• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.3
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• pp.80-90
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• 1995

The scattering parameters of a microstrip single line, a right-angle bend and a coupled line are calculated using the multiport network model for the frequency range from 1 to 18 GHz. The single line is analyzed using the planar waveguide model. The right-angle bend is broken into two rectangular segments, and each segment is analyzed in a similar fashion as the single line. Impedance matrices corresponding to the two segments are combined by the segmentation method. In the analysis of elec- tromagnetic coupling of the coupled line, a new method is employed resulting in much less computation time than those previous methods involving Green's functions. A good agreement between the numerical results for the three structures and those from SuperCompact reveals the usefulness of the multiport network medel in analyzing complicated mirostrip single and coupled line discontinuities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1846-1855
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• 2015

In this paper, a precise relative positioning with TD(time differenced) carrier phase measurements from a low-cost GNSS(Global Navigation Satellite System) receiver is proposed and analysed. The proposed method is using carrier phase measurement from a single GNSS receiver that reference receiver is not required and stand alone positioning is possible. TD operation removes the troublesome integer ambiguity resolution problem, and if the time interval is short, other error, such as, ionospheric, tropospheric delay and ephemeris error are effectively eliminated. The error analysis of the proposed method shows that a precise and positioning with carrier phase is possible. The implemented system is evaluated using a real car experiments. The results show that the horizontal positioning error was less than 3m during 10 minutes experiments, which is 4 times more precise than the results of normal code based absolute positioning.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.6
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• pp.582-589
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• 2002

This paper presents 12.2 GHz ~ 12.7 GHz frequency band reflection type 5-bit digital phase shifter with constant insertion loss property that was fabricated with relatively low cost's InGaAs HEMT for amplifier. The unavoidable large insertion loss difference between on and off states of HEMT, when it is designed by conventional design theory based on ideal switching device, is removed by transforming the HEMT impedances at on and off states to other proper values connecting a certain length transmission line to HEMT and then applying the conventional design theory. The fabricated 5-bit digital phase shifter shows very good insertion loss properties of less than 1.5 dB insertion loss difference and -4.5 dB ~ -6 dB insertion loss in 35 phase steps at 12.2 GHz ~ 12.7 GHz. These results verify the design method presented in this paper, which is useful to design phase shifter of constant insertion loss with non-ideal switching device.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.1 s.116
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• pp.1-6
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• 2007

This paper presents an equal 3-way planar-type power divider. In conventional 3-way Wilkinson dividers, it has been difficult to realize the circuit because of the crossover of isolation resistors. In the proposed divider, the isolation resistors can be easily attached to the planar structure of the divider. In addition, no phase difference is observed at output ports without extra line compensation because of its symmetric structure. The fabricated 3-way divider has a greatly improved bandwidth by 160 % in $S_{11}$, 22.4 dB, min of isolation, and in phase characteristics between output ports at 2.4 GHz of center frequency from measurement.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.5
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• pp.677-684
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• 2021

This paper presents a time-to-digital converter for measuring absolute time differences. The time-to-digital converter was designed and fabricated in 0.18-um CMOS technology and it can be applied to Light Detection and Ranging system which requires long time-cover range and 50ps time resolution. Since designed time-to-digital converter adopted the reference clock of 625MHz generated by phase locked loop, it could have absolute time resolution of 50ps after automatic calibration and its cover range was over than 800ns. The time-to-digital converter adopted a counter and chain delay lines for time measurement. The counter is used for coarse time measurement and chain delay lines are used for fine time measurement. From many times experiments, fabricated time-to-digital converter has 50 ps time resolution with maximum INL of 0.8 LSB and its power consumption is about 70 mW.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.1
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• pp.68-77
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• 2018

In order to analyze the overall characteristics of the lunar orbiter, the Variable Coast method, which can be launched everyday, is applied to the 3.5 phasing loop transfer trajectory. The mission scenario for the entire process from launching to entering the lunar orbit is set up and performed simulation by selecting the launch pad and launch vehicle. In particular, the SEM(Satellite-Earth-Moon) angle defined in Earth-Moon rotating frame is an important constraint to comprehensively evaluate the 3.5 phasing loop transfer trajectory. The simulation using SEM angle is analyzed from various viewpoints such as launch epoch, coast duration, perigee altitude and ${\Delta}V$ not only trans-lunar trajectory but lunar orbit insertions and the optimum SEM angle is suggested in this study. It is expected that this results will be helpful to evaluate the characteristics of the 3.5 phasing loop transfer trajectory according to the launch vehicle selection by comparison with Fixed Coast analysis results in the future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.12
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• pp.3235-3245
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• 1996

