This paper proposes a single-radiator multi-port (SRMP) compact chip antenna for ultra-wideband (UWB) direction-finding. The antenna proposed in this paper is miniaturized to a physical size of 11.5 mm $\times 9.46$ mm $\times 1.6$ mm by utilizing a ceramic substrate with high-permittivity of 20. Furthermore, we designed a CPW feed line for the proposed chip antenna and verified its performance when mounted on a board through simulation and measurement. This small structure includes a multi-port system that can replace a conventional array system, utilizing the tripod-shaped single radiator. To verify the feasibility, the proposed antenna is fabricated and the antenna characteristics such as reflection coefficients, mutual couplings, and radiation patterns are measured in a full anechoic chamber. The proposed antenna has an operating bandwidth of 7 GHz to 9 GHz, which makes it well-suited for UWB Channel 9 (7.737 GHz–8.236 GHz) in Korean mobile devices. The measured mutual coupling result is below −10 dB across the operating frequency band. In addition, the radiation patterns in the zx-plane and zy-plane are anlayzed, and a bore-sight gain of 4.2 dBi is observed at 8 GHz. To verify the direction-finding performance, the proposed antenna is connected to the Nordic board nRF52840 DK with the commercial Qorvo DW3000 module to obtain channel impulse response (CIR) data. Then, the direction of arrival (DoA) is measured at distances of 0.3 m, 1 m, and 2 m according to the incident angle from −30° to 30°. The root mean square (RMS) errors at distances are 1.1°, 1.2°, and 1.5°, respectively. These results demonstrate that the proposed compact chip antenna is suitable for use in mobile devices equipped with UWB direction-finding technology.

In this paper, we propose a signal intelligence (SIGINT) drone swarm system with a three-dimensional (3-D) volumetric self-complementary array configuration. In the proposed system, multiple drones form two array layers separated along the boresight direction of the system, providing sufficient spacing between drones mounting an antenna element. The antenna elements in one array layer are arranged in a complementary manner to fill empty spaces in the other layer, allowing the system to maximize the number of drones deployed within the aperture area. As a result, the effective electrical spacing at 300 MHz is reduced from 1.7λ and 0.9λ to 0.85λ and 0.45λ along the x- and y-axes, respectively. The array gains of the proposed system are 3.96 dBi, 6.40 dBi, and 15.3 dBi at 100 MHz, 200 MHz, and 300 MHz, and the side-lobe levels (SLLs) are −13.0 dB, −12.7 dB, and −13.0 dB. In addition, the proposed drone swarm SIGINT system is evaluated in a practical SIGINT environment that considers terrain features, and then the detection performance is compared with those of conventional ground-based and airborne SIGINT systems. In this SIGINT scenario, the proposed system can detect signals over an extended detection range of 150 km than those of ground-based and airborne systems.

This paper analyzes performance degradation caused by mechanical errors in rib-type deployable mesh reflectors to propose error tolerance levels that can be used as a reference when designing antennas composed of these reflectors. In rib-type deployable mesh reflectors, five types of errors may occur: joint stop angle error, feeder alignment error, feeder pointing error, defective surface error, and wrinkled surface error. In this study, antenna performance degradation stemming from these mechanical errors are analyzed, and error tolerances corresponding to a reduction in the boresight gain by 1 dB (20.6%), 2 dB (36.9%), and 3 dB (50%) are suggested. These boresight gain reduction levels are widely adopted as intuitive indicators of antenna performance degradation. In addition, the corresponding variations in half-power beamwidth, sidelobe level, and main lobe direction are calculated for each error case. The error tolerances at which a performance degradation of 1 dB occurs for each error type are as follows: 0.32° at 10 GHz for joint stop angle error, 9.5% at 3 GHz for defective surface error, 0.0071 m at 10 GHz for wrinkled surface error, 0.016 m at 10 GHz for feeder alignment error, and 23.6° at 3 GHz for feeder pointing error. These results reveal that the most sensitive and critical error is the joint stop angle error, which must be significantly minimized when designing and fabricating rib-type deployable mesh reflector antennas.

