Active Electromagnetic Interference Research Articles

UAV-Mounted GPR for Object Detection Based on Cross-Correlation Background Subtraction Method

Unmanned aerial vehicle (UAV) ground-penetrating radar (GPR) is an important research topic for target detection in many fields. In this paper, we develop a UAV-mounted GPR system with a frequency band at 150 MHz–309 MHz. However, the received signal in the complex background is covered by various clutter and interference, leading to the serious obscuring of the target. To meet this challenge, a cross-correlation-based background subtraction (CCBS) method and an interference suppression technique are adopted in combination for more accurate detection. The CCBS method processes the raw echo by establishing a background-removal model and using the similarity between each A−Scan and a reference wave. In addition, a Butterworth filter is adopted to get rid of the active electromagnetic interference beyond the working frequencies of the system; then, a lateral Doppler filtering (LDF) technique is introduced to suppress the passive interference generated by the rotation of the UAV rotor itself. Moreover, a practical method for estimating the dielectric constant is introduced by the calibration process of the measured radar echo. Numerical simulations and experimental results by our UAV-GPR system demonstrate that the proposed method has presented a better performance than the traditional methods, and the system has great potential in detecting deeply buried targets.

An Active EMI Filter in Grounding Circuit for DC Side CM EMI Suppression in Motor Drive System

In this article, an active electromagnetic interference (EMI) filter is designed to reduce the dc side common mode (CM) EMI in motor drive system. Different from the traditional passive EMI filter which is added in the main circuit, the designed active EMI filter (AEF) in this article is added in the grounding circuit which is connected between motor frame and the ground and it can be decoupled from the main circuit. By properly setting the components value, the dc side CM EMI can be suppressed while maintaining a low motor frame voltage. The structure of the AEF is simple and the volume of the AEF can be kept small. The operation principle of the AEF is introduced first and the performance of this AEF is evaluated through simulation. Experiment results verified the effect of this AEF that it can suppress the dc side CM EMI and the motor frame voltage can be kept low.

A Customized Integrated Circuit for Active EMI Filter With High Reliability and Scalability

This article proposes an active electromagnetic interference (EMI) filter (AEF) realized by a customized integrated circuit (IC) to reduce conducted emission noises. A fully transformer-isolated feedforward current-sense current-compensation structure is selected as a base topology of the AEF. To achieve the high reliability of the proposed AEF by using low-voltage IC devices, the injection transformer is added to protect IC devices from high-voltage hazards. The operation of the proposed AEF is theoretically demonstrated, and practical design guidelines for the IC part and nearby components are developed. The designed IC was fabricated by a 0.18 μm bipolar-CMOS-DMOS process. The fabricated IC is implemented in a compact printed circuit board for application to a three-phase inverter motor system. The performance, stability, and surge immunity of the AEF are experimentally demonstrated. A designed 1stage AEF achieves better noise-attenuation performance than 2stage passive EMI filters (PEFs) over 6 dB at 150 kHz without critical resonance peak at the high-frequency range. Weak points of the conventional PEFs in both low and high frequencies are effectively improved by using the proposed 1stage AEF. In addition, the surge immunity of the designed IC within the AEF is validated under numerous 5 kV surge tests.

Active EMI Filter Design With a Modified LCL-LC Filter for Single-Phase Grid-Connected Inverter in Vehicle-to-Grid Application

More and more attention has been gained in the vehicle-to-grid (V2G) system due to its attractive features, such as transferring bidirectional power between electric vehicles and grid, regulating grid voltage/frequency. This paper develops the active electromagnetic interference (EMI) filter (AEF) with significant system volume and weight reduction compared to the traditional passive EMI filter (PEF). While the high-frequency parasitic parameters of the AEF and the restricted loop gain result in limited AEF EMI noise attenuation in the high-frequency range. Thus, an additional passive EMI filter is commonly needed to suppress the EMI noise. For avoiding external passive filter components, the active EMI filter is designed and integrated with a modified LCL-LC filter as a hybrid filter to guarantee EMI noise attenuation. The modified LCL-LC filter can maintain satisfactory harmonic suppression with a higher EMI reduction ability compared to other types of harmonic filters. Based on a single-phase grid-connected inverter, the total harmonic distortion (THD) and the conducted EMI measurement results are compared with the results of traditional LCL, LLCL, LCL-LC filters. The effectiveness of the proposed circuit is verified by simulation and experimental results. The proposed circuit successfully improves the filter design of the inverter in the suppression of harmonics and EMI noise.

