Jungsuek Oh

Low Profile, Miniaturized, Inductively Coupled Capacitively Loaded Monopole Antenna

A novel high-gain low-profile miniaturized antenna with omnidirectional vertically polarized radiation, similar to a short dipole is presented. The proposed design focus is on increasing the gain and improving the polarization purity of the radiated field in the horizontal plane. The gain and polarization improvement are achieved by isolating the feed structure from a miniaturized resonant radiating structure composed of an in-plane capacitor and a structurally embedded transformer. The antenna topology is developed, based on circuit model and through full-wave simulations the equivalence is established. The equivalent circuit model assists in the initial design, and then minor modifications are required to achieve the desired frequency of operation. The initial topology of the proposed antenna, the so-called Inductively Coupled Capacitively Loaded Monopole Antenna (ICCLMA), consists of two metal layers, a feeding pin and a shorting pin. The performance of the proposed antenna is compared to that of an ordinary inverted F antenna and a more recent low profile vertically polarized antenna (LMMMA) . It is shown that the gain of ICCLMA is 9 dB and 4 dB higher than that of the conventional inverted-F antenna and the LMMMA, respectively. To simplify the fabrication process a modified single-layer ICCLMA topology is presented and optimized. Finally, a design procedure to further reduce the lateral dimension of ICCLMA is presented. A procedure for accurate measurement of antennas with small ground planes is also presented.

Extremely Small Two-Element Monopole Antenna for HF Band Applications

This paper presents a novel antenna architecture to achieve an extremely small form factor for HF band applications. The approach is based on manipulating the topology of a short monopole antenna without utilizing a high index material. A new architecture incorporating two radiating elements is configured, which allows significant gain enhancement. It is shown that such architecture can render a miniaturized HF antenna on air substrate having lateral and height dimensions as small as 0.0115λ0 × 0.0115λ0 × 0.0038λ0 (150 mm× mm × 50 mm for operation at 22.9 MHz). It is found that the measured gain of such architecture can be as high as - 18.1 dBi, which is 16.7 dB higher than a reference inverted-F antenna realized on a high index material (εR = 10.2) having exactly the same dimensions. The proposed antenna architecture is composed of two in-phase radiating vertical elements connected to two inductors between which a capacitive top load is connected to achieve the desired resonant condition. The two vertical elements act effectively as a monopole having increased height. It is also shown that the gain of the antenna can be increased monotonically by increasing the quality factor (Q) of the phase shifter. High Q air-core inductors that can be accommodated in electrically small monopole antenna are designed and incorporated in the phase shifter to achieve a gain value of - 17.9 dBi. Details about the proposed design approach, simulation, and measurement results are discussed.

A Topology-Based Miniaturization of Circularly Polarized Patch Antennas

A novel approach for the miniaturization of circularly polarized patch antennas is presented. This enables a size reduction of as high as 75%, compared to a conventional corner-truncated circularly polarized patch antenna. The proposed design procedure consists of a number of intermediate steps, each of which produces antenna miniaturization as well as the desired polarization and impedance matching properties. This is very challenging in miniaturizing circularly polarized probe-fed patch antennas. It is shown that two resonant frequencies can be tuned independently to produce a dual band antenna with two orthogonal polarizations. Finally, two circularly polarized miniaturized patch antennas with different miniaturization factors are fabricated, and their input impedances, radiation patterns and axial ratios are discussed.

Compact, Low Profile, Common Aperture Polarization, and Pattern Diversity Antennas

This paper presents compact and low profile two-port antennas that can provide polarization or pattern diversity schemes from a common aperture. The proposed antennas make use of a novel small microstrip antenna topology with an open area at its waist. The two sections of the small-size microstrip antenna are connected through a magnetic coupling mechanism facilitated by two vertical metallic strips connecting the top plates to the ground plane. This allows for placement of another small antenna element within the same aperture having either polarization or pattern that is orthogonal to the microstrip antenna with low envelope correlation. Topologies of polarization and pattern-diversity antennas are optimized for size reduction and minimum envelope correlation. Although the proposed diversity antenna consists of two antenna elements with different polarizations or radiation patterns, they just occupy about 30% of the area of a conventional microstrip antenna over the same substrate. It is shown that the envelope correlation between radiation patterns of the two antenna elements is lower than -30 dB over the 10-dB return loss bandwidth of the proposed antenna.

