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

Circuit designers often reach for a particular printed-circuit-board (PCB) material based on what they know of its essential material properties, such as dielectric constant (Dk) and dissipation factor (Df). At lower frequencies, having accurate material parameters may be helpful but not crucial whereas, at higher frequencies, knowing such circuit-material parameters as Dk and Df can be critical to the success of a circuit design. For those who need to know, fortunately, a number of different methods have been developed over the years for measuring and calculating a PCB material’s Dk at different frequencies, perhaps other than what is provided on the data sheets by a circuit-material’s manufacturer. One of the most reliable methods for determining a PCB material’s Dk and Df values is through the use of microstrip ring resonator circuit elements, due to the relationship of the resonant frequency of these circuit elements to the permittivity of the PCB material.

PrintRing resonators represent one method for determining the Dk of a PCB material. Resonance measurement techniques are narrowband and an alternative approach to more broadband transmission-reflection techniques for determining PCB material Dk. A major difference in the two approaches is that resonance measurement methods, which fabricate ring resonator circuit structures on a PCB, work at one frequency at a time, while transmission-reflection approaches can be used for swept-frequency measurements, to determine a circuit-material’s dielectric constant across a range of frequencies.

Especially as available higher frequencies are being used more and more for communications applications, there is a greater need for accurate characterization of the PCB materials used to fabricate those higher-frequency circuits. Ring resonators have often been used to measure the Dk of PCB materials, although they must be used with knowledge and with care. Ring resonators can be formed on a PCB material of interest using standard circuit-fabrication techniques. They can be constructed as single-port or two-port ring resonator structures. The simpler, single-port structure can be used to determine Dk but not Df. The two-port ring resonator, which is a thru-type circuit design with transmission lines leading to and from the resonant circuit, includes feed lines to and from the resonator structure, a closed microstrip transmission-line structure, and coupling gaps between the resonator and the feed lines. The method is well established and proven, and is typically the resonator structure of choice for measurements of PCB material Dk and Df.

This type of resonator structure typically suffers minimal radiation losses, rendering additional calculations or measurements of radiation losses unnecessary. For high-loss PCB materials, calculations of conductor losses can have minimal impact on estimations of Df. Conductor losses are more pertinent for low-loss materials, where those losses may play a more dominant role in the total loss behavior of the PCB material.

The frequency response of the two-port ring resonator structure can be measured with an RF/microwave vector network analyzer (VNA). The unwanted effects of connector interfaces of the ring resonator structure must be eliminated, which can be done through the use of a thru-reflect-line (TRL) calibration of the VNA with appropriate TRL calibration standards.

What are the PCB parameters of interest when using ring resonators to determine dielectric constant? Some pertain to the material itself, such as the thickness of the substrate material and the thickness of the conductor metal. For thinner circuit materials (less than 5 mils in thickness), a ring resonator may not represent the optimum method for measuring PCB material Dk, since it can be difficult to develop a clean resonant peak from the material and ring resonator for a measurement. Some of the PCB parameters of interest are related to the ring resonator structure, such as the fundamental resonant frequency, the line width of the ring resonator, the length of the feed lines, and the length of the coupling gaps.

A microstrip ring resonator is coupled through gaps to the microstrip feed lines for a two-port ring resonator (and single microstrip feed line for a single-port ring resonator). The operation of a two-port ring resonator is based on satisfying a simple condition for resonance defined by the equation:

2πR = nλg for n = 1, 2, 3…


R = the mean radius of the resonator’s ring;
n = the harmonic order of the resonance; and
λg = the wavelength of the resonance.

Based on the measured frequency response of the ring resonator, the PCB material’s Dk value can be calculated by determining the frequency-dependent value of the effective permittivity for that resonant frequency. The PCB material’s measured frequency response can also reveal other details about the material, including Df, dielectric material losses, and/or conductor losses. Of course, the surface roughness of PCB conductors can also contribute to conductor losses, with increased surface roughness resulting in higher conductor losses.

