A new electrically small antenna for on-demand 3.6/5.8 GHz wireless applications

This article presents a highly miniaturized dual-band electrically small antenna (ESA) for on-demand 3.6 and 5.8 GHz wireless applications. A partial rectangle-shaped structure is printed on the back face of the dielectric material, forming the antenna's ground (GND) plane. The radiating structure of the antenna consists of a C-shaped structure and a U-shaped ring connected to it, which is printed on the dielectric material's front face. The overall dimensions of the designed antenna are 0.160λo × 0.160λo × 0.02λo at the lowest operating frequency. The proposed antenna has a ka value of 0.56 at the lowest operating frequency, which is 3.59 GHz. Thus, the proposed antenna is considered as electrically small. The characteristic mode analysis is adopted to provide a clear understanding of the antenna's resonance behavior. The antenna has been fabricated and the simulation results were validated through measurements. Good agreement between simulated and measured results was obtained. Dual-band operation at 3.62 and 5.75 GHz was achieved, according to the measured reflection coefficient. The proposed antenna offers an adequate performance in terms of gain and efficiency, based on simulation and measurement results. Because of these characteristics, the antenna is well-suited to new wireless applications.

A Convex Optimization Approach for the Design of Supergain Electrically Small Antenna and Rectenna Arrays Comprising Parasitic Reactively Loaded Elements

<div><div><div><p>A convex optimization formulation is provided for antenna arrays comprising reactively loaded parasitic elements. The objective function consists of maximizing the array gain, while constraints on the admittance are provided in order to properly account for reactive loads. Topologies with two and three electrically small dipole arrays comprising one fed element and one or two parasitic elements respectively are considered and the conditions for obtaining supergain are investigated. The admittance constraints are formulated as linear constraints for specific cases as well as more general, quadratic constraints, which lead to the solution of an equivalent convex relaxation formulation. A design example for an electrically small superdirective rectenna is provided where an upper bound for the rectifier efficiency is simulated.</p></div></div></div>

A Convex Optimization Approach for the Design of Supergain Electrically Small Antenna and Rectenna Arrays Comprising Parasitic Reactively Loaded Elements

<div><div><div><p>A convex optimization formulation is provided for antenna arrays comprising reactively loaded parasitic elements. The objective function consists of maximizing the array gain, while constraints on the admittance are provided in order to properly account for reactive loads. Topologies with two and three electrically small dipole arrays comprising one fed element and one or two parasitic elements respectively are considered and the conditions for obtaining supergain are investigated. The admittance constraints are formulated as linear constraints for specific cases as well as more general, quadratic constraints, which lead to the solution of an equivalent convex relaxation formulation. A design example for an electrically small superdirective rectenna is provided where an upper bound for the rectifier efficiency is simulated.</p></div></div></div>

Metamaterial-inspired electrically small antenna for microwave applications

Electrically small antennas are becoming more important to compete with the rising modern civilization. Hence, this study presents a new approach of electrically small antenna inspired by a metamaterial structure which creates an impact by achieving a multi-band property that can be applied for different microwave applications. A high-frequency electromagnetic simulator was utilized to design, simulate, and analyze the antenna performance. About 58% reduction was achieved due to the incorporation of the modified electric field-driven capacitor-driven metamaterial. The initial length of the antenna was 0.61λ0 × 0.58λ0 × 0.12λ0; however, after embedding metamaterial, 58% reduction was achieved and the size of the electrical length of the reduced antenna becomes 0.254λ0 × 0.207λ0 × 0.013λ0, where λ0 denotes free-space wavelength. The electrical limitation factor (ka) of the antenna that was 0.94 (below 1) satisfied the conditions of electrically small antenna. The antenna achieved the highest measured gain of 4.79 dB. Due to its compact miniaturized size and resonance characteristics, the proposed antenna is compatible for broad spectrum of applications in the field of microwave communication.

A Tunable and Electrically Small Antenna for Compact GNSS Receivers

The electronic receivers of global navigation satellite systems (GNSSs) are implemented in various handheld electronic devices such as laptops, smartphones, and smartwatches; therefore, their dimensions are of critical importance. Achieving a GNSS terminal of a small size is difficult due to its relatively low operational frequency (L-band), which is equivalent to a wavelength of approximately 24 cm. As an efficient half-wavelength antenna is too large for compact devices, in this paper, an electrically small antenna (ESA) for GNSS terminals is presented. The antenna was miniaturized by using a dielectric block with relatively high permittivity, making some parts virtual, and optimizing its geometry. The operational frequency of the ESA is tunable by means of metallic rods of variable heights inserted into a cylindrical cavity drilled inside the dielectric block. The results confirm the feasibility of the concept and the usability of the ESA for compact GNSS terminals.

Underground meter wave antenna based on a patch structure with a metamaterial substrate

The antenna devices of the stationary radio communication centers of the old park no longer fully meet modern requirements. This applies to the extensive structure of receiving radio centers with expensive and bulky antenna fields. Maintaining such facilities in working condition, reconstruction and modernization is a very expensive and time-consuming task. Thus, the search for new technical solutions in the development of technologically technologically small antennas (EMA), characterized by reduced overall dimensions and cost, the use of which will increase the reliability of the radio reception centers of decameter (DCMW), meter (MW) waves, due to the hidden underground placement of antennas, is an urgent scientific and technical task. A compact, technological design of the patch antenna type (PA) with a metamaterial substrate (MMS) is proposed as a buried antenna of the MV range. By choosing this type and parameters of the antenna device, the main goal was achieved: to provide a minimal size of the antenna device, the possibility of performing the assembly of the finished product in a full technological cycle in indoor conditions (factory conditions), at the same time, there was an understanding that this design is an electrically small antenna (ESA) for the MV range. Therefore, this antenna has a high Q-factor therefore, it will be narrow-band. The problem is solved by introducing an MMS patch antenna into the structure, implemented on 4 resonators, each of which is a "fungus" with a flat square-shaped cap, the center of which is shorted to the underlying surface of the antenna by a copper wire. The use of an MMS located between the strip and the underlying surface made it possible to reduce the size of the side of the strip to m, which makes it possible to reduce the overall dimensions of the antenna device, reduce the cost of its design and increase the strength of the structure. The effective refractive index of the metamaterial structure was about 3, which corresponds to the use of a substrate with a permittivity of 9. The numerical experiment of the patch antenna model with MMS confirmed the possibility of ensuring good alignment with a load of 50 ohms, allowed us to expect a gain of about 6 dB from the current antenna sample and a radiation pattern width of at least 90 degrees. The results of a full-scale experiment in the laboratory and field tests on the current model of the patch antenna made it possible to verify the adequacy of the developed model of the antenna device and its operability.