• Journal of the Korean Institute of Telematics and Electronics
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• v.12 no.3
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• pp.30-36
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• 1975

Distortions are analyzed and compared for two TDM channel expansion methods- periodic sample skipping and sampling frequency reduction. Signal is assumed to be stationary random signal with zero.mean. Channel noise and interference are not considered in the analysis. For speech signal, it is shown that the periodic sample skipping method could be a better choice under practical design constraints.

• ETRI Journal
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• v.45 no.2
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• pp.277-290
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• 2023

This paper proposes a method that can reduce the complexity of a system matrix by analyzing the characteristics of a pseudoinverse matrix to receive a binomial frequency division multiplexing (BFDM) signal and decode it using the least squares (LS) method. The system matrix of BFDM can be expressed as a band matrix, and as this matrix contains many zeros, its amount of calculation when generating a transmission signal is quite small. The LS solution can be obtained by multiplying the received signal by the pseudoinverse matrix of the system matrix. The singular value decomposition of the system matrix indicates that the pseudoinverse matrix is a band matrix. The signal-to-interference ratio is obtained from their eigenvalues. Meanwhile, entries that do not contribute to signal generation are erased to enhance calculation efficiency. We decode the received signal using the pseudoinverse matrix and the removed pseudoinverse matrix to obtain the bit error rate performance and to analyze the difference.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2209-2212
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• 2003

In this paper, we propose the method to extract the important frequency bands from the EMG signal, and for generation of feature vector using the important frequency bands. The EMG signal is measured with 4 sensor and is recorded as 4 channel’s time series data. The same frequency bands from 4 channel’s frequency components are selected as the important frequency bands. The feature vector is calculated by the function formed using the combination of selected same important frequency bands. The EMG signals acquired from seven wrist motion type are recognized by changing into the feature vector formed. Then, the extraction and generation is performed by using the double combination of the genetic algorithm (GA) and the neural network (NN). Finally, in order to illustrate the effectiveness of the proposed method, computer simulations are done.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2628-2635
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• 2010

This paper analyzes the detection probability of FMCW (Frequency Modulated Continuous Wave) radar based on Doppler frequency and analog-digital converter bit and designs and implements signal processing part of FMCW radar. For performance evaluation, the FMCW radar system consists of a transmitted part and a received part and uses AWGN channel. The system model is verified through analysis and simulation. Frequency offset occurs in the received part caused by the mismatching between the received signal and the reference signal. In case of Doppler frequency less than about 38KHz, performance degradation of detection does not occur in FMCW radar with 75cm resolution The analog-digital converter needs at least 6 bit in order not to degrade the detection probability. And, we design and implement digital signal processing part based on DDS chip of digital transmitted signal generator for FMCW radar.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1058-1063
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• 2010

In this paper, we designed self-frequency synchronizing circuit using image rejection mixer(IRM) and single-sideband(SSB) up-converter which can effectively eliminate the image frequencies occurred in multi-channel super-heterodyne receivers and help us to match inter-channel phase. Also the self-frequency synchronizing circuit simplifies system because there need no extra devices for making intermediate frequency(IF) by creating the local signal within several nanoseconds by means of generating the same frequency of IF signal and modulating radio frequency(RF) signal. We adopt the limiting amplifier for the purpose of protecting the circuit from spurious signals which come from the front end side having wide instantaneous bandwidth characteristics and constantly injecting same level into the input local signal of IRM. The IRM we fabricated has image rejection ratio of 27dB, which is good over 7dB for foreign company's. Also, the SSB up-converter we fabricated has 1dB compression point of 18dBm, which is good over 16dB for foreign company's. And the size is compact about one-forth.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2189-2196
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• 2009

Theoretical analysis is presented for expending of the usable frequency range of optoelectronic mixing detection in the radio over fiber network system. We define the normalized gain to evaluate the performance of the optical mixing detection, and conform the possibilities of detection for the high frequency signals beyond the cutoff frequency of a photodiode. Optical mixing detection mechanism is analyzed by solving the continuity equation for the carriers of a photodiode. The normalized gain is independent on the signal frequency and the frequency difference between the optical signal and the local signal. Also, the amplitude of the local signal and the bias voltage are needed to be optimized at the same time in order to maximize the normalized gain.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.259-268
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• 2007