Rogers offers “design Dk” values of dielectric constant for its PCB materials, optimized for use in modern computer simulation programs. These dielectric constant values are determined by careful measurements, using ring resonator approaches as well as a microstrip differential phase-length technique. It is based on fabricating two microstrip transmission-line segments on a PCB material of interest. The transmission lines are identical in every way except for length. As characterized on an RF/microwave VNA, this difference in length will result in a difference in phase for the two transmission lines. The phase responses of the two transmission lines also depend on the Dk characteristics of the PCB material upon which the transmission lines have been fabricated.

The electrical contributions of the associated coaxial connectors and test fixtures, such as the reactances at the signal launches, must be minimized when using the microstrip differential phase-length approach, in order to produce results that reveal the PCB materials properties based on those two transmission lines. Further details on the microstrip differential phase-length technique can be found at the Rogers Corp. web site. The method can be used in combination with the ring resonator method when determining a PCB material’s Dk, with the combination helping to minimize issues with gap coupling for the ring resonator 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 Engineertoday.


The Rogers Innovation Center in Burlington, Massachusetts is home to a new industry-academic partnership between Rogers Corporation and Northeastern University. The goal is for research in the areas of nanotechnology and nanomaterials to lead to commercially-viable innovations in advanced materials to address global challenges for clean energy, Internet connectivity, safety, and security. Researchers, engineers, faculty and students, and employees gathered to celebrate at the ribbon cutting on March 25, 2014.



A message from Bruce Hoechner, CEO, Rogers Corporation:

Read the corporate financials news release: Rogers Corporation Reports 2014 First Quarter Results.

I’m very pleased to share with you Rogers’ first-quarter results for 2014. Over the past two years we have reported on the transformational efforts we have undertaken to deliver greater value to our customers, shareholders and employees. Those activities, together with growth in our key markets, have helped us realize positive results in recent quarters. Today, I am pleased to say that the momentum we saw in the last half of 2013 clearly carried forward into the first quarter of 2014.

Screen shot 2013-11-01 at 10.53.55 AMIn Q1, Rogers set a first-quarter sales record, achieving $146.6 million in net sales, which is an increase of 16.4% over quarter one 2013. I’d like to take a moment to recognize the all-time revenue record quarter our Printed Circuit Materials division achieved. This was a simply outstanding performance that I will discuss in greater detail shortly.

In addition, as a Company we achieved earnings of $0.79 per diluted share, a 102.5% increase over our Q1 2013 performance. This comparison, as well as those that follow, are to the prior period’s non-GAAP measures, which exclude special charges.

We also demonstrated continued improvement in our gross margins, moving to 36.8% from 32.8% in Q1 2013, driving our overall operating margin to 14.6% from 8.6% in Q1 2013. Dennis will share more with you in detail on our financial performance in a few minutes.


Overall, we are very encouraged by our performance and realize more opportunities lie ahead. We attribute our Q1 results to increased demand in our megatrend categories of Internet connectivity and clean energy, as well as substantial sales increases in safety and protection applications.

In particular, we saw orders increase for applications in telecom infrastructure, variable frequency motor drives, and automotive safety sensors. Growth in these key categories, in combination with our cost management discipline, enabled us to exceed our earnings guidance. Overall, we are very pleased with the strong start to 2014, which makes this the fifth quarter in a row where we have achieved year-over-year quarterly sales growth.

Looking at first-quarter revenue performance by market, for the quarter, 62% of our sales were in our strategic megatrend categories, as we continue to provide our customers with specialty material solutions that support their robust — their pursuit of growth in these global megatrend categories.

In the clean energy category, sales were up 29.8% over Q1 2013, with growth across all major segments. We saw particular strength in demand for power modules for variable frequency drives, automotive x-by-wire systems and solar applications. The continued global buildout of telecom infrastructure contributed to an impressive 33.4% growth in year-over-year revenues and Internet connectivity. We continue to see the benefit of the increase in 4G LTE-base station deployment around the world and especially in China.