A DDFS(Direct Digital Frequency Synthesizer) used in spread spectrum communication systems must need fast switching speed, high resolution(the step size of the synthesizer), small size and low power. The chip has been designed with four parallel sine look-up table to achieve four times throughput of a single DDFS. To achieve a high processing speed DDFS chip, a 24-bit pipelined CMOS technique has been applied to the phase accumulator design. To reduce the size of the ROM, each sine ROM of the DDFS is stored 0-.pi./2 sine wave data by taking advantage of the fact that only one quadrant of the sine needs to be stored, since the sine the sine has symmetric property. And the 8 bit of phase accumulator's output are used as ROM addresses, and the 2 MSBs control the quadrants to synthesis the sine wave. To compensate the spectrum purity ty phase truncation, the DDFS use a noise shaper that structure like a phase accumlator. The system input clock is divided clock, 1/2*clock, and 1/4*clock. and the system use a low frequency(1/4*clock) except MUX block, so reduce the power consumption. A 107MHz DDFS(Direct Digital Frequency Synthesizer) implemented using 0.8.mu.m CMOS gate array technologies is presented. The synthesizer covers a bandwidth from DC to 26.5MHz in steps of 1.48Hz with a switching speed of 0.5.mu.s and a turing latency of 55 clock cycles. The DDFS synthesizes 10 bit sine waveforms with a spectral purity of -65dBc. Power consumption is 276.5mW at 40MHz and 5V.

• 전자공학회논문지 IE
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• v.47 no.4
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• pp.39-47
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• 2010

This paper proposes a numerical analysis to prove that the performance of the differential phase detections (DPDs) with the decision feedback, such as the decision feedback DPD (DF-DPD) and the DPD with recursively generated phase reference (DPD-RGPR), approach the performance of the coherent detection with differential decoding. The conventional differential phase detection for M-ary DPSK can make the receiver architecture simple, while it can make the bit-error rate (BER) performance poor because of the previous noisy phase as a reference phase. To improve the BER performance of the conventional differential detection, multiple symbol differential detection methods, including DF-DPD and DPD-RGPR, have been proposed. However, the studies on the analysis and on the comparison of these methods have been little performed. Then, this paper mathematically intends to analyze and compare the performance of the DPDs with the decision feedback. The analysis results show that the DPDs with the decision feedback can have the performance equal to that of the coherent detection with differential decoding and be available for the noncoherent detection in the improved performance. Considering the hardware complexity, the DPD RGPR with the simple detection process by using the recursively generated phase reference can be more simply implemented than the DF-DPD based on the architecture whose complexity increases according to the increasing detection length.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.12
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• pp.16-21
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• 2007

In this paper, the dual-band voltage-controled oscillator (VCO) using the composite right/left-handed (CRLH) transmission line (TL) and the tunable negative resistance based on the fin diode is presented. It is demonstrated that the CRLH TL can lead to metamaterial transmission line with the dual-band tuning capability. The dual-band operation of the CRLH TL is achieved by the frequency offset and the phase slope of the CRLH TL, and the frequency ratio of the two operating frequencies can be a non-integer. Each frequency band of VCO has to operate independently, so we have used the tunable negative resistance based on the pin diode. When the forward bias has been into the pin diode, the phase noise of VCO is $-108.34\sim-106.67$ dBc/Hz @ 100 kHz in the tuning range, $2.423\sim2.597$ GHz, whereas when the reverse bias has been fed into the pin diode, that of VCO is $-114.16\sim-113.33$ dBc/Hz @ 100 kHz in the tuning range, $5.137\sim5.354$ GHz.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.538-544
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• 2000

A phased array ultrasonic nondestructive inspection system is being developed to obtain images of the interior of steel structures by modifying a medical ultrasound imaging system. The medical system consists of 64 individual transceiver channels that can drive 128 array elements. Several modifications of the system were required mainly due to the change of sound speed. It was necessary to fabricate array transducers for steel structure and to obtain A-scan signal that is necessary for the nondestructive testing. Boundary diffraction wave model was used for the prediction of radiation beam field from array transducers, which provided guidelines to design array transducers. And a RF data acquisition board was fabricated for the A-scan signal acquisition along a selected un line within an image. For the proper beam forming in the transmission and reception for steel structure, delay time was controlled. To demonstrate the performance of the developed system and fabricated transducers, images of artificial specimens and A-scan signals for selected scan lines were obtained in a real time fashion.