Ralf BrueningExact adaptations of impedance are often not necessary. Instead, minimize impedance deviations.

In part 1 last month, we took a back-to-basics approach and discussed line impedance and its effects on signal integrity. Every electrical conductor comprises capacitance, an inductance, and a frequency-dependent ohmic resistance. With increasing frequencies, these electrical characteristics will influence and distort the signal.

Applying a transmission line model based on the telegrapher’s equations (as typically common in signal integrity considerations, except for when considering extremely high data rates, e.g., Serdes channels), one often-used general expression for the characteristic impedance of a lossy transmission line is:
designersequation1Eq 1

Read more: Inside Signal Integrity: Impedance Control – Part 2

Ralf Bruening

The basics of line impedance influences.

Read more: Inside Signal Integrity: Impedance Control – Part 1

Ralf BrueningThe basics of line impedance influences.

Read more: Inside Signal Integrity: Impedance Control – Part 1

Ralf BrueningFive rules of thumb for getting it right.

As we welcome increasing numbers of IoT devices into our industries, offices and homes, we shouldn’t be surprised to see increasing electromagnetic (EM) congestion. Or, as it’s now dubbed, the “Interference of Things.”

This is because the majority of IoT devices are wireless, and many use multiple communications protocols – WiFi, Bluetooth and Zigbee – to interface with other devices, routers and the cloud. Creating an IoT device requires a rich mix of design elements and disciplines, including digital and analog, electromechanical (e.g., actuation), mixed-signal transducers (sensors) and RF.

Consider the whole device. From an EMC perspective, the entire IoT device needs to be considered, rather than a single PCB in isolation. Indeed, a typical IoT device is a 3-D multi-board design challenge, where some of the boards might be flexible. The flexible materials and the shapes they form when flexed all contribute to the device’s EM profile in terms of radiation and susceptibility.

Read more: IoT Device Design for EMC and the ‘Interference of Things’

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