Earticle

본 논문에서는 AMI시스템과 전기차 충전시스템 간의 발생하는 간섭을 억제하는 기법을 제안하고 분석하였다. 한전에서 진행하고 있는 AMI 시스템에 사용되는 PLC 기술인 IEC12139-1와 전기자동차 충전 시스템에 사용되는 HomePlug GP, 두 통신기술 모두 2-30Mhz 주파수 대역을 사용하는 고속 PLC 기술이다. 두 방식이 같은 주파수 대역을 사용하면서 서로의 시스템에 간섭이 발생되게 된다. 본 논문에서는 Walsh code를 이용한 채널 분리를 통하여 간섭을 억제 시키는 방식을 실험하였다. 본 논문의 실험 결과는 스마트 그리드에서 사용하는 다양한 전력선 통신기술에 적용될 수 있다.

In this paper, we proposed Interference suppression method of between AMI system and EV charging system. IEC12139-1 and HomePlug GreenPhy are using 2-30Mhz frequency band in power line communication. Both method while using the same frequency band, interference occurs in the system of each other. In this paper, we experiment a way to suppress the interference through the channel separation using a Walsh code.

본 연구에서는 개발된 모터 조립체의 누설 잡음신호 감쇠 방안을 시험을 통해 제안한다. 개발된 장치는 항공기 외부에 장착되어 안테나를 회전시키기 위한 장치로서 전자기 간섭 측면에서 MIL-STD-461F의 RE102 요구규격을 충족해야한다. RE102 시험결과를 통해 장치의 누설 잡음신호가 전원 및 제어 케이블을 통한 외부 유입과 모터 회전에 의해 발생됨을 확인하였다. 그리고 회전을 위해 내 외부의 물리적 차폐가 어려운 부분에서 잡음신호가 누설됨을 확인하였다. 누설 잡음신호에 대한 감쇠를 위해 장치 동작을 고려한 전기적 접지 보강, 전기적 차폐 구조를 적용하여 시험을 수행했고 규격 충족 여부를 확인하였다. 최종적으로 잡음누설 경로에 맞물리는 형태를 갖는 원형 주름 초크 구조와 전도성 그리스를 함께 적용하여 요구규격을 충족함을 확인하였다.

In this study, we propose a method of suppressing the leakage noise signal of motor assembly through the test. The motor assembly is mounted on outside of the aircraft to rotate an antenna and must satisfy RE102 requirement on MIL-STD-461F in terms of electromagnetic interference. It is confirmed by RE102 test result hat the leakage noise signal of the equipment occurs due to external influx through the power and control cable and rotation of the motor. And it is ascertained that the part where internal/external physical shielding is difficult to rotate is the leakage path. To reduce the leakage noise signal, the electrical ground reinforcement and the electric shielding structure considering the operation of the equipment is applied and it is verified that the requirement is satisfied. Finally, we verified that required specification are met by applying circular corrugated choke with interlocking shapes and conductive grease to the noise leakage path.

영상 레이다(Synthetic Aperture Radar)는 전자파를 이용하여 영상을 생성함에 따라 주·야간 상황과 무관하게 안정적인 광역 관측 자료를 확보할 수 있으며 기상 제약 환경과 무관하게 전략적·상업적 목적으로의 감시 및 관찰 기능을 요구하는 임무에 광범위하게 활용될 수 있다. 그러나 SAR 위성 시스템의 경우 넓은 대역의 주파수를 사용하기 때문에 인접대역을 사용하는 레이다 시스템 및 통신기기로부터 간섭 영향에 의해 영상품질을 저하시킬 수 있다. 본 논문에서는 SAR 영상의 품질향상을 위해 간섭 제거 기법인 고유치 기반 필터(Eigen-subspace based Filter) 기법을 제안하였으며, SAR 위성의 간섭제거 알고리즘인 고유치 기반 필터 기법의 정량적인 성능 분석을 위해 일반적인 노치 필터(Notch Filter) 기법을 적용한 결과를 토대로 비교 검증하였다.

SAR(Synthetic Aperture Radar) uses electromagnetic signals to acquire ground information and has been used for wide coverage reconnaissance missions regardless of weather conditions. However SAR is known to be vulnerable to interference signals by other communication devices or radar instruments and may suffer from undesirable performance degradations and image quality. In this paper, a modified Eigen-subspace based filter is proposed that can be easily applied to SAR images affected by interference signals. The method of constructing Eigen-subspace based filter is briefly described and various simulations are performed to show the performance of the interference mitigation process. The suppression filter is applied to a ALOS PALSAR raw data affected by interfering signals in order to verify its superiority over the Notch filter.

