• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.87-90
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• 2003

In this paper, A feedforward linear power amplifier is analyzed for imperfect signal cancellation and negative feedback for basestaion of IMT2000 band. the distortion generatied by the error amplifier is reduced using an imperfect signal cancellation for a 1-carrier WCDMA source by 4.3dB at 2.5MHz offset and 6dB at 5MHz offset of IMSR(intermodulation signal power ratio) compared to a perfect signal cancellation system. additionally, An imperfect signal cancellation using negative feedback improved 1.3dB and 8.2dB at 2.5MHz and 5MHz offset of IMSR compared to an imperfect signal cancellation.

• 한국통신학회논문지
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• 제32권5A호
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• pp.409-416
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• 2007

In cellular orthogonal frequency division multiplexing (OFDM) networks, co-channel interference (CCI) leads to severe degradation in the BER performance. To solve this problem, maximum-likelihood estimation (MLE) CCI cancellation scheme has been proposed in the literature. MLE CCI cancellation scheme generates weighted replicas of the transmitted signals where weights represent the estimated channel transfer functions. The replica with the smallest Euclidean distance from the received signal is selected and data are detected. When the received power of the desired and interference signals are nearly the same, the BER performance is degraded. In this paper, we propose a closed-loop power control (PC) scheme capable of detecting the equal received power situation at the mobile station (MS) receiver by using the newly introduced parameter power ratio (PR). When this situation is detected, the MS sends a feedback to the desired base station (BS) which boosts the transmission power in the next frame. At cell edge where signal to interferer ratio (SIR) is considered to have average value between -5 dB and 10 dB, computer simulations show that the proposed CCI cancellation scheme has a gain of 7 dB at 28 Km/h.

• 한국통신학회논문지
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• 제39A권2호
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• pp.100-108
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• 2014

본 논문에서는 RF(radio frequency) Cancellation과 Digital Cancellation을 사용하는 SSD(simultaneous single band duplex) 시스템을 구성하고, 이 시스템에서 직접 자기 간섭 신호가 있는 환경에서 RF Cancellation의 오차가 발생하였을 경우 남은 자기 간섭 신호의 전력 크기 특성을 분석한다. 또한 이를 해결하기 위해 Digital Cancellation을 사용하였을 때, 추가적인 잔류 자기 간섭 신호 제거를 통한 성능 특성을 분석한다. RF Cancellation에서 사용하는 위상 천이기에 0, 0.5, 1, 2도의 위상 천이 오차가 발생하였을 경우 잔류 자기 간섭 신호가 자국에 수신되는 상대국의 송신 신호보다 매우 크기 때문에 상대국의 데이터를 수신할 수 없는 것을 확인하였고, Digital Cancellation 방법을 사용하면 이러한 잔류 자기 간섭 신호 성분을 제거하여 상대국의 송신 데이터를 수신할 수 있는 것을 확인하였다. 또한 RF Cancellation에서의 소자 설계 오차에 대한 시스템의 성능을 분석하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.355-356
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• 2015

This paper proposes a control strategy of total output power ripple cancellation for both of Machine-Side Converter (MSC) and Grid-Side Converter (GSC) in a DFIG under unbalanced grid conditions. The proposed control strategy for the MSC is the zero torque ripple control algorithm with an enhanced LVRT capability. The control algorithm for the MSC exhibits reduced torque pulsation in steady-state unbalanced grid conditions. In addition, this control algorithm also minimizes a peak value of rotor current in transient unbalanced grid conditions. The total output power ripple cancellation control algorithm is adopted in the GSC. The total output power ripple cancellation is achieved by nullifying the oscillating component of the total output active and reactive power at the summing point of stator and rotor of DFIG. The proposed control strategy for the GSC reduces the output power oscillation leading to the improved quality of wind farms output.

• 한국전자파학회논문지
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• 제11권7호
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• pp.1156-1160
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• 2000

Feed-forward 기법을 사용하여 송신 전력 증폭기에서 RX 신호들을 제거하기 위한 제거 loop 회로를 제안하였다. 본 논문에서 제안한 제거 loop의 효과 증명하기 위해 WLL 대역 1W급 증폭기를 제작하였다. 다양한 무선 통신 시스템에서 제안된 제거 loop를 가진 전력 증폭기 모듈을 사용하면 절 엄격한 RX 대역 감쇠특성으로 인한 낮은 TX 경로 삽입손실을 갖는 duplexer를 재공할 수 있다. 이 실험은 RX 대역 제거 loop가 없는 전력 증폭기 모듈과 비교할 때 적어도 90%의 향상된 RX 주파수대의 제거 효과를 보인다.

