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

PCB Formulated For Reliability

Achieving high reliability for a high-frequency circuit or system starts with the printed circuit board (PCB). The PCB material must deliver consistent performance over time and changing conditions, such as temperature. As explained in the previous Blog (part one of this two-part series), it is possible to spot PCB materials that are “built to last” by assessing a number of their key performance parameters, such as coefficient of thermal expansion (CTE). In fact, PCB materials such as Rogers RO4835™ laminates can be engineered for high reliability through a careful combination of material components resulting in specific performance characteristics.
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Picking A PCB For High Reliability

High reliability is a goal and desire for all designers and end-users of high-frequency printed-circuit boards (PCBs). Since all of the components mounted on the PCB depend on it, it is expected to deliver dependable and consistent performance over time. But depending on the operating conditions, it can sometimes be difficult to achieve. In an attempt to help, the next two Blogs will explore PCB material reliability: this blog, Part 1, will review some of the general obstacles for a PCB material to achieve good long-term reliability while the next blog, Part 2, will take a close look at how the characteristics of one particular PCB material add up to good long-term reliability.
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Looking Back Over Using PCB Materials

50th ROG blog posting

This ROG Blog series on printed-circuit-board (PCB) materials from Rogers Corp. (www.rogerscorp.com) has reached the half-century mark, already covering a wide range of topics on circuit materials with this, the 50th ROG Blog. It has even detailed the effects of different PCB material thicknesses on circuit performance, and described the influence of conductor roughness on circuit performance. While it would be difficult to pick out the top 10 Blogs from the first 49 Blogs appearing since August 2010, at least 10 of these ROG Blogs deserve mention for how they have attempted to help readers with their different uses of PCB materials.


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Making the Most of Millimeter-Wave Circuits

Millimeter-wave frequencies (about 30 to 300 GHz) were once associated with at least two things: circuits for these frequencies are extremely difficult to fabricate, and they will probably be used for some military-electronics application. Because these frequencies are available for use without licenses, a growing number of circuit designers are considering different applications at these higher frequencies and, of course, choosing the right printed-circuit-board (PCB) material is an important part of any practical efforts to realize millimeter-wave circuits. Here are some things to be aware of and tips on how to design for millimeter-wave circuits.
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Taming Loss In Transmission Lines

Transmission lines are akin to electronic roadways, routing signals along different paths of a printed-circuit board (PCB). At RF/microwave frequencies, circuit designers often create PCBs based on three popular planar transmission line approaches: microstrip, stripline, or coplanar waveguide (CPW). Each uses circuit-board materials in a different way, with different results in terms of insertion-loss performance. By getting a grasp on the insertion-loss mechanisms for these different transmission-line formats, circuit designers can better match the mechanical and electrical characteristics of their circuit substrates to their intended applications and transmission lines when choosing PCB materials.
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Matching Materials To Bandpass Filters

Bandpass Filters, Part 2
Part 1 of this two-part series on bandpass filters—highlighted the versatility of one circuit material from Rogers Corporation, RT/duroid® 6010.2LM laminate, for fabricating RF/microwave bandpass filters. But not all circuit materials are the same and there may be some advantages to designing bandpass filters on other materials, such as Rogers RO4000® family of printed-circuit-board (PCB) materials. This blog will examine different grades of these and other circuit materials and the impact they have on the design and fabrication of high-frequency bandpass filters, especially compared to filters formed on filled-PTFE-based circuit materials.
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Choose Circuit Materials For Bandpass Filters

Bandpass Filters, Part 1

Bandpass filters are essential to many RF/microwave circuits and systems. They eliminate unwanted signals and noise, and can work with both receivers and transmitters. This first of two blogs on RF/microwave bandpass filters will review some of their basic performance parameters and how they relate to PCB material characteristics, with a focus on one material in particular, RT/duroid® 6010.2LM circuit material from Rogers Corp. As a followup, the next blog will explore how bandpass filters perform on other circuit materials.


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Prime Material Parameters For Impedance Matching

Impedance matching, Part 2
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. 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. (www.rogerscorp.com), 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.
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The Role of PCB Materials In Impedance Matching

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. 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.
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Dielectric Concerns For Directional Couplers

Directional couplers are vital components for sampling signal power in an RF/microwave system without necessarily disturbing the signal path. Such couplers come in many forms, including in metal housings with coaxial connectors. A typical coaxial directional coupler has four connectors, for input, output, coupled, and isolated ports. The coupled port provides a small amount of power taken from the input port, defined by the coupling factor, such as a 20-dB coupler. This blog posts covers the advantages of using high quality PCB materials for directional couplers.
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