Manseok Uhm

Ultra-Wideband Bandpass Filters Using Quarter-Wave Short-Circuited Shunt Stubs and Quarter-Wave Series Transformers

This letter introduces a topology of a very wideband filter intended for the use in ultra-wideband 3.1-10.6 GHz applications. Basic filter configuration consists of quarter-wave short-circuited stubs and quarter-wave series transformers. To improve the out-of-band rejection, a low-pass filter is added across the symmetry plane. The proposed component is fabricated in a planar microstrip configuration; however, the topology can be easily adopted for other technologies including those based on surface micromachining. The measurements have shown an insertion loss below 0.86 dB, return loss above 14 dB, group-delay variation under 0.15 ns, and the third harmonic rejection better than 16 dB.

A Compact Ku-Band SiGe Power Amplifier MMIC With On-Chip Active Biasing

A Ku-band power amplifier monolithic microwave integrated circuit (MMIC) with an output power density of 726 mW/mm2 is demonstrated using 0.25 ¿m SiGe BiCMOS technology. No inductor matching scheme is applied to minimize the MMIC size, but an active biasing topology is used to enhance the power-added efficiency (PAE) and linearity of the MMIC. The fabricated one-stage cascode power amplifier MMIC, including input/output matching and biasing circuits, has a compact size of 0.384 mm2 (0.6 mm × 0.64 mm), and exhibits a saturated output power (Psat) of 24.45 dBm and a PAE of 29.1 % at 14 GHz.

Dual-wideband log-periodic antennas

Two log-periodic (LP) antenna configurations able to suppress a specific frequency band are introduced in this paper. LP antennas belong to the class of frequency independent antennas and are able to achieve multi-decade wide bandwidths. We start with a parametric study of a traditional planar curved tooth LP antenna aimed in determining the means for achieving specific bandwidth. Two techniques for accomplishing consistent near/far-field dual-band performance are introduced next. The first is a LP antenna integrated with a dual-wideband feed line, and the second one is a LP with removed resonant teeth. Antennas and feeds are designed on a microstrip substrate and method of moments modeling within FEKO is used to demonstrate their performance. Required dual-band operation is 1.8-5 GHz and 7-11 GHz.

Automated Microwave Filter Tuning Using Curve Similarity and Weighted Least Squares

This letter presents an automated microwave filter tuning algorithm that emulates manual tuning. Measured S-parameter curves shape similarity and value similarity with a target one are utilized for coarse tuning. A sensitivity matrix of S-parameter curves feature points and a weighted least squares method are used for fine tuning. The utility of algorithm is demonstrated with an X-band four-pole dual-mode cavity filter.

A Triple-passband Waveguide Filter with Dual-mode resonators for Ka band Satellite Applications

This paper describes the design and realization of a Ka-band triple-bandpass waveguide filter with dual-mode resonators. This filter adopts dual-mode technique for mass and volume saving and the in-line configuration for easy fabrication and tuning. An appropriate equivalent circuit model for in-line structure is used to design and tune the filter. For validation of the proposed design results, an 8-pole dual-mode triple-passband filter for Ka band satellite applications is realized. Very good agreement between the measured and computed responses is obtained.

Optimization of complex excitation of array-fed elements for communications and broadcasting large reflector satellite anntenna

The design of a antenna for the Korean Peninsula is presented. 30 m class large reflector and feed array system with 25 elements for both communication and broadcasting is optimally designed by Geometrical Optics (GO) and Physical Optics (PO). The antenna radiation pattern by the optimal complex excitation is described. The influence of failed component on the antenna performance is analyzed and the broken radiation pattern is improved by re-optimization.

Multipaction Free Ka-band Diplexer with an Asymmetric Iris

very low electrical current across the interface 3 . Therefore, an E-plane T-junction is more desirable than an H-plane T-junction in view of the RF performance. Multipaction is a discharge occurring in high power RF equipment operating under vacuum condition in the presence of free electrons. It is necessary to perform the multipaction risk analysis based on electromagnetic theory at the design phase. The high multipaction margin is obtained by inducing much smaller peak voltage in the resonator with minimum gap than the threshold voltage. The diplexer needs the additional plate, so called radiator, for radiating heat. The radiator was designed as part of one diplexer half. Adaptable tuning without disturbance of the radiator got accomplished by using an asymmetric iris in the receiving filter. It is critical to select the asymmetric iris corresponding to symmetric iris. Through the measurement results, we have found that the RF performance of the diplexer met the specifications and the design method was adequate. II. Diplexer Design for High Power Handling

Multibeam Reflector Antenna for Ka-Band Communication Satellite

This paper presents the multibeam service coverage of GEO(Geostationary Orbit) satellite and the practical antenna scheme scenarios to provide the universal communication services on the Korean peninsula. The proposed antenna systems consist of the simplest scheme and feed network so that they can be mounted on satellites. The feed networks are effectively organized according to the frequency and polarization plan. Despite simple structure, all scenarios meet the electrical performance by the optimization of feed allocation and feed excitation.

Design of a Waveguide 8×8 Butler Matrix for Ka-Band Broadband Multi-Port Amplifiers(MPAs)

Herein, we design a wideband waveguide Butler matrix in order to use in a multi-port amplifiers(MPAs) at Ka-band. To achieve the broadband characteristic, we design a binomial 6-slot 3 dB directional coupler which is used to configure the Butler matrix. The measured results of the fabricated Butler matrix have low insertion loss of less than 0.3 dB, good return loss of over 26 dB and high isolation of over 35 dB within the design bandwidth of 3 GHz.

New circular-shaped dual-mode cavity for mm-wave filters using LTCC technology

This paper presents a new circular-shaped dual-mode cavity for mm wave filters in the LTCC substrate. The cavity enables a resonator filter to include the cross couplings between input and output ports for high frequency selectivity. Two mm-wave filters are demonstrated to verify the effectiveness of proposed cavity.