Seung-Hyeub Oh

Multi-beam Antenna Analysis

This paper describes the antenna analysis of the multi-beam for communication satellite. The design core parameters of the antenna system are optimal antenna diameter, feed horn type and horn size, F/D, and the coordinate of offset horns. The paper deals with the method to determine design core parameters of optimal antenna diameter, feed horn type and horn size. F/D. and the coordinate of offset horns, and the performances of design result

Design of Ka-band Satellite Ground Station Antenna/RF System

This paper describes the design of the Ka-band Antenna/RF system, which was developed for the experiment of the high-speed satellite communications with geostationary satellite. The design issues described here are the ka-band characteristics for having an optimum performance. and the system characteristic for having a reliable and an extensional operation.

Enhanced f T and f MAX SiGe BiCMOS Process and Wideband Power Efficient Medium Power Amplifier

In this paper, a wideband power efficient 2.2 ㎓ - 4.9 ㎓ Medium Power Amplifier (MPA) has been designed and fabricated using 0.8 ㎛ SiGe BiCMOS process technology. Passive elements such as parallel-branch spiral inductor, metal-insulatormetal (MIM) capacitor and three types of resistors are all integrated in this process. This MPA is a two stage amplifier with all matching components and bias circuits integrated on-chip. A P1㏈ of 17.7 ㏈m has been measured with a power gain of 8.7 dB at 3.4 ㎓ with a total current consumption of 30 ㎃ from a 3 V supply voltage at 25 ℃. The measured 3 ㏈ bandwidth is 2.7 ㎓ and the maximum Power Added Efficiency (PAE) is 41%, which are very good results for a fully integrated Medium PA. The fabricated circuit occupies a die area of 1.7 ㎜ × 0.8 ㎜.

Analysis of UE RF parameters for 3GPP specifications

The paper describes the key RF factors of UE (user equipment) for W-CDMA systems based on 3GPP specifications. The transmitter and receiver parameters are derived from the viewpoint of RF. In order for UE to retain high performance, the transceiver design requirements - such as ACLR (adjacent channel leakage power ratio), EVM (error vector magnitude), peak code domain error, spectrum emission mask for transmitter and reference sensitivity level, blocking characteristics, noise figure, ACS (adjacent channel selectivity), receiver AGC dynamic range - are considered. The UE transceiver is implemented and its performance requirements analysed through test scenarios.

Design and Implementation of Wideband Ultra-Fast High Precision Frequency Synthesizer for ELINT Equipment

본 논문은 2.5 ㎒ 간격으로 광대역 주파수를 발생하며 응답 시간이 400 nsec 이하인 초고속 이산(discrete)주파수 합성기를 제안한다. 제안한 주파수 합성기는 고정 주파수 위상 제어 루프(PLL)와 주파수 분배기를 이용해 16개의 기준 신호를 생성하고, 이들을 선택하여 주파수 혼합하는 방식으로 710～1,610 ㎒ 내에서 2.5 ㎒ 간격의 이산 주파수 신호를 고속으로 생성한다. 제작된 주파수 합성기의 주파수 천이 응답 시간은 평균 350 nsec, 고조파를 비롯한 모든 불요파 신호는 －60 ㏈c 이하, 위상 잡음 특성은 －94 ㏈c/㎐ @100 ㎐, 출력 세기는 평균 21.5 ㏈m, 평탄도는 2.65 ㏈ 이하로 측정되었다. 또한 주파수 천이 응답 속도를 측정하는 새로운 기법의 측정 방법이 제안되었다.

Parallel-Branch Spiral Inductors with Enhanced Quality Factor and Resonance Frequency

In this paper, we present a cost effective parallel-branch spiral inductor with the enhanced quality factor and the resonance frequency. This structure is designed to improve the quality factor, but different from other fully stacked spiral inductors. The parallel-branch effect is increased by overlapping the first metal below the second metal with same direction. Measurement result shows an increased quality factor of 12 % improvement. Also, we show an octagonal parallel-branch inductor which reduces the parasitic capacitances for higher frequency applications.

Angular error of LEO tracking system

This paper describes the angular error of the tracking antenna system for LEO (Low Earth Orbit) satellite through the alignment experiment. The purpose of this alignment experiment is to reduce the angular error due to the structural alignment and the monopulse null point alignment error. The angular error that can occur during installation on-site, is the key performance parameter of the tracking antenna system. The angular error is analyzed via a simulation and boresight measurement. The simulation is done with formulas to be derived from vector concept for 3-axis movement. The formulas of the structural alignment are verified by comparing the formula result with the field measurement. Also, the angular error due to monopulse null shift is obtained via boresight measurement. The calibration results for both alignments are described.

Design of a Fully Integrated Low Power CMOS RF Tuner Chip for Band-III T-DMB/DAB Mobile TV Applications

This paper describes a fully integrated CMOS low-IF mobile-TV RF tuner for Band-III T-DMB/DAB applications. All functional blocks such as low noise amplifier, mixers, variable gain amplifiers, channel filter, phase locked loop, voltage controlled oscillator and PLL loop filter are integrated. The gain of LNA can be controlled from -10 dB to +15 dB with 4-step resolutions. This provides a high signal-to-noise ratio and high linearity performance at a certain power level of RF input because LNA has a small gain variance. For further improving the linearity and noise performance we have proposed the RF VGA exploiting Schmoock`s technique and the mixer with current bleeding, which injects directly the charges to the transconductance stage. The chip is fabricated in a 0.18 um mixed signal CMOS process. The measured gain range of the receiver is -25~+88 dB, the overall noise figure(NF) is 4.02~5.13 dB over the whole T-DMB band of 174~240 MHz, and the measured IIP3 is +2.3 dBm at low gain mode. The tuner rejects the image signal over maximum 63.4 dB. The power consumption is 54 mW at 1.8 V supply voltage. The chip area is .

Design of Cartesian Feedback Loop Linearization Chip for UHF Band

In this paper, the designed and implemented results of CFL linearization chip which can be used in mobile radio and TRS terminal of UHF band(380~910 MHz), using BiCMOS process based on Si, are shown. As gain control circuits for modifying transmit power are inserted not only in feedback path but also in forward path, the stability of CFL is maintained. And, DC-offset correction function of S/H structure, which is suitable for walkie-talkie PTT operation and is easily implemented, is realized. The performance test results of transmitter show that the regulation of FCC emission mask at PEP 3 W(34.8 dBm) is satisfied when the CQPSK modulated signal is fed and more than 30 dBc improvement of 3rd order IMD is achieved when two-tone signal is inputted.

Down Conversion Mixer for Millimeter Band

A lot of demand for parts of millimeter wave band, as would be expected 57~63 GHz band down conversion mixer was designed and fabricated using IHP 0.25 um SiGe process. Designed and fabricated mixer was double balanced type and located reduced 3D balun at RF port and buffer amplifier at outport for suppression LO signal and conversion gain. Fabricated mixer measured conversion gain of 13.8 dB, -17 dBm and 88 mA of current consumption characteristics, respectively.