™ laminates from Rogers Corp. Part 2 will provide a “teardown” of those two materials and how their various properties contribute to achieving successful impedance matching in narrowband and broadband RF/microwave circuits.

Do you have a design or fabrication question? John Coonrod and Joe Davis are available to help. Log in to the Rogers Technology Support Hub and “Ask an Engineer” today.