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The discovery of topological insulators and their photonic counterparts has led to significant advancements in electromagnetics. These materials offer an innovative way to control electromagnetic fields at the interface of trivial and topological materials. One exciting development in this field is the creation of topological metasurfaces that use propagating line waves as the edge mode, allowing for the introduction of topological transmission lines. The main focus of this study is to utilize a spin photonic topological insulator structure that has been designed using 30-degree rhombic cells to develop a leaky wave antenna application. Along with validating the topological behavior of the unit cell, we have also examined the angle of connection between the proposed topological and classical lines to optimize the transmission. This article presents a low-profile leaky wave antenna with one beam at either side, which is completely realizable because of the proportional pattern and little coupling between radiating elements. Moreover, the proposed antenna is a uniform left-handed leaky wave antenna that operates in the frequency range of 17.5-20 GHz, which is in the fast wave region. As a result, it achieves a directivity of 19.57 dB at 18.5 GHz with a 22.5-degree wide beam scan.

A novel approach is presented for synthesizing radiation patterns of substrate-integrated waveguide leaky wave antennas in two stages. In the first stage, the antenna is considered an equivalent rectangular waveguide with slots, and a comprehensive equivalent circuit model is constructed. Varying slot configurations are accommodated by the developed equivalent circuit model. Each slot section is represented as an admittance with the incorporation of Elliott’s slot theory. Computations of the relative aperture fields are performed using circuit theory, and the far-field pattern is estimated through array theory. In the second stage, the circuit model is utilized for genetic algorithm-based optimization, enabling customization of the radiation pattern to meet specific requirements. The methodology has a computational advantage over full-wave simulations, resulting in a significantly faster and more efficient design process. Numerical verification through simulation of various examples and experimental validation through antenna fabrication are presented, affirming agreement between calculated and measured results. Remarkable effectiveness in antenna engineering can be attained for future wireless communication systems by using the proposed technique.

This paper introduces a beam‐scanning holographic antenna composed of a substrate‐integrated waveguide (SIW) feeding structure and a rectangular microstrip array. The antenna innovatively combines holographic theory with liquid crystal electrical tunability to realize single‐frequency large‐angle beam scanning function which can effectively solve the problem of beamforming reconfiguration in traditional array antenna systems. In this paper, the variation of dielectric constant of liquid crystal under different bias voltages is quantitatively analyzed. Additionally, the beam forming technology is analyzed under hologram amplitude weighting theory. The relevant theories are verified by manufacturing and testing. The prototype antenna achieves the ultra‐wide beam scanning angle of −63° to 63° at 36 GHz. [ABSTRACT FROM AUTHOR]

Major constraint in leaky wave antenna (LWA) is open stop band. In this paper study of different techniques used by researchers to remove the open stop band problem has been done. Different characteristics of leaky wave antenna with the design of substrate integrated waveguide is also discussed. This paper explain theory and design of the unit cell and array of leaky wav antenna in different frequency range i.e. X-band, Kuband and higher frequency range. Study of various techniques to achieve high beam scanning and higher gain has been done. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) need high data rate connectivity, which is achievable through mm-waves and sub-THz bands. The proposed two-port leaky wave MIMO antenna, employing a coplanar proximity technique that combines capacitive and inductive loading, addresses this need. Featuring mesh-like slots and a vertical slot to mitigate open-stopband (OSB) issues, the antenna radiates broadside and bidirectionally. H-shaped slots on a strip enhance port isolation, and a coffee bean metasurface (MTS) boosts radiation efficiency and gain. Simulations and experiments considering various realistic scenarios, each at varying vertical and horizontal distances, show steered beam patterns, circular polarization (CP), and high-gain properties, with a maximum gain of 13.8 dBi, an axial ratio (AR) 9.98 dB, and an envelope correlation coefficient (ECC)

