RF Desensitization in Wireless Devices

The Internet of Things (IoT), where data are exchanged via wireless connection between devices, is rapidly becoming inextricable from our daily lives. A variety of IoT devices ranging from smart homes to autonomous vehicles and health care have grown explosively. While wireless communication makes the devices conveniently connected, it also makes them inherently vulnerable to electromagnetic interference (EMI). Any radio frequency (RF) antenna used as a radio receiver can easily pick up the unintended electromagnetic noise from integrated circuits (ICs) populated within the same device. The radio range is limited by interference, called RF desensitization, which in turn often limits the usefulness of IoT devices. While the amount of EMI can be estimated using numerical simulations tools like HFSS and CST, engineering issues such as where to place the IC or setting the radiation specification of the IC cannot be so easily addressed. In this chapter, an insightful and efficient RF desensitization model necessary to estimate EMI levels on RF antennas will be addressed. The approach will be focused on two representative areas: noise radiation source modeling and coupling estimation associated with an embedded RF antenna

Modeling And Mitigation Of Radio Frequency Interference For Wireless Devices

This article reviews the electromagnetic framework used to model radio frequency interference (RFI) and the resulting development of mitigation methods. With the rise of IoT devices, wireless devices in which RF antennas are integrated with high-performance digital systems in small form factors suffer from electromagnetic interference, known as RF interference or RF desensitization. The simple yet rigorous framework can be used for a systematic RFI-aware design, saving time and effort for trial-and-error troubleshooting

Efficient and Accurate Phase-Measurement Method for Core-Loss Characterization

Accurate core-loss characterization is essential to push the power density of power converters to their limits. However, existing core-loss measurement methods still have some limitations, such as a slow test speed and a complex probe calibration procedure. In particular, accurate phase-difference measurement is time-consuming because a fast Fourier transform analysis with a kHz-range frequency interval is typically applied to reduce the influence of noise. An automated measurement system for magnetic core-loss characterization is described in this paper. An accurate phase-detection block with programmable attenuators is developed to measure the phase difference between voltage and current waveforms. The proposed system considerably improves the test speed while providing comparable accuracy to the existing method

A Stub Equalizer for Bidirectional and Single-Ended Channels in NAND Memory Storage Device Systems

In memory devices, such as solid-state drive, multitopology is used for interfaces where multiple memory packages are connected to a controller using a branched transmission line. Impedance mismatching caused by the branches and unwanted reflection from deactivated packages inevitably degrades signal quality, limiting the data rate of the interface. In this article, a simple stub equalizer is proposed to improve the data rate of the memory interface. An open-ended stub is placed between a transmitter and a receiver, and the length, impedance, and location of the stub line are determined to properly cancel the reflection from other branches. Parameters are optimized based on the peak distortion analysis and an exhaustive search considering both read and write modes. The improvements are validated through eye-diagram simulations

Clock Duty Cycle Tuning for Desense Mitigation in Modulation -Involved Cases

Nowadays consumers\u27 electronic devices are highly integrated, and modules and integrated circuits (ICs) are usually placed close to each other due to the compact size. The modules and ICs may interfere with the radio frequency (RF) antennas and cause desense issues. In recent years, desense caused by direct coupling from the noise sources to the victim RF antennas has been well studied. However, more complicated mechanisms such as modulations between transmitting signals and low-frequency clock or data signals can also result in desense problems, especially in frequency divide duplex (FDD) applications. Typical solutions to desense problems will focus on suppressing the noise sources and/or the coupling paths, and little studies have shown the feasibility that desense in FDD applications can also be mitigated by engineering the spectral power distribution over the frequency range. This paper provides a comprehensive study on how to mitigate desense with the change in the spectrum distribution by tuning the duty cycle of the interfering clock. Measurements conducted on a real cellphone showed a 10 dB suppression of desense for certain TX bandwidth condition

Coupling Path Analysis for Smart Speaker Intentional Electromagnetic Interference Attacks

