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.

Why TCDk Circuit Performance Testing is Critical, in Order to Understand Environmental Influences

TCDk is a property which all circuit materials possess and it is how much the Dk of the material will change, with a change in temperature. The default test method for determining TCDk is typically done as a raw-material test and this video gives an outline of how to perform TCDk testing in circuit form. The circuit form testing for TCDk is considered a real-world test as opposed to the raw-material test method, which is typically intended for material characterization. Watch this video from John Coonrod covering this topic.

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Process Variations Can Mean Circuit Performance Variations

Modern computer-aided-engineering (CAE) software design tools based on electromagnetic (EM) simulation are quite good at predicting circuit performance using different models. But even the best simulation software can fall short of predicting the effects of some normal circuit fabrication process variations, specifically, deviations in copper plating thickness and how it can affect how conductors are shaped and the resulting performance of edge-coupled circuits. Read some of the variations that can effect your designs.

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Searching for a Standard Millimeter-Wave Dk Test Method

Characterizing a circuit material for such higher-frequency circuits, typically to about 80 GHz, requires measuring the material’s dielectric constant (Dk) or relative permittivity at mmWave frequencies, within a frequency range where industry-standard Dk measurements have not yet been established.

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Calculator Predicts PCB Performance

The characteristics of circuit materials have a great deal to do with how well a printed circuit board (PCB) performs, especially at RF/microwave frequencies. Circuit material parameters such as dielectric constant (Dk), dissipation factor (Df), even material thickness can affect the way that different transmission lines, such as microstrip, stripline, and coplanar waveguide, perform in high-frequency circuits. Fortunately, there is a simple and pain-free way to predict how different high-frequency transmission lines will behave when fabricated on different circuit materials: the Microwave Impedance (MWI) Calculator software.

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Skin Depth and its Impact on Different RF PCB Structures

Skin depth is often used to describe the behavior of current flow through circuit conductors, i.e., the copper on a PCB, especially at RF/microwave frequencies. Direct current (DC) may exhibit evenly distributed flow through a conductor such as copper, but high-frequency, sinusoidal current experiences changing energy density as it flows through a PCB’s conductors, with areas of lower and higher current density relative to the surface of the conductor.

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Finding a Circuit Material for 77 GHz Automotive Radar - Part 2

As explained in the previous ROG Blog, vehicular radars are already being designed and fabricated at millimeter-wave frequency bands such as 77 GHz. Specifiers of circuit materials for millimeter-wave frequencies (30 to 300 GHz) are faced with special requirements that are often different than those for circuits at microwave frequencies of 30 GHz and below. However, practice and experience of circuit designers working at millimeter-wave frequencies has shown that some circuit material parameters can be tightly linked to achieving high performance in millimeter-wave circuits, and that some circuit materials embody the material parameters as needed for excellent performance at 77 GHz and beyond.

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