• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.7 s.337
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• pp.49-56
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• 2005

In this paper, we describe a solution to improve the effects of the transmitter leakage signals on the frequency modulated continuous wave (FMCW) radar with a single antenna configuration. We analyze characteristics of the IF noise caused by insufficient isolation between transmitter and receiver. The magnitude of the intermediate frequency (IF) noise from a front-end can be reduced by matching the LO signal delay time with that of the largest leakage source. Because the IF noise has periodic singularities at nT$_{m}$/2, t=0,1,2$\cdots$, we find that spectrum of the IF noise due to the leakage signals is very similar to that of the VCO moduation signal except low frequency elements in the vicinity of DC. Based on the studies, we fabricated a W-band homodyne FMCW radar sensor and verified the proposed solution. The results are applicable to design of the homodyne FMCW radar with a single antenna configuration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.251-256
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• 2001

An error probability analysis is performed far a hybrid DS/SFH spread-spectrum system using minimum shift keying(MSK) modulation. The channel is assumed to be a Rayleigh fading channel with partial-band noise interference. Expressions are derived for the bit error rate(BER) in the context of Rician and Rayleigh fading channels, as a function of the average signal-to-noise ratio(SNR) $E_b/N_0$, the average signal-to- interference ratio(SJR) $E_b/N_J$, and channel parameters. As a result, in the fading channel with large Rician factor, K, which denotes the ratio of power of the direct and the diffused components, the partial-band interference is the worst case. On the other hand, in Rayleigh fading channel(K=0), the full-band interference($\rho$=1) brings the system to the worst case. Performance comparisons among various channels show that the factor K has much large effect on overall performance. For example, in conditions of $\rho$=0.1 and BER=$10^-2$, the system in Rician channel with K=10 requires more 1.9 dB SNR than that in AWGN channel, whereas it is less 5 dB SNR than that in the Rayleigh channel with K=0.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.707-714
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• 2012

After a single-stage, second-order, multiple-feedback ${\Delta}-{\Sigma}$ modulator and a two-stage, second-order MASH ${\Delta}-{\Sigma}$ modulator were analyzed and simulated using Simulink and Matlab and their characteristics were compared, the following result was obtained: 1) The two ${\Delta}-{\Sigma}$ modulators do not have group delay distortion. 2) The characteristics of the noise shaping are nearly identical. As a result of the noise shaping, the power spectral densities have slope of 40 dB/dec. 3) There was no spurious tone. 4) The input range of the two modulators is from -1 to +1 in common. 5) Because the output of the two-stage MASH modulator is 2-bits (4-levels), design of frequency dividers and charge pumps of PLL are more demanding.

• Korean Journal of Remote Sensing
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• v.34 no.3
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• pp.535-543
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• 2018

Recently, level meters have been associated with the safety and maintenance of industrial sites and require a wide measurement range. Generally, to ensure the measurement range of the level meter, the measurement environment is improved to reduce the noise or to compensate the distortion of the signal through signal processing. The noise of FMCW (Frequency Modulated Continuous Wave) radar level meter or the distortion of the signal affects the near region characteristics of the level gauge, resulting in a reduction of the minimum detection distance. In this paper, an equalizer filter considering characteristics of window function and bit spectrum is applied to remove the noise in the near region of the level meter to improve the minimum detection distance performance and to improve the measurement reliability in the vicinity of the level meter, which is relatively difficult to detect, we want to improve the detection range.

• The Journal of the Korea Contents Association
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• v.11 no.12
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• pp.552-559
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• 2011

In this paper, a new image watermarking algorithm is proposed which can hide specific information of an ID card's owner in photo image for preventing ID's photo forgery. Proposed algorithm uses the image segmentation and the correlation peak position modulation of spread spectrum. The watermark embedded in photo ensures not only robustness against printing and scanning but also sufficient information capacity hiding unique number such as social security numbers in small-sized photo. Another advantage of proposed method is extracting accurate information with error tolerance within some rotation range by using $2^h{\times}2^w$ unit sample space not instead $1{\times}1$ pixels for insertion and extraction of information. 40 bits information can be embedded and extracted at $256{\times}256$ sized ID photo with BER value of 0 % when the test condition is 300dpi scanner and photo printer with 22 photos. In conclusion, proposed algorithm shows the robustness for noise and rotational errors occured during printing and scanning.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.8A
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• pp.671-678
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• 2005

