Design Of Leaky-wave Antenna Research Articles

Design of Leaky Wave Antenna for V2V Communications

In this article, a low-profile, microstrip-based, periodic leaky wave antenna has been proposed for vehicle-to-vehicle (V2V) communications. The leaky-wave structure, loaded periodically with stepped impedance resonator stubs operates in the 5.4–6.2 GHz frequency band, which includes the WAVE (Wireless Access in Vehicular Environments) band (5.85–5.925 GHz) required for automated vehicular communications. The S11 obtained in the spectrum is below −12.68 dB. While the majority of the antennas designed for V2V communications produced omnidirectional patterns, the structure proposed in this work yields a directional pattern, preventing unnecessary outages of signals. The periodic structure gives an added advantage of beam scanning, resulting in a wider, yet directive coverage in the desired frequency band. A backward beam scan from −13˚ to −31˚ is obtained in the frequency range of 5.4–6.2 GHz with a gain variation of around ±0.6 dB only.

Design of Leaky-Wave Antenna With Wide-Angle Backfire-to-Forward Beam Scanning Based on Generalized Pattern Synthesis

Frequency-scanning antenna has been extensively explored in radar and vehicle communication systems, but it is a challenge to provide methodological guidance to achieve a wide scanning angle. Here, a generalized pattern synthesis method is proposed and a leaky-wave antenna with wide scanning range is designed to verify the technique. First, a generalized antenna element (GAE) is presented, whose main beam can steer continuously with frequency. Meanwhile, the phase constant of the leaky wave determines the beam direction of the array factor. Then, a leaky-wave antenna can steer with a large beam scanning angle and stable gain as patterns of the array factor and the GAE are manipulated simultaneously. To verify, a prototype SIW LWA with double-layer transverse slots is fabricated and measured. Experimental results show this antenna achieves continuous dual-beam scanning from backfire (-90∘) to forward (±20∘) from 12.4 GHz to 19.9 GHz with a total coverage range of 220∘ and the realized gain varying from 8.3 dBi to 12.8 dBi.

Double-Periodic Patch-Loaded Spoof Surface Plasmon Polariton Leaky-Wave Antennas With Suppressed Open-Stop Band Effects

A leaky-wave antenna (LWA) based on split-ring-shaped spoof surface plasmon polaritons (SSPPs) is designed, simulated, and measured. We proposed a double-periodic patch-loaded method to suppress the open-stop band (OSB) effect and introduced an SSPP power divider with a 180° phase shift for the anti-phase excitation to enhance the gain in the main radiation direction of the antenna. Both methods are analyzed and verified. The investigated results show that both S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> and S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> are less than -10 dB in 7-11 GHz and no bulge is observed around the broadside radiation frequency of 10 GHz, demonstrating good OSB suppression (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> < -26 dB, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> < -45 dB). Furthermore, the LWA also demonstrates good performances with a wide-angle (-48° to +15°), high scanning rate (1.57°/%), high gain (10 dBi), and high average efficiency (97%). This work provides a new way to realize efficient OSB suppression for LWA designs.

SIW Leaky Wave Antenna for THz Applications

This paper proposes a new design of leaky wave antenna (LWA) based on substrate integrated waveguide (SIW) technology for THz applications. The suggested LWA structure has a combination of longitudinal and transverse slots and makes a 10-element linear array of radiating elements. To address the problem of open-stop-band (OSB), four additional smaller slots were etched on the corners of longitudinal and transversal slots. At the broadside, this LWA provided a gain of 12.33 dBi, and a continuous wide beam scanning range from +78° to −6° via the broadside while exhibiting efficient radiation performance over the operating frequency bands of 105 GHz to 109 GHz with a peak gain of 16.02 dBi.