We proposed a method to enhance the gain of a truss reflector antenna by optimizing the placement of a minimal number of tension ties. To analyze the impact of tension tie placement on antenna performance, the bore-sight gain was compared by adjusting the length of each subdivision ln. The bore-sight gain of the optimized reflector antenna was then compared with those of two conventional truss reflector models (N sub = 4 and 5). The optimized model, which utilized the same number of tension ties as the conventional design with Nsub = 4, achieved a 0.6 dB improvement in bore-sight gain. Subsequently, the optimized antenna obtained a bore-sight gain comparable to that of the reflector with 30 additional tension ties. These results demonstrated that the proposed optimization method can design reflector antenna with high gain characteristic while reducing the number of tension ties.

In this paper, we propose the deployable mesh reflector antenna for satellite applications. To analyze the performance degradation caused by multiple flat divisions of the mesh surface, the bore-sight gain and HPBW characteristics depending on the number and position of tension ties are analyzed while considering the asymmetric structure of the offset reflector. The proposed antenna is fabricated and measured in the near-field anechoic chamber. The bore-sight gain and HPBW of the measurement results are 23.89 dBi and HPBW 4.43°, which are agree well with simulation results of 23.14 dBi and 4.65°.

We propose a wire-based parabolic reflector antenna capable of electrically controlled beam steering through the integration of voltage-programmable RF switches. By toggling the switch modes, the surface current distribution on the reflector is reconfigured in real time, enabling angular adjustments of the main beam within the azimuthal plane. The antenna was designed and optimized using the FEKO electromagnetic simulator, with performance verified through experimental measurements. Key parameters including reflector diameter, focal length, and feed dimensions were carefully selected to maximize gain and demonstrate controllable beam steering. The fabricated prototype operates at 1.7 GHz with a 50 cm aperture and a 75 cm focal length, achieving a measured gain of 7.5 dBi. Beam steering up to 1° was demonstrated without mechanical reconfiguration. For low Earth orbit (LEO) altitudes of around 1500 km, this angular variation corresponds to approximately 26 km of ground spatial coverage, whereas for medium Earth orbit (MEO) altitudes of around 5200 km, it corresponds to approximately 90 km. The proposed antenna offers a compact, lightweight, and electronically reconfigurable solution suitable for integration into future spaceborne and mobile communication platforms.

In this paper, we propose a method for deriving beam pattern masks to maximize the aperture efficiency of the offset reflector antenna. The beam pattern mask is designed to be proportional to the square of the distance from the feed to the reflector, and we obtain the optimum beam pattern using beam synthesis. As a result, employing the synthesized beam as the feed for the offset reflector yields an aperture efficiency of 81.6%, sidelobe level (SLL) of 36.7 dB, and an axial ratio (AR) of 2.30 dB. These results demonstrate that the proposed mask provides superior aperture efficiency, enhanced sidelobe suppression, and improved CP characteristics.

In this paper, we propose the optimal jammer trajectories for maintaining a constant J/S ratio. To maintain a constant J/S ratio over time, the jammer constantly transmits the interference signals toward a fixed sidelobe angle of the ground station antenna. The potential trajectories are derived to maintain a constant sidelobe angle from the straight line connecting the ground station and the satellite. Among these trajectories, we choose the trajectory that maximizes the horizontal distance between the jammer and the ground station to minimize the detection probability. We conduct J/S ratio analysis for different trajectories generated by different ψ values. The STK simulations indicate that the J/S ratio varied by up to 5.4 dB on trajectory 1, 6.9 dB on trajectory 2, and 7.9 dB on trajectory 3. These results demonstrate that relatively consistent J/S ratios are maintained throughout the operation and are in good agreement with the MATLAB results, with a maximum error of less than 4.6 dB.