To characterize the radiated noise sources in the radio-frequency interference simulations, a novel equivalent dipole source extraction method was proposed by our group previously. An iteration algorithm and the genetic algorithm work together to reconstruct an equivalent source using near-field magnitude information only while minimizing the number of dipoles needed. In this letter, the previously proposed equivalent dipole extraction algorithm is extended to efficiently extract an equivalent source of harmonics. Furthermore, the algorithm is verified using the actual product instead of simplified test boards. A rigorous and systematic validation process is proposed and conducted, which ensures the robustness and credibility of the extraction algorithm for future applications.

With the trend of higher integration, 3D/2.5D IC solutions such as CoWoS (Chip-on-wafer-on-substrate) have become more popular in recent years. Power integrity (PI) is always a critical part of the design especially when the power consumption requirements are important specs for high-performance computing. DC-IR drop is one of the criteria within power integrity considerations. However, ordinary electrical-only simulation for DC-IR drop will be an underestimation because it neglects the copper conductivity dropping due to the temperature rising. Thus, an engineering solution for electrical-thermal co-simulation is important to help to provide both an accurate PI analysis and the proper mitigations of the IR drop along the power rails. This paper uses a 2. 5D IC chiplet as an example to conduct the thermal-aware DC-IR simulation workflow. By iterating and exchanging the power map and temperature map files between an electrical simulator and a thermal simulator, detailed layer-by-layer IR drops and the temperature map results can provide good insights for efficiently mitigating the IR drop for PI by establishing a better cooling condition in thermal solution.

The parasitic inductance of a capacitor depends on its physical structure. Due to the geometry of 3-terminal capacitors, they boast a lower parasitic inductance compared to 2-terminal capacitors of the same and possibly smaller package sizes. While the parasitic inductance of a single 3-terminal capacitor may be lower, using multiple 2-terminal capacitors may result in similar performance. In this work, the inductance of 2-terminal (0201, nominal 2.2 uF) and 3-terminal (0402, nominal 4.3 uF) capacitors is extracted and compared through measurements. From our de-embedding method and characterized capacitors, the inductance of 2-terminal capacitors is only about ~20 pH higher than the characterized 3terminal capacitor. On a power net of a real product, 3-terminal capacitors of the same type as characterized were replaced with 2-terminal capacitors of the same type as characterized. From measurement results, the measured inductance at 100 MHz is lower by only about 3.45 pH, or 2.62%, when using 3-terminal capacitors.

Radio frequency interference can degrade the receiving sensitivity of antennas. The interference is usually caused by certain coupling structures, such as layouts without adequate grounding for the radio frequency signal return path. Those structures can be modeled as a set of equivalent dipole moments when they are electrically small. Herein, the dipole moment model-based coupling framework is applied to a practical cellphone design case to devise an engineering solution. The coupling framework incorporates dipole moments as radiation sources and a coupling model based on the reciprocity theorem. Unfortunately, near-field scan probes often lack access to all locations, owing to the complex phone platform structure. A combined measurement-simulation method is used to obtain the field quantities lacking direct access to measurements. The dipole-moment-based coupling framework helps estimate the couplings from different noise sources individually. Thus, the priority of solving for better layout designs can be determined according to the coupling estimations. Furthermore, the physics associated with the reconstructed dipole moment can provide insights and suggest possible mitigation methods. Several practical mitigation methods are discussed, including the suppression of the dominant noise source (reducing/cancelling the radiation or suppressing the specific noise spectrum) and the coupling path to the victim antenna.

Modularized designs have been widely used in today's consumer electronic devices and flexible RF springs are used for electrical connections between the modules. In the meantime, aluminum alloy material becomes a common chassis option. It is well known that the oxidized chassis surface introduces a certain level of nonlinearity when contacted by the springs, as known as passive intermodulation (PIM). PIM is one of the well-known root causes of the RF desensitization (desense). This paper is focused on investigating the relationship between PIM and contact conditions of the springs, especially contact area. The PIM level behavior is explained mathematically by the regrowth rate and the RF power distributions on the contacts. Full-wave simulations and mechanical simulations were conducted to further support the hypothesis.

Passive intermodulation (PIM) commonly exists in non-ideal metallic contacts. Since PIM typically represents an extremely low level of nonlinearity, it has not drawn enough attention over the years except for extremely high-power applications such as base stations. However, in recent years, the study on PIM has become essential in universally used consumer electronics design because of the higher requirement on the radio frequency (RF) sensitivity of wireless communications. The metal contacts caused PIM can create the sideband spectrum to interfere with the receiving band in the frequency divide duplex (FDD) mode. Therefore, the study on PIM for the frequently used flexible metallic components is important in the industry. The PIM characterizations for the flexible components at least demand the compression variability and the capability to inject high-power signals while monitoring the sideband spectrum. It is preferred to have the access to measuring more relevant quantities. This paper aims to summarize the practical experience in designing a high-dynamic range and multi-purpose applicable test setup for characterizing PIM in the flexible components. Capabilities to precisely measure/control PIM, gap variability, tilted angle variability, and DC resistance (DCR) are presented with measurement examples.