In addition, growth in certain new applications enabling wireless connectivity for mobile Internet devices for one major OEM also helped boost demand for Rogers’ high-frequency Printed Circuit Materials. We experienced modest growth in mass transit with a 3.2% increase in sales over Q1 2013.

Screen shot 2014-05-01 at 4.14.44 PM

Outside of our strategic megatrend categories, demand for radar-based automotive safety systems continues to drive growth for Rogers’ Printed Circuit Materials division. We believe we will see further adoption around the world as governments increase their mandates for automotive safety measures, and as consumers become increasingly aware of the benefits of such systems.

Advanced Circuit Materials

As I mentioned earlier, the Printed Circuit Materials division achieved all-time record sales in Q1 2014. Sales were up 34.4% over Q1 2013. This was driven by the previously mentioned global growth of 4G LTE wireless infrastructure, as well as wireless antenna and automotive safety sensor applications. Overall, this performance was the result of strong market demand supported by outstanding work from our Printed Circuit Materials team. And I thank the PCM team for their dedication to excellence.

Power Electronics Solutions

The Power Electronics Solutions division achieved another strong quarter, with 19% sales growth over Q1 2013. Demand was strong across nearly all of our major clean energy application areas. As a reminder, we are now reporting our earnings for Power Electronics Solutions as one core strategic element that is comprised of two main product lines, RO-LINX power distribution systems and curamik direct bonded copper substrates.

High Performance Foams

High Performance Foams revenues were down 2.9% versus Q1 2013. Growth across many of our HPF segments was offset by the continued affect of design changes in the applications for mobile Internet devices. We saw continued strong volume in hybrid electric vehicle battery applications and consumer applications for advanced support impact protection.

Growth Enablers

I want to highlight our growth enablers. The Innovation Center at Northeastern University is now officially open, and our teams are actively collaborating on new engineered solutions that we can take to our customers in the global market. In the short term, we continue to take an outside-in view, collaborating closely with our customers to build a high-quality pipeline of solutions.

At the end of the first quarter in our targeted megatrend categories of clean energy, Internet connectivity, and mass transit, we were tracking a cumulative total of 781 major design opportunities, with 458 in the design-in phase of the selling process.

During the quarter we moved 20 megatrend opportunities from design into production. The key message here is that we continue to take both a long-term and short-term approach to building a robust sales pipeline that we will continue to refill as we convert projects into sales.

Finally, we continue to invest in activities to standardize processes and systems, and we remain committed to our investments in operational improvements across the organization. Here, too, we are taking an outside-in view, ensuring these improvements reflect industry best practice across all departments

Thank you.

Read the full transcript here.

View the accompanying presentation here.




Achieve Better Flexo Print Results

On April 29, 2014, in R/bak, by mdippel

Your choice of cushion mounting tape is crucial to achieving high quality printing whether it’s on boxes, shopping bags, beverage cartons or labels. The improvement in print quality using an open-cell cushion mounting product is shown below.

CushionThe open-cell structure of R/bak® cushion mounting materials has a greater resistance to compression set compared to typical closed-cell products.  Compression set is defined as the ability of the product to return to its original thickness after being compressed. R/bak materials typically hold 97% of their original thickness even after one million impressions.  Closed-cell competitor products typically maintain 70-90% of their original thickness.  This means that R/bak open-cell foams will provide the most consistent print results over long runs while making little or no adjustments.  Closed-cell products require multiple adjustments due to loss of impression.

Banding is the visible web direction variation in print results, typically in tonal areas that appear to be “gear bands.” There are many causes for banding including machine vibration and the design on the plate. If this problem plagues your work, this is a great time to try R/bak cushions, which absorb shock and reduce pressure, to determine if they can eliminate this defect.

If this article has made you curious about experimenting with tape, you should first ask yourself what issues do you face: Do you have long runs, are you unable to reach high line speeds, do you struggle with banding, is it difficult to achieve solid ink density while minimizing dot gain? Hopefully the information above provides some direction in your efforts to improve your print quality and effectiveness.