With the change in lifestyles, emerging stress and physical parameters of the environment, health-related issues have affected many people worldwide. An important indicator of serious illness is the abnormality in respiration rate. This abnormality leads to asthma, obstructive sleep apnea (OSA) and heart-related diseases. This leads to having more accurate and robust healthcare monitoring and diagnosis facilities. The respiration rate and vital signs are detected through electromagnetic (EM) waves using different antennas. Different types of previous antennas (parabolic, horn, yagi-uda, helical and patch) used for respiration monitoring are studied and compared with the proposed antenna. The limitations of currently used antennas include the bulky size of setup and less directional beam, which may interfere with other devices leading to errors. Substrate integrated waveguide (SIW)-based leaky-wave antenna (LWA) is proposed with better results than current antennas available for respiration monitoring. Experimental work is carried out for the validation of simulated results. The proposed antenna has a gain of 9.72 dB with angular width or approximately HPBW 37.5°. The simulated s11 of the antenna is −16 dB, and the measured s11 is −22.97 dB. VSWR shows antenna radiation efficiency is approx 97%. An experimental setup using VNA is used to detect respiration monitoring in real-time; the system could detect the respiratory activity of the subject with a confidence interval accuracy of 93% and an average error of 7%. [ABSTRACT FROM AUTHOR]

Controlling objects with body language is an extremely interesting ability for human beings. Recognizing different gestures is an effective way to collect valuable information, which is used to switch the radiation characteristic of beam scanning antennas. However, most existing beam scanning antennas are wire-connected and manually controlled by users. Thereby, a novel framework of gesture-controlled antennas is proposed in this paper. Rather than DC voltages supplied by powers or AC voltages supplied by signal generators, the beam scanning antenna can be effectively controlled by different gesture commands collected in real time from the user. On this basis, considering the advantages of the low cost and wide frequency band of liquid crystal (LC) materials, a LC-based fixed-frequency beam scanning leaky wave antenna (LWA) with gesture-controlled systems is demonstrated as one example. Different gestures can be recognised as controlled information to supply corresponding output signals by field programmable gate arrays (FPGAs) for the LC-based LWA. Based on the proposed framework, a verification system is tested, which demonstrates that the radiation characteristic can be effectively controlled by the user's gesture. This work supplies a novel way for intelligent beam scanning antennas with potential applications in the internet of things (IoT), satellite and 5 G/6 G communications. [ABSTRACT FROM AUTHOR]

In the proposed paper a Substrate Integrated Waveguide in Half Mode (HMSIW) is designed for making a novel leaky wave antenna which was further analysed. The novel leaky wave antenna is designed with periodic variation in the longitudinal slots in the upper part of the substrate in a selective frequency along with band pass filter in the particular range with pass band at Centre frequency of 16.8GHz, 24.7GHz and 28.6GHz. The Filter is designed with the use of Defective Ground plane (DGS) by cutting slots of SRR in the lower ground plane. The leaky wave antenna which has been suggested in paper resonates at 17GHz and 24.6GHz, which is very close to the operating mid frequency of the band pass filter which is 16.8GHz, 24.7GHz and 28.6GHz. By designing of leaky wave antenna in the proposed manner, various advantages can be obtained such as reduction in size, frequency selectivity, removal of unwanted noise with the help of band pass filter. The novelty which can be achieved in this proposed antenna is that it leads to gain enhancement up to 6dB and 8dB at selective frequency of 17GHz and 24.6GHz with the reduced size HMSIW in which further size reduction is achieved with the assistance of DGS in ground plane. [ABSTRACT FROM AUTHOR]

A multi-layer beam-scanning leaky wave antenna (LWA) for remote vital sign monitoring (RVSM) at 60 GHz using a single-tone continuous-wave (CW) Doppler radar has been developed in a typical dynamic environment. The antenna's components are: a partially reflecting surface (PRS), high-impedance surfaces (HISs), and a plain dielectric slab. A dipole antenna works as a source together with these elements to produce a gain of 24 dBi, a frequency beam scanning range of 30 ° , and precise remote vital sign monitoring (RVSM) up to 4 m across the operating frequency range (58–66 GHz). The antenna requirements for the DR are summarised in a typical dynamic scenario where a patient is to have continuous monitoring remotely, while sleeping. During the continuous health monitoring process, the patient has the freedom to move up to one meter away from the fixed sensor position.The proposed multi-layer LWA system was placed at a distance of 2 m and 4 m from the test subject to confirm the suitability of the developed antenna for dynamic RVSM applications. A proper setting of the operating frequency range (58 to 66 GHz) enabled the detection of both heart beats and respiration rates of the subject within a 30 ° angular range. [ABSTRACT FROM AUTHOR]