This paper proposed symbol rate method which does not require a priori knowledge on the symbol rate and simplified modulation identification method to classify BPSK, QPSK, 8PSK signal. In order to estimate the unknown symbol rate, sliding FFT and simple moving average to estimate the spectrum of the signals is utilized, and sliding window and decimation, LPF blcok to estimate the proper symbol rate is used. Although conventional modulation ID method must use SNR value as the test statistics, the receiver cannot estimate the SNR value since the receiver cannot know the modulation type at the start of communication, and bit resolution is high due to using nonlinear function such as log, cosh. Therefore, we proposed the simplified fixed SNR value method. The performance of symbol rate estimation and modulation ID is shown using Monte Carlo computer simulation. This paper show that symbol rate estimation also has good performance in low SNR, and proposed simplified fixed SNR method has almost equivalent performance compared to conventional method.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.309-316
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• 2007

We demonstrate the wavelength swept source and signal processing for the frequency domain optical coherence tomography. The laser output performance is improved by using a semiconductor optical amplifier with a booster amplifier. The laser generates 14 mW of average power of which wavelength shift in the lasing spectral shape is compensated. Adopting a Fabry-Perot etalon and digital signal processing, the broadening of the beat frequency due to the variance of wavelength-sweep-velocity is calibrated. The optical coherence tomography system shows 154.4 kHz of axial scanning speed, 0.95mm of depth range, and $12{\pm}0.37{\mu}m$ of axial resolution.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.8 s.338
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• pp.53-60
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• 2005

Recently, sub-micron CMOS technologies have taken the place of III-V materials in a number of areas in integrated circuit designs, in particular even for the applications of gjgabit optical communication applications due to its low cost, high integration level, low power dissipation, and short turn-around time characteristics. In this paper, a four-channel transimpedance amplifier (TIA) array is realized in a standard 0.35mm CMOS technology Each channel includes an optical PIN photodiode and a TIA incorporating the fully differential regulated cascode (RGC) input configuration to achieve effectively enhanced transconductance(gm) and also exploiting the inductive peaking technique to extend the bandwidth. Post-layout simulations show that each TIA demonstrates the mid-band transimpedance gain of 59.3dBW, the -3dB bandwidth of 2.45GHz for 0.5pF photodiode capacitance, and the average noise current spectral density of 18.4pA/sqrt(Hz). The TIA array dissipates 92mw p in total from a single 3.3V supply The four-channel RGC TIA array is suitable for low-power, high-speed optical interconnect applications.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.7-12
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• 2014

The data forwarding transmission is an important function of the relay in cooperative communication in wireless communication systems. However, additional relay cause the waste of power consumption and cost. Therefore, in this paper, we consider how to use the user mobile devices in stead of relays to deal with this problem. In this paper, we proposed the protocol that divide each relay into two states of idle and non-idle. The receiver has two functions of base station and user mobile device. In this case, it is possible that no additional cost, and improve the spectral efficiency and network capacity. We verified BER performance for the proposed protocol over Rayleigh fading through Monte-Carlo simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.3
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• pp.27-33
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• 2008

In this paper, we propose a cognitive beamforming scheme for coexistence of CR (Cognitive Radio) and IR (Incumbent Radio) systems. In order to maintain the priority of the IR in spectrum utilization the proposed cognitive beamforming scheme needs to have the CR not cause any interference to the IR systems occupying the same frequency band at the same time. In addition the proposed scheme has to provide maximum channel gain to the CRU (CR User) in a boundary of satisfying the former criterion. For this purpose, the proposed scheme does not cause any interference to the IRU (IR User), while the CRU is served without additional radio resource consumption. From simulation, we confirmed that when using the proposed scheme the CRU does not interfere with the IRU and there is little bit error rate performance degradation of the CRU as compared to that of the ideal beamforming system, which does not consider the IR priority.