Now you can be first in line to receive ZEMgear’s new 2014 fall/winter footwear styles via the ZEMgear KickStarter campaign. Choose your favorite style, color, and size. Then the ZEM team gets to work. The KickStarter funds will be used to buy materials and manufacture your shoes — footwear that delivers exceptional performance and comfort with the ’WOW’ factor of total flexibility.

Screen shot 2014-04-28 at 2.38.07 PMOur PORON Cushioning team recently caught up with ZEMgear founder Christina Bracken to get an inside look at the new styles. The ZEMgear KickStarter Campaign ends on May 20th. Every Pair of Happy Feet Counts!

Rogers: Tell us a little about the ZEM team…

Bracken: Our small ZEM team is a group of great people with an exceptional range of expertise. Together we manage a complex business and work hand in hand on the challenges that come with building a brand and company. Our experience comes from designing and working with some of the biggest brands in the business. As a result our team has built a reputation for innovative design, sourcing, manufacturing, customer service, logistics, sales, marketing and G&A.

Rogers: What does ZEM stand for?

Bracken: ZEM stands for the Zone of Endless Motion. Born in the vibrant city of Miami, we believe it’s a place where all dreams can come true.

ZEMgear Men's U-Cross

Men’s U-Cross

Rogers: How did the first ZEMgear styles come about?

Backen: My  footwear design company in Miami was approached by a group of beach volleyball athletes who wanted a shoe to protect them from hot and cold sand and debris that could injure them. As we started to understand their specific concerns and needs, we knew we could design a basic shoe. The biggest challenge was that it had to articulate just like a natural foot while offering the power, balance, and agility necessary for a true athlete. It also had to stay securely on the foot during rigorous athletic activity.

We took our designs and put them to the test at a beach sport camp with 250 serious athletes and with their affirmation. The ‘Original Ninja’ Design was born.

Rogers: How has ZEMgear footwear evolved since the first styles?

Bracken: Today, the ZEM brand offers a comprehensive collection of designs for wind, water, sand and land. It includes shoes for fitness, fashion, and an active lifestyle. While our basic philosophy of responding to the needs of our customer remains the same, our technology, our materials, our manufacturing processing, and our designs have evolved substantially.

Rogers: What benefits does PORON® Cushioning give to ZEMgear wearers?

Bracken: PORON® Performance Cushioning brings long lasting comfort and high performance shock absorption in a durable material that withstands even the toughest daily wear. PORON® Performance Cushioning Foam has been engineered to provide maximum shock absorption and impact mitigation from minimum thickness. All of our designs maximize super-lightweight materials and combine them with functional technology for the highest level of flexibility, performance, and comfort.

Terra Misu

ZEMgear Women’s Terra Misu

Rogers: What advice do you offer to people who have never tried a pair of ZEM shoes?

Bracken: Our shoes are Engineered for WOW! That’s the “new normal” response when people try on a pair of ZEMs. WOW – so comfortable! WOW – great colors! WOW – so easy to put on!  WOW – love the way they make my feet feel!

Strengthening your foot muscle is just like working your bicep or you gluts because your whole body benefits. It helps the sensory highway between your feet and your brain work more smoothly.  What kind of message do you think your brain gets when you slap on a shoe that doesn’t allow the 250,000 nerve endings in your feet to communicate because they are so strangled or tilted or muffled by “well marketed shoes?”

Rogers: What new offerings or designs are being presented on KickStarter?

Bracken: The KickStarter Campaign focuses on our 2014 Fall Winter collection, including our first endeavor into the seasonal shoe and boot market! We are energized to be offering our ZEMfans who live where the four seasons prevail, something new and exciting for the seasonal months of the year.

We also offer several new designs with a new outsole ideal for training and active lifestyle: U-Cross, U-Ex, and the U-Jane all feature our NuNatural outsole with ventilation for air and water, extra stability and  feature PORON Performance Cushioning insoles.

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