Seong-Pal Lee

V-band MMIC low-noise amplifier design based on distributed active device model

A V-band two stage MMIC low-noise amplifier using 0.15 /spl mu/m pHEMT based on a distributed active device model has been designed. This model is successful in constructing the equivalent circuit of HEMT that cannot be scaled from a standard HEMT model. An MMIC amplifier based on the distributed model and careful EM simulation exhibits a maximum gain of 9.6 dB and a minimum noise figure of 3.6 dB at 61 GHz. This results indicate that the distributed HEMT model is effective for the design V-band MMIC low noise amplifiers.

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.

Reconstruction of KOMPSAT-l GPS navigation solutions using GPS data generation and preprocessing program

Abstract GPS navigation solutions and GPS-related telemetry points are analyzed using one-day playback data from the KOMPSAT-1 Spacecraft. Then, the GPS navigation solutions are reconstructed using simulated GPS raw measurements such as pseudo-ranges between the KOMPSAT-1 and GPS satellites constellation. GPS data generation and preprocessing computer programs are developed and used for the generation of the GPS raw measurement and reconstruction of the GPS navigation solutions. The playback GPS data and the reconstructed data are compared with each other.

An enhanced PIN diode model for voltage-controlled PIN diode attenuator

This paper presents an enhanced PIN diode model for the voltage-controlled PIN diode attenuator. The proposed model operates well when it is used in the voltage-controlled mode as well as current-controlled mode, and it is a simple and straightforward model, since the PN junction diode of this model has the same I-V curve as that of the PIN diode. The validity of the proposed model is demonstrated by the measured data.

COMMUNICATIONS SATELLITE SYSTEM BY USING MOON ORBIT SATELLITE CONSTELLATION

A communications satellite system placed in three-Lagrange points, , and , of the restricted three-body problem in Earth-Moon system is proposed in this paper. LEO satellite constellation has been another choice of communications system. The proposed system which is alternatives of limited geostationary orbit resources, has some weak points such as long distance from the Earth, relatively expensive launch cost, long delay time, more required power, and so on. It has good points like less efforts (fuel) for station keeping, less eclipses, etc. This system has limitations for applications to provide commercial services but it is still some attractive points.

Development of Ku-band Receiver/Downconverter for satellite transponders

This paper presents the development of a Ku-band Receiver/Downconverter with the Noise figure of 1.83 dBmax and the conversion gain of 55 dB at the frequency range from 14/spl sim/14.5 GHz to 12.252/spl sim/12.752 GHz for Ku-band Satellite transponders. This Ku-band Receiver/Downconverter consists of a LNA module, a 2-pole combline image rejection filter, a Downconverter module, a 7-pole IF filter, and an IFAMP module. All components except the cavity type filters were assembled using a hybrid technology with 15 mil thin-film substrates. Its other performances show the C/IM3 of 45.67 dBcmax, group delay of 0.6 ns/36 MHz, and gain variation of 1.68 dBmax at -15/spl deg/C/spl sim/+65/spl deg/C of operating temperature range.

Ka-Band Antenna Design Using the Reflector Shaping for the Communications & Broadcasting Satellite

The electrical design of the Ka-band antenna for the domestic Communications and Broadcasting Satellite (CBS) is described. The antenna has the offset Gregorian structure and is installed on the Earth-facing panel of the satellite. The electrical performance specifications for the antenna were determined from the required EIRP and G/T through the payload level performance analysis. This paper utilized the reflector shaping technology for the trade-off among the major performance parameters, resulting in compliance of all the parameters. The designed antenna shows 37.95 dBi EOC (End of Coverage) gain and 28.7 dB sidelobe isolation for transmit band, and 37.49 dBi EOC gain and 31.1 dB sidelobe isolation for receive band, The electrical performances of the antenna have been verified via the electrical testing of a manufactured EQM (Engineering Qualification Model) antenna.

Voltage-Controlled Ku-Band PIN Diode Attenuator with a Temperature Compensation Circuit

This paper presents voltage-controlled Ku-band PIN diode attenuators and the temperature-compensation method of these attenuators. Measurements over temperature of these PIN diode attenuators were performed. After carefully investigating the temperature characteristics of PIN diode attenuators, we designed voltage-controlled PIN diode attenuators showing the linear attenuation characteristics with input voltage within the temperature range. The fabricated attenuator has demonstrated the improvement of attenuation variation from 15dB to 0.5dB in the temperature range from ¿15°C to 65°C.

The Design and Implementation of Electrical Ground Support Equipment (EGSE) for COMS Ka band Transponder Testing

Communication, Ocean, and Meteorological Satellite (COMS) is a hybrid satellite which will be launched on the middle of 2009. In the meantime, many of Korean research institutes and industries are participated in COMS program. The communication payload in COMS is made by ETRI with Korean industries. The on-board RF switch matrix for multi-beam connection and spot beam antenna technologies are adapted in the communication payload. After assemble and integration payloads to the spacecraft, payload performances will be validated by the special testing system called Electrical Ground Support Equipment (EGSE). The EGSE for communication payload can monitor and control transponder configuration and performs RF performance testing of the transponder. In this paper COMS Ka band multi-beam communication payload are described, and EGSE configurations and test methods are also described.

PRECISE ORBIT DETERMINATION BY DGPS TECHNIQUE FOR THE KOREA MULTI-PURPOSE SATELLITE-2

The main mission of the KOrea Multi-Purpose Satellite-2 (KOMPSAT-2) that will be launched in 2004 is a high resolution imaging for the cartography of Korea peninsula. The requirement for enhancing the image product is that precise orbit has one-meter (one sigma) position accuracy. The precise orbit determination software using single frequency GPS tracking data, as one of ground functions, was developed. This software consists of two parts, one is a preprocessing process for the error correction and the double differential data generation of the GPS tracking measurements and the other is an estimation process based on dynamic parameters estimation and weighted least square batch filter. The differential GPS technique applied this software uses the L1 frequency GPS data generated KOMPSAT-2 on-board GPS receiver and the GPS measurement data of GPS reference ground stations over the world for the generation of double differential measurement data on the thirty seconds interval. The GRAPHIC and total electron content scale factor estimation techniques are also used in the estimation process for the elimination or reduction of the ionospheric path delay in GPS measurements. The test was performed using the real GPS measurements of the Topex/Poseidon and the Challenging mini satellite payload and the simulation data of KOMPSAT-2 for verification of accuracy and performance of the software.