MIMO (multi-input multi-output)–OFDMA (orthogonal frequency division multiple access) systems have been recognized as a key technology for next-generation wireless communications, offering high spectral efficiency and multiuser support. However, their performance is constrained when the number of users exceeds the allocated bandwidth and further deteriorates under adverse wireless environments. In this paper, we propose a novel scheme that integrates beamforming and distributed subcarrier allocation (DSA) in MIMO–OFDMA systems to address performance degradation caused by interference and adverse channel conditions. We mitigate interference through beamforming and enhance robustness against channel impairments via distributed allocation, thereby improving BER performance and increasing user capacity. We further conduct computer simulations to validate the effectiveness of the proposed scheme in terms of both user capacity and BER performance, demonstrating its potential as a valuable contribution to next-generation wireless communication research.

In this paper, an improved adaptive monopulse scheme based on modified projection approximation subspace tracking deflation (MPASTd) approach is proposed. Owing to the fast convergence speed of MPASTd for recursively estimating the interference subspace, the proposed algorithm can obtain the formula for adaptive monopulse ratio calculation by a subspace projection. Therefore, it is able to accurately estimate the source location using less training data and reduce the computational complexity significantly. The effectiveness and fast convergence speed of the proposed method is verified by simulation results.

The channel sharing in wireless networks leads to user mutual interference, which also exists in the centralized, cooperative, cloud, and clean-radio access network (C-RAN) which is considered as the access architecture of the 5G mobile communication system. In this paper, the problem of uplink interference suppression in the architecture of C-RAN wireless network was investigated. Taking advantage of the centralized processing in the C-RAN architecture, the correlations of the signals from each RRU are analyzed, based on which we proved that under certain condition, interference can be eliminated by utilizing the correlations among signals. According to the theory before, interference matrix between network users was established based on signals from each user to its nearby RRU. Then, the interference cancellation matrix can be gotten. The uplink signals in the network were processed by making use of the interference cancellation matrix, which can turn the interference part caused by the transmit signal of mobile terminal into useful signal.

Frequency-hopping communication has the capability to resist narrowband interference, which is in direct proportion to the hopping rate. In frequency-hopping system, interference signals exist in partial de-hopping frequency-hopping signals, equivalent to time-varying interference signals existed in the frequency-hopping signals. Through integrating the diversity combining techniques of fast frequency-hopping communication with singular value decomposition method, this paper detects the frequency-hopping points, masks them, and then combines with undisturbed frequency-hopping signals. MATLAB simulation shows that narrowband interference is well restrained and the system BER is obviously improved.

In this paper, an online receding robust predictive control scheme is proposed for input-constrained semi-trailer system with delay and disturbance. The controller method meets the requirements of control constraint and, based on dual-mode control, the method is obtained by online optimization of performance index. The performance index is the cumulative sum of quadratic weighted value of minimal states. Controller output is calculated by means of linear matrix inequality (LMI), and the controller itself can ensure the asymptotic stability and disturbance attenuation of semi-trailer closed-loop system. Finally, simulation results confirm the effectiveness of the method.

The goal of this paper is to suppress time-varying single tone jamming (STJ) in the CDMA system by using the frequency interference cancellation method. We consider the practical scenario where STJ signal experiences time-varying fading channel. In this approach, the parameters (i.e. frequency, amplitude and phase) of the time-varying STJ are estimated in frequency domain, and then it is reconstructed and subtracted from the raw signals. The theoretical BER (bit error rate) expression is analyzed to assess the performance of the method, and computer simulations are executed. Simulation results demonstrate the effectiveness of the method in mitigating time-varying STJ and approaching the interference-free performance limit over practical ranges of STJ power levels and mobility levels.

It has been shown that the principal subspace-based multichannel Wiener filter (MWF) provides better performance than the conventional MWF for suppressing interference in the case of a single target source. It can efficiently estimate the target speech component in the principal subspace which estimates the acoustic transfer function up to a scaling factor. However, as the input signal-to-interference ratio (SIR) becomes lower, larger errors are incurred in the estimation of the acoustic transfer function by the principal subspace method, degrading the performance in interference suppression. In order to alleviate this problem, a principal subspace modification method was proposed in previous work. The principal subspace modification reduces the estimation error of the acoustic transfer function vector at low SIRs. In this work, a frequency-band dependent interpolation technique is further employed for the principal subspace modification. The speech recognition test is also conducted using the Sphinx-4 system and demonstrates the practical usefulness of the proposed method as a front processing for the speech recognizer in a distant-talking and interferer-present environment.