In this study, a combined structure is proposed to develop ultra-thin silicon solar cells. This integrated structure consists of silver fractal-like nano-particles and leaky wave nanoantennas. The nano-cuboid pattern embedded inside anti-reflective coating benefits from different optical modes, such as surface plasmons and cavity modes, which trap more light and amplify the electric field in the upper region of the absorber layer. On the bottom side, the hybrid plasmonic mode in the structure of the optical nanoantenna makes it possible to focus and direct the incoming light on the bottom of the absorber layer and increase the optical pathlengths in the ultra-thin film solar cell. The nanoantenna behavior and three-dimensional finite-difference time-domain analysis show that photon absorptions improve significantly at long wavelength lightwaves through this proposed combined structure. The short circuit current enhancement of the solar cell under 1 sun standard illumination is obtained by a factor of 1.94 and 1.80 for TM and TE polarization of incident light, respectively. Due to the acceptable results for different incident angles and polarizations, ultra-thin thickness, and nano-cuboids synthesis feasibility, our structure has the potential to be applied in the design of miniaturized photovoltaic devices.

A groove gap waveguide (GGW) leaky wave antenna with a wide scan angle in the terahertz (THz) band (430–560 GHz) is presented in this study. The unnecessary tight contact between the top plate and pins of the GGW makes it easy for the fine fabrication and assembly of this THz antenna. Scanning of pointing directions with frequency, together with the low side‐lobe level (SLL), is designed for the pins' heights and intervals as well as the groove cavity width. Measurement results of S11 parameters remain about −20 dB, besides, the antenna scan angle range is 15o within 430–560 GHz, and the gains are also above 15 dB within that working frequency bands. [ABSTRACT FROM AUTHOR]

In this article, a multi‐resonance frequency scanning antenna with a Luneburg lens is designed. This antenna operates in the X‐band and can achieve beam steering by changing the frequency in this band. The steering angle of the designed model is ±50°. This antenna is a good candidate for a wide range of telecommunication, automotive radar, and search radar applications. The advantage of this model over most of other works in this field is that just one multi resonant slot antenna in front of the Luneburg lens is used instead of several antennas and separate feed networks. This development leads to a compact structure with more straightforward and cost‐effective fabrication. The antenna structure is based on a substrate integrated waveguide technology. Full‐wave simulations are performed using the software of CST. The proposed model is designed and fabricated on Rogers RO4003C substrate with a height of 20 mils. A perforated Teflon sheet is designed and fabricated to approximate the inhomogeneous refractive index of the Luneburg lens. [ABSTRACT FROM AUTHOR]

A leaky wave antenna (LWA) based on half‐mode substrate integrated waveguide (HMSIW) is presented. Integrated phase inverters are used to eliminate the far‐field cancelation from the adjacent radiating element with half‐wave spacing. The ground plane is extended to reflect the quasi‐magnetic‐dipole radiation pattern from the backfire to the boresight for enhanced antenna gain. Two linear arrays with differential feeding are deployed back‐to‐back along their longitude, by which the far‐field radiation adds constructively that leads to further increased antenna gain. The proposed antenna features shorter electric length compared with counterparts of the same gain. Agreement is achieved between simulation and measurement. The proposed antenna has a measured impedance bandwidth of 11–12.8 GHz (15.6%), the measured maximum gain of 16.2 dBi @ 11.6 GHz. The antenna's beam scans from 20° to 50° in the boresight with the input signal's the frequency. By using the phase inverter, the extended ground plane and the back‐to‐back deployment, the proposed antenna produces equal gain with shorter antenna's electric length. [ABSTRACT FROM AUTHOR]

In this paper, an antenna array for the X-band aerial landing system has been proposed. The proposed antenna is an ellipse-shaped leaky-wave array radiating in slow mode wave and has a scanning range of 75° for different inter-element spacing. Four antenna arrays were designed: two with 60 elements and two with 30 elements each, all operating from 9.3 GHz to 12.3 GHz providing a gain of 30 dBi and 20 dBi, respectively. To verify the performance, a 15-element sub-array having an overall size of 210 mm × 30 mm and achieving a total gain of 17 dBi was fabricated and tested. The proposed sub-array was fabricated using Rogers Duroid5880 (ɛr = 2.2 and h = 1.575 mm). It has been shown through comparison of radiation patterns that measured and simulation results are in good agreement.