This Paper Shows an Improved Understanding of the Coupling Path for Intentional Electromagnetic Interference (IEMI) Attacks on Smart Speaker Devices. This Includes a Method for Finding the Ideal Attack Angle and Locating the Region Sensitive to the Coupled EMI. in Previous Works, It Was Shown to Be Possible to Send RF Commands to a Smart Speaker and Have These Commands Be Interpreted as Voice Commands by the Microphone. However, the Attack Still Had Some Limited Understanding in Terms of the Coupling Path Location and Long-Distance Attack Potential. using the Improved Understanding of the Attack, a Longer Attack Distance is Achieved (6 Meters) with Only 6.5 Watts of Power

Near Field Scanning-Based EMI Radiation Root Cause Analysis in an SSD

In Modern Portable Electronic Devices, Solid-State Drives (SSDs) Are Commonly Used and Have Been Identified as One of the Dominant Electromagnetic Interference (EMI) Noise Sources that Can Cause RF Desensitization Issues. in This Paper, the EM Emission Source from an SSD Module is Identified and Analyzed using Near Field Scanning and Dipole Moment Source Reconstruction. the Identified Noise Current Path Including the Power Management Integrated Circuit and the Decoupling Capacitor is Validated with the Assistance of Full-Wave Simulation. the Measured Noise Voltage is Used as an Excitation in the Simulation and the Simulated Near Fields Showed a Good Correlation with Measured Near Fields in Both Pattern and Magnitude. based on the Validated Radiation Mechanism, an Optimized Layout is Proposed and Validated in Simulation Reducing the Far Field Radiation by 10 DB

Analysis of Electromagnetic Interference Problems Caused by Split Reference Plane on High-Speed Multilayer Boards

Digital/Analog Ground Partitioning Has Been Used to Isolate Noisy Digital and Power Current from Sensitive Analog Currents in High-Speed Multiplayer Printed Circuit Boards. This Design, However, Breaks the Current Return Path for Signal Traces that Cross the Two Separated Grounds, Which Causes Undesired Effects Such as Signal Distortion and Radiated Emission. Electromagnetic Mechanism Associated with Them Needs to Be Understood to Control and Suppress These Undesired Effects. in This Paper, Equivalent Circuit Diagrams Are Presented to Explain the Current Path in a Practical Camera Device with the Separated Ground. Finally, Optimal Stitching Via Locations is Determined to Provide a Good Return Current Path and Thus Suppress the Radiated Emission. Numerical Simulations Are Conducted for Validation in Frequency Ranges from 10MHz to 2GHz

Fixture Design for Parasitic Capacitances of Mosfets for Emi Applications

Due to the fast-switching nature of modern power converters, up to hundreds of MHz of common-mode noise can easily be generated. The characterization of switching components, e.g., Si MOSFETs, is essential for noise reduction. However, limited by the bandwidth of instruments, the voltage-dependent capacitances of high voltage MOSFETs are typically characterized at approximately 1 MHz, which is insufficient for EMI applications. In this paper, the measurement method and the test fixtures are presented. The measurement bandwidth is pushed to 30 MHz and higher, and frequency-dependent capacitances of a MOSFET are observed through measurements

Investigation Of The Radiation Mechanism Of Heatsinks Based On Characteristic Mode Theory

Heatsinks may cause radiated emission and radio frequency interference problems when they are mounted on printed circuit boards. In this article, the radiation mechanism of heatsinks is systematically investigated using characteristic mode theory. The dipole moment is a commonly used equivalent source model for integrated circuits that drive radiated emission from heatsinks. On the basis of a simplified modal weighting coefficient formulation, the interactions between the dipole moment and the significant modes of the heatsink are efficiently evaluated, thus providing a clear physical insight into noise source placement. Finally, the grounding post design, a commonly used EMI mitigation method, is also discussed. The relative error of the mode-based field prediction is less than 3 dB compared with the full-wave simulation