A TM11 High-Order Mode Leaky Wave Antenna

A novel leaky-wave antenna (LWA), which operates at the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$TM_{11}$ </tex-math></inline-formula> high-order mode, is proposed. This LWA achieves a 4.6 times higher gain than the traditional TE10-based LWAs. An analytical formulation is derived, which shows that a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$TM_{11}$ </tex-math></inline-formula> -based LWA couples more energy to free space through an appropriately designed slot than traditional TE10-based LWAs. Simulations are used to compare the performance of our proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$TM_{11}$ </tex-math></inline-formula> -based LWA with a similar LWA that operates at its fundamental TE10 mode. Specifically, it is shown that our <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$TM_{11}$ </tex-math></inline-formula> high-order mode LWA achieves 6.67 dB higher gain than a TE10-mode LWA that operates at the same frequency. Also, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$TM_{11}$ </tex-math></inline-formula> -mode LWA is designed to mitigate the open-stopband (OSB) problem. This design achieves a fan beam with a maximum gain of 15.4 dBi and a scanning elevation range of 18° (through the broadside direction) in a bandwidth of 2 GHz. Prototypes of our LWA designs are manufactured using a cost-effective additive manufacturing method (i.e., selective laser melting), and their performance is measured. The measurements exhibit good agreement with simulations, thereby validating the proposed designs.

A Conformal Leaky-Wave Antenna Design for IoMT-Based WBANs

A Conformal Leaky-Wave Antenna Design for IoMT-Based WBANs

Analysis, Design, and Measurement of Directed-Beam Toroidal Waveguide-Based Leaky-Wave Antennas

Leaky-wave antennas (LWAs) have been widely investigated for wireless systems. Most LWAs reported to date are open-path based, i.e., their guided traveling waves follow a non-closed path. A substrate-integrated (SI) toroidal waveguide-based LWA is developed in this article. A coaxial-fed probe structure effectively excites traveling waves that propagate along a closed path in the toroidal waveguide. Inverted L- and planar helical-shaped radiators, whose pickup structures extract power from the waveguide through its top wall, are introduced to radiate, respectively, linearly-polarized (LP) and circularly-polarized (CP) directed beams. The dispersion properties of the closed waveguide’s traveling wave are determined and the associated propagation phase along circular paths with specific radii guides the placement of these radiators to achieve a directive beam at a specified angle. Prototypes of both the LP and CP toroidal LWA (TLWA) systems were fabricated and tested. Good agreement between the simulated and measured results was obtained. The measurements of the compact, low-cost LP and CP prototype systems confirm they radiate beams pointed in their distinctly different, specified directions with realized gains of 13.2 dBi and 13.9 dBic, respectively, at 9.75 GHz.

Dual-Frequency Microstrip Leaky-Wave Antenna for High-Gain Broadside Radiation

This article presents a resonator-fed dual-frequency dual-mode bidirectional leaky-wave antenna to provide attractive high-gain broadside radiation at dual desired frequencies. First, by analyzing the dispersion diagrams of the first (EH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ) and third (EH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) higher order modes of a microstrip line, it is theoretically verified that these two modes can both be suitably employed for bidirectional leaky-wave antenna design. In addition, it is also determined that the ratio between these two operation frequencies can be handily controlled by appropriately loading periodical shorting pins along the nodal lines of the EH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> modal field. As such, the dual-frequency operation principle is thoroughly investigated and determined. Afterward, to effectively excite the desired modes and suppress any unwanted modes of the microstrip line, a dual-frequency resonant-fed strategy is adopted. More specifically, the introduced feeding resonator is first fed by a pair of differential probes, and then, the microstrip EH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and EH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> modes are excited through the coupling gap. In this way, the desired pure EH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and EH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> modes are successfully excited. As an example, a dual-frequency bidirectional microstrip leaky-wave antenna is designed to work at 3.6 and 4.9 GHz, and its prototype is simulated, fabricated, and tested. The obtained far-field radiation patterns from simulations and measurements show a reasonable agreement, and the concerned high-gain radiation at the broadside is well achieved at both frequencies.