A bidirectional leaky wave antenna (LWA) with beam scanning capabilities was developed based on the dielectric image line for single-tone continuous-wave Doppler radar (DR) for remote vital sign monitoring (RVSM) in a dynamic environment. It consists of a conductor-backed copper dielectric image line with two of the same dielectric layers mounted on top of each other for performance improvement. A RO6010 substrate with high permeability is used for the top two layers. The bottom layer is a RT/duroid 5880 low permittivity substrate stacked on top of the copper DIL to prevent higher order modes from being excited in the DIL channel. The dominant mode of the DIL is perturbed by making holes periodically in the DIL, and fast-wave space harmonics are generated. The scanning range of the proposed antenna through the broadside is 70.19°(−42.49° to 27.7) with an impedance bandwidth of 15 GHz (50-65 GHz), an optimum gain in the fast wave area ranging from $15.5 \,\mathrm {dBi}$ to $19.79 \, \mathrm {dBi}$ and an efficiency of 83.8% at $57.5 \,\mathrm {GHz}$ . Detailed RVSM tests have been performed with the proposed antenna system. It is shown that by adjusting the operating frequency from $50 \,\mathrm {GHz}$ to $65 \,\mathrm {GHz}$ , multiple targets’ breathing rates (BR) and heart rates (HR) can be detected within 70° of the angular range.

In this article, a novel miniaturized wide beam scanning range multi‐layered mm‐wave leaky‐wave antenna (LWA) based on slow‐wave (SW) substrate‐integrated waveguide (SIW) is presented. The SW effect is introduced by loading conventional SIW with internal metalized blind vias connected to the bottom ground plane. The SW effect in the SIW structure causes the separation of the electric and magnetic field components in the structure which leads to the reduction in lateral dimensions of the proposed topology by 35% as compared to the conventional SIW. The proposed LWA exhibits a miniaturized volume of 6.6 × 0.41 ×.07 λ3. The radiation in the proposed design is realized by introducing U‐shaped slots in the unit cell of the SW‐SIW structure. Experimental results show that the proposed SW‐SIW LWA achieves almost symmetric and continuous beam scanning from −48° to 52° including the broadside direction within the impedance bandwidth of 23.7–28.1 GHz. The proposed antenna achieves a peak gain of 14.52 dBi and the half‐power beamwidth of LWA is as low as 10°. The proposed antenna also exhibits radiation efficiency of above 90% within the bandwidth. The proposed design can be a potential candidate for mm‐wave frequency beam scanning applications. [ABSTRACT FROM AUTHOR]

In this article, a periodic leaky‐wave antenna (LWA) with wide‐angle beam scanning and stable gain is proposed based on the meandering microstrip line. Due to the meandering property of the microstrip line, the longitudinal dimension of the antenna is reduced. Firstly, the radiation characteristic of the meandering microstrip line is analyzed in detail. Each corner of the meandering microstrip line is modeled by a shunt capacitance and shunt radiation conductance to acquire the equivalent circuit. Then, the frequency balanced condition is investigated based on the established equivalent circuit to realize continuous beam scanning through broadside. Subsequently, the method of open‐stop band (OSB) suppression is studied by introducing asymmetric perturbation on the LWA unit cell, which actually can be applied to eliminate the OSB effect in arbitrary symmetric LWAs. Finally, an antenna prototype is simulated and measured. The measured results agree well with the simulated results, validating the proposed method of OSB suppression. The measured results show that the designed antenna exhibits the beam scanning capacity of −47° to +76° with the frequency varying from 5.0 to 7.8 GHz and gain variation of 2.9 dB. [ABSTRACT FROM AUTHOR]

