Differential Mode Research Articles

Variety of attenuation of RF suppression filters

Differential mode attenuation of RF suppression filters can be measured directly. Alternatively, this attenuation can be derived as modal S-Parameters from the S-Parameters measured for the single multiport paths which in fact the filter is. This paper outlines the differences between the two approaches. The first consists in direct measurement with separation transformers and the second with calculation from single ended measurement. In addition, the paper presents the method of determining the differential mode attenuation for the case of input and output impedance different from those used in direct measurements, i.e. by 50Ω/50Ω. At the same time, the presented method of determining the differential mode attenuation for different input and output impedances will require a change in the assumptions of the CISPR 17 document entitled ”Methods for measuring the attenuation characteristics of passive EMC filtering devices”, since the modal S-Parameter formulas presented in this document are only valid for the case when the RF suppression filter is in perfect balance. Otherwise, for different impedances it should be done taking into account the modification of the modal S-Parameters, as shown in this paper.The inclusion of this innovative change in the CISPR 17 document will allow the approach presented in this document to be used for various cases of the RF suppression filter, which is undoubtedly a significant progress in determining its attenuation.Frequency span by measurement of attenuation of RF Suppression filter is spanned from 10 kHz to 30 MHz.The comparison presented in this paper confirms that the S parameters are identical only if the filter is in equilibrium (ZL=ZN).From the results, three frequency areas can be distinguished. In the first interval between 10 kHz and 150 kHz the filter is in balance, which was demonstrated with identical measurement results. Between 150 kHz and 1.5 MHz, the attenuation is superimposed on the dynamics of the measurement system and therefore on the random frequency dependence of both measurements. Above 1.5 MHz there is a clear filter asymmetry, so the curves move away from each other.

Analyzing the applicability of wetland ecological modes in the Minjiang Estuary wetland

Wetlands are badly damaged in many parts of the world. The wetland management of Minjiang Estuary wetland has achieved remarkable results. This provides valuable experience for wetland management in other areas. Minjiang Estuary wetland can achieve the effect, mainly because of the adoption of the water quality management, ecological restoration, and ecological tourism development. However, different management modes have their own scope of application. In order to spread its successes, three differential game modes related to Minjiang Estuary wetland management are constructed, and their equilibrium results are compared and analyzed. Finally, research shows that the amount of water quality control by governments is directly proportional to the resilience of wetlands. The amount of social organization culture is proportional to the degree of better water quality. The amount of development by the government and social organizations is directly proportional to the decrease of investment in the spontaneous tourism industry. When the loss caused by flood or the ecological restoration effect is large, the wetland should adopt the ecological restoration mode. When the increased income or reputation of ecotourism is large, the ecotourism development mode should be adopted. This provides a reference for how to manage wetlands and how to promote the management mode of Minjiang Estuary wetland to other areas more effectively.

Design of highly selective balanced bandpass filter with wide differential-mode stopband and high common-mode suppression

A highly selective and wide stopband bandpass filter (BPF) with multiple transmission poles (TPs) and transmission zeros (TZs) has been proposed. The BPF employs a box-like coupling structure consisting of two half-wavelength resonators and a dual-mode open stub loaded resonator, enabling the generation of two TZs and four TPs. Three controllable TZs are obtained by adding an annular spiral open stub to the terminal of the input and output coupling lines, which significantly improves the selectivity of the BPF. To achieve a wide stopband characteristic, a wide stopband unit with three additional TZs is cascaded within the structure. A balanced BPF is realized by introducing a microstrip-slotline-microstrip balun structure to the input and output ports of the proposed BPF. Experimental results validate the feasibility of the proposed BPF and balanced BPF applied in 2.45 GHz ISM band. The introduction of eight TZs gives the BPF a 20 dB rectangular coefficient of 1.3 with an upper stopband exceeding than 12 GHz. The balanced BPF can achieve 40 dB of high common-mode(CM) suppression in the passband, while differential-mode (DM) transmission is close to the performance of the proposed BPF. The minimum insertion loss for BPF and balanced BPF is 0.8 dB and 1.3 dB, respectively.