A knock detection circuit that is based on the signal of an accelerometer installed on the engine block of a spark ignition automotive engine has a band-pass filter with a certain frequency as a parameter to be calibrated. A new statistical method for the determination of the frequency which is the most suitable for the knock detection in real-time applications is proposed. The method uses both the cylinder pressure and block vibration signals and is divided into two steps. In both steps, a new recursive trigonometric interpolation method that calculates the frequency contents of the signals is applied. The new trigonometric interpolation method developed in this paper improves the performance of the Discrete Fourier Transformation, allowing a flexible choice of the size of the moving window. In the first step, the frequency contents of the cylinder pressure signal are calculated. The knock is detected in the cylinder of the engine cycle for which at least one value of the maximal amplitudes calculated via the trigonometric interpolation method exceeds a threshold value indicating a considerable amount of oscillations in the pressure signal; this cycle is selected as a knocking cycle. In the second step, the frequency analysis is performed on the block vibration signal for the cycles selected in the previous step. The knock detectability, which is an individual cylinder attribute at a certain frequency, is verified via a statistical hypothesis test for testing the equality of two mean values, i.e. mean values of the amplitudes for knocking and non-knocking cycles. Signal-to-noise ratio is associated in this paper with the value of t-statistic. The frequency with the largest signal-to-noise ratio (the value of t-statistic) is chosen for implementation in the engine knock detection circuit.

• Korean Journal of Applied Biomechanics
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• v.27 no.4
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• pp.263-268
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• 2017

Objective: The purpose of this study was to show differences in impact variables between treadmills with (treadmills B, C, and D) and treadmills without a shock-absorbing function (treadmill A) to propose the development of a treadmill with improved or added shock-absorbing function to reduce impact shock. Method: Thirteen male students in their twenties who had habitual rear foot strike during running ran on four treadmills at 2.67 m/sec while ankle and neck acceleration data were collected. The magnitude of the ankle and neck acceleration peaks and peak positive ankle acceleration were calculated. The power spectral density of each signal was calculated to transform the ankle and neck accelerations in the frequency domain. Results: The peak positive ankle acceleration on treadmill B was significantly lesser than that on treadmills A and D, and that on treadmill C was significantly less than that on treadmill A (p < .01). Peak positive neck acceleration was not statistically different between the treadmills. The frequencies of the peak power of the ankle and neck acceleration signal within the lower and higher frequency ranges were not statistically different between the treadmills. The signal power magnitude of the ankle in higher frequency ranges on treadmill B was significantly less than that on treadmills A, C, and D (p < .01). The signal power magnitude of the ankle in higher frequency ranges was not statistically different between the treadmills. The signal power magnitudes of the neck acceleration signal within the lower and higher frequency ranges were not statistically significantly different between the treadmills. Conclusion: Our results indicate that the shock-absorbing function of a treadmill plays a role in reducing impact shock. Therefore, in future treadmill development, shock-absorbing function should be improved or incorporated to reduce impact shock to the body.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.725-733
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• 2006

In this paper, we propose an algorithm which makes the frequency of output signal synchronize with frequency of input signal in Equalization Digital On-channel Repeater (EDOCR) system which was proposed to overcome the disadvantage of conventional Digital On-Channel Repeater (DOCR). Also, we verify the algorithm by using the mathematical equivalent model and analysis the performance by implying the algorithm to EDOCR. The main idea is to use the frequency offset information, which comes from carrier recovery in the receiving part of EDOCR, when the demodulated symbol is re-modulated in transmitting part. Based on the proposed algorithm, EDOCR not only makes the output signal synchronized with input signal in frequency but also emit the output signal which satisfies the ATSC transmission standard without additional equipments such as Global Positioning System (GSP).

• Journal of Biosystems Engineering
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• v.25 no.5
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• pp.351-358
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• 2000

This study was conducted to develop a speed control system of a DC motor which drove a barley seeder mounted on a combine harvester. Barley seeder mounted on a combine has been known to reduce labor and cost of barley cultivation. However, development of the seeder has been unsuccessful because the combine, a dedicated rice and barley harvester has not enough space and proper power take-off for barley seeder. To develop a barley seeder, small powered motor speed controller was required. A proximity sensor for detecting working speed of the combine and a programmable one board microprocessor was used to develope a control system. Motor parameters and motor constant, relationship between seeding rate, motor speed, groove volumes of a tested roller, torque were measured. The proximity sensor sent a frequency signal to the microprocessor. In laboratory experiments, the excitation voltage of the motor was shown not to be proportional to the size of pulse width (duty ratio). A table transforming frequency signal, that represented for working speed to proper pulse width was developed from seeding rate experiments. However, seeding rate at low frequency signal was not proportional to the working speed. Seeding rate control proportional to the frequency signal was achieved by shifting of the frequency signal.