The Rogers ACS Division has introduced a new design program that is free to download called the MWI-2010 Microwave Impedance Calculator, a transmission line modeling tool for electronics engineers (setting up an account is required).

The MWI-2010 Microwave Impedance Calculator software doesn’t replace sophisticated suites of modeling tools, such as the Advanced Design System (ADS) from Agilent Technologies or Microwave Office from AWR. Nor can it challenge the prediction capabilities of a planar or 3D electromagnetic (EM) simulator such as the Sonnet suites from Sonnet Software. But what it does, it does well, which is to calculate key parameters for most common microwave transmission lines, including microstrip, stripline, and coplanar-waveguide transmission lines. The software is downloaded as an executable (.exe) file and runs on most Windows-based personal computers, including those with Windows XP, Windows Vista, and Windows 7 operating systems. To speed and simplify the use of the software, Rogers also offers a 22-page operator’s manual in PDF file format.

Using the Transmission-Line Modeling Tool

The MWI-2010 program is based on closed-form equations derived from Poisson’s wave equations. The simple-to-use software can determine key parameters for a selected transmission-line type and laminate material, such as the conductor width and conductor metal thickness needed to achieve given impedance at a target frequency. The software’s intuitive graphical user interface (GUI) screen allows a user to select from a variety of different transmission-line types, including conventional microstrip, edge-coupled microstrip, conventional stripline, offset stripline, and conductor-backed coplanar-waveguide (CPCPW) transmission lines. The on-screen menus allow a user to select a transmission-line technology and a laminate material. Once a material, such as Rogers RT/duroid® 6035HTC material, is selected, its pertinent characteristics are also shown on the screen, including relative dielectric constant (permittivity), dissipation factor (loss), thermal conductivity, and thermal coefficient of dielectric constant. Moving a mouse cursor over any material name reveals additional information about the material.

Enter Parameters such as Thickness, Operating Frequency and RF Power Level

With a material in place, the next step is to pick a standard dielectric thickness from a menu, or enter a custom thickness. A standard copper cladding thickness must also be selected from a menu, or a custom thickness entered manually. Copper conductor roughness is also accounted for, either selected from a menu as a standard value, or entered manually as a nonstandard value. Similarly, a standard value for copper conductivity can be used in a calculation, or a custom value entered, although any change in the value for copper conductivity will affect all metal layers in a multilayer circuit.

The MWI-2010 software allows an operator to enter parameters pertinent to a specific application, such as operating frequency and RF power level. Once a user has selected the desired transmission-line type, dielectric material, material thickness, conductor width, thickness of the conductive metal cladding, etc., a calculation will provide results in terms of such transmission-line parameters as conductor width and conductor spacing for a selected impedance. The software can generate insertion loss tables of data that can be used to create plots of loss versus frequency, and these plots can then be compared to actual measured results from a microwave vector network analyzer (VNA).

This exact procedure was performed to evaluate the accuracy of the MWI-2010 software for calculations of conventional microstrip parameters. MWI-2010 calculations performed for conventional microstrip transmission lines have proven to be extremely accurate since they include the effects of dispersion as well as copper roughness. For example, calculations performed on RT/duroid 6035HTC laminates have compared quite closely with actual measurements. These are ceramic-filled PTFE composite materials with a dielectric constant of 3.5 at 10 GHz and dissipation factor of 0.0013 at 10 GHz. In a comparison of MWI-2010 predictions versus measurements for a 20-mil-thick microstrip transmission line on RT/duroid 6035HTC with 1-oz. copper cladding, predicted and measured data matched almost exactly through 6 GHz. The predictions do not maintain the same accuracy above 7 GHz for this particular model, but still track the measured data very closely even at those higher frequencies.

The MWI-2010 software may not be able to match the accuracy of an EM simulator for a given prediction, but it is considerably faster, providing results almost instantaneously. It has been found to be most accurate for calculations on conventional microstrip and stripline, very accurate with edge-coupled microstrip and offset stripline transmission lines, and fairly accurate with conductor-backed coplanar-waveguide (CBCPW) transmission lines, although in the case of CBCPW transmission lines, vias must be properly placed to ensure accurate results.

Calculating the impedance of transmission lines is not trivial, since a number of factors can affect impedance. In microstrip, the width of the conductor and thickness of the dielectric substrate impact impedance. In CBCPW, not only the conductor width and dielectric thickness, but the spacing on the signal plane between the signal conductor and the adjacent ground planes will affect impedance. The MWI-2010 software is free, and provides results fairly quickly that are accurate and can be saved for use in other programs, including in word processors or in spreadsheets for creating x-y plots. In addition to calculating the impedance and loss of a transmission line, the MWI-2010 software provides information on a laminate’s effective dielectric constant, signal wavelength, skin depth, the electric length for a transmission line at a selected frequency, and propagation delays. It can even calculate the temperature rise above ambient temperature for a selected laminate based on an input RF power level.

