ROG Blog

The Rog Blog is contributed by John Coonrod and various other experts from Rogers Corporation, providing technical advice and information about RF/microwave materials.

Charting Conductor Profile Effects On Stripline

Microwave circuits are generally susceptible to the effects of copper conductor surface roughness, some less than others. As circuit designers learned in the last blog, microstrip designs that must minimize loss can benefit from the use of circuit materials with low-profile copper conductors, such as RO4000® LoPro™ series circuit laminates from Rogers Corp. As the last blog pointed out, CPW and conductor-backed CPW (CBCPW) circuits will not benefit at higher frequencies from the use of laminates with low-profile conductors to the same degree as microstrip circuits. But is this also the case with high-frequency or high-speed stripline circuits? Just how does conductor surface roughness influence high-frequency stripline circuit performance?

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CPW Can Minimize Conductor Profile Effects

Conductor surfaces on a printed-circuit board (PCB) can vary widely, from a “smooth-as-glass” finish to a more typically rough profile. As detailed in an earlier ROG Blog, a conductor surface profile can impact the performance of a sufficiently high frequency circuit, increasing insertion loss and dispersion and even causing propagation delays and changes in the effective dielectric constant of the circuit. But are all RF/microwave transmission-line technologies affected by conductor surface profiles in the same way? What about designs based on coplanar-waveguide (CPW) transmission lines, or stripline? Do they require circuit materials with low-profile conductors, or are they less affected than microstrip by conductor surface roughness?
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Celebrating ROG Award Contest Winners at IMS 2012

The ROG Award Contest kicked off in November 2011. We invited customers to enter the contest by telling us about their applications using Rogers?materials. For the next several months, customers shared stories about their Best Digital Application, Most Challenging Board Build, Most Unique and Creative Use of Material, Most Innovative Design, Longest Product Life, and Most Extreme Conditions, all accomplished together with Rogers?materials. One winning application was chosen for each category.
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Picking Prepregs For Multilayer Microwave PCBs

Multilayer microwave PCBs can pack much circuitry into a small volume. But creating a multilayer microwave circuit is more than just stacking layers. It takes planning and knowledge of the multilayer fabrication process. In particular, an understanding of how prepreg materials are used in multilayer circuits can be helpful.
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Minimize Microstrip Radiation Effects

Radiation loss can be a concern in microstrip circuits at higher microwave frequencies. Fortunately, its effect can be minimized by reducing the number of discontinuities in a circuit design, and by carefully weighing the choice of circuit substrate material in terms of thickness and dielectric constant, where thinner materials and higher dielectric constants can both contribute to lower radiation losses.
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Low-Loss PCBs Enable MM-Wave Auto Electronics

Evolution of the electronic systems in automobiles and other vehicles is exciting to watch, and many technologies once associated with the military, such as radar systems, are becoming available to average drivers. As highlighted in the previous ROG blog, 24-GHz short-range-radar (SRR) systems are being offered more and more in car models around the world. But vehicle designers and manufacturers are also looking ahead to the greater resolution possible with 77- and 79-GHz automotive radar systems. And for that evolution in automotive electronic systems to truly take place, printed-circuit-board (PCB) materials are important building blocks that will enable the potentially much safer automobiles of the future.
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PCB Advances Drive Automotive Applications

Automotive electronic circuits were once as simple as switches for headlights and windshield wipers. But modern automobiles take advantage of electronic circuit technology more than ever, often working with high-frequency signals at RF, microwave, and even millimeter-wave frequencies. For consumers, these advanced systems promise greater safety and an enhanced driving experience. For the manufacturers of these systems, these automotive applications offer the potential of bringing high-frequency technologies to millions of users. And to suppliers of printed-circuit-board (PCB) materials, such as Rogers Corporation, these emerging applications pose challenges of providing high-performance reliable circuit materials at acceptable prices that help fuel mass-market applications.
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PCB Considerations For Defected Structures

As strange as it may sound, the use of circuit defects is a growing trend in high-frequency circuit design, especially for passive circuits such as filters. More precisely, the trend is in the increased use of defected ground structures (DGSs) and defected microstrip structures (DMSs) to alter the responses of microstrip circuit designs. Just what are these DGS and DMS forms, and does incorporating them into a high-frequency circuit change the way the PCB material should be specified?
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Learning To Launch Onto Different Circuit Thicknesses

The transition, from a waveguide or coaxial connector to the PCB, is critical to the performance of the circuit, and the PCB’s thickness can impact how an end launch transition is made. Waveguide and coaxial connectors come in many shapes and sizes, as do PCB thicknesses, and matching the connector to the substrate thickness can play a large role in the overall performance and reliability of that design.
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Matching Materials To Millimeter-Wave Circuits

Millimeter-wave frequencies offer great potential for transferring wide-bandwidth, high-data-rate signals. But handling signals at these frequencies with minimal distortion requires the right printed-circuit-board (PCB) material, along with an understanding of how to apply that material to the requirements of circuits in the millimeter-wave frequency range. Processing signals from 30 to 300 GHz—the classic millimeter-wave frequency range—presents a unique set of challenges, and choosing the right PCB material can go a long way towards helping to meet those challenges.

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