Design of Periodic End-Coupled Leaky-Wave Antenna With Asymmetrically Loading Unit

In this letter, a periodic end-coupled leaky-wave antenna is designed based on an asymmetrically loading unit. A simple balancing condition in the equivalent distributed circuit model is developed for the open stopband suppression by introducing a complex effective resonant frequency. The proposed balancing condition naturally satisfies both the frequency-balancing condition and Q-balancing condition in the lumped circuit model. Based on the derived formula, the physical parameters could be quantitatively determined. Subsequently, two typical periodic end-coupled leaky-wave antennas are designed, implemented, and verified experimentally. The measured reflection coefficient and the radiation results show that the open stopband at the broadside frequency is successfully suppressed.

Archimedean Spiral Slotted Leaky-Wave Antenna

In this work, a novel leaky-wave antenna (LWA) with Archimedean spiral slots is proposed for realizing high radiation efficiency and stable gain performance in both frequency-controlled and fixed-frequency beam-scanning applications. The structural feature of the proposed Archimedean spiral slot privileges LWA with properties of easy impedance matching and high leakage rate, because it avoids the strong reflection from large-size slots that commonly used in LWA design for high leakage rate. The bandwidths of the final designed Ka-band LWA defined by radiation efficiency larger than 90% and 80% are 13% and 25%, respectively, while the bandwidth defined by return loss less than −10 dB is 29%. And the gain fluctuations between different scanned beams are less than 2.4 dBi in the whole broadband. The LWA is further applied in designing a new-type antenna with double-layer substrate-integrated waveguide (SIW) structures, which has four feeding ports at the ends and a coupling plane in the middle interface and can realize the fixed-frequency beam switching between directions of −46°, −36°, 34°, and 45° at 28 GHz through changing the excitation port. The proposed LWAs are potential candidates for applying in future millimeter wave communication systems where multifunction integrated and multifrequency adaptive antennas are required.

Increasing radiation power in half width microstrip leaky wave antenna by using slots technique

&lt;p class="Default"&gt;The radiation power in the endfire is decreased while the main beam of half substrate integrated waveguide scan from broadside to endfire in a forward. The design of half-width microstrip leaky-wave antenna (HW-MLWA) has been presented in this work to increase the power radiation near endfire by using the slots technique in the radiation element. This slot leads to a decrease the cross-polarization. The proposed design comprises one element of HW-MLWA with repeated meandered square slots in the radiation element. One aspect of this antenna is generated by using a half substrate integrated waveguide with a full tapered feed line. The proposed antenna was terminated by load of 50 Ω, and feed on the other end of the antenna. Finally, the suggested design is simulated and acceptable results were found. The released gain is increased from 10.6 dBi to 12 dBi at 4.3 GHz. This design is suitable for unmanned aerial vehicle UAVs at C band application.&lt;/p&gt;

An investigation of the dynamic beam-steering capability of a liquid-crystal-enabled leaky-wave antenna designed for 5G applications

In this Letter, an investigation is performed on the utilization of nematic liquid crystal (NLC) cells in the design of leaky-wave antennas (LWAs) for millimeter-wave (mm-wave) radiation in order to dynamically control its beam scanning capability at a single frequency. A NLC compound is sandwiched between two single-sided copper-plated substrates allowing a traveling wave to be guided through a substrate-integrated waveguide. The tuning capabilities of the structure, based on the use of K15 or GT7-29001 as the middle layer, were evaluated for different biasing conditions demonstrating the associated dynamic scanning of the main beam. A quasi-periodic LWA was designed to operate in the 5G mm-wave band, thus supporting a fast-wave propagation with tunable phase constant and dynamic beam steering at a single frequency. The simulated results clearly illustrate a dynamic beam scanning range of 45° through the use of an external bias voltage ranging between 0 and 40 V. These results are quite promising creating a fertile ground for the utilization of NLCs in the design and fabrication of LWAs for 5G wireless communication networks.