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A dual‐band leaky wave antenna (LWA) based on substrate integrated waveguide (SIW) is presented in this paper. The radiation elements are composed of a set of periodical transverse slots and a long longitudinal slot that can radiate scanning beams at two different bands under TE10‐mode and TE20‐mode excitation, respectively. The scanning beams in the two bands both cover the forward region, and polarizations are perpendicular. Under TE10 excitation, the proposed antenna radiates scanning beams in the low band (8.2 GHz ~ 9.1 GHz) with gain varying from 10.6 to 15.9 dBi. Under TE20 excitation, the beams of the proposed antenna scan in the high band of 18.8 GHz ~ 22 GHz with gain varying in 11.7 dBi ~ 16 dBi. The measured results of the fabricated prototype confirm the design theory and simulated results. [ABSTRACT FROM AUTHOR]

A multi-layer beam-scanning leaky wave antenna (LWA) for remote vital sign monitoring (RVSM) at 60 GHz using a single-tone continuous-wave (CW) Doppler radar has been developed in a typical dynamic environment. The antenna’s components are: a partially reflecting surface (PRS), high-impedance surfaces (HISs), and a plain dielectric slab. A dipole antenna works as a source together with these elements to produce a gain of 24 dBi, a frequency beam scanning range of 30°, and precise remote vital sign monitoring (RVSM) up to 4 m across the operating frequency range (58–66 GHz). The antenna requirements for the DR are summarised in a typical dynamic scenario where a patient is to have continuous monitoring remotely, while sleeping. During the continuous health monitoring process, the patient has the freedom to move up to one meter away from the fixed sensor position.The proposed multi-layer LWA system was placed at a distance of 2 m and 4 m from the test subject to confirm the suitability of the developed antenna for dynamic RVSM applications. A proper setting of the operating frequency range (58 to 66 GHz) enabled the detection of both heart beats and respiration rates of the subject within a 30° angular range.

Home-based healthcare monitoring is becoming an essential part of people's lives, with an increasing percentage of the population suffering from chronic diseases such as apnoea, asthma, and heart disease. For respiration monitoring using electromagnetic (EM) waves, the frequency of 10 GHz is in the non-ionizing spectrum and is the limit of the permitted specific absorption rate value. Selecting the proper dielectric material is very crucial to getting a proper performance from any antenna. In this article, experimental work is reported on the analysis of the performance of a dielectric material as an antenna. The modeling of a one-port substrate-integrated waveguide (SIW)-based leaky wave antenna (LWA) with linear horizontal slots is analyzed to investigate the effects on the antenna of different dielectric materials provided as a substrate. Using the radio frequency (RF) module of software CST, the effects on the performance of an antenna are studied in terms of radiation pattern, return loss, electric field, and voltage standing wave ratio (VSWR) for 10 GHz. Different commonly used dielectric materials, like printed circuit boards (PCBs), fused silica (quartz), polymethyl methacrylate (PMMA), mica, flame retardant (FR)-4, and Rogers (RT)-5880 are used to evaluate the performance of the proposed antenna. by finite element method modeling. The results of antenna performance obtained after simulation were compared, and the dielectric RT-5880 showed better results than the others. For the RT-5880, the electric field is 12,663 V/m, the return loss is 16 dB, and the gain of the antenna is 9.52 dBi, with an angular width of 37.5° and a VSWR of 1.2. Using the experimental setup, respiratory movement was successfully detected. [ABSTRACT FROM AUTHOR]

In this paper, an antenna array for the X-band aerial landing system has been proposed. The proposed antenna is an ellipse-shaped leakywave array radiating in slow mode wave and has a scanning range of 75° for different inter-element spacing. Four antenna arrays were designed: two with 60 elements and two with 30 elements each, all operating from 9.3 GHz to 12.3 GHz providing a gain of 30 dBi and 20 dBi, respectively. To verify the performance, a 15-element sub-array having an overall size of 210 mm × 30 mm and achieving a total gain of 17 dBi was fabricated and tested. The proposed sub-array was fabricated using Rogers Duroid5880 (εr=2.2 and h =1.575 mm). It has been shown through comparison of radiation patterns that measured and simulation results are in good agreement. [ABSTRACT FROM AUTHOR]

