Coupling Path Research Articles

Compact quint‐band Bandpass Filter design in a rigorous manner utilizing multimode stub‐loaded taper

AbstractOn a basis of 2 multimode resonators (MMRs) using stub‐loaded taper, a compact quint‐band BPF is proposed. Progressively, triple open‐circuited stubs and notch are loaded to taper without introducing extra coupling paths, and both tri‐, quad‐ and quint‐band BPF responses are available. In this way, design procedure is rigorous and reduction of coupling paths minimizes the quint‐band BPF design complexity, simultaneously. Meanwhile, owing to the cancelling effect of notch, independent control on central frequencies of 2 passbands can be achieved. The insertion loss is lower since taper is adopted to the building of MMR. Good agreement between simulated and measured results validates the design method.

Reduction of Electromagnetic Noise Coupling to Antennas in Metal-Framed Smartphones Using Ferrite Sheets and Multi-Via EBG Structures

Recent smartphones increasingly employ a metal frame for a sophisticated design. However, the metal frame becomes a good coupling path for electromagnetic (EM) noise within smartphones and increases noise coupling to radio-frequency antennas located at the top and bottom sides of the smartphones. This paper proposes two novel metal frame structures with ferrite absorbing sheets or electromagnetic band gap patterns to reduce the coupling of EM noise to the antenna. Using a fabricated test board, the effects of the proposed metal frames on noise coupling suppression are experimentally validated.

In-Line Fiber Michelson Interferometer for Enhancing the Q Factor of Cone-Shaped Inwall Capillary Coupled Resonators

An in-line fiber Michelson interferometer in a cone-shaped inwall capillary with the whispering gallery mode microsphere resonator integrated inside is demonstrated for enhancing the Q factor, which is fabricated on the etched capillary by the femtosecond laser micromachining to decrease the coupling paths. The modulated symmetric WGM resonances and asymmetric Fano resonances induced by the Michelson interferometer are observed in the reflection spectra, with a slope of 91.87 dB/nm and Q factor as 3.85 × 104 achieved. Numerical simulations with the transfer matrix method also validate the resonator spectra modulated by the Michelson interference. This method shows a perspective potential for the enhancement of the Q factor by tailoring interacting paths through the femtosecond laser micromachining.

New Integrated Crystal Oscillator Design With Improved Robustness Against ESD Disturbances in Operation

This paper investigates the influence of electrostatic discharge (ESD) in operation on an integrated Pierce crystal oscillator for clock signal generation. We show that ESD, which has been capacitively coupled into the circuit, can cause temporary suspension of the clock signal. We analyze the coupling path and in addition we present a new, more robust crystal oscillator design for integrated circuits (IC) and compare design parameters, e.g., ESD compliance, power consumption, chip area, and phase noise. Simulations are confirmed by measurements on test circuits.

A fully tunable two‐pole bandpass filter with wide tuning range based on half mode substrate integrated waveguide

AbstractA two‐pole tunable bandpass filter (BPF) which allows for the operational agility of both center frequency and bandwidth is proposed in this article. The fundamental structure is based on half mode substrate integrated waveguide (HMSIW) with different dimensions. Two sets of varactors placed at various nodes separately are utilized for adjusting center frequency and bandwidth over a wide tuning range. By adding a source‐load coupling path, two transmission zeros are produced on both sides of the passband to improve filter selectivity significantly. A second‐order 1.52–2.76 GHz filter with 3 dB constant bandwidth tuning from 240 to 350 MHz is developed, analyzed, simulated, and fabricated. Good agreement is obtained between simulated and experimental results.

Integrated Circuit Model for Generation and Propagation of High Power Electromagnetic Pulse

As pulsed power systems and electromagnetic generators develop, the hazard of a high power electromagnetic (HPEM) pulse has gradually become more prominent. Generally, the propagated microwave has two main coupling paths. One is the front-door coupling path, which is a direct path through antennas to impact signals. The other is the back-door coupling path, which is an indirect path through untargeted parts, such as slots and cables. Because front-door coupling is coupled with the targeted parts, it can be vulnerable to an HPEM pulse. In this paper, we propose an integrated circuit model for an HPEM pulse, which considers each phenomenon of generation and propagation. The HPEM source model consists of a Marx generator and a virtual cathode oscillator, which are commonly used to make an HPEM pulse. The propagation model is composed of a series-parallel resistor, and the value of each resistor is determined by the propagation distance. The proposed model can be used to analyze the generation/propagation of HPEM pulses as one whole process, and it is easy to understand for various input waveform shapes.