Continuous dyeing of graphene on cotton fabric: Binder-free approach for electromagnetic shielding

In this paper, Graphene oxide dyed on the cotton fabric through an efficient and industrially used continuous dyeing method. The graphene oxide dyed cotton fabric was reduced by using green reducing L-ascorbic at 100 °C microwave-assisted reduction. The effect of with different weight percent of rGO on sheet resistance and active electromagnetic interference (EMI) shielding of the studied. The surface modification of the fabric was achieved by using dopamine; the results showed significant improvements for the adhesion of (rGO) distributed uniformly on the fibre surface. Also, the rGO dyed fabric showed higher electrical conductivity 2.3 × 10−1S/cm−1 and EMI SE of −26 to −35 dB in the range of 30–1530 MHz in X-band.

A Balanced Feedforward Current-Sense Current-Compensation Active EMI Filter for Common-Mode Noise Reduction

This paper proposes a balanced feedforward current-sense current-compensation (CSCC) common-mode (CM) active electromagnetic interference (EMI) filter (AEF). The advantages of the feedforward CSCC-type AEF are theoretically demonstrated. The operation of the proposed AEF is completely analyzed, and practical design guidelines are developed regarding performance and stability. The proposed AEF is applied to an L–C–L EMI filter for a 2.2 kW resonant inverter, and CM noises are further reduced by 3 to 18 dB from 150 kHz to 10 MHz. The problem of CM-to-differential mode noise transformation due to an unbalanced AEF structure is also investigated by the measurements using a vector network analyzer.

Active Electromagnetic Interference Control in Time Domain: Application to Software Correction of Defective Lossy Transmission-Line Networks

This paper introduces a generalized approach of the linear combination of configuration field (LCCF) method. The technique developed in this paper provides a way to identify the temporal profile of electromagnetic sources satisfying particular properties for a given target (fields, voltage, or current). Here, we focus on identifying voltage signals that would lead to a specified voltage over a time interval at some points of a network. To experimentally apply the same idea, we propose two possibilities to decrease the maximum frequencies of the voltage signals. The LCCF method is then applied to bring a software correction to a lossy transmission-line network presenting soft or hard defects.

Quantified Design Guidelines of a Compact Transformerless Active EMI Filter for Performance, Stability, and High Voltage Immunity

This paper proposes and analyzes a compact transformerless common mode active electromagnetic interference (EMI) filter (AEF) using a push-pull amplifier. Quantified design guidelines are then rigorously derived from the analysis with consideration for performance, stability, and high voltage transient immunity. The proposed AEF is manufactured based on the design guidelines, and its performance is validated by measurements using a vector network analyzer. The AEF is then implemented into a real 2.2 kW current resonant inverter, and the conducted emissions are reduced by 5-25 dB at a frequency range from 150 kHz to 6 MHz. In addition, the AEF's immunity against high voltage transients is demonstrated by lightning surge tests.

An Active EMI Choke for Both Common- and Differential-Mode Noise Suppression

In this paper, an active electromagnetic interference (EMI) choke for both common-mode (CM) and differential-mode (DM) noise suppression is proposed. Three isolated windings with a different number of turns are wound on the same magnetic core. One of the windings is served as the auxiliary winding connecting to an active circuit called the negative impedance circuit. The inductance of the EMI choke is substantially boosted up to effectively attenuate the low-frequency noise. This technique leads to a greater inductance but fewer turns and smaller size of the EMI choke. Different from the design of a conventional EMI filter, which uses separated CM and DM chokes, this proposal saves the cost and space of the EMI filter. The enhancement to the CM and DM impedance is individually analyzed and experimentally confirmed. Based on the classical CM and DM noise models, CM and DM noise insertion losses are predicted using computer simulation. The simulation results are validated by a network impedance analyzer. Finally, conducted EMI tests are carried out to verify the effectiveness of the proposed technique.

Design and Implementation of an Active EMI Filter for Common-Mode Noise Reduction

This paper presents the analysis and design of an active electromagnetic interference (EMI) filter (AEF) for the common-mode (CM) noise reduction of switching power converters. The features of the several types of AEFs are discussed and compared in terms of implementation. The feed-forward AEF with a voltage-sensing and voltage-cancellation (VSVC) structure is implemented for an LLC resonant converter to replace a multiple-stage passive EMI filter and thereby reduce CM noise. The characteristics and performance of the VSVC-type AEF are investigated through theoretical and experimental works.