In this letter, a periodic coplanar waveguide leaky-wave antenna with enhanced gain and continuous backward-to-forward beam scanning is presented. The leaky-wave antenna is made of coplanar waveguide with two symmetric transversal slots on the ground plane. The gain of the antenna is enhanced because of the radiation of the two slots superimposing in the H-plane. The relationship between Bloch impedance and characteristic impedance of the host coplanar waveguide is then investigated. By introducing a pair of matching slots, an improved impedance matching approach is presented to remove the dramatic variation of Bloch impedance at broadside frequency. Hence, the open-stop band (OSB) can be effectively suppressed and broadside radiation is achieved. Finally, a design prototype is implemented and fabricated as an experimental verification. The simulated and measured results show a good agreement. Both the reflection coefficient and radiation patterns verify that the open-stop band of the antenna is eliminated, while the gain is enhanced. [ABSTRACT FROM AUTHOR]

In this paper, periodic perturbations are employed on the broad wall of a substrate integrated waveguide (SIW) long slot leaky-wave antenna (LWA) to eliminate the excited unwanted mode. The presence of unwanted mode in the uniform LWA is identified by using the amplitude and phase of the electric field at the slot. Using the electric field data in the structure, propagation constants and amplitudes of desired and unwanted modes are obtained. In order to preserve the desired leaky mode and suppress the unwanted mode, periodic transverse slots are added to one side of the uniform longitudinal slot. Suppressing unwanted mode results in good consistency between the desired and designed radiation characteristics. Comparison between two LWA designs, with and without suppressing unwanted mode, for achieving −25 dB sidelobe level (SLL) and beam direction of 40° at 17 GHz, demonstrates high accuracy of the proposed design procedure. A prototype of the modified antenna is fabricated, and measured results are presented at 16, 17, and 18 GHz for validation.

A simple method to synthesize multibeam radiation patterns with modulated linear spoof surface plasmon polariton (SSPP) leaky-wave antennas (LWAs) is proposed. We analytically proved that, for this specific type of LWA, the superposition of modulated antenna shapes can lead to a direct superposition in its radiation pattern. To validate this method, several simulations are performed, and two antennas are fabricated and tested. These results show that various types of radiation pattern, e.g., single-beam, dual-beam, or multibeam at various directions, can be achieved with little need for design efforts. The proposed antennas have features of the highly diverse radiation pattern, high gain (up to $\sim 14.6$ dBi, measured), wideband, large frequency scanning capability ($\sim 120$ ° with ignorable open stopband effect at broadside), and have very simple structures that are easy to design and fabricate. [ABSTRACT FROM AUTHOR]

In this paper, a leaky wave antenna is presented based on the substrate integrated waveguide structure. The proposed antenna has a periodic structure with a combination of rectangular and H‐shaped slots on the top of the antenna. By providing this new design for slots, a better angular scanning achieved rather than the previous designs from broadside to end‐fire, so that with this design, the leaky wave antenna can scan from 2.5 to 87° by changing the feeding frequency, which is the highest scanning angle relative to the design of uniform rectangular slots, the butterfly shaped slots and the H‐shaped slots. The proposed antenna was designed to have circular polarization in the entire operating frequency range. [ABSTRACT FROM AUTHOR]

A class of 45° linearly polarized and circular polarized high scanning rate leaky wave antennas are proposed in this paper, which is based on slow-wave substrate integrated waveguide structure. High scanning rate leaky wave antennas have recently become attractive for imaging applications and automotive radar. These applications also require a continuous scanning range without an open stopband, as seen at broadside for ordinary leaky wave antennas. Furthermore, both 45° linearly polarization and circularly polarization are required in practical applications. In this paper, we propose an all-in-one leaky wave antenna design, which features high scanning rate, continuous scanning capability across the broadside, 45° linear polarization or circularly polarization, single-layer configuration, and single-side radiation. Two design examples are provided to illustrate the proposed principle. Both simulation and experimental validation are given.