Analysis of 3D positions processed from CORS in southern Ghana

Differential mode of processing GNSS in the preferred choice for high precision assignments in areas where there are active reference stations. Studies into the performance of these continuously operating reference stations (CORS) have mainly been centered on either session times or baseline lengths. Active CORS have emerged replacing the old passive stations. However, these innovations in the science of spatial data acquisition needs to be monitored for networks strength and sensitivity. In this study, GPS data from five CORS stations for 12 days were used and processed with RTKLib. The research was restricted to baseline lengths of 2.5 to 13.5 km with varying session lengths starting from 1 hour to 24 hours. 3D error for each baseline and 3D RMS for each group of baselines were subsequently computed. A plot of the results was analyzed and compared. This comparison reveals that Geodetic accuracy (below 1cm) is achieved after 4 hours of observation session showing that the precision of Rtklib baseline solution can reach sub-centimeter level and therefore can yield reliable results in almost any professional project.

Equalization system of low differential mode delay few-mode fibers based on the neural network MIMO algorithm.

In recent years, with the development of information networks, higher requirements for transmission capacity have been recommended. Yet, at the same time, the capacity of single-mode fiber is rapidly approaching the theoretical limit. The multidimensional multiplexing technique is an effective way to solve this problem. Since the high differential mode delay (DMD) of transmission fiber increases the complexity of demultiplexing in equalization algorithms, we use an intelligent design method to optimize the trench-assisted gradient refractive index structure in this paper. The maximum DMD of the optimized optical fiber structure is 19.6 ps/km. A least mean squares-feedforward neural network constant modulus algorithm (LMS-FNNCMA) is also designed by using the theory of the least mean squares (LMS), constant modulus algorithm (CMA), and the multiple input multiple output (MIMO) neural networks. In order to verify the accuracy of the algorithm, a polarization division multiplexing-wavelength division multiplexing-mode division multiplexing (PDM-WDM-MDM) optical transmission system is constructed through simulation. The algorithm successfully realizes the de-crosstalk over a transmission distance of 1200 km at a rate of 1.2 Tbps under simulation conditions.

Electrochemical detection of paracetamol using zeolitic imidazolate framework and graphene oxide derived zinc/nitrogen-doped carbon

A composite of zeolitic imidazolate frameworks and graphene oxide (ZIF-GO) derived 3D–2D Zn/N-doped carbon (ZnNC-rGO) was developed for the electrochemical detection of the analgesic paracetamol (PCT). The pyrolysis of ZIF-GO led to the formation of a nanoscale structure featuring ZnNC cubes embedded in rGO sheets. The Zn0-to-ZnO phase transition was found to mediate electrons during the reversible paracetamol redox reactions, which contributed to the sensing current response. Upon 800 °C heating under a N2 atmosphere, the mesoporosity of ZnNC-rGO(800) was significantly enhanced, thereby increasing the electrochemical surface area and charge transfer efficiency. The electrode sensitivity was optimized at a calibration linearity of 0.526 μA μM−1) with detection limit (0.077 μM) in the range of 0.5 – 70 μM using differential pulse voltammetry mode (DPV). The precision of analytical recovery for trace paracetamol concentrations was maintained based on the excellent reproducibility and selectivity trials in the presence of interference chemicals and in real water samples.

Design of compact balanced filters with wide DM upper stopband and CM rejection band based on semi‐circular patch

AbstractA new design approach to achieve compact size and high common‐mode (CM) suppression of balanced filters is proposed with two back‐to‐back microstrip semi‐circular patch resonators. In feeding structures, metalized via holes are adopted to vertically feed patches by differential pairs. Then, TM11 mode is excited and TM31 mode can be rejected, resulting in wideband differential‐mode (DM) harmonic rejection. Besides, with a slotline etched in the common ground plane, desired coupling strength can be achieved for a target bandwidth. Meanwhile, by virtue of the stacked structure, source‐load coupling can be easily introduced to generate transmission zeros close to the passband. With theory guidance, two balanced filter prototypes centered at 2.4 GHz are designed. Simulation and measurement results both indicate that proposed balanced filters exhibit high DM and CM performances as well as a compact size about 0.26λg × 0.53λg.

Mechanistic Analysis of Riboswitch Ligand Interactions Provides Insights into Pharmacological Control over Gene Expression.