A multi-channel audio CODEC with inter-channel interference suppression is proposed, in which channel switching noise-referred sampling error is significantly reduced. It also supports a coarse/fine mode operation for fast frequency tracking with good harmonic performance. The proposed multi-channel audio CODEC was designed in a 65 nm CMOS process. Measured results indicated that SNR and SNDR of ADC were 93 dB and 84dB, respectively, with SNDR improved by 43 dB. Those of DAC were 96 dB and 87 dB, respectively, with SNDR improved by 45 dB when all the channels are running independently.

An M-ary bi-orthogonal modulation scheme for ultra-wideband (UWB) systems capable of narrowband interference (NBI) suppression is proposed in this letter. We utilize a set of bi-orthogonal pulse series to achieve NBI suppression. Through analysis and simulation, we verify that the proposed scheme can suppress NBIs effectively.

In this letter, we analyze an ultra-wideband ranging system based on non-linear chirp waveforms with the ability of narrowband interference suppression. A number of non-linear chirp waveforms are proposed and evaluated by simulation. The results verify that the proposed schemes can suppress the Narrowband interference to a certain degree.

The applications of Global Navigation Satellite System (GNSS) receivers are becoming wider in various commercial and military systems including even small weapon systems such as artillery shells. The precision-guided munitions such as Small Diameter Bomb (SDB) of United States can be used for pinpoint strike by acquiring and tracking GNSS signals in high mobility situation. In this paper, a small GNSS receiver with embedded interference suppression capability working under high dynamic stress is developed which is applicable to the various weapon systems and can be used in other several harsh environments. It applies a kind of matched filter and multiple correlator schemes for fast signal acquisition and tracking of even weak signals and frequency domain signal processing method to eliminate the narrowband interference. To evaluate the performance of the developed GNSS receiver, the test scenario of high mobility and interference environment with the GNSS simulator and signal generator is devised. Then, the signal acquisition time, navigation accuracy, sensitivity, and interference suppression performances under high dynamic operation are evaluated. And the comparison test with the commercial GNSS receiver which has high sensitivity is made under the same test condition.

This paper analyzes, through simulations, GNSS interference mitigation performance against wideband and narrowband interferences by using spatial-temporal adaptive processing(STAP). The mathematical analysis results demonstrate that the array configuration has a considerable effect on the spatial-temporal correlation function. Based on the results, different array configurations are presented to evaluate and observe the effect on interference mitigation. The analysis results are further assessed through simulations.

Objective: The core deficit of attention deficit hyperactivity disorder (ADHD) is associated with frontal cortex and related circuitry. Children with ADHD and a medication history have shown atypical brain activation in prefrontal and striatal brain regions during cognitive challenge. We investigated two cognitive control operations such as interference suppression (IS) and response inhibition (RI) in children with ADHD. We also assessed the brain functions affected by the methylphenidate (MPH) effect by comparing the blood-oxygen level dependent (BOLD) signals in ADHD children on and off medication. Methods: Eight children (9-11 years of age) with combined-type ADHD underwent rapid event-related functional magnetic resonance imaging (fMRI) during performance of a modified flanker task. Two fMRI (3.0 T) scans were conducted with a one week interval-one with MPH treatment and the other without. Functional maps were generated through group averaging and performance-based correlational analyses. Results: Performances of the two cognitive control operations did not differ significantly between on-MPH and off-MPH status other than the reaction time to incongruent stimuli in ADHD children. In those affected by MPH treatment, an increased activation in the right prefrontal cortex during incongruent task was observed relative to a neutral trial in children with ADHD. Conclusion: On the treatment of MPH, the ADHD children exhibited increased activation of the right frontal cortex during interference suppression. This finding suggested that MPH affected the right frontal cortex in ADHD compensating for a reduced level of interference suppression. Future studies will be required to ascertain the MPH effect of cognitive brain regions among large number of children with ADHD.