EMI Analysis of DVI Link Connectors

Electromagnetic interference (EMI) is correlated with mode conversion, from differential-mode signals to common-mode currents and further to antenna-mode currents on the outside of cables or enclosures. This paper presents methods to quantify the mode conversion caused by discontinuities in the digital visual interface (DVI) signal link. These discontinuities are mostly present in the DVI connector, the DVI cable, and the connector–cable interface. A systematic approach was developed in this study to isolate and identify the different coupling paths in a high-speed interface (in this case, DVI is shown) and also to identify which discontinuity is most critical to mitigate EMI. The method developed in this study can be used for any high-speed interface in modern communication systems.

Interference coupling analysis based on a hybrid method: application to a radio telescope system

Working in a way that passively receives electromagnetic radiation from a celestial body, a radio telescope can be easily disturbed by external radio frequency interference as well as electromagnetic interference generated by electric and electronic components operating at the telescope site. A quantitative analysis of these interferences must be taken into account carefully for further electromagnetic protection of the radio telescope. In this paper, based on electromagnetic topology theory, a hybrid method that combines the Baum-Liu-Tesche (BLT) equation and transfer function is proposed. In this method, the coupling path of the radio telescope is divided into strong coupling and weak coupling sub-paths, and the coupling intensity criterion is proposed by analyzing the conditions in which the BLT equation simplifies to a transfer function. According to the coupling intensity criterion, the topological model of a typical radio telescope system is established. The proposed method is used to solve the interference response of the radio telescope system by analyzing subsystems with different coupling modes separately and then integrating the responses of the subsystems as the response of the entire system. The validity of the proposed method is verified numerically. The results indicate that the proposed method, compared with the direct solving method, reduces the difficulty and improves the efficiency of interference prediction.

Shielding Technique for Planar Matrix Transformers to Suppress Common-Mode EMI Noise and Improve Efficiency

Isolated high output current dc/dc converters are critical for power supplies in information technology industries. LLC converters with a matrix transformer are suitable for these applications due to their high efficiency and high power density. By pushing switching frequency up to MHz with GaN devices, planar matrix transformers with printed circuit board (PCB) windings are advantageous over conventional transformer designs, but the large interwinding capacitance of the PCB windings provides a critical coupling path for common-mode (CM) noise. In order to analyze the CM noise, the interwinding capacitance of the PCB windings is analyzed, and a related CM noise model is provided in this paper. To suppress the CM noise, shielding layers can automatically be inserted into the PCB windings between the primary and secondary windings in the fabrication process. This paper proposes a novel shielding technique, in which half of the shielding serve as the primary winding. The proposed shielding technique not only suppresses CM noise but improves the efficiency as well. The proposed shielding is verified by experiments on 1-MHz 400 V/12 V 800-W LLC converters with a peak efficiency of 97.7% and a power density of 900 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The proposed shielding reduces CM noise by 30 dB and improves full-load efficiency by 0.2%.

How Pairwise Coevolutionary Models Capture the Collective Residue Variability in Proteins?

Global coevolutionary models of homologous protein families, as constructed by direct coupling analysis (DCA), have recently gained popularity in particular due to their capacity to accurately predict residue-residue contacts from sequence information alone, and thereby to facilitate tertiary and quaternary protein structure prediction. More recently, they have also been used to predict fitness effects of amino-acid substitutions in proteins, and to predict evolutionary conserved protein-protein interactions. These models are based on two currently unjustified hypotheses: 1) correlations in the amino-acid usage of different positions are resulting collectively from networks of direct couplings; and 2) pairwise couplings are sufficient to capture the amino-acid variability. Here, we propose a highly precise inference scheme based on Boltzmann-machine learning, which allows us to systematically address these hypotheses. We show how correlations are built up in a highly collective way by a large number of coupling paths, which are based on the proteins three-dimensional structure. We further find that pairwise coevolutionary models capture the collective residue variability across homologous proteins even for quantities which are not imposed by the inference procedure, like three-residue correlations, the clustered structure of protein families in sequence space or the sequence distances between homologs. These findings strongly suggest that pairwise coevolutionary models are actually sufficient to accurately capture the residue variability in homologous protein families.

Independently Tunable/Controllable Differential Dual-Band Bandpass Filters Using Element-Loaded Stepped-Impedance Resonators

This paper presents a new approach for designing differential bandpass filter (BPF) with independently tunable/controllable dual passbands using the element-loaded stepped-impedance resonators (SIRs). The frequency-agile ability of the fundamental and third-harmonic resonant frequencies ( $f_{1}$ and $f_{3})$ of the element-loaded SIR against the value of the loaded element under different loading positions on the SIR is theoretically analyzed. It can be found that there must be a position that could be utilized to load element to realize the independent control of $f_{1}$ without affecting $f_{3}$ . This feature is successfully applicable to design independently tunable differential dual-band BPF when the loaded elements are tunable capacitors. Furthermore, by making the loaded elements to be shunt stubs, a new coupling path can be constructed for $f_{1}$ , and then the coupling coefficients for the two bands can be separately varied. Both the operational frequencies and bandwidths of the two bands can be separately adjusted. As a result, the traditional design procedure for the differential dual-band BPF can be simplified significantly. For demonstration, two examples are designed, implemented, and measured, and their simulation and measured results are presented, showing good accordance.