For anyone needing a quick impedance calculation for designing a filter, coupler, or other high-frequency circuit, the MWI-2010 software provides usable results. And the price is right!

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This post by Dave Sherman originally appeared on the PORON Cushioning Blog.

Many customers are often surprised when we explain to them that all PORON® Performance Cushioning Materials are open cell polyurethane foams. It seems that the standard cushioning foams that they see on the market are typically closed cell EVA foams or closed cell polyurethane foams.

In fact, the open cell nature of PORON Cushioning foams is one of the material properties which help to make PORON Materials have the best resistance to compression set (C-Set) or for the non-foam geeks out there: resistance to break down after multiple uses.

Closed Cell Foams vs. Open Cell Foams

What do you need, a tennis ball or a spring?

EVA foams, commonly used in insoles and sports padding, are closed cell foams, meaning that all the bubbles of trapped air in the foam are complete bubbles, with cell walls all around, like a million balloons all stuck together. This kind of foam gets most of its properties from the air trapped inside the bubbles. When the foam is compressed, say when you’re walking on an insole or when you land on your elbow pad, the air inside the bubbles is compressed, and the return force is caused by the decompression of the air. This behavior is just like the behavior of a tennis ball, which gets its bounce from the air inside the ball. Like a tennis ball, the air eventually leaks out of the cell, and the foams go flat, or “take a set” in foamese. That means the foam insole is less comfortable on the next step, or less protective on the next hit.

Closed Cell Foam:

PORON Cushioning materials are an open cell foam, which has little connections or portals between the cells that allow air flow between them. So PORON materials are not dependent on the air for their properties, but instead on the properties of the materials in their cell walls. They operate more like spring, and return to their original position after being compressed, time after time because the air moves freely in and out of each cell.

Open Cell Foam:

Being closed cell offers some advantage and disadvantages in applications. The foams can be very light, as their cell walls can be very thin, but are usually stiff because of the incompressibility of the air inside them They can also be better at resisting liquid penetration.

Likewise, in addition to being resistant to taking a set, open cell foams have some other advantages, like being breathable and soft (better Compression Force Deflection – CFD). The table below summarizes some of the advantages (marked with an A) each foam has.

Foam Properties

Measures

Closed

Open

CFD Softness/Conformability A
Compression Set Resistance Life of Properties A
Anti Microbial Integral Coating
Breathability MVTR-Yes/No A
Water Absorption % Uptake After Some Time A
Washability Cycles at Setting A
Closed/Open Cell

So as you design something that will use a foam, ask yourself what are the most important properties you want. If you want light weight and great washability, then use a closed cell foam. If you want reliability over time, softness and breathability, choose PORON? Performance Cushioning Materials.

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By Human Resources Department, Rogers Corporation

Earth Day This year’s Earth Day theme was “A Billion Acts of Green®,” and that is exactly how we kicked off the celebration in local communities.

On April 21, members of our Rogers Corporation team joined together for a clean-up of our local streets at the Rogers and Woodstock, Connecticut locations.  This year was extra special as Easter was just around the corner, and participants found Easter eggs along the way with great prizes hidden inside.

Earth Day may come just once a year, but it should be celebrated every day!  The Earth Day Network reminds us that “real change occurs best when millions of people commit to it with their actions.”  Every effort to help the environment, no matter how small, is important.

“Real change occurs best when millions of people commit to it with their actions”, Earth Day Network

Here are some tips we learned from our Earth Day celebration to make any clean up event “greener” and more fun:

  • Participants picking up trash received reusable shopping bags, a great reminder to keep a few in your car for shopping trips.
  • Rather than driving to a location for Earth Day, participants cleaned up their local streets and parks.
  • We had a great time searching for Easter eggs along the way!  Having fun going green with rewards and challenges encourages sustainable change.

To date, A Billion Acts of Green has reported over 45 million acts, both great and small.  Our team is working to take these acts to one billion and beyond!

Do you have ideas for next years’ celebration? Share them with your team and your local community!

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By the Human Resources Department, US Career Center

Volunteers aren’t paid, not because they are worthless, but because they are priceless.  This anonymous quote truly touches upon the importance of volunteering.  Offering your time to a worthy cause, whether it’s disease research, helping a family in need, or feeding the hungry is an excellent way to feel good while helping others.

Volunteer in Your CommunityIn addition to helping your community, volunteering can serve as an excellent tool for the working professional.  In the workplace, you interact with people every day, whether it’s with a co-worker, client, or supervisor.  Volunteering offers new opportunities to meet others in a whole new atmosphere.  Enjoy a walk or 5k for your favorite charity while simultaneously expanding your network of contacts.

Another benefit of volunteering is simply learning something new.  Participating in a large food or clothing drive demands expert organization, a skill that can certainly benefit both you and your workplace.

Working in a team outside the office can also teach you new ways to approach challenges inside it.  Would you like to become a better project leader?  Consider managing a team of other volunteers working toward a common goal.  Improving your leadership skills outside the office will give you the confidence to shine at work.