Riboswitches are structured RNA elements that regulate gene expression upon binding to small molecule ligands. Understanding the mechanisms by which small molecules impact riboswitch activity is key to developing potent, selective ligands for these and other RNA targets. We report the structure-informed design of chemically diverse synthetic ligands for PreQ1 riboswitches. Multiple X-ray co-crystal structures of synthetic ligands with the Thermoanaerobacter tengcongensis (Tte)-PreQ1 riboswitch confirm a common binding site with the cognate ligand, despite considerable chemical differences among the ligands. Structure probing assays demonstrate that one ligand causes conformational changes similar to PreQ1 in six structurally and mechanistically diverse PreQ1 riboswitch aptamers. Single-molecule force spectroscopy is used to demonstrate differential modes of riboswitch stabilization by the ligands. Binding of the natural ligand brings about the formation of a persistent, folded pseudoknot structure, whereas a synthetic ligand decreases the rate of unfolding through a kinetic mechanism. Single round transcription termination assays show the biochemical activity of the ligands, while a GFP reporter system reveals compound activity in regulating gene expression in live cells without toxicity. Taken together, this study reveals that diverse small molecules can impact gene expression in live cells by altering conformational changes in RNA structures through distinct mechanisms.

Improving the efficiency of using tractors by equipping the drive wheels with a built-in differential

.Relevance. The efficiency of the use of agricultural wheel units, the process of interaction of the wheel mover with the support surface is influenced by structural parameters, the properties of the support surface and the tire tread, the ratio of vertical load and longitudinal pushing force. In order to reduce wheel slipping, a built-in differential with an off-center application of external knobs and a driving torque is proposedMethods. For a quantitative and qualitative description of the operation of the wheel, methods of analytical, comparative, information-logical and system analysis of factors that have a causal relationship with the performance of mobile units, wheel propellers were used. The analysis of the propeller operation was carried out by the methods of theoretical mechanics on the provisions of the theory of rolling of a deformable wheel on a deformable supporting surface. The subject of the study is a two-stage process of interaction between the surface and the drive wheel during acceleration. At the first stage, the sprung mass of the tractor moves with a stationary wheel rim within its radius. At the second stage, the movement of the tractor masses occurs with a rotating wheel, the wheel gear operates in differential mode, preventing its external slip.Results. The wheel differential contributes to maintaining the maximum value of the friction coefficient and the rational ratio of the driving moment and the moment of resistance to rolling. The use of a built-in differential in wheel propellers is a promising option for their improvement, it helps to maintain a high specific longitudinal reaction, preventing slipping and, thereby, destruction of the soil structure. As a result, the productivity of wheeled mobile units increases, fuel consumption and tire wear decrease, soil compaction decreases.

High common‐mode rejection balanced bandpass filter using novel coupling scheme and source‐loaded coupling technique

AbstractA balanced bandpass filter (BPF) with a novel coupling scheme and source‐loaded coupling (SLC) technique is proposed. The J‐inverter is directly connected to the source or load, and the single‐band cell (SBC) is fed by the J‐inverter. Meanwhile, the J‐inverter is also coupled to a resonator. Equivalent differential‐mode (DM) and common‐mode (CM) circuits are presented, and their ideal frequency responses under DM and CM are also provided. Furthermore, the SBC equals paralleled short‐ and open‐circuited stubs in DM and equals two paralleled open stubs in CM. To validate the design concept, a four‐pole balanced BPF working at 2.66 GHz with fractional bandwidth (FBW) of 13.8% is designed and fabricated. Three transmission zeros (TZs) are generated, and the upper stopband suppression level reaches 34 dB. Meanwhile, a high CM rejection level attains 54 dB within the DM passband.