Microstrip leaky wave antenna for wide range of beam scanning in X band

AbstractIn this work, design of a pattern reconfigurable antenna is presented for X‐band applications as a leaky wave antenna (LWA) realization. Due to the advantages of simple design schematic, low profile, and easy impedance matching, LWA designs have been using as an efficient solution for reconfigurable antenna in many wireless communication applications. Optimization and simulation of the proposed LWA is carried out in 3‐D Microwave simulation CST environment and Honey Bee Mating is used as the optimization algorithm. Dimensions of the proposed LWA is 130 × 30 mm, which is fabricated on Rogers 5880 as capacitive loaded eight identical rectangular microstrip patches operating over 9.5‐12 GHz with a fractional bandwidth. The proposed LWA exhibits a measured peak gain of 11.8 dBi at 10 GHz with an overall gain characteristic of between 9.5 and 11.8 dBi over the range of 9.5 to 12 GHz with a steerable pattern characteristics between −45 and 50° as agreed with the theory. Furthermore, the fabricated LWA has been found to have the superior performance as compared with its counterparts.

Removing broadside null of symmetric long‐slot antennas by using a coating layer

This study presents a new concept in the design of symmetric long-slot leaky-wave antennas. Theoretically, a radiation null in the broadside direction of these antennas exists. The main idea of this study is to use a cover or coating layer to convert this null to a peak in the radiation pattern. The presence of the coating on the slot not only changes the leaked mode of the waveguide but also rotates its polarisation by 90°. As a proof of concept, a relatively small long-slot LWA is designed and fabricated on a C-band WR-159 waveguide, which is covered by an FR4 layer. The simulated relative broadside gain of the antenna with the coating over the antenna without the coating tends to infinity because of the presence of the null. Our simple measured results of the radiation pattern confirm the theory with more than 18 dB improvement. The realised gain of the antenna with a coating layer at broadside is 11.1 dBi with 9.8° half-power beam-width.

A Compact Conformal Stub-Loaded Long Slot Leaky-Wave Antenna With Wide Beamwidth

This letter presents a compact, conformal, stub-loaded longitudinal slot leaky-wave antenna at Ku -band. The antenna is designed with a short length of 2.75λ at the center frequency. The effect of flange length on the transverse plane half-power beamwidth (HPBW) is studied. The design of leaky-wave antenna within this short length and flange studies on transverse plane HPBW are the novelty of this letter. Antenna design, dispersion curves, and a comparison of the simulation and measurement results are presented. The radiation efficiency of 95%, a gain of 8 dBi, a tilt angle of 30°, and longitudinal plane HPBW of 42° are achieved. Transverse plane HPBW of 168° and 4 dB beamwidth of 180° are achieved, which aids to achieve an omnidirectional pattern using two antennas when placed in the cylindrical shell with a 180° angular separation.

Gain Enhancement of Transversely Slotted Substrate Integrated Waveguide Leaky-Wave Antennas Based on Higher Modes

A technique for gain enhancement of transversely slotted substrate integrated waveguide (SIW) leaky-wave antennas is proposed based on higher modes. Two SIW leaky-wave antennas based on the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m0</sub> ( m = 3, 5) higher modes are investigated. The antennas possess the advantage of simplicity, in which the feeding structures are compact and simple. Compared with published transversely slotted SIW leaky-wave antenna based on the fundamental mode (TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode), the proposed antennas exhibit higher and more consistent gains. Besides, the antennas maintain the scanning capability from near broadside to endfire. The working principles of the antennas are explained. The propagation characteristics are investigated with a magnetic field integral method. The aperture efficiencies are analyzed. Two leaky-wave antenna designs based on the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> higher modes are demonstrated and compared with a TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> -mode antenna design (with almost the same dispersion characteristics). Prototypes of the three designs are fabricated and measured for comparisons. Compared with the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> -mode antenna, the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> - and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> -mode antennas have the transverse beamwidths markedly narrowed and have the gains improved by about 5.5 and 8 dB, respectively.