Think about the skills you’d like to improve upon, whether it’s organization, leadership and team building, or simply meeting new people.  Find any one of the many volunteering opportunities available in every community and join in.  Learn something new, and feel good while doing it!

Which community projects are you involved in and passionate about?

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This post authored by John Coonrod originally appeared on the Rog-Blog hosted by Microwave Journal

Performance requirements typically guide the selection of a PCB material. Some applications may also be cost-sensitive, and require evaluation of the total costs of choosing a circuit material. This includes the cost of the material as well as costs associated with processing the material. For example, FR-4 is a low-cost material with minimal processing costs. However, its performance is also low relative to some higher-costing materials, such as PTFE- or hydrocarbon-based circuit materials, although these materials can have considerably different processing requirements and associated costs. By considering the costs of the material as well as its processing requirements, it’s possible to determine if “you get what you pay for” truly applies to circuit materials.

Halogen-free Circuit Materials

For example, Theta® halogen-free circuit materials from Rogers Corporation have a slight premium in cost to FR-4 materials, but with more stable dielectric constant over frequency and lower loss. Ideal for high-speed digital circuits and multilayer constructions, they feature high heat resistance for use in lead-free applications. Theta materials exhibit a dielectric constant of 3.90 at 1 GHz and 4.01 at 10 GHz (in the z-axis), with dissipation factor of 0.0080 at 1 GHz and 0.0118 at 10 GHz. While Theta laminate does not deliver the electrical performance of a PTFE-based laminate material such as Rogers RT/duroid® 6035HTC ceramic-filled PTFE composites, its material costs and processing costs are lower.

Circuits on Theta materials can be fabricated with standard processing methods, to minimize processing costs. The materials themselves are available with a wide range of laminate and prepreg thickness options for covering widespread applications, and they can be processed with the same methods used for FR-4 circuit materials, using standard pin or slotted tooling. Theta material requires no more than a standard chemical cleaning process with micro-etch for preparing board surfaces for the application of a liquid or dry film photoresist to “image” the desired circuitry; the copper surface can even be prepared for photoresist application by means of a basic mechanical scrub without damage to the material. The photoresist can be developed, etched, and stripped (DES) using any commercial chemical treatment. In many ways, Theta material circuit processing is just like that for FR-4 but Theta material features a z-axis coefficient of thermal expansion (CTE) that is 30% lower than FR-4, with significantly more stable dielectric constant over frequency and temperature than FR-4.

PTFE-based Circuit Materials

In contrast, PTFE-based circuit materials such as Rogers RT/duroid 6035HTC provide considerably better electrical performance than a hydrocarbon-based Theta material, although the cost of processing the material, and the material itself, is somewhat higher. RT/duroid 6035HTC is a ceramic-filled PTFE composite with low-profile, reverse-treated copper foil for excellent thermal dissipation, stability, and low loss. As a result, it is designed for much higher power-handling capability than Theta material.

The higher cost of the RT/duroid 6035HTC material itself and its processing, however, delivers a laminate with extremely stable dielectric constant of 3.50 in the z-axis at 10 GHz, with low dissipation factor of 0.0013 at 10 GHz and impressive thermal conductivity of 1.44 W/m/K for outstanding performance in high-power circuits.

Between Theta laminate and RT/duroid 6035HTC in terms of performance, material costs, and processing costs lies Rogers XT/duroid™ 8000 and RO4000® LoPro™ non-PTFE hydrocarbon circuit materials. XT/duroid 8000 is a halogen-free thermoplastic material designed for ease of processing. The material has a similar dielectric constant to that of RT/duroid 6035HTC: 3.23 in the z-axis at 10 GHz. It is resistant to the solvents and reagents typically used to process PCBs, and has a higher maximum operating temperature (MOT) than PTFE-based materials for handling higher-temperature environments. It is lower in material cost and in processing than RT/duroid 6035HTC, but with a higher 0.0035 dissipation factor (for increased loss) and much lower thermal conductivity for less power-handling capability.

Also, Rogers RO4000 LoPro circuit material is based on a thermoset hydrocarbon resin system. Ideal for multilayer circuits, it features low-profile reverse-treated copper foil for low passive intermodulation (PIM) performance in RF/microwave circuits and excellent signal integrity in digital circuits. It is compatible with lead-free processing and designed for ease of fabrication to minimize processing costs. It cannot match the electrical performance of a PTFE-based circuit material like RT/duroid 6035HTC, but it is also less in material and processing costs. As can be seen from this sampling of Rogers’ materials, when considering a circuit material, tradeoffs in costs—both material and processing costs—also mean tradeoffs in performance.

Those attending the technical sessions at the IPC APEX EXPO in Las Vegas, NV (April 10-14, 2011, www.ipcapexexpo.org) can learn more about some of the performance, cost, and processing differences among circuit materials by attending John Coonrod’s presentation “Understanding when to use FR-4 laminates or high-frequency laminates.”

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