RNA interference (RNAi) is an acknowledged useful and effective tool to study gene function in various cells. Here, we suppressed the Connexin 43 (Cx 43) gene expression during in vitro development of ovine pre-implantation embryos using the RNAi method. The 353 bp Cx 43 double-stranded RNA was microinjected into in vitro fertilized ovine zygotes, and the levels of target mRNA and protein were investigated. Control groups included uninjected zygotes or those injected with RNase-free water. The dsRNA injection resulted in the specific reduction of Cx 43 transcripts as analyzed by quantitative real-time RT-PCR and decreased protein levels as shown by Western blot analysis at the blastocyst stage. Microinjection of Cx 43 dsRNA led to 20.3%, 21.7% and 34.5% blastocyst rates and 19.2%, 37.5% and 41.3% hatched blastocyst rates in Cx 43 dsRNA-injected, water-injected and uninjected groups, respectively. Then the RNAi could not significantly affect cell number and cell death rates of blastocysts. Therefore, suppression of Cx 43 dsRNA and proteins did not apparently affect the development potential of ovine pre-implantation embryos but may play a role in embryo quality. RNAi technology is a promising approach to study gene function in early ovine embryogenesis.

Interference from IEEE 802.11a systems affects ultra-wideband (UWB) systems significantly. In this letter, we suggest a novel narrow-band interference (NBI) suppression technique based on the singular value decomposition (SVD) algorithm in time-hopping pulse amplitude modulation (TH-PAM) UWB systems. The SVD algorithm is used to approximate the interference which then is subtracted from the received signals. In contrast to the conventional notch filter and rake receiver, our method is more effective and the receiver complexity can be greatly reduced.

SHAPE 알고리즘은 펄스의 스펙트럼 형태를 원하는 대로 성형하면서, 이 외의 특성에는 왜곡을 발생시키지 않도록 설계할 수 있다는 장점이 있어 기존의 능동소나 펄스 설계에 활용되었다. 본 논문에서는 다중상태 소나 시스템을 위한 펄스를 설계할 때, 주파수 대역에서 인접한 펄스 간의 상호상관도를 감소시키면서도 펄스 자체의 성능 저하를 방지하기 위해 SHAPE 알고리즘을 적용한 펄스 신호 설계 기법을 제안한다. 이를 위해서 SHAPE 알고리즘의 경계함수를 펄스 대역폭으로 제한하도록 설정하였다. 제안하는 설계 기법을 사인화 주파수 변조 펄스 신호에 적용한 결과 상호상관도를 의미하는 peak cross-correlation level (PCCL)이 44.23 dB 감소하였다. PCCL이 수십 dB 감소하였음에도 모호성 함수의 변화가 크게 관찰되지 않았으며, 부엽의 평균값을 의미하는 integrated sidelobe level (ISL)이 11.64 dB 증가하였다.

The SHAPE algorithm has the advantage of being able to shape the pulse spectrum as desired and design it not to distort other characteristics, so it was used in the active sonar pulse design. In this paper, we propose a pulse design using the SHAPE algorithm for a multi-static sonar system to reduce the cross-correlation between frequency-adjacent pulses and prevent the performance degradation of the pulses themselves. The boundary function of the SHAPE algorithm is set to be limited to the pulse bandwidth. As a result of applying the proposed design method to the sinusoidal frequency modulated pulse, the peak cross-correlation level (PCCL), which means the degree of cross-correlation, was reduced by 44.23 dB. Although the PCCL decreased by several tens of dB, no significant change in the ambiguity function was observed, and the integrated sidelobe level (ISL), which means the average value of the side lobe, increased by 11.64 dB.

본 논문에서는 2차의 격자 IIR 노치 필터를 이용하여DS-CDMA 시스템에서 협대역 간섭신호를 제거한다. 본 노치필터는 구조가 간단하고 다양한 간섭 신호 모델에 따라 필터의 계수를 조절할 수 있어 간섭신호의 효과적인 제거가 가능하다. 노치필터의 앞단에는 주파수 추정부를 평행하게 구성하여 간섭신호 주파수의 위치와 파워를 검출한다. 제안된 적응 필터링 알고리듬은 이러한 정보를 이용하여 노치필터의 주파수를 조절하고 간섭 신호의 파워와 대역폭에 따라 노치의 넓이와 깊이를 조절한다. 즉, IIR 노치 필터의 특성을 이론적으로 분석하여 출력 신호대 잡음비를 입력과 필터의 파라미터에 관한 수식으로 유도하였고 이를 이용하여 주어진 입력에 따른 최적의 필터 파라미터를 구하여 적용시키는 것이다. 입력의 간섭 주파수와 파워를 검출하는 방법에는 여 러가지가 있지만 본 논문에서는 비교적 간단한 IIR ALE[6]를 사용하였다. 제안된 알고리듬을 사용한 결과 신호대 잡음비와 에러율에 있어서 FIR 필터를 사용한 기존의 방법[4]에 비하여 좋은 성능을 보임을 알 수 있다.