Accurate imepdance measurement of O clip and near field coupling estimation using equivalent dipole moment model

As cellphones and electronic devices moves towards higher date rates yet smaller form factor, designer face more electromagnetic interference (EMI) and radio frequency interference (RFI) problems. In order to better guide the early design; designers want to know the exact electrical performance of small components, coupling estimation between components. In Section 1, a de-embedding method is proposed to measure the impedance of an innovative O-shape spring contact, for frequency up to 30 GHz. The measurements are performed under the same condition when it\u27s actually used in cellphones. De-embedding method will be applied to remove the fixture effects of the measurement setup, hence only the electrical performance of the DUT is obtained. In Section 2, a dipole moment model is studied to investigate the near field RF coupling. A set of dipoles (both electric dipoles and magnetic dipoles) will be used to fit the measured tangential H field of the near field scanning. The dipoles will be built in 3D simulation tool. Together with the nearby antenna, the coupling between the dipole source and the victim antenna can be obtained. This dipole moment method is verified by both measurement and direct simulation data --Abstract, page iii

Radio-Frequency Interference Estimation for Multiple Random Noise Sources

As more compact designs and more assembled function modules are utilized in modern electronic devices, radio-frequency interference (RFI) source reconstruction is becoming more challenging because different noise sources may contribute simultaneously. This article presents a novel methodology to reconstruct multiple random noise sources on a real-world product, including several double-data-rate (DDR) memory modules and a high-speed connector. The DDR modules located beneath a heatsink cause random noise-like signals, which renders phase measurements challenging. An approach based on the tuned-receiver mode of a vector network analyzer is developed to measure the field phase from the random DDR signals, which can be further modeled with a Huygens\u27 box using the measured field magnitude and phase. Moreover, the connector can be modeled using an equivalent magnetic dipole. Furthermore, the total RFI power from the DDR memory modules and the high-speed connector, which generate uncorrelated RFI noise, is found to equal the summation of the individual power values obtained by an root mean square detector, which can be mathematically corroborated. Using the proposed method, the reconstructed source model can predict RFI values close to measurement results with less than 5 dB deviation

Seizing the window of opportunity to mitigate the impact of climate change on the health of Chinese residents

The health threats posed by climate change in China are increasing rapidly. Each province faces different health risks. Without a timely and adequate response, climate change will impact lives and livelihoods at an accelerated rate and even prevent the achievement of the Healthy and Beautiful China initiatives. The 2021 China Report of the Lancet Countdown on Health and Climate Change is the first annual update of China’s Report of the Lancet Countdown. It comprehensively assesses the impact of climate change on the health of Chinese households and the measures China has taken. Invited by the Lancet committee, Tsinghua University led the writing of the report and cooperated with 25 relevant institutions in and outside of China. The report includes 25 indicators within five major areas (climate change impacts, exposures, and vulnerability; adaptation, planning, and resilience for health; mitigation actions and health co-benefits; economics and finance; and public and political engagement) and a policy brief. This 2021 China policy brief contains the most urgent and relevant indicators focusing on provincial data: The increasing health risks of climate change in China; mixed progress in responding to climate change. In 2020, the heatwave exposures per person in China increased by 4.51 d compared with the 1986–2005 average, resulting in an estimated 92% increase in heatwave-related deaths. The resulting economic cost of the estimated 14500 heatwave-related deaths in 2020 is US$176 million. Increased temperatures also caused a potential 31.5 billion h in lost work time in 2020, which is equivalent to 1.3% of the work hours of the total national workforce, with resulting economic losses estimated at 1.4% of China’s annual gross domestic product. For adaptation efforts, there has been steady progress in local adaptation planning and assessment in 2020, urban green space growth in 2020, and health emergency management in 2019. 12 of 30 provinces reported that they have completed, or were developing, provincial health adaptation plans. Urban green space, which is an important heat adaptation measure, has increased in 18 of 31 provinces in the past decade, and the capacity of China’s health emergency management increased in almost all provinces from 2018 to 2019. As a result of China’s persistent efforts to clean its energy structure and control air pollution, the premature deaths due to exposure to ambient particulate matter of 2.5 μm or less (PM2.5) and the resulting costs continue to decline. However, 98% of China’s cities still have annual average PM2.5 concentrations that are more than the WHO guideline standard of 10 μg/m3. It provides policymakers and the public with up-to-date information on China’s response to climate change and improvements in health outcomes and makes the following policy recommendations. (1) Promote systematic thinking in the related departments and strengthen multi-departmental cooperation. Sectors related to climate and development in China should incorporate health perspectives into their policymaking and actions, demonstrating WHO’s and President Xi Jinping’s so-called health-in-all-policies principle. (2) Include clear goals and timelines for climate-related health impact assessments and health adaptation plans at both the national and the regional levels in the National Climate Change Adaptation Strategy for 2035. (3) Strengthen China’s climate mitigation actions and ensure that health is included in China’s pathway to carbon neutrality. By promoting investments in zero-carbon technologies and reducing fossil fuel subsidies, the current rebounding trend in carbon emissions will be reversed and lead to a healthy, low-carbon future. (4) Increase awareness of the linkages between climate change and health at all levels. Health professionals, the academic community, and traditional and new media should raise the awareness of the public and policymakers on the important linkages between climate change and health.</p

Efficient estimation and mitigation for radio-frequency interference

With rapid innovations in Internet of Things (IoT) and wireless technology, more and more consumer electronic devices around the world are now connected to the internet. In a small form factor electronic device, there are plenty of potential noise sources such as System On Chip (SoC), high speed traces, flexible cables and power converters, etc. Those noise sources can possibly introduce radio frequency interference (RFI) issues. In this dissertation, a transfer function based calculation method is proposed to estimate radio frequency interference (RFI) problems. The derived equations can clearly decompose the RFI problem into two parts: the noise source and the coupling transfer function to the antenna. The proposed method is validated through numeric simulations and real cellphone experiments. Based on this method, a novel RFI mitigation method is proposed. Through near-field scanning of a real product, an equivalent dipole moment of the noise source (CPU and DDR3) is reconstructed, and the near-field components of the victim (Wi-Fi antenna) are measured. By determining the relationship between dipole moment and antenna near field, the noise source is rotated by a certain angle to reduce RFI. New boards with the suggested changes are fabricated and the measured results show a good RFI reduction (up to 8 dB) compared to original boards. Novel machine learning method is also introduced to accurately extract equivalent dipole moments from the near field scanning of a noise source. Compared to the conventional least square method, the proposed machine learning based method is believed to have a better accuracy. Also, machine learning based method is more reliable in handling noise in practical applications --Abstract, page iv

Machine Learning Based Source Reconstruction for RF Desense

In radio frequency interference study, equivalent dipole moments are widely used to reconstruct real radiation noise sources. Previous reconstruction methods, such as least square method (LSQ) and optimization method are affected by parameter selections, such as number and locations of dipole moments and choices of initial values. In this paper, a new machine learning based source reconstruction method is developed to extract the equivalent dipole moments more accurately and reliably. Based on the near-field patterns, the proposed method can determine the minimal number of dipole moments and their corresponding locations. Furthermore, the magnitude and phase for each dipole moment can be extracted. The proposed method can extract the dominant dipole moments for the unknown noise sources one by one. The proposed method is applied to a few theoretical examples first. The measurement validation using a test board and a practical cellphone are also given. Compared to the conventional LSQ method, the proposed machine learning based method is believed to have a better accuracy. Also, it is more reliable in handling noise in practical applications

IC Placement Optimization for RF Interference Based on Dipole Moment Sources and Reciprocity

A method to optimize the IC placement in mobile devices from RF interference perspective is proposed. The coupling from the IC to an antenna is estimated by combining the equivalent dipole moment source and reciprocity, which facilitates understanding of coupling physics and design insight for the mobile devices. Based on the proposed method, optimal place for the noisy ICs can be quantitatively determined for each frequency of interest

Differential E-Field Coupling to Shielded H-Field Probe in Near-Field Measurements and a Suppression Approach

In near-field scanning using H-field probes, E-field coupling is a major concern. E-field suppression performance must be characterized before an H-field probe can be used for near-field scanning. Common method of measurement involves measuring the E-field coupling in the same location where the strongest H-field coupling occurs. In microstrip line traces, it is assumed that this occurs right above the center of the trace and less coupling at all other locations across the microstrip line. In this paper, we show that the maximum E-field coupling occurs at a location slightly offset from the trace center. The E-field coupling to a shielded H-field probe at such a position leads to differential-mode coupling, which the standard shield of an H-field probe is unable to suppress. The coupling mechanism is investigated and a differential E-field coupling suppression approach is proposed. For the H-field probe used in this paper, a proposed floating plate is shown to improve the measured E-field suppression ratio by a factor of 18 dB compared to a similar probe without this modification