Changoo Kwak

Electronics and Telecommunications Research Institute | ETRI · RF

Provided is an antenna apparatus which employs a small number of antenna devices and is intended to obtain a desired pattern without adjusting amplitude level and phase of each antenna device. The antenna apparatus includes a first ridge horn antenna, and a second ridge horn antenna spaced apart from the first ridge horn antenna by a determined dis...

A 1000-h steady state life test at a temperature of 125 °C was performed on ten X-band MMIC multifunction chips for use in active phase array radar systems. Internal switches, phase shifters, and attenuators were operated through an integrated serial-to-parallel converter under the five-second stepped external control signal for the life test perio...

Tunable filters using the TE011 mode have slot irises for coupling between cavities. Unless the slot iris is appropriately designed, the coupling value of the iris varies as an operating frequency changes and the filter performance deteriorates as a result. In this reported work, it was found that the frequency-dependent coupling characteristic of...

This paper presents a new coupling matrix synthesis method. The method synthesizes a coupling matrix by moving poles and zeros to their own target positions in the complex plane. Mathematically speaking, the procedure is to solve a system of nonlinear equations using Newton's method. In addition, a new algorithm for generating the initial values is...

A butler matrix includes at least one input coupler that is positioned at an input end of the butler matrix, receives an input signal, and divides and outputs it to a plurality of paths, and at least one output coupler that receives a signal from the input coupler and divides the signal into a plurality of paths to output it as an output signal. A...

In this paper, a combline filter is studied to see if the filter can be used for a reconfigurable filter that covers a frequency range of 2.0 GHz to 2.7 GHz and a bandwidth ranging from 50 MHz to 80 MHz. Since the bandwidth as well as the center frequency should vary in a wide range, the coupling between the load/source and the first/last resonator...

This paper presents an efficient design method based on genetic algorithm and design results for Ka band reconfigurable beam antenna composed of an array-fed reflector. The effective cost functions for the contoured beam and the boosted beams were used to find the best solution. During the optimization, it was confirmed that the average cost and th...

A system for controlling temperature of an antenna module including a heat generating module, and a radome and an underbody cover that enclose the heat generating module. The system includes: a heat collecting unit mounted on inner surface of the antenna module; a heat discharging unit mounted on outer surface of the antenna module; and a heat tran...

The present invention relates to an antenna system mounted on a mobile vehicle. In the present invention, a power distributor and a part of a high-frequency module that includes a frequency converter are placed in an external fixed unit that is placed outside a radome. In addition, an active cooler/cooling fin, a heater, and an air circulation fan...

Provided is a line filter. The line filter includes a plurality of dielectric layers stacked one another, a plurality of line resonator each comprising transmission lines on at least two of the dielectric layers, and a tuning unit adjusting a binding amount and resonance frequency of the line resonators. Since the line filter includes at least one...

This letter presents an automated microwave filter tuning algorithm that emulates manual tuning. Measured S-parameter curve's shape similarity and value similarity with a target one are utilized for coarse tuning. A sensitivity matrix of S-parameter curve's feature points and a weighted least squares method are used for fine tuning. The utility of...

An easy and straightforward technique for the synthesis of lossy coupled-resonator filters is presented. A lossy filter designed by attachment of attenuators is transformed into a realisable lossy filter through linear operations of its admittance matrix and optimisations. This technique can synthesise lossy symmetric filters, asymmetric filters an...

A new algorithm for obtaining a flat-faceted reflector's radiation pattern is introduced. This method is noble in that uneven amplitude distribution due to facets is considered. And a facet generation method for various segmentations is suggested. With these, the effect of the facet's size and shape on the radiation pattern is studied.

Regressive equations that calculate the maximum channel temperature of a GaAs monolithic microwave integrated circuit (MMIC) have been made through a lot of finite element (FE) analyses. And this paper suggests how to estimate the maximum channel temperature with those regressive equations for frequent cases. As an example, a medium power amplifier...

Thermal resistance of a 3 GHz power amplifier MMIC has been calculated with finite element (FE) analyses. Through comparative FE analyses it has been found that a carrier for infrared (IR) scan test should have high thermal conductivity if it is for measuring thermal resistance of an MMIC only. IR scan results showed that the FE analysis provided t...

Thermal resistances (R_th) of monolithic microwave integrated circuits (MMIC) for the Ka-band communications satellite's transponder, which is being developed by ETRI, have been calculated by the finite element method (FEM). Through the analyses of finite element models with or without selective metal layers, additional MMIC's thermal cha...