Changsoo Kwak

K-Band Frequency Tunable Substrate-Integrated- Waveguide Resonator Filter With Enhanced Stopband Attenuation

In this paper, we present a K-band substrate-integrated waveguide resonator bandpass filter structure. The filter uses an antisymmetric mode of the resonator for the first time. A design method for the external coupling structure of the resonator utilizing the antisymmetric mode is described. In addition, a methodology for suppressing neighboring resonances close to the passband is demonstrated. This method can enhance stopband attenuation performance without additional loss. The proposed filter can tune the center frequency by adjusting tuning components. In order to verify the proposed filter structure and design method, we have fabricated and measured a K-band filter and demonstrated higher order filter design.

The analysis method for a flat-faceted reflector and the effect of facet configuration on radiation pattern

A new algorithm for obtaining a flat-faceted reflectors 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 facets size and shape on the radiation pattern is studied.

A New Class of K-Band High-Q Frequency-Tunable Circular Cavity Filter

A new type of K-band high-Q frequency-tunable waveguide filters is proposed in this paper. The presented filter structure adopts a new technique for tuning the resonant frequency of each resonator. A dielectric plate is inserted in each resonator and rotating it leads to the frequency tuning. Unlike the conventional frequency tuning methodologies for tunable waveguide cavity filters, the new frequency tuning technique alleviates the electrical grounding issue for tuning devices. In addition, we demonstrate a new design method that allows the filter to have an absolute constant bandwidth in the frequency tuning range without using tunable coupling structures.

K-band tunable cavity filter using dual TE211 mode

In this paper, a K-band tunable cavity resonator filter is introduced. The tunable filter uses a dual TE211 mode cavity to reduce the size of the filter. To improve the tuning range of a pseudo-low pass filter that uses short irises, dummy iris is introduced. To enhance selectivity at band edge, additional cavity is introduced. A transmission zero generated by the additional cavity is controlled by only the cavity. To extend the rejection band, we use interaction between TE211 mode and adjacent modes. We fabricate and test the two-cavity, three-transmission zero tunable filters to verify the design results.

Design of Ka band reconfigurable beam antenna using genetic algorithm

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 the best cost were converged. The contoured beam antenna is designed with the gain ripple less than 3 dB over the coverage. The boost level greater than 7 dB for Seoul area is obtained.

Feasibility study on combline filter for tunable filters

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 must be changeable. This study proves that the combline filter can meet the frequency requirements by designing the combline filter that meets four extreme frequency requirements using full-wave electromagnetic simulations. The input/output coupling proves that it can be tuned enough to be used for the reconfigurable filter of interest.

Practical Method for Obtaining Maximum Channel Temperature of GaAs MMIC

[Abstract] 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’s maximum channel temperature was calculated and its result was larger than that of a complete FE model by about 4%. The medium power amplifier’s temperature distribution was obtained through an infrared scan and, even though the maximum channel temperature could not be obtained due to the test’s inherent shortcoming, temperature other than gate fingers showed good agreement with FE analysis results. Therefore it can be said that the practical method for obtaining the maximum channel temperature using regressive equations can give thermal resistance of a GaAs MMIC very easily and quickly without time-consuming FE analyses.