Design of Active Electromagnetic Interference Filter to Eliminate Common-mode Noise in Conducted Interference

Design of Active Electromagnetic Interference Filter to Eliminate Common-mode Noise in Conducted Interference

Suppression of common-mode input electromagnetic interference noise in DC–DC converters using the active filtering method

This study introduces a technique that combines passive and active electromagnetic interference (EMI) filtering methods to attenuate the common mode conducted noise in the input bus of the DC/DC converter and to minimise the size and the cost of the existing passive EMI filters. The technique presented can be implemented in all DC/DC converters topologies to provide a level of compliance with the electromagnetic directives. The circuit analysis and the attenuation curves showing the performance and the viability of this technique is provided. The filter input/output impedance criterion is verified to ensure the stability of the converter, by measuring the gain and the phase margins of the open-loop frequency response of the converter. The proposed technique provides a valuable design solution for compliance engineers where the Printed Circuit Board real-estate is an issue. Experimental results reveal more than 30 dB attenuation across the electromagnetic compatibility spectrum. This method contributes to the reduction of the size and weight of the input passive EMI filter. The proportion of the passive filter as compared to the DC/DC converter device can vary from 5 to 3%, depending on the converter specifications. Experimental results to demonstrate the performance and the effectiveness of the input active EMI filter in DC/DC converters are presented.

Investigation of Hybrid EMI Filters for Common-Mode EMI Suppression in a Motor Drive System

This paper begins with an analysis of the common-mode (CM) noise in a motor drive system. Based on the developed CM noise model, two cancellation techniques, CM noise voltage cancellation and CM noise current cancellation, are discussed. The constraints and impedance requirements for these two cancellation methods are investigated. An active filter with a feedforward current cancellation technique is proposed, implemented, and tested, and techniques to improve the performance of active filters are explored. It is found that due to the limitations of speed, power loss, and gain bandwidth of active filters, active electromagnetic interference (EMI) filters are not good at suppressing high di/dt or high amplitude noise current. Hybrid filters that include a passive filter and an active filter are proposed to overcome the shortcomings of active filters. Hybrid EMI filters are investigated based on the impedance requirements and frequency responses between the passive and active filters. The experiments show that the proposed active filter can greatly reduce noise by up to 50 dB at low frequencies (LFs), and therefore, the corner frequency of the passive filter can be increased considerably; as a result, the CM inductance of the passive filter is greatly reduced. The power loss of the proposed active EMI filter can be well-controlled in the experiments.

An Experimental Study of Common- and Differential-Mode Active EMI Filter Compensation Characteristics

Most reported compensation schemes for active electromagnetic interference filters (AEFs) use either voltage canceling or current canceling to deal with high-frequency noise interference. The purpose of this paper is to investigate the compensation characteristics of these two kinds of AEFs for different types of noise sources, i.e., common mode (CM) and differential mode (DM) noise source. This is examined by experimental identification and theoretical analysis of the insertion losses of AEF with voltage- or current-cancellation scheme. It is demonstrated that current-canceling AEFs are effective in eliminating high-impedance CM noise, while voltage-canceling AEFs are good compensation solutions for low-impedance DM noise. The results reported in the paper enable the choice of optimized compensation schemes, using the aforementioned indicated aspects.

Analysis of Insertion Loss and Impedance Compatibility of Hybrid EMI Filter Based on Equivalent Circuit Model

The hybrid active electromagnetic interference filter (HAEF) is considered one of the best options for improving power quality for a number of considerations. A systematic classification and identification of HAEF configurations is given, including their insertion losses, impedance compatibilities, potential applications, and comparative features. It is aimed at providing a broad perspective on the status of HAEF technology to researchers and application engineers dealing with EMI issues. The basis of discussion is an equivalent circuit model that includes all possible combinations of active and passive elements and matches these to the desirable attributes. The evaluation indicates those topologies that are known and those topologies that are relatively new.

An Active EMI Filtering Technique for Improving Passive Filter Low-Frequency Performance

In recent years, there has been considerable interest in the development and applications of active electromagnetic interference (EMI) filters. An active EMI filter (AEF) for integrated power electronics module (IPEM) is proposed in this paper, where large passive EMI filter is replaced by small passive components and active op-amp circuit. The technique is appropriated when improved attenuation is required at relatively low frequencies and the high-frequency filtering requirements are easily met. The effectiveness of the proposed circuit has been verified by experimental results. It is demonstrated that the proposed approach is most effective in a case where it is desirable to minimize the amount of passive components in the filter.