Multistability Analysis and Function Projective Synchronization in Relay Coupled Oscillators

Regions of stability phases discovered in a general class of Genesio−Tesi chaotic oscillators are proposed. In a relatively large region of two-parameter space, the system has coexisting point attractors and limit cycles. The variation of two parameters is used to characterize the multistability by plotting the isospike diagrams for two nonsymmetric initial conditions. The parameters window in which the jerk system exhibits the unusual and striking feature of multiple attractors (e.g., coexistence of six disconnected periodic chaotic attractors and three-point attraction) is investigated. The second aspect of this study presents the synchronization of systems that act as mediators between two dynamical units that, in turn, show function projective synchronization (FPS) with each other. These are the so-called relay systems. In a wide range of operating parameters; this setup leads to synchronization between the outer circuits, while the relaying element remains unsynchronized. The results show that the coupled systems can achieve function projective synchronization in a determined time despite the unpredictability of the scaling function. In the coupling path, the outer dynamical systems show finite-time synchronization of their outputs, that is, displaying the same dynamics at exactly the same moment. Further, this effect is rather general and it has a wide range of applications where sustained oscillations should be retained for proper functioning of the systems.

Effective modulation of intramolecular ferromagnetic interaction of diradicals by functionalization of cross-conjugated coupler.

Cross-conjugated molecules are an interesting class of conjugated systems possessing a spatially separated HOMO and LUMO. Most previous studies have taken advantage of this property by using it in organic semiconductor applications. Herein, we undertake a new investigation on the use of this type of molecule, in particular benzo[1,2-d;4,5-d']bisoxazole (BBO), as a coupler for organic diradicals. BBO has two sites available for adding a substituent and a spin center (SC) which are along its 4,8- and 2,6-axes. Functionalizations using electron donating (ED) and electron withdrawing (EW) groups were imposed to tune its FMOs and it was found that the longer 2,6-axis is an ideal site with a broader LUMO range via substituent effects. Diradicalization of these BBOs using nitronyl nitroxide (NN) and nitroxide (NO) as SCs was done using the remaining available axis. The calculated J values are linearly dependent on the LUMO energy of the coupler, but with 4,8-NH2-2,6-SC as an outlier. This exceptional case is related to 4,8-NH2-2,6-SC having the lowest BBO-NN dihedral angle. Moreover, the diradicals 4,8-X-2,6-SC (with X = H, NH2, CH3) have higher J values than 2,6-X-4,8-SC (with X = H, NH2, CH3), which is counterintuitive because the latter have a shorter coupling path. These diradicals are positioned to the right of the intersection of their trend lines, which implies that diradicals with LUMO values to the right of this intersection have the tendency to attain J values that are higher than those diradicals with a shorter coupling path. 4,8-NH2-2,6-SC even surpasses the projected JMax values which we associate with the highest attainable J values due to LUMO tuning via substituent effects. These results provide useful insights, especially into the interplay between the LUMO and the dihedral angle and how these affect magnetism in diradicals. In conclusion, we found that BBO can be a good candidate as an effective coupler for diradicals with tunable J values via incorporation of ED and EW groups. This first approach to studying the application of cross-conjugated molecules as couplers also paves the way for new candidates for the development of more effective diradical systems.

Open source cable models for EMI simulations

One of the most significant coupling paths for electromagnetic interference into systems is via cables [1], This may be cable to cable coupling within a bundle of conductors or coupling from an illuminating electromagnetic field [2]–[4], These coupling effects may be enhanced by non-ideal cable terminations such as pigtail connections of shields or by crosstalk within connectors [5], In addition, imperfect cable shields allow coupling via transfer impedance and transfer admittance [6][7].

Tunable double optomechanically induced transparency in photonically and phononically coupled optomechanical systems

The absorption properties in double optomechanical cavities coupled by the photonic and phononic paths are investigated. The sideband absorption peaks and the transparency dips, located symmetrically around the resonant point, characterize the respective effects of the photonic and phononic interactions on the transparency spectra: the sideband absorption peaks move outward with increase of the photonic interaction due to the normal-mode splitting, and the distance between the two sideband transparency dips is determined by the phononic interaction strength. Meanwhile, the study reveals the competition and the harmonization between the photonic and phononic interactions. When simultaneously switching on the photonic and phononic paths, it is shown from the absorption spectra that the features of the interacting path with stronger strength dominate over the other one with weaker strength. Additionally, the transparency around the resonant point manifests the destructive interference between the photonic and phononic coupling paths when the strength of two paths are comparable. These findings display the flexible tunability of the transparency, and can be used to distinguish between the two quantum paths in the absorption spectrum.