Air-Filled Substrate Integrated Waveguide Leaky-Wave Antenna With Wideband and Fixed-Beam Characteristics

In this communication, a novel wideband fixed-beam leaky-wave antenna (LWA) is proposed. The antenna is designed based on air-filled substrate integrated waveguide (SIW), which is composed of one layer of printed circuit board (PCB) in the middle and two layers of thin copper plates on the top and bottom. The different layers are aligned and fixed by screws. A long slot is etched on the top surface of air-filled SIW as a radiator. Due to the dispersive characteristic of the air-filled SIW, the antenna can radiate at a fixed direction over a wideband. To the best of our knowledge, this is the first time that the air-filled SIW is adopted for LWA design. The proposed antenna is designed, fabricated, and tested. The measured results show that its wide operating bandwidth reaches up to 37.0%, ranging from 11 to 16 GHz. The excellent fixed-beam radiation performance is obtained over the operating bandwidth. The radiation direction is fixed at 59° with only ±3° variation, and the peak gain is within 14.0-15.3 dBi. Although the beam angle can only be fixed nearly the endfire, this method offers a simple way to realize wideband fixed-beam feature.

Printed planar tunable composite right/left‐handed leaky‐wave antenna based on a tunable polymer‐BST substrate

AbstractThis article presents a printed tunable right/left‐handed leaky wave antenna (LWA) on a new flexible, tunable low density polyethylene‐barium strontium titanate composite substrate using an aerosol jet printer. The new substrate had a dielectric constant of 16 and tunability of 3.5% at f = 10 GHz. Interdigital capacitors (IDC) were utilized in the leaky wave antenna design not only to act as shunt capacitor in CRLH transmission line design but also as tunability element to implement tuning capability of the LDPE‐BST substrate for antenna beam steerability for a fixed operated frequency in X‐band frequency range. Up to 15° beam steering was achieved by applying DC voltage through the printed leaky wave antenna.

Broadband scanning leaky‐wave antenna based on interdigital coupled‐type composite right/ left‐handed transmission line structure

Owing to its unique nonlinear dispersion characteristics, the composite right/left-handed (CRLH) transmission line (TL) have been widely implemented in the design of leaky-wave antennas. A novel CRLH-TL unit is proposed in this article using the metal patch and pillars to connect the interdigitated line. Not only the parasitic resonance in the conventional interdigital CRLH TL is eliminated by etching the annular gap on the ground, but the miniaturization is also achieved. Then, a broadband high-performance full-plane scanning leaky-wave antenna is designed based on the unit in balanced state. The measured bandwidth with return loss <−10 dB is 3.97 to 5.86 GHz and the peak gain over the operating bandwidth is higher than 9.17 dB. There is no parasitic resonance in the operating bandwidth and the antenna has a lower operating frequency than the classic Interdigital Coupled-Type (ICT) CRLH leaky-wave antenna of the same length.

The Periodic Leaky-Wave Antenna With Different Unit Cells Based on Consistent Fundamental Mode

In this article, we present a novel periodic microstrip leaky-wave antenna (MLWA) design based on different unit cells. The proposed antenna consists of three different kinds of unit cells developed in our previous works, in which the wavenumber of fundamental mode is basically consistent. Big period cascaded by the three different unit cells is introduced for producing a relatively narrow radiation beam. Almost same radiation angle of the antenna is obtained regardless of the permutation of unit cells, which provides more design freedom on antenna structure. Slotting and pins loading technique are applied in unit cells for canceling the reactance of the big period, thus a continuous beam scanning with small gain fluctuation around broadside direction could be achieved. The prototype is fabricated and measured, demonstrating the feasibility of this novel periodic antenna design and well agreement between simulated and measured results. Measurement results show the main beam steers continuously from −46° to 31° with the operating frequency changes from 6 to 9 GHz. The peak gain reaches up to 12.8 dBi at the frequency of 7 GHz.