• Title/Summary/Keyword: SNR Degradation

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Construction of Magnetic Resonance Imaging Inside-out probes for Internal Imaging (핵자기공명 영상법을 위한 내부 영상용 뒤집음-탐침의 제작)

  • Ko, R.K.;Lee, D.H.;Jeong, E.K.
    • Proceedings of the KOSOMBE Conference
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    • v.1995 no.11
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    • pp.78-81
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    • 1995
  • In imaging the samples or human internal organs in a tube shape, general RF-probe types (that encircles a sample or places on top of the sample) are usually unsuitable for the internal imaging due to the degradation of signal-to-noise ratios(SNR's). In the present study the inside-out probes for Magnetic Resonance Imaging (MRI) have been constructed in the three different shapes such as an anti-solenoidal, a saddle and a dual surface types which are positioned as close to the area as possible by putting the probe inside the tubelike sample to improve filling factor. RF-field distributions have also been calculated depending upon the geometrical changes of anti-solenoid probes. Moreover, the performance of the inside-out probes has been checked by measuring SNR's of the images acquired. The inside-out probes constructed in this study produced better SNR's and rf-field uniformity in the area close to the probes in comparing with any other commercial probes. There is a high possibility that the constructed probes in the present study are applicable to the diagnosis of human bodies.

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A Study for SNR Degradation of OFDM Demodulator Output by Impulsive Noise in Power Line Communication Channel (전력선 채널 Impulsive Noise에 의한 OFDM Demodulator 출력 SNR 열화에 관한 연구)

  • Oh, Hui-Myoung;Choi, Sung-Soo;Kim, Young-Sun;Kim, Kwan-Ho;Whang, Keum-Chan
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.1880-1881
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    • 2007
  • 전력선 통신 채널에는 특징적으로 충격 잡음이 존재하며, 전력선 통신 시스템의 성능 열화에도 많은 영향을 준다. 이는 일반적인 배경 잡음에 비해 많게는 수십 dB 이상의 레벨을 가지면서, 임의 시간적으로 발생함으로써 추정 및 제어 또한 어렵기 때문이며, 전력선 통신 시스템이 Mbps급으로 고속화 되면서 주파수 대역이 확장되고, 확장된 대역상에 다중 반송파를 이용하여 대용량의 데이터를 전송하는 변복조기법들이 적용됨에 따라, 시간 영역에서 비교적 짧은 시간 동안 존재하는 충격 잡음이 주파수 영역에서 사용 주파수 전체 대역상에 영향을 줌으로써 시스템 전체 성능 저하의 큰 요인이 되고 있다. 본 논문에서는 이러한 충격 잡음이 고속 전력선 통신 시스템에서 사용되는 OFDM(또는 DMT) 방식 수신기의 복조기 출력단 SNR에 미치는 영향을 분석 및 단순화하고, 시뮬레이션을 통해 검증한다.

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Evaluation of New Material Mammopad (맘모패드의 새로운 재질에 관한 평가)

  • Moon, Young-Ju;Kim, Sang-Hyun
    • Journal of radiological science and technology
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    • v.42 no.4
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    • pp.265-270
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    • 2019
  • Mammography is the most useful test for the early diagnosis of breast cancer. The MammoPad can be used for the purpose of reducing the pain felt by the patient due to the pressure of the breast. MammoPad cushion the pressure between the breasts and the equipment and reduce the patient's discomfort. A new material pad was fabricated to solve the problem of the H-pad which is currently in circulation. Quantitative evaluation of SNR and CNR and qualitative evaluation of imitation lesion using ACR Phantom were performed. In the quantitative evaluation, SNR and CNR of Non pad and Filter pad were not statistically significant.(p>0.05) In the qualitative evaluation, Fiber and Imitation lesion of H-pad and Filter pad were statistically significant(p<0.05), and all values of Calcification and Mass were not statistically significant. (p>0.05) In addition, Fiber, calcification, mass, and imitation lesion were not statistically significant in both Non pad and Filter pad.(p>0.05) Through this study, it was confirmed that the newly created Filter pad minimizes image quality degradation and can replace existing products.

Combined ML and QR Detection Algorithm for MIMO-OFDM Systems with Perfect ChanneI State Information

  • You, Weizhi;Yi, Lilin;Hu, Weisheng
    • ETRI Journal
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    • v.35 no.3
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    • pp.371-377
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    • 2013
  • An effective signal detection algorithm with low complexity is presented for multiple-input multiple-output orthogonal frequency division multiplexing systems. The proposed technique, QR-MLD, combines the conventional maximum likelihood detection (MLD) algorithm and the QR algorithm, resulting in much lower complexity compared to MLD. The proposed technique is compared with a similar algorithm, showing that the complexity of the proposed technique with T=1 is a 95% improvement over that of MLD, at the expense of about a 2-dB signal-to-noise-ratio (SNR) degradation for a bit error rate (BER) of $10^{-3}$. Additionally, with T=2, the proposed technique reduces the complexity by 73% for multiplications and 80% for additions and enhances the SNR performance about 1 dB for a BER of $10^{-3}$.