Multimode and single-mode transmission over universal fiber for data center applications

Abstract Universal fiber is a multimode fiber that has an LP01 mode field diameter approximately matched to that of standard single-mode fiber. It can transmit both multimode and single-mode signals using transceivers designed for either multimode fiber or single-mode fiber. By using universal fibers, one can bridge the needs for both single-mode and multimode transmission through a uniform and simplified cable infrastructure to accommodate the full distance range needed, while having upgradability from 10G to 40G to 100G and to even higher data rates. We build on our previous work that analyzed the dependence of LP01 mode-field diameter on fiber parameters, and the coupling loss for both single-mode and multi-mode transmission, with a further study of mode coupling and multiple path interference associated with single-mode operation. We demonstrate system performance in both single-mode and VCSEL-based multimode transmissions for a number of 100G transceiver types using a QSFP form factor − the preferred choice in data centers.

Compact Broadband Dual-Sense Circularly Polarized Microstrip Antenna/Array With Enhanced Isolation

This paper presents a novel method of designing the compact dual-sense circularly polarized (CP) microstrip antenna/array with improved impedance bandwidth, axial ratio (AR) bandwidth, and interpolarization isolation. The left-hand and right-hand CP characteristics are achieved simultaneously by conceiving a vertically coupled resonant structure for the first time. Different from traditional methods, the antenna shows a compact size but exhibits the wide impedance and 3 dB AR bandwidths. For each input, two coupling paths are purposely designed to excite the TM10 and TM01-mode of the patch, respectively. By composing different coupling units in the two paths, an intrinsic ±90° phase difference over a broadband can be obtained, resulting in the broadband CP characteristics. In addition, a novel method of using the neutralization line between the two feeds is investigated to improve the isolation between the polarizations. Based on the dual-sense CP element, a $1 \times 4$ dual-sense CP array is composed to exemplify its potential applications in large arrays. Compared with traditional CP antennas, the proposed antennas have the advantages of compact size, simplified feed, broad impedance and 3 dB AR bandwidths, and improved isolation. Experimental results verify the predictions.

EMI Coupling Paths and Mitigation in Optical Transceiver Modules

Optical transceiver modules are commonly used in telecommunication and data communication systems, and are among the most troublesome electromagnetic interference (EMI) problems for regulatory compliance at their operation frequencies and/or harmonics. In this study, simulations and measurements are performed on an optical subassembly module, including the silicon photonics submodule assembly, in order to identify and characterize the EMI coupling paths. The total radiated power is measured and computed. Through simulation and corroborating measurements, the dominant EMI coupling paths at high frequencies above 10 GHz are identified and characterized, and currents on the silicon photonic subassembly conductor housing and optical fiber connection ferrule are a dominant radiating source. EMI mitigation methods are developed and shown to be effective in reducing the radiated emissions from real product hardware.

Electromagnetic coupling to an apertured enclosure via a penetrated transmission line based on electromagnetic topology

An efficient analytical model based on electromagnetic topology (EMT) has been developed for predicting the electromagnetic (EM) field coupling to a rectangular enclosure with an electrically large aperture via a penetrated transmission line (TL), excited by an external plane wave of oblique incidence. First, the electric field in the enclosure is calculated based on the modified Bethe’s small holes theory and mirror procedure. Then, the topology networks of the EM interaction are constructed by analyzing the coupling paths and mechanism, and the electric current induced at the termination loads of the TL is obtained using the generalized Baum–Liu–Tesche equation combined with the Agrawal’s model. The analytical model has been successfully verified by the finite difference time domain method over a wide frequency band of 0.5~3 GHz, which consumes less time than numerical methods. Finally, the analytical model is employed to analyze the effect of various parameters on the induced current, including the length, the height, and the direction of the line.

Effect of deprotonation on the magnetic exchange coupling constant of fluorene‐based verdazyl diradical: A computational study

AbstractThe magnetic behavior of the fluorene bridged verdazyl diradicals has been studied theoretically in their neutral and deprotonated states. The deprotonation of C9‐H site of the fluorene ring opens a new coupling pathway, which changes the nature of magnetic coupling. The transmission spectra analysis reveals that the transmission through fluorine has also increased due to the opening of a new coupling path after deprotonation.