This article presents a nonlinear leaky wave antenna (LWA) with frequency dependent parametric radiation based on a fundamentally slow‐wave transmission line (TL) structure. Unlike a conventional LWA that radiates at the excitation frequency, the radiation for the proposed travelling wave structure relies on the parametric frequencies based on the injected pump signals. The proposed nonlinear fundamentally slow wave structure utilizes a periodic sharply bend TL loaded by varactor diodes as nonlinear elements. By utilizing the n = −1 spatial harmonic, the fundamentally slow wave structure can enter the leaky wave region at higher frequencies, where the parametric radiation results from the bifurcation of the injected pump signals. Such TL‐based nonlinear LWA reduces the design complexity and fabrication difficulty. The resulting parametric frequency radiation can be used for beam steering, which provides additional degree of design freedom. [ABSTRACT FROM AUTHOR]

This article presents broadband, high gain, and highly efficient, leaky wave antenna for X‐band applications. The proposed leaky wave antenna consists of periodic unit cells created by a combination of modified asymmetric meander line slots and an array of metallic via. The proposed unit cell configuration work as a composite left hand‐right hand leaky wave transmission line and it is characterized using dispersion analysis. The simulated and measurement results indicate that the proposed antenna offers a wide bandwidth of 52.94% (*with stop band of 2.1%) and a large beam scanning range from −59° to 70° with a maximum measured gain of 13.1 dBi. [ABSTRACT FROM AUTHOR]

In 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. [ABSTRACT FROM AUTHOR]

In this article, a substrate integrated waveguide (SIW) based double longitudinal slots loaded leaky wave antenna (LWA) is presented. Unit cell of the proposed antenna consists of two longitudinal slots with quarter wavelength distance apart from each other for impedance matching at broadside frequency, providing suppressed open‐stop band and seamless scanning. Both the slots participate in radiation resulting higher gain. Novelty of the design lies in using two longitudinal slots per unit cell to get higher gain and optimum design to provide wide angle scanning. Dispersion diagram and equivalent electrical circuit have been used to get insight of the behavior of the unit cell. An array of 19 such unit cell of length 11 λ0 (λ0 wavelength corresponds to lowest operating frequency) is used to realize the LWA. The proposed antenna can scan seamlessly from backward to forward direction through broadside with enhanced gain. The antenna can scan 840 (from −640 to 200) with a maximum gain of 16.5 dB and minimum radiation efficiency 66% in the frequency range 10.5 to 17.5 GHz. Finally, a prototype is fabricated, and measurements are done to verify the antenna performances. [ABSTRACT FROM AUTHOR]

Directive optical leaky wave antennas (OLWAs) with tunable radiation pattern are promising integrated optical modulation and scanning devices. OLWAs fabricated using CMOS-compatible semiconductor planar waveguide technology have the potential of providing high directivity with electrical tunability for modulation and switching capabilities. We experimentally demonstrate directive radiation from a silicon nitride (Si3N4) waveguide-based OLWA. The OLWA design comprises 50 crystalline Si perturbations buried inside the waveguide, with a period of 1 μm, each with a length of 260 nm and a height of 150 nm, leading to a directive radiation pattern at telecom wavelengths. The measured far-field radiation pattern at the wavelength of 1540 nm is very directive, with the maximum intensity at the angle of 84.4° relative to the waveguide axis and a half-power beam width around 6.2°, which is consistent with our theoretical predictions. The use of semiconductor perturbations facilitates electronic radiation control thanks to the refractive index variation induced by a carrier density change in the perturbations. To assess the electrical modulation capability, we study carrier injection and depletion in Si perturbations, and investigate the Franz-Keldysh effect in germanium as an alternative way. We theoretically show that the silicon wire modulator has a -3 dB modulation bandwidth of 75 GHz with refractive index change of 3×10-4 in depletion mode, and 350 MHz bandwidth with refractive index change of 1.5×10-2 in injection mode. The Franz-Keldysh effect has the potential to generate very fast modulation in radiation control at telecom wavelengths.