Double-ring high-frequency common-mode switching oscillation current sensor for inverter-fed machine winding insulation monitoring

Double-ring high-frequency common-mode switching oscillation current sensor for inverter-fed machine winding insulation monitoring

Time-Varying Model and Boundary Model of Differential Mode Circulating Switching Harmonics Among Multiple Inverters

Time-Varying Model and Boundary Model of Differential Mode Circulating Switching Harmonics Among Multiple Inverters

How Group Leaders Build Stable Community Buying Groups: A Perspective Based on the Differential Mode of Association

How Group Leaders Build Stable Community Buying Groups: A Perspective Based on the Differential Mode of Association

Separation of common and differential mode conducted emission: Power combiner/splitters

A conducted emission measurement contains a common and a differential mode component. Accurate separation of these two components is critical, when designing the input filter of a switch mode power supply. Many techniques exists for performing such separation. Some authors suggested the use of wideband transformers, while other prefer current probes. In this paper the use of commercial power splitters/combiners as noise separators are considered. The performance of the noise separators are analyzed and validated based on scattering parameters (S-parameters). Impedance and rejection ratios (common and differential mode) are shown. The results based on S-parameters are used to propose a complete noise separator design. This separator is verified through experimental measurements. Finally an example on how to use the separator, when measuring conducted noise is given.

High frequency Modelling of Cables in PWM Motor Drives by Using Polynomial Functions based Parameters

- The high frequency behaviour of the cables in pulse width modulation (PWM) motor drives is of a crucial importance in the analysis of transient overvoltages and conducted electromagnetic interference (EMI) propagation, both common and differential mode. In order to give a tool for simulation of the above cited phenomena, a new method for high frequency cable modelling is proposed in this paper. The method is based on the measurement of the impedance frequency responses of the cables in short and open circuit conditions. The lumped parameters cable behaviour is described by polynomial functions in frequency domain. For a given frequency a simple equivalent circuit representation of the cable is obtained. The proposed model is easily implemented in Matlab/Simulink and it is validated comparing the computed frequency impedance responses of the cable, loaded by either a resistive load or an induction motor, to the corresponding measured ones. Moreover, the prediction, by the model, of the overvoltage at the motor terminals in a long-cable PWM drive is performed. The proposed model are also compared with some commonly used high frequency cable models presented in technical literature.

Analysis of Current-Bidirectional Buck-Boost Based Switch-Mode Audio Amplifier

The following study was carried out in order to assess quantitatively the performance of the buck-boost converter when used as switch-mode audio amplifier. It comprises of, to begin with, the delimitation of design criteria based on the state- of-the-art solution, which is based in a differential mode buck- based amplifier with a boost converter as power supply. The averaged switch modelling of the differential mode current bidirectional topology is also used, in order to analyze the steady state and frequency-wise behaviour of this parameterize it to meet the design criteria converter and Next, several piecewise-linear simulation results are shown with detail enough to emphasize the features of the converter. A simple prototype is implemented to verify the main predicted features. Presently no previous publication could be found containing a thorough analysis of this topology in such configuration when applied for audio

Nonlinear compensation for few-mode fiber MDM-WDM systems using probabilistic neural network

In this paper, we propose for the first time to apply probabilistic neural network (PNN) to fiber nonlinear compensation (NLC) in a high-speed coherent optical communication system that combines few-mode fiber (FMF) mode division multiplexing (MDM) with wavelength division multiplexing (WDM). By training on a small number of symbols, the PNN equalizer can compute the statistical distribution of the signal nonlinearity, make decisions on test symbols, and thereby compensate for the nonlinear impairments of the signals. To verify the effectiveness of the proposed scheme, we construct a MDM-WDM simulation system with 28 GBaud polarization division multiplexing (PDM) 16-quadrature amplitude modulation(QAM) and 64 GBaud PDM-64QAM, 6 spatial mode signals are transmitted over 11 wavelength channels with link lengths of 1500 km and 400 km, respectively. The results show that the PNN equalizer can make nonlinear judgments on received signals and effectively compensate the signal impairments caused by Kerr nonlinearity and device nonlinearity in a large launch power range after undergoing carrier phase recovery (CPR). Meanwhile, this scheme exhibits strong robustness against residual linear mode coupling (LMC), differential mode group delay (DMGD), and amplified spontaneous emission (ASE) noise. Finally, by the computational complexity comparison, it is proved that the complexity of the probabilistic neural network nonlinear compensation (PNN NLC) scheme is lower than that of digital back propagation (DBP) with comparable performance, which is on the order O(N).