• 한국전기전자재료학회논문지
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• 제16권3호
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• pp.253-262
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• 2003

In this paper, the interference cancellation system, which is used to cancel the feedback signal in the wireless communication system with the same frequency, is studied. The time varying feedback signal generated from transmitter antenna to receiver antenna reduces the performance of the receiver system. the interference cancellation system using adaptive feedback method(AF-ICS) is suggested to prevent the oscillation of the receiver system and maintain the maximum output power of the power amplifier by the reduction of time-varying feedback signal and also this paper conforms that the oscillation disappears from the output signal by cancellation of the feedback signal and the total output power is satisfied the system specification.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.69-74
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• 2005

The High Peak to Average Power Ratio (PAPR) could be a severe Problem in OFDM performance since it causes the significant distortion to the transmitting signal through a nonlinear device such as High Power Amplifier (HPA). In this paper, the performance of Peak cancellation method according to the HPA characteristic is comparatively analyzed with the clipping and windowing methods. The BER performances and the out-band power spectrums are demonstrated in detail.

• 전기학회논문지
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• 제56권7호
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• pp.1191-1198
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• 2007

In this paper, the fault detection and noise cancellation algorithm based on wavelet transform was developed to locate the fault more accurately. Specially, noise cancellation algorithm was based on the correlation of wavelet coefficients at multi-scales. Fault detection, classification and location algorithm were tested by EMTP simulation on real power cable system. From these results, the faults can be detected and located even in very difficult situations, such as at different inception angle and fault resistance.

• 한국정보통신학회논문지
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• 제6권2호
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• pp.221-227
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• 2002

본 논문에서는 3GPP(3rd Generation Partnership Project) 비동기(asynchronous) WCDMA(Wide-band CDMA) 시스템에 HIC(Hybrid Interference Cancellation) 기법의 MUD (Multi-User Detector)를 적용하여 Rayleigh 페이딩 채널에서 BER (Bit Error Rate) 성능을 컴퓨터 시뮬레이션을 통해 구하였다. 이 결과를 감산형 간섭제거기법의 대표적인 방식인 SIC(Successive Interference Cancellation) 기법, PIC(Parallel Interference Cancellation) 기법의 BER(Bit Error Rate) 성능과 비교 분석하였다. 분석한 결과, 전송률이 높은 사용자들은 PIC 기법이나 HIC 기법을 사용하여 간섭을 제거하는 것이 효과적이고, 전송률 이 낮은 사용자들은 SIC 기법이나 HIC 기법을 사용하는 게 효과적이라는 것을 알 수 있었다. 또한, 전송률에 의존하지 않고 모든 사용자의 성능을 고루 만족시키기 위해서는 HIC 구조를 사용하는 것이 효과적이었다. 그 이유로서는 페이딩 채널상의 이유에서 또는 원하는 서비스를 만족시키기 위해서 사용자가 전력을 높일지라도 HIC 기법에서는 전단에 사용하는 SIC에 의해 전력이 낮은 사용자들의 성능을 보장해주고 후단에 사용하는 PIC에 의해 SIC 과정에서 전력이 센 사용자가 받는, 전력이 약한 사용자로부터의 간섭이 효과적으로 제거되기 때문이다.

• Journal of Power Electronics
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• 제19권5호
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• pp.1326-1335
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• 2019

Common mode (CM) chokes are a crucial part in EMI filters for mitigating the electromagnetic interference (EMI) of switched-mode power supplies (SMPS) and for meeting electromagnetic compatibility standards. However, the parasitic capacitances of a CM choke deteriorate its high frequency filtering performance, which results in increases in the design cycle and cost of EMI filters. Therefore, this paper introduces a negative capacitance generated by a negative impedance converter (NIC) to cancel the influence of equivalent parallel capacitance (EPC). In this paper, based on a CM choke equivalent circuit, the EPCs of CM choke windings are accurately calculated by measuring their impedance. The negative capacitance is designed quantitatively and the EPC cancellation mechanisms are analyzed. The impedance of the CM choke in parallel with negative capacitances is tested and compared with the original CM choke using an impedance analyzer. Moreover, a CL type CM filter is added to a fabricated NIC prototype, and the insertion loss of the prototype is measured to verify the cancellation effect. The prototype is applied to a power converter to test the CM conducted noise. Both small signal and EMI measurement results show that the proposed technique can effectively cancel the EPCs and improve the CM filter's high frequency filtering performance.