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Author: search.filters.author.Chivapreecha, S.

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    Microwave sensor for defected fruit classification
    (2016-03-07)
    Leekul, P.
    ;
    Chivapreecha, S.
    ;
    Krairiksh, M.
    This paper presents a microwave sensor operating at the frequency of 2.45 GHz that can detect defected fruits. In this work, orange is used as an example. Granulation of orange is detected by measuring mean and standard deviation of the magnitudes of S-parameters of the orange at different positions. From the simulated S-parameters of patch antennas surrounding the fruits, it was found that the reflected signal from the fruit and the coupled signal to the antenna oriented perpendicular to the fruits provide the obvious variation and can be used as indicators for justification. This cost effective sensor is a good candidate for fruit classification.
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    An efficient filter structure for multiplierless sobel edge detection
    (2009-11-12)
    Pradabpet, C.
    ;
    Ravinu, N.
    ;
    Chivapreecha, S.
    ;
    Knobnob, B.
    ;
    Dejhan, K.
    This paper presents a multiplierless Sobel edge detection filter structure based on the gradient of Gaussian lowpass filter concept. This concept is same as the idea that used for evaluation of Sobel edge detection kernels. The proposed Sobel edge detection filter structure consists of 4 sets of the so-called lowpass-type 2nd order 1-D DPF (Discrete Pascal Filter) and the filter structure does not need any multipliers, only 14 adders are needed for realization. Consequently, the high efficiency multiplierless Sobel edge detector can be achieved. © 2009 IEEE.
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    A new PAPR reduction technique for OFDM-WLAN in 802.11a systems
    (2008-12-24)
    Pradabpet, C.
    ;
    Eupree, K.
    ;
    Chivapreecha, S.
    ;
    Dejhan, K.
    In this paper, we proposed a new PAPR reduction technique using selective mapping (SLM) cascade with adaptive peak power reduction (APPR) methods. This technique is used in a system based on Orthogonal Frequency Division Multiplexing (OFDM). OFDM has many orthogonally modulated sub-carriers which unexpectedly produce high peak to average power ratio (PAPR). The high PAPR will occasionally reach the amplifier saturation region and therefore result in signal distortion, which causes bit error rate (BER) degradation. The proposed method, a sequence of input data is rearranged by SLM for the reduction of PAPR and then fed into the APPR process in the proposed system. The APPR method controls the peak levels of the modulation signal by an adaptive algorithm. It reduces modulation signals over a predefined range. The parameter for simulation used standard WLAN in IEEE 802.11a system. In simulation results, the proposed method shows the improvement on PAPR, power spectrum density(PSD) and high performance BER compared with conventional APPR. © 2008 IEEE.
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    PAPR reduction in OFDM systems using SLM cascade with APPR methods
    (2008-10-06)
    Eupree, K.
    ;
    Chivapreecha, S.
    ;
    Dejhan, K.
    ;
    Pradabpet, C.
    In this paper, we proposed a new PAPR reduction technique using selective mapping (SLM) cascade with adaptive peak power reduction (APPR) methods. This technique is used in a system based on Orthogonal Frequency Division Multiplexing (OFDM). OFDM has many orthogonally modulated subcarriers which unexpectedly produce a peak to average power ratio (PAPR) and tend to reduce the power efficiency of a RF amplifier. A sequence of input data is rearranged by SLM for the reduction of PAPR and then fed into the APPR process in the proposed system. The APPR method controls the peak levels of the modulation signal by an adaptive algorithm. It reduces modulation signals over a predefined range. In simulation results, the proposed method has shown better PAPR reduction compared to the SLM and the APPR. ©2008 IEEE.
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    Design and implementation of biquad digital filter
    (2003-01-01)
    Pradabpet, C.
    ;
    Yimman, S.
    ;
    Hinjit, W.
    ;
    Chivapreecha, S.
    ;
    Dejhan, K.
    This paper presents a design and implementation of biquad digital filter based on poles-zeros placement on a unit circle of z-plane. The proposed digital filter can be given three frequency-responses as lowpass filter (LPF), highpass filter (HPF) and bandpass filter (BPF) at the same time. In the design process the Matlab program was used, for real world implementation by using TMS320C31 DSP board. The experimental results shown by the dynamic signal analyzer to indicate that the obtained frequency responses give the same results as design specifications.