High sensitivity miniaturized multi-pass absorption enhanced differential Helmholtz photoacoustic gas sensor

A high sensitivity photoacoustic (PA) gas sensor based on multi-pass absorption differential Helmholtz cell with a chamber volume of only 37 mL was proposed. The reported cell has an absorption path length of 2.5 m, which can effectively enhance the optical excitation. The differential Helmholtz structure can heighten the photoacoustic signal and effectively suppress ambient noise. To optimize the differential Helmholtz resonant PA cell, the PA field distribution of the cell was calculated by thermoviscous acoustic theory using the finite element method. The detection performance of the sensor was evaluated using a distributed feedback laser operating at a center wavelength of 1650.44 nm and targeting CH4 gas. Compared with a single pass, the PA signals were enhanced by 11 times in multiple pass mode. The differential mode suppressed 30 % of background noise. The calculated normalized noise equivalent absorption (NNEA) coefficient was 3.45 × 10-10 cm-1WHz1/2. The experimental results showed that the minimum detection limit (MDL) of CH4 was 6.6 ppb with an averaging time of 100 s.

A cost-effective joint multi-parameter optical performance monitoring scheme for high baud rate mode division multiplexing system

Inter-symbol interference (ISI), mode coupling (MC) and other impairments present in high baud rate mode division multiplexing (MDM) systems significantly degrade the reliability and accuracy of optical signal transmission. Therefore, performing joint multi-parameter optical performance monitoring (OPM) is crucial to ensure the efficient operation of the system. We propose a scheme that combines asynchronous single channel sampling (ASCS) images with a multi-task residual neural network (MT-ResNet) to enable cost-effective joint OPM at intermediate nodes in a 100 GBaud MDM system. The scheme requires only one photodetector to receive the signal. Based on the distinct characteristics exhibited by ASCS images for different parameters in the MDM system, the MT-ResNet is improved to capture correlations among parameters and learn residual information between inputs and outputs. This enables high-precision and rapid simultaneous implementation of modulation format identification (MFI), MC estimation, optical signal-to-noise ratio (OSNR) estimation, and chromatic dispersion identification (CDI) in the intermediate nodes of a 100 GBaud MDM system. The effectiveness of the proposed scheme is verified using a 100 GBaud QPSK/8QAM/16QAM/32QAM/64QAM MDM simulation transmission system with five spatial modes (LP01/LP11a/LP11b/LP21a/LP21b). The results show that under the influence of different linewidth (LW) of laser and differential mode group delay (DMGD), a 100 % identification success rate can be achieved for five commonly used MFs and eight different cumulative CD values in high baud rate MDM systems, across a wide range of OSNR. Additionally, the mean absolute error (MAE) of OSNR estimation corresponding to the five MFs is 0.22 dB, 0.26 dB, 0.30 dB, 0.32 dB, and 0.36 dB, respectively. The MAE of the eight different MC intensities fluctuate between 0.015 and 0.030. These results fully demonstrate the superior performance of the proposed scheme. Furthermore, the scheme exhibits favorable tolerance to large LWs and fiber nonlinear effects. Moreover, the complexity of the scheme is accurately analyzed through floating-point operations (FLOPs) and parameters (Params), which are much less than existing typical schemes, with specific values of 14.8849 M and 1.3798 M.

Compact dual‐band balanced bandpass filter with controllable passbands using coplanar waveguide spiral cross resonators

AbstractIn this article, a novel coplanar waveguide (CPW) spiral cross resonators (SCRs) is introduced for creating a dual‐band balanced bandpass filter (BPF) with adjustable passbands. The resonant properties of the SCRs in both the differential mode (DM) and common mode (CM) are scrutinized. Furthermore, DM bisection offers two distinct parameters for internal coupling adjustment, enabling independent passband width control. A novel grounding wire feeding arrangement matches the external Q factor of the dual DM passbands. An additional stepped‐impedance short‐circuited conducting stub between resonators prevents excessive coupling while obtaining moderate bandwidths. Inherent CM suppression can be attained by distinguishing CM resonant frequencies distinct from the DM frequencies. To validate the design, a dual‐band balanced BPF designed and fabricated to operate at 2.42 and 5.2 GHz exhibits closely matching measured results compared to the simulated ones.