Low Profile Vertically Polarized Omnidirectional Wideband Antenna With Capacitively Coupled Parasitic Elements

This communication presents a low profile and electrically small wideband antenna with omnidirectional radiation pattern and vertical polarization. A novel design approach manipulating the topology of a low profile folded monopole antenna with capacitively coupled parasitic elements in the same plane is presented to achieve omnidirectional radiation pattern. The 10-dB return loss fractional bandwidth of 43% is achieved with the dimension of 0.2λLF ×0.2λLF ×0.06λLF where λLF is the wavelength at the lowest frequency of the operation. Unlike the convention wideband λ/4 monopole antennas utilizing inductively coupled parasitic elements, the λ/2 folded monopole antenna allows for positioning the capacitively coupled parasitic elements in the middle of the antenna where maximum electric stored energy is formed. This, together with reducing the lateral dimension of the folded monopole antenna, enables the cancellation of radiated fields from electric currents in the horizontal plane of the proposed antenna, which is essential to achieve vertically polarized omnidirectional radiation. The compact parasitic elements introduce additional resonances that significantly increase the antenna bandwidth. Effects of design parameters on two resonant frequencies and impedance matching to a 50 Ω feed are investigated using the equivalent circuit model of the parasitic element and full-wave electromagnetic (EM) simulations. Based on this analysis, a design procedure to optimize the antenna topology is established.

Measurements and Physics-Based Analysis of Co-Located Antenna Pattern Diversity System

This paper investigates the advantages offered by radiation pattern diversity using a new physics-based analysis that takes into account the complex radiation patterns of the transmit(Tx) and receive(Rx) diversity antennas in conjunction with an accurate deterministic, coherent, and polarization preserving propagation model for a complex indoor scenario. Unlike techniques that utilize spatial diversity, radiation pattern diversity offers a unique opportunity to achieve compact diversity antenna systems especially with the advent of enabling antenna miniaturization techniques. In this work, a co-located antenna radiation pattern diversity system is proposed and its performance is analyzed using an accurate physics-based diversity analysis technique. The proposed analysis technique utilizes an efficient deterministic propagation model modified by incorporating the complex gain of the Tx and the complex effective heights of the Rx antennas into the rays launched and received by the antennas in a coherent manner. The proposed system is realized and tested in complex indoor scenarios based on which complex correlation coefficients between various channels and the effective diversity gain are computed which are then utilized as a figure of merit for improved channel reliability. For the scenarios considered, it is shown that the apparent diversity gain is at least 9.4 dB based on measured results.

A Sub-Wavelength RF Source Tracking System for GPS-Denied Environments

A sub-wavelength source tracking system utilizing highly miniaturized antennas in the HF range for applications in GPS-denied environments including indoor and urban scenarios is proposed. A technique that combines a high resolution direction finding and radio triangulation utilizing a compact transmit (Tx) and receive (Rx) antenna system is pursued. Numerical models are used to investigate wave propagation and scattering in complex indoor scenarios as a function of frequency. We choose HF band to minimize attenuation through walls and multipath in indoor environments. In order to achieve a compact system, a low-profile and highly miniaturized antenna (

Flexible Antenna Integrated With an Epitaxial Lift-Off Solar Cell Array for Flapping-Wing Robots

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Wave-propagation management in indoor environments using micro-radio-repeater systems

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A low-profile omnidirectional planar antenna with vertical polarization employing two in-phase elements

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