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ROG Blog

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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.

Finding the Right Fit For Ferromagnetic Materials

 Ferromagnetic materials come in many forms and can serve RF/microwave applications in many ways. These materials are often recruited for high-frequency circuits for their resonant qualities as building blocks for such components as filters and oscillators. These materials are typically used with printed-circuit-board (PCB) materials to add inductance and resonance and enable the fabrication of resonant circuits at specific frequencies. 


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Making the Most Of Coplanar Waveguide

 High-frequency circuit designers have a number of different circuit types from which to provide solutions from radio frequency (RF) through millimeter-wave frequencies and coplanar waveguide (CPW) might be an approach to consider as an option to popular microstrip techniques. Traditional CPW circuitry consists of a conductor separated by a pair of ground planes, on the same plane on top of a dielectric material. A variation on that circuit approach is grounded coplanar waveguide (GCPW), also known as conductor-backed coplanar waveguide (CBCPW). It adds a ground plane to the bottom of the basic CPW circuit structure, with plated through holes (PTHs) connecting the top and bottom ground planes. 


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Delay Lines Draw Upon Stable Dielectric Constant

Delay lines are useful component building-block functions for adjusting signals in both analog and digital circuits on printed-circuit boards (PCBs). High-frequency and high-speed delay lines are characterized by their bandwidths and delay times, as well as their insertion loss across their operating frequency range, their return loss, VSWR, rise time, and their delay stability.


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Suppressing Spurious Modes in Microwave PCBs

Spurious modes can occur in printed circuit boards (PCBs) in spite of the best-laid plans. These modes support extra, unwanted signals, in addition to the intended signals, that can wreak havoc on a PCB and its application, causing interference and degradation of the intended signals. Although minimizing spurious modes in PCBs is largely a result of careful design practices, the choice of PCB material can have some bearing on the final spurious mode behavior, especially at higher frequencies.


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Survey Multilayer Circuit Possibilities With Stripline

Stripline is one of the transmission-line options facing high-frequency circuit designers, especially for circuits where minimal electromagnetic (EM) radiation is important. Stripline can be thought of as a flat conductor suspended between two ground planes, with dielectric material separating the conductor from the ground planes. The choice of printed-circuit-board (PCB) material can contribute a great deal to the success of a single-layer or multilayer stripline circuit assembly.


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Effectively Launch Signals Onto PCBs

 High-frequency signals must survive many transitions in an RF/microwave system, with one of the more challenging being the point at which signals are “launched” from a coaxial connector to a printed-circuit board (PCB). Following some general guidelines can help improve the effectiveness of an RF/microwave signal launch in double-copper-layer and multilayer PCBs, even when they contain different types of transmission-line formats, such as microstrip, stripline, and coplanar-waveguide (CPW) transmission lines. 


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Match Circuit Materials to Power Dividers and Couplers

 Power dividers/combiners may be among the most popular and most used of high-frequency components. And couplers, such as directional couplers, are not far behind. When designing and fabricating power dividers/combiners and couplers, it can be helpful to better understand how different PCB material properties relate to the final performance possible with these components, to help set limits on a number of different performance parameters, such as frequency coverage, operating bandwidth, and power-handling capability. 


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Making Microstrip Coupled Features Work

 The printed-circuit-board (PCB) material plays a major role in how microstrip transmission lines perform their duties in RF and microwave circuits, and it can be helpful to understand how certain PCB material characteristics contribute to the ways that microstrip transmission lines and their coupled features perform in these different high-frequency components. 


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Taming Discontinuities in Microwave Circuits

 Designing high-frequency microwave circuits and, with increasing frequency, millimeter-wave frequencies require for the most part laying out carefully conceived transmission lines to carry those high-frequency signals across a printed-circuit board (PCB). Of course, if the task of fabricating the PCB was simply a matter of adding circuit elements, such as resistors, capacitors, and inductors, to create the necessary frequency-domain/time-domain response for the PCB, it might go somewhat easier. But every PCB with high-frequency transmission lines must also manage any number of circuit discontinuities and junctions. Since these and similar discontinuities can be found on all but the simplest of RF/microwave circuits, the question is “How can the effects of these discontinuities be minimized through the thoughtful choice of PCB material?” 


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Probing Microwave PCB Heating Patterns

Learn more about this topic at IMS 2014

RF/microwave power applied to a printed-circuit board (PCB) will generate heat. A key to designing a practical circuit on a given PCB material is to understand how different circuit material properties can impact the heating patterns on an RF/microwave PCB, and to work within the limits of a high-frequency circuit material.


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