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

## How Glass-weave Affects Millimeter-wave PCB Performance

John Coonrod explains in this video

This video gives more details of the glass weave effect and shows how to quantify the glass weave effect in certain laminates.

## Decipher Glass-Weave Effects at Millimeter-Wave Frequencies

This blog will attempt to “see through” the effects of glass on high frequency circuit boards, especially on the millimeter-wave circuits that are becoming so important in emerging automotive radar systems (at 77 GHz) and Fifth Generation (5G) cellular wireless communications systems.

## 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.

## 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.

## 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.

## 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.

## Finding a Circuit Material for 77 GHz Automotive Radar - Part 1

This ROG BLOG is Part One of a two part series introducing the key criteria to consider when selecting a PCB substrate which will minimize circuit losses for 77 GHZ radar PCB antenna applications.  First we will discuss components of PCB circuit loss, and then introduce six key material properties critical to developing low loss millimeter wave circuits at 77 GHz.

## Patrolling PIM in RF/Microwave Circuits

Unwanted levels of PIM can result from several different factors, including the amplitudes and frequencies of the multiple transmitted tones, the configuration of a circuit’s transmission lines, and the current density and power level of the application. Multiple signal tones are usually denoted by their fundamental frequencies, such as f1 and f2, with the frequencies of their PIM spurious signals resulting from the differences between different harmonics of the fundamental tones. Learn about how PCB designs can reduce PIM.

## How to Include the Effects of Circuit Material Copper Surface Roughness in EM Simulations

Copper is an excellent electrical conductor for RF/microwave printed-circuit boards (PCBs). However, the surface roughness of copper can vary from one circuit material to the next, even across a single sheet of circuit material, affecting high-frequency performance. Read this blog to understand how to incorporate this effect into simulations.

## Compare Materials in a Meaningful Way

Selecting a circuit board material for an application often comes down to a choice based on which has better specifications on the data sheet. Two different PCB materials from different suppliers might look identical in terms of key specifications, such as dielectric constant (Dk) and dissipation factor (Df), making a choice difficult. But how close are those two materials really? When can the data sheets look the same but the two materials be quite different?