The Research of Reducing the Fixed Codebook Search Time of G.723.1 MP-MLQ (잡음 환경에서의 전송율 감소를 위한 G.723.1 VAD 성능개선에 관한 연구)

  • 김정진;박영호;배명진
    • Proceedings of the IEEK Conference
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    • 2000.06d
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    • pp.98-101
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    • 2000
  • On CELP type Vocoders G.723.1 6.3kbps/5.3kbps Dual Rate Speech Codec, which is developed for Internet Phone and videoconferencing, uses VAD(Voice Activity Detection)/CNG (Comfort Noise Generator) in order to reduce the bit rate in a silence period. In order to reduce the bit rate effectively in this paper, we first set the boundary condition of the energy threshold to prevent the consumption of unnecessary processing time, and use three decision rules to detect an active frame by energy, pitch gain and LSP distance. To evaluate the performance of the proposed algorithm we use silence-inserted speech data with 0, 5, 10, 20dB of SNR. As a result when SNR is over 5dB, the bit rate is reduced up to about 40% without speech degradation and the processing time is additionally decreased.

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Phase Offset Enumeration Method with Error Detection and Its Application to Synchronization of PN Sequences

  • Song Young-Joan
    • Journal of electromagnetic engineering and science
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    • v.5 no.1
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    • pp.26-30
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    • 2005
  • It is important to know phase offsets of PN(Pseudo Noise) sequences in spread spectrum communications since the acquisition is equivalent to making a phase offset between a receiving PN sequence and a PN sequence of local PN generator be identical. In this paper, a phase offset enumeration method for PN sequences with error detection, and its application to the synchronization are proposed. The phase offset enumeration for an n-tuple PN sequence and its error detection are performed when one period of the sequence is received. Once the phase offset of the receiving sequence is calculated, we can easily accomplish the synchronization by initializing shift registers of a local PN generator according to the phase offset value. The mean acquisition time performance of the proposed scheme was derived analytically. Since this synchronization scheme can be realized by using simple circuit and acquires very rapid acquisition in high SNR but shows performance degradation in low SNR, it can be especially useful in indoor and office environments.

Weighted Hadamard 변환을 이용한 Image Data 처리에 관한 연구

  • 소상호;윤재우;이문호
    • Proceedings of the Korean Institute of Communication Sciences Conference
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    • 1983.10a
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    • pp.68-72
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    • 1983
  • The Hadamard matrix is a symmetric matrix made of plus and minus ones as entries. There fore the use of Hadamard transform in the image processing requires only the real number operations and results in the computational advantages. Recently, However, certain degradation aspects have been reported. In this paper we propose a WH matrix which retains the main properties of Hadamard matrix. The actual improvement of the image transmission in the inner part of the picture has been demonstrated by the computer simulated image developments. The orthogonal transform offers a useful facility in the digital signal processing. As the size of the transmission block increases, however, the assigment of bits for each data must increase exponentially. Thus the SNR of the image tends to decline accordingly. As an attempt to increase the SNR, we propose the WH matrix whose elements are made of $\pm$1, $\pm$2, $\pm$3, and the unitform is 8$\times$8 matrix.

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Image Data Processing by Weighted Hadamard Transform. (Weighted Hadamard변환을 이용한 Image Data 처리에 관한 연구)

  • 이문호
    • Journal of the Korean Professional Engineers Association
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    • v.16 no.4
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    • pp.15-19
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    • 1983
  • Therefore the use of Hadamard transform in the image processing requires only the real number operations and results in the computational advantages. Recently, however, certain degradation aspects have been reported. In this paper we propose a WH matrixtwhich retains the main properties of Hadamard matrix. The actual improvement of the image transmission in the inner part of the picture has been demonstrated by the computer simulated image developments. The orthogonal transforms such as Hadamard transform offers a useful facility in the digital signal processing. As the size of the transmission block increases, however, the assignment of bits for each data must increase exponentially. Thus the SNR of the image tends to decline accordingly. As an attempt to increase the SNR, we propose the WH matrix whose elements are made of ${\pm}$1, ${\pm}$2, ${\pm}$3, ${\pm}$4, and the unitform is 8${\times}$8 matrix.

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Viterbi-based Decoding Algorithm for DBO-CSS

  • Yoon, Sang-Hun;Jung, Jun-Mo
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2011.10a
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    • pp.646-649
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    • 2011
  • Differential detection algorithm for DBO-CSS based on maximum signal energy detection (MSED) using viterbi algorithm is proposed. In order to mitigate SNR degradation caused by differential decoding, a modified viterbi algorithm with so called correlation metric (CM) in every state is proposed. It is shown that the performance gain of the proposed algorithm when compared with that of the conventional differential detection with the block decoding algorithm is about 2.5dB at BER = $10^{-5}$.

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Detection Performance of Noncoherent Radar: MIMO Radar, Phased Array Radar, Directional MIMO Radar (비동기식 레이더의 검출 성능 비교: MIMO 레이더, 위상 배열 레이더, 지향성 MIMO 레이더)

  • An, Chan-Ho;Yang, Jang-Hoon;Pak, Ui-Young;Ryu, Young-Jae;Han, Duk-Chan;Kim, Dong-Ku
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.12B
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    • pp.1752-1757
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    • 2011
  • In a traditional phased array radar, closely spaced antenna elements transmit a scaled version of single waveform to maximize the signal energy. On the contrary, a multiple-input multiple-output (MIMO) radar consists of widely separated antennas and transmits an arbitrary waveform from each antenna element. These waveforms and spatial diversity enable superior capabilities compared with phased array radar. At high signal-to-noise ratio (SNR), the detection performance of the MIMO radar is better than the phased array radar due to the diversity gains. However, the phased array radar outperforms the MIMO radar at low SNR, due to the energy maximization. In this paper, we investigate the compromised scheme between the MIMO radar and the phased array radar. Employing the MIMO radar equipped with phased array elements, the compromised scheme achieves both array gain and diversity gain. Also, we compare the performance degradation when the steering direction is incorrect.