• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.4
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• pp.535-543
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• 2002

In this paper, we propose $\pi$/8 shift 8PSK and trellis-coded $\pi$/8 shift 8PSK-OFDM techniques by applying $\pi$/4 shift QPSK to trellis-coded modulation (TCM), and performing signal set expansion and set partition correspondingly based on phase difference. In our Viterbi decoding algorithm, up to L phase differences from successively received symbols are employed in the new branch metrics. Such sliding multiple symbol detection (SMSD) method provides improved bit-error-rate (BER) performance in the differential detection of the trellis-coded $\pi$/8 shift 8PSK-OFDM signals. The performance improvements are achieved for different communication channels without sacrificing bandwidth and power efficiency. It thus makes the proposed modulation and sliding detection scheme more attractive for power and band-limited systems.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1108-1121
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• 2019

The non-inverting buck-boost converter (NIBB) is a step-up and step-down DC-DC converter suitable for wide-input-voltage-range applications. However, when the input voltage is close to the output voltage, the NIBB needs to operate in the buck-boost mode, causing a significant efficiency reduction since all four switches operates in the PWM mode. Considering both the current stress limitation and the efficiency optimization, a novel design methodology for the optimal phase-shift modulation of a NIBB in the buck-boost mode is proposed in this paper. Since the four switches in the NIBB form two bridges, the shifted phase between the two bridges can serve as an extra degree of freedom for performance optimization. With general phase-shift modulation, the analytic current expressions for every duty ratio, shifted phase and input voltage are derived. Then with the two key factors in the NIBB, the converter efficiency and the switch current stress, taken into account, an objective function with constraints is derived. By optimizing the derived objective function over the full input voltage range, an offline design methodology for the optimal modulation scheme is proposed for efficiency optimization on the premise of current stress limitation. Finally, the designed optimal modulation scheme is implemented on a DSPs and the design methodology is verified with experimental results on a 300V-1.5kW NIBB prototype.

• Korean Journal of Materials Research
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• v.3 no.1
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• pp.3-6
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• 1993

Abstract We report the result of measurement for the ferro-to paramagnetic phase transition temperature shift of a gadolinium film. The phase transition temperature has been determined by measuring the resistance changes of film as function of temperature. At the ferro-to paramagnetic transition temperature, we can observe the inflection point of resistance changes. The phase transition temperature of 6600$\AA$ gadolinium film is found to be shifted by 4 $\pm$ 0.$3^{\circ}C$ below the transition temperature of bulk gadolinium. This is the first measurement for the phase transition temperature shift of ferromagnetic gadolinium film. This and further results might give a milestone in resolving the differences between experiments and finite-size scaling theory.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.2
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• pp.82-89
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• 2018

This paper presents a novel prototype of dual mode control based phase shift ZVS PWM high frequency load resonant inverter with lossless snubber capacitors in addition to a single active auxiliary resonant snubber for electromagnetic induction heating(IH) foam metal based consumer fluid dual packs(DPA) heater. The operating principle in steady state and unique features of this voltage source soft switching high frequency inverter circuit topology are described in this paper. The lossless snubber and auxiliary active resonant snubber assisted constant frequency phase shift ZVS PWM high frequency load resonant inverter employing IGBT power modules actually is capable of achieving zero voltage soft commutation over a widely specified power regulation range from full power to low power. The steady state operating performances of this dual mode phase shift PWM series load resonant high frequency inverter are evaluated and discussed on the basis of simulation and experimental results for induction heated foam metal heater which is designed for compact and high efficient moving fluid heating appliance in the consumer pipeline systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6C
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• pp.453-461
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• 2012

This paper proposes an improved phase estimation method for AM(Amplitude Modulation) range measurement system. The previous phase estimation method induces errors by Doppler shift of a moving target. The proposed method compensates phase estimation error through the ADC(Adaptive Doppler Correction) to take the Doppler shift, thus can improve distance measurement accuracy. When compared with the previous method through simulation results, the Doppler shift compensation and accuracy are improved by 94.7% and 50%, respectively. Target distance error in an acoustic tank is estimated to be 7.7cm, which confirms that the proposed method can be used to estimate the distance in the marine environment.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.4
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• pp.13-22
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• 2018

In this paper, double encryption technology of image based on scramble operation and phase-shifting digital holography is proposed. For the purpose, we perform first encryption digitally using scramble operation for the to be encrypted image, and perform phase modulation to the first encrypted image. Finally, we get the secondary encryption information through the interference between the phase-shifted reference wave and phase modulated image. The decryption process proceeds in the reverse order of the encryption process. The original image is reconstructed by digitally decoding the two encrypted images through a phase shift digital holography technique that appropriately performs arithmetic processing, phase-demodulating and then using the encryption key information used in the scramble operation. The proposed cryptosystem can recover the original image only if both the key information used in the scramble operation, the distance information used in the phase shift digital holography technique, and the wavelength of the light source are known accurately.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.89-92
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• 2001

In this paper, as a study of programmable software radio digital communication, we implemented ASK(Amplitude Shift Keying), FSK(Frequency Shift Keying), and PSK(Phase Shift Keying) modulation using programmable software(algorithm) of DSP(Digital Signal Processor). Moreover, it is possible to select one of those three modulation methods by realizing on single DSP. We adopted Motorola DSP56002 and Crystal CS4215(A/D and D/A converter) for our purpose. The DSP56002 is 24-bit and operates 20 MIPS at 40 MHz, and the CS4215 is 16-bit and supports the maximum 50 kHz sampling frequency.

• Journal of Drive and Control
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• v.17 no.3
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• pp.47-56
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• 2020

As a shift control of automatic transmission was managed with the electronic control unit (ECU), shift quality which is a measure of shift shock during gear change has markedly improved. However, the initial clutch pressure control of the clutch filling phase should continue to rely on the predetermined control input since the input and output speeds are unchanged until the shifting process attains the inertia phase. It is critical to minimize the clutch response time and control the clutch pressure accurately at the end of clutch fill to achieve quick shift response and smoothness. Advanced transmission companies have adopted an auto calibration method which establishes the databases for the clutch piston fill-up attributes and the frictional characteristics of the disks. In this study, a distinctive auto calibration algorithm for forklift transmission under development is proposed and verified with the real-vehicle test. The experimental calibration results showed consistent turbine dynamics at the initial stage of shifts with the properly calibrated clutch-fill control parameters. By using this technique, it is necessary to finalize the shift control for the various operation conditions.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.2
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• pp.3-10
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• 1995

In this paper, the phase shifter using the p-i-n diode is designed and analyze. The large phase shift can be achieved by the swithched-line and the hybrid branch line phase shifter, however the small phase shift can be achieved by the loaded-line phase shifter, according to the bias state of the p-i-n niode. The results of the experiment agree with those of computer simulation at the center frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.4
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• pp.325-334
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• 1987

Microwave integrated circuit phase shifters have undergone remarkable development to satisfy the fast and precise phase control requirements for phased array antennas. It is shown how relection type phase shift circuits using PIN diode can be analyzed and implemented so as to derve design equations for any phase shift. The reflection properties are achieved by the use of an impedance transforming two-port network and the virtual matching impedance method. Experimental and theoretical performance of 2-bit hybrid phase shifter designed by this method are found to be in good agreement for each bit.