Interference-Free Design of Electronic Devices

Have you ever relaxed on the patio on a beautiful autumn day while using your mobile phone to talk to a friend, stream some relaxing music over the phone’s WiFi connection and maybe use the built-in GPS location capability while you map out your next family road trip, all at the same time?

Just think about how amazing it is that you can do all of that — and more — with a device that you hold in the palm of your hand. Your mobile phone has more computing power than the computers that put man on the moon, and more wireless connectivity than we would have thought possible less than a generation ago!

cell phone complex RF environment interference-free design

Modern electronic devices with their dense high-speed electronic circuits and multiple wireless functions present a complex RF environment. Interference issues must be considered early in the design cycle to avoid costly issues down the road.

Insuring that all the wireless functions available in today’s electronic devices, whether it is our mobile phone, tablet computer, home thermostat or internet connected refrigerator, engineers must design devices not only so that each of the wireless systems meets its performance specifications, but also so that it can do so in the presence of all the other systems and sources of radio frequency (RF) energy that have the potential to interfere with each wireless system’s performance.

For example, if adequate consideration is not given when integrating wireless functions into our mobile phones, a file download via WiFi could be interrupted due to interference from the phone’s cellular signal when we answer a phone call. For integrated wireless functions to perform well when operating simultaneously, design engineers must consider the coexistence of all wireless systems within the device.

A related interference issue is desense. Desense occurs when unintended radiation from a device’s high-speed circuitry decreases the sensitivity (desensitizes) of a wireless system. For example, a high-speed USB signal on a printed circuit board (PCB) can couple into the Bluetooth receiver and interrupt the music being sent to our wireless headphones.

Careful consideration must be given when designing and locating antennas and high-speed circuits if coexistence and desense issues are to be avoided. Becoming aware of serious radio frequency interference (RFI) issues after a device is built severely decreases the options available for mitigating the interference and dramatically increases the cost of doing so. For effective cost-efficient design then, it becomes imperative to include coexistence and desense evaluation very early in the device’s design, and software simulation tools provide an effective way of doing so.

Effective simulation of desense and coexistence in the complex RF environment that constitutes modern electronics presents a particularly challenging modeling problem, as it involves multiple domains: three dimensional computational electromagnetic simulation for predicting the coupling between antennas and circuits when installed on the device, circuit simulation for analyzing the signals and waveforms, and RF system simulation to model the interactions and quantify the interference effects. Using these tools together in an integrated workflow, along with automated diagnostic tools for quickly identifying interference and its cause allows the engineer to design for desense and coexistence by evaluating the impact of different design decisions from very early in the process, thus reducing the likelihood of encountering pesky RFI issues after the design is committed to hardware.  ANSYS Electronics Desktop with HFSS and RF Option gives designers a complete simulation workflow for modeling desense and coexistence in electronics.

ANSYS Electronics Desktop is an integrated simulation environment that provides all the RF system & circuit and three-dimensional EM modeling tools needed to effectively analyze desense and coexistence in complex RF environments.

ansys webinarsIf you’d like to learn more about using ANSYS simulation tools to tackle this challenging design problem, please join me for a free webinar on November 7th by registering here: Interference-free Design of Electronic Devices Webinar.

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About Fred German

Fred is a Senior Manager of Research & Development at ANSYS where leads the design and development of simulation technologies used for modeling complex RF environments. He holds a Ph.D. in Electrical Engineering with a focus on computational electromagnetics from Auburn University.

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