In modern consumer electronic devices, for the purpose of having easier access for assembly and repair in a compact designed product, metallic connection components such as springs are universally used for metallic connections between modules or chassis. However, the non-ideal metallic connections tend to have a certain level of non-linearity. Therefore, significant attention has been aroused recently because the passive-intermodulation (PIM) can degrade the radio-frequency (RF) antennas’ receiving quality especially when the unsatisfying spring connections are placed near the RF antenna. Typically, advanced and expensive instruments and components are required to estimate the non-linearity levels of the springs. However, those instruments are usually not available for the manufacturing factories for massive tests. This paper is focused on investigating the feasibility of estimating the nonlinearity level of spring contacts using DC resistance (DCR), which has easier access to be tested with much lower cost. Study showed that the DCR, when under certain conditions, can serve as the alternative figure of merit for PIM prediction. Then, the Gaussian process regression (GPR) analysis based on measured data can provide a statistical estimation to the generated PIM from the DCR values.

Accurate noise source characterization is critical in increasing the accuracy of desense simulations. However, characterization of the emission sources in full-wave simulations often lacks accuracy. In this paper, a fast and accurate method to extract equivalent dipole moments of radiated noise sources is proposed. The proposed method uses the genetic algorithm to optimize the position and type of dipoles, and it also uses a back-and-forth iteration algorithm to retrieve phase based on the magnitude information of two observation planes with different heights. Compared with the traditional equivalent dipole extraction algorithms, this method can minimize the number of reconstructed dipoles and avoid the complicated and time-consuming phase measurement. This method is verified by comparing the measurement and simulation of coupled noise from an image sensor to a nearby cellular antenna.

Passive intermodulation (PIM) is one of the most common nonlinear behavior that exists in a variety of applications. Nowadays, consumer electronics designs use a variety of mechanical features for radio-frequency (RF) antenna feeds and grounding, such as springs, gaskets, screws, etc. When these components are placed in the path or nearby the RF antennas, the unsatisfying connection such as loose contact will generate PIM and create noise in the receiving frequency range. This can potentially cause RF desense issues. In product design, the most intrinsic method to improve the electrical connection is applying more compression between the spring tip and the landing substrate, but seldom will the engineers notice the spring structure itself can also introduce a lot of PIM. This paper concentrates on characterizing and validating the captured RF springs that can introduce noticeable PIM due to its structural self-contact phenomenon. An integrated camera recorded the spring side-view under compression. The measured information indicates that high PIM tends to occur when the spring contacts itself unintentionally.

This paper presents a general formulation of the generalized multiconductor transmission line (GMTL) method to model a parallel cable harness including straight and bent wires. The parallel cable harness here indicates the uniform cross-sectional wire distribution. The GMTL equations are solved recursively based on the perturbation theory. This GMTL method facilitates an accurate evaluation of the current distributed on a cable harness. On top of that, the current obtained in a radiation problem is decomposed into two traveling currents, i.e., the positive-going and the negative-going currents, based on the least-squares method. With the decomposed currents, the steepest descent method is further adopted to achieve a fast approximation of the total radiated power. Finally, the capability and the limitations of the GMTL method in terms of the electrical wire separation and length are investigated. The necessity of the recursive corrections is also studied.

Non-ideal ground structures in flexible printed circuit board, such as the meshed ground or discrete ground nets, can cause severe RFI to the nearby antennas. Those RF radiators can be modeled as a set of equivalent dipole moment(s) when they are electrically small. Then, the dipole moment based reciprocity theorem can be applied to estimate the noise coupling level. In this article, a practical methodology using the dipole moment based reciprocity is proposed to identify multiple radiation sources of a real cellphone product. Multiple equivalent dipole moments are constructed with one-to-one correspondence to the physical structures. The reciprocity calculations can eventually provide the noise contributions of each noise source.

To accelerate the simulation timing for more general structures like a stripline connected between vias, generic models were developed for a differential strip line connecting differential pair of vias. While a less time consuming 2-dimensional (2D) simulations are used for striplines, an analytical approximation has been employed for vias. The models developed have shown close correlation (within +/- 1.5 dB) with that of 3D full wave simulation models with frequency ranges of 10 MHz to 20 GHz.

This paper studies a specific G-S-S-G style high-speed differential pair. Simulation shows that resonances exist in both common- and differential-mode signals. With the further investigation, it turns out to be that a quarter-wavelength resonant structure is incautiously created, which is responsible for the resonances. To remove the resonances, two methods are recommended in this paper. Each method has its own benefits and limitations. The proposed solutions can be treated as design rules when similar differential pairs are designed.