Directive optical leaky wave antennas (OLWAs) with tunable radiation pattern are promising integrated optical modulation and scanning devices. OLWAs fabricated using CMOS-compatible semiconductor planar waveguide technology have the potential of providing high directivity with electrical tunability for modulation and switching capabilities. We experimentally demonstrate directive radiation from a silicon nitride (Si3N4) waveguide-based OLWA. The OLWA design comprises 50 crystalline Si perturbations buried inside the waveguide, with a period of 1 μm, each with a length of 260 nm and a height of 150 nm, leading to a directive radiation pattern at telecom wavelengths. The measured far-field radiation pattern at the wavelength of 1540 nm is very directive, with the maximum intensity at the angle of 84.4° relative to the waveguide axis and a half-power beam width around 6.2°, which is consistent with our theoretical predictions. The use of semiconductor perturbations facilitates electronic radiation control thanks to the refractive index variation induced by a carrier density change in the perturbations. To assess the electrical modulation capability, we study carrier injection and depletion in Si perturbations, and investigate the Franz-Keldysh effect in germanium as an alternative way. We theoretically show that the silicon wire modulator has a -3 dB modulation bandwidth of 75 GHz with refractive index change of 3×10-4 in depletion mode, and 350 MHz bandwidth with refractive index change of 1.5×10-2 in injection mode. The Franz-Keldysh effect has the potential to generate very fast modulation in radiation control at telecom wavelengths.

In this communication, a novel 2-D beam scanning antenna array is designed and fabricated in metallic 3-D printed technology with high integration and reduced fabrication complexity in millimeter waves. The array is composed of four leaky wave antennas and a Butler matrix based on groove gap waveguide (GWG) technology. One dimension of the beam scanning performance is realized by moving one row of pins along the groove based on the GWG concept. Meanwhile, the sidelobe levels of the radiation patterns are reduced to −20 dB by controlling the height and distance of pins along groove. The beam direction of the low sidelobe leaky wave antenna changes from 110° to 140°, while the frequency shifts from 25 to 35 GHz. Another dimension of the beam scanning capability is realized with the Butler matrix in groove GWGs. The design of this Butler matrix is based on the coupling between multilayered groove GWGs. By this means, the low sidelobe leaky wave antennas are connected directly to the Butler matrix with no more transition structures. The main beam direction of the antenna array shifts from −41° to 41°, when the exciting ports change in order. The simulated and measured port isolations are lower than −15 dB over the frequency band of 27–35 GHz, and they match well with each other. [ABSTRACT FROM AUTHOR]

This paper aims to review the work of various researchers for an old and latest advancements on Leaky Wave Antenna (LWA) theory and design. In microwave engineering, the leaky waves had been the most emerging field of research in last few decades. The basis for LWA is a guiding structure that allows the propagation of wave along the length of the antenna structure, with the wave leaking continuously along the structure. This type of antenna is classified into two categories, namely one dimensional and two dimensional LWAs. These LWAs radiate generally at the end fire direction and broadside direction to achieve the maximum scan angle for the radiation beam and these LWAs are uniform, quasi-uniform and periodic. After reviewing the working principles and characteristics of LWAs, an essence of some recent developments of designs have been discussed. Past advances include LWA designs that can scan to the endfire, LWA designs that can scan through the broadside, LWA designs that are conformal to the surfaces, and LWA designs that are capable of power recycling or include active elements. This paper also include the most demanding and latest beam scanning structures, bull's eye structures, full and half mode SIW planar LWA structures and RCS microstrip LWA structures. Some of these novel designs are derived by the recent developments in the field of metamaterials. Some other important development of LWAs such as artificial surfaces, plasmonic leaky wave nano antennas, subdiffractive plasmonic leaky wave antennas and graphene leaky wave antenna also have been reviewed. [ABSTRACT FROM AUTHOR]

A novel fully on-chip antenna based on a metasurface fabricated in a 180-nm BiCMOS process is presented. Inspired by the concept of high impedance surface (HIS), this metasurface is not used as a reflector below an antenna as commonly done. Instead, it is used as a radiator by itself. The extremely thin metasurface is composed of a patterned top two metal layers and the ground plane placed in the lowest metal layer in the process. The ground plane on the lowest metal layer of the process provides a solid shielding from the substrate and other possible circuitries. The fundamental of the antenna radiation and design are described. The measured antenna shows 2.5 dBi peak broadside gain with 8-GHz 3-dB gain bandwidth and an impedance bandwidth larger than 10 GHz. In its class of broadside radiating fully on-chip antennas, with a ground plane on the lower metal layer of the process, and without additional fabrication processing, this structure achieves the widest impedance bandwidth at W-band and one of the highest gain and gain bandwidth. It is noteworthy that this is achieved with an extremely thin antenna substrate thickness and a shielding ground plane.

A miniaturized frequency scanned leaky wave antenna (LWA) based on half mