In this study, the structure of a circular four-array antenna was designed for a monopulse radar attached to a conical small missile warhead with a diameter of 29 mm and a lateral length of 63 mm. A printed monopole Yagi-Uda antenna was adopted as the basic model for the antenna to decrease production cost and reduce weight. The director structure of the printed monopole Yagi-Uda antenna that we proposed was modified to λ/2 to improve the beam direction. Unlike the existing structure, the proposed director was made to be separated from the ground, so that it could act as a director. The antenna was expanded to a four-array structure for the detection of vertical and horizontal planes. As a result of the design, the S₁₁ had excellent matching characteristics at the center frequency of 9.375 GHz, and the beam pattern also had directivity in the same direction as the missile travel direction. In the case of gain, it showed more than 6 dBi performance. Finally, the proposed four-array structure antenna was fabricated to verify that the S₁₁ and radiation patterns were maintained.

This study designed an electrically and frequency-tunable printed inverted-F antenna (PIFA) with a perturbed parasitic element between the antenna and the ground plane. The resonant frequency of the proposed antenna can be changed via the short- and open-circuit operation of the parasitic element. This operation is activated using an electrical switch, which in this case is a PIN diode with an inductor and a resistor. The antenna was designed on the basis of the principles of the perturbation method, which enables control over resonant frequencies through modifications to the volume of a metal cavity. Meandered gaps were incorporated into the parasitic element for the independent operation of each PIN diode switch. The size of the PIFA’s radiator is 4.8 × 10 mm², and the tunable resonant frequency at the –10 dB bandwidth is 340 MHz (17.3%).

In this paper, mathematical modeling of a small scale ducted-fan UAV is conducted, and the modeling results are compared with wind tunnel test. Wind tunnel test is performed and bunch of test data were acquired. A set of wind tunnel test data was categorized and approximated as mathematical functions. Mathematically modeled force and moments acting on the UAV are then compared with those of the wind tunnel data. A gradient-based algorithm is applied to extract trim states with respect to various flight conditions. Numerical analysis shows reasonable flight status with respect to airspeed. Nomenclature d C = drag coefficients of x, y, z axis D = the duct drag force h = the distance between the center of gravity and center of pressure of the duct   k  = the drag coefficient with various angle of attack L = the duct lift force l = the distance between aerodynamic center of control surface and center of gravity S = vehicle platform area d S = the duct area v = velocity vector of vehicle in the body fixed-frame i v = the induced velocity Fuselage z = the distance between the aerodynamic center and the center of gravity of vehicle

본 논문에서는 소형 기기에 탑재가 가능하도록 소형화한 GPS 대역(  : 1.575 GHz) 안테나를 제안하였다. 소형화 된 안테나는 12×11×10 mm(0.06×0.06×0.05 λ) 크기의 styrofoam(ε r =1.06, 두께=10 mm) 표면에 장착 가능한 인쇄형으로 제작 하였다. 임피던스 매칭을 위해 급전 선로 두께 및 길이와 단락 스터브 간의 간격을 조절하였으며, 그 결과, 제작된 안테나 는 중심주파수 1.575 GHz에서 S 11 은 −38.6 dB를 얻었으며, 방사패턴 측정 결과, xz-plane에서 E θ 성분이 0° 방향에서 최대 이득 −2.3 dBi를 나타내었고, yz-plane에서 E θ 성분은 평균이득 −3.2 dBi의 무지향성 특성을 얻었다. 결과적으로, λ/2 마이크로스트립 패치 안테나와 비교하여 87 %의 면적 축소율을 확보함으로써, 소형 기기에 탑재가 가능한 초소형 마이 크로스트립 안테나로써 활용이 가능함을 제시하였다.

This study proposes an array synthesis horn antenna with an extended horn and a stepped corrugated structure for a high-power microwave system. The horn antenna is designed by joining four pyramidal horn antennas and an extended horn to obtain a high gain. To improve the beam pattern in the H-plane, the length of the vertical junction of the pyramidal horns is controlled. Two-stepped and partitioned corrugated structures are attached to both horizontal edges of the aperture for a good front-to-back ratio. The designed 2 × 2 array synthesis horn antenna has a gain of 19.7 dBi and front-to-back ratio of 39.6 dB in the measurement.