This paper proposes a generalized multiple-scattering (GMS) method to evaluate the current distribution on a cable harness with ground connections to a nearby metal surface. The GMS method is a hybrid method combining the transmission line theory and the method of moments. The GMS method uses the generalized multiconductor transmission line (GMTL) solver for the cable harness part and the mixed-potential integral equation (MPIE) solver for the rest of the structure including the metal surface and the grounding wires. Neither the GMTL nor the MPIE solver alone takes into account the mutual interactions between the cable harness and the rest of the structure. Therefore, an iterative scheme is arranged in the GMS method to compensate the above-mentioned interactions. These interactions occur via not only field couplings, but also current conducting through the grounding points on the cable harness. A numerical test case is provided to benchmark the proposed GMS method.

Infinitesimal electric and magnetic dipoles are widely used as an equivalent radiating source model in far field radiated emissions and near field coupling scenarios. In this paper, a hybrid method for physical dipole extraction based on genetic algorithm and linear least square method is proposed. It offers an automatic flow to extract the equivalent dipoles without prior decision of the type, position, orientation and number of dipoles. Compared with conventional linear least square method, this algorithm can extract physical dipoles which are close to original radiating source and minimize the number of dipoles. Compared with conventional genetic algorithm based method, this method reduces the optimization time and is more robust. This method is validated by both simulation and measurement data, and its advantages are proved. It is applied to modeling of the radiation from a clock buffer chip. The extracted equivalent dipoles are used to estimate the near field coupling from the clock buffer chip to a victim inverted F antenna (IFA) in a practical printed circuit board (PCB) by full wave simulation. The estimation matches well with measurement.

Infinitesimal electric and magnetic dipoles are widely used as an equivalent radiating source model. In this paper, an improved method for dipole extraction from magnitude-only electromagnetic-field data based on genetic algorithm and back-and-forth iteration algorithm [1] is proposed. Compared with conventional back-and-forth iteration algorithm, this method offers an automatic flow to extract the equivalent dipoles without prior decision of the type, position, orientation and number of dipoles. It can be easily applied to electromagnetic-field data on arbitrarily shaped surfaces and minimize the number of required dipoles. The extracted dipoles can be close to original radiating structure, thus being physical. Compared with conventional genetic algorithm based method, this method reduces the optimization time and will not easily get trapped into local minima during optimization, thus being more robust. This method is validated by both simulation data and measurement data and its advantages are proved. The potential application of this method in phase retrieval is also discussed.

Edge plating and via stitching connecting ground planes are two common edge treatments to suppress electromagnetic interference (EMI) from multilayer printed circuit boards (PCB). One critical parameter for stitching via is the spacing between vias. At higher frequencies, it is desirable to plate the edges of PCB, and a gap is required in the plating to accommodate the break-off tabs. In this paper, the shielding performance of these two scenarios are studied in both simulation and measurement. By sweeping the parameters of via pitch size and the length of each plated edge, the near-field shielding effectiveness (SE) of these different cases are compared. In general, the edge plating cases have much better shielding performance than the stitching via ones. Since edge plating implements the shielding on PCB walls, it leaves no interference with signals and moreover saves space for dropping GND stitching vias, with a trade-off of 5% more cost. Design guidelines for PCB edge treatments are provided in the end of the paper.

A modal approach for parallel plate impedance and equivalent inductance extraction for power integrity analysis including ball grid arrays (BGAs) between two parallel plates is presented. Since the BGAs are placed close to each other, the current flowing through each ball is not uniformly distributed due to the proximity effect. In this paper, a modal-based cavity method is proposed to count for this proximity effect. Analytical solutions for both the parallel plate impedance and the equivalent inductances associated with the BGAs are derived from the modal-based cavity method. The proposed method is validated by finite element method simulations and the application of the proposed method for power distribution network design is demonstrated.

Characteristic mode (CM) analysis has been widely used in antenna geometry design, antenna location optimization, and feeding positions, etc. CM analysis has seldomly been used in electromagnetic interference (EMI) modeling. Meanwhile, interactions between the antenna and the vehicle body were modeled with full-wave simulation, but the coupling mechanism has been veiled. In this paper, characteristic mode analysis is applied into the vehicle body to better understand the coupling mechanism of the vehicle modes and the antenna-chassis coupling mechanism. A few typical modes of the vehicle body are discussed first, and how to excite a specific mode is also investigated by looking at the eigen-current and eigen-charge distributions. This paper potentially provides a guideline in tackling EMI problems using CM analysis.

A correct antenna pattern is required to ensure the accurate evaluation of antenna design, total radiated power (TRP), total isotropic sensitivity (TIS), receiver sensitivity and etc. However, in some cases the antenna pattern is obtained off-center, which degrades its accuracy. In this paper, an algorithm based on the equivalent dipole moment method is proposed to correct the offset antenna pattern. Detailed derivations and workflow are presented. Besides, the dipole moment extraction is automated by optimization algorithms. A numerical test case is used to benchmark the proposed antenna pattern correction algorithm.