Gangil Byun

Design of a Dual-Band Quadrifilar Helix Antenna Using Stepped-Width Arms

This communication proposes the design of a quadrifilar helix antenna (QHA) with stepped-width arms and a meander feeding network. The stepped-width arms are applied to reduce the antenna size and adjust the frequency interval for dual-band operation. The feeding network includes a 90°-hybrid chip coupler and two meander lines that are designed to give a 180°-phase delay. The proposed QHA is optimized using a genetic algorithm (GA) and then fabricated to measure its performances in a full anechoic chamber. The results demonstrate that the proposed antenna is suitable to be used for dual-band global positioning system (GPS) applications.

Optimum Placement of DF Antenna Elements for Accurate DOA Estimation in a Harsh Platform Environment

This paper presents a systematic approach to the optimum placement of direction finding (DF) antennas in a harsh platform environment. A circular array with omni-directional elements is considered for azimuthal direction of arrival (DOA) estimation based on the multiple signal classification (MUSIC) algorithm. The element positions are optimized by the use of a genetic algorithm (GA) in conjunction with the FEKO electromagnetic simulator. The proposed approach is first tested with a generic platform shape. It is then extended to a more realistic military aircraft model with a strong scattering object. The optimized results show a significant performance improvement over the uniform circular array in both platform environments.

Improvement of Pattern Null Depth and Width Using a Curved Array With Two Subarrays for CRPA Systems

This communication proposes a curved array split into two subarrays to improve the pattern null depth and width for controlled reception pattern antenna (CRPA) systems. The proposed array consists of a single reference element at the center and two subarrays that are arranged on a spherical coverture. To consider both signal processing and electromagnetic (EM) perspectives, array patterns are calculated by using a microstrip patch antenna in conjunction with a constraint least-mean-square (LMS) algorithm. The proposed array shows significant improvement in the pattern null depth and width compared to a uniformly distributed circular array.

Optimum Array Configuration to Improve Null Steering Time for Mobile CRPA Systems

This paper proposes an optimum array configuration to improve null steering time for mobile controlled reception pattern antenna (CRPA) systems. The proposed array consists of a single reference element at the center and nine auxiliary elements arranged in a circular array. The array radius and the vertical positions of the center element are optimized using a genetic algorithm in conjunction with a constrained least-mean-square algorithm. The results demonstrate that the proposed array is suitable for mobile CRPA systems without significant side nulls in satellite directions.

Design of Aircraft On-Glass Antennas Using a Coupled Feed Structure

This communication proposes a glass-integrated antenna using a coupled feed structure for military FM radio communications on aircraft. The proposed antenna consists of a feed strip and two radiators, printed on the left-side window of the cockpit. The proposed antenna structure is optimized with the genetic algorithm in conjunction with the FEKO EM simulator. The optimized antenna is built and installed on a 1/10-sized KUH-Surion mock-up and antenna performance, such as reflection coefficient and bore-sight gain, is measured in a semi-anechoic chamber. The optimized antenna shows a half-power matching bandwidth of 28% at the center frequency of the military FM radio band and an average bore-sight gain of about -2.60 dBi. The results show that the proposed antenna is suitable for use as a military FM antenna for aircraft applications.

Design of a Small Arc-Shaped Antenna Array with High Isolation for Applications of Controlled Reception Pattern Antennas

This communication proposes the design of an arc-shaped antenna array with high isolation to increase the null depth for controlled reception pattern antenna applications. The array is composed of three identical antennas, and each array element is transformed from a rectangular shape to an arc shape to maximize the distance between antenna edges for isolation improvement. The proposed array is fabricated on a 5.5-inch circular substrate to measure antenna characteristics in a full anechoic chamber and is further evaluated by estimating its null depth in conjunction with the conventional power inversion method. The results prove that the array is suitable to effectively improve the isolation and the null depth at low-elevation angles.

Performance Evaluation and Analysis of a VHF-UHF Blade Antenna

In this paper, we propose a performance evaluation process of aircraft blade antennas. The process consists of various sub-processes that should be considered for a stable communication link with the base station. The process begins with the settlement of the ground shape and size to evaluate the impedance matching characteristics of a stand-alone antenna. Next, the main communications area of the antenna is determined by considering a flight scenario, and then the minimum gain requirements of the antenna are derived in the operating frequency band. Finally, the proposed evaluation process is applied for a commercial aircraft blade antenna. The results demonstrate that the proposed process is suitable to be adopted for the evaluation of aircraft blade antennas.

Design of a Dual-Band Microstrip Loop Antenna With Frequency-Insensitive Reactance Variations for an Extremely Small Array

This paper proposes a design for a dual-band microstrip loop antenna with an electromagnetically coupled feed for frequency-insensitive reactance variations. The antenna consists of two microstrip loops that are coupled to each other, and the ratio of the electric and magnetic coupling strengths is adjusted to lower the reactance slope. To demonstrate the suitability of the proposed feeding mechanism, antenna characteristics are measured in a full-anechoic chamber, and its operating principle is interpreted from a circuit standpoint. The results prove that the proposed structure exhibits a frequency-insensitive behavior without a significant gain reduction in the presence of strong mutual coupling.

Design of Single-Layer Microstrip Antennas for Dual-Frequency-Band Ratio Adjustment with Circular Polarization Characteristics

ABSTRACT This article proposes the design of a single-layer circular polarization antenna for flexible dual-frequency-band ratio adjustment. The antenna consists of an inner circular patch and an outer ring patch that is electromagnetically coupled to the circular patch. The circular patch is fed by two ports of a hybrid chip coupler, and the dual-frequency-band ratio is adjusted by varying the gap distance between the two patches. For verification, the proposed antenna was fabricated to measure its antenna characteristics in a full anechoic chamber, and the results demonstrated that the antenna is suitable for flexible adjustment of the dual-frequency-band ratio from 1.24 to 1.8, with an average axial ratio of 2.4 dB.

Design of microstrip patch antennas with parasitic elements for minimized polarization mismatch

This paper proposes the design of microstrip patch antennas to minimize the polarization mismatch. The proposed antenna consists of a circular radiating patch and multiple parasitic elements. The number, length, and angular positions of the parasitic elements are adjusted to vary the antenna polarization as well as the orientation of the main axis. To demonstrate the feasibility, we design two sample antennas with different axial ratios and the orientation angles. The first sample antenna has linear polarization with a orientation angle of 0°, and the second sample antenna is elliptically polarized with a orientation angle of 5°. The results prove that the proposed antenna can adjust the polarization in the entire range of the axial ratio with the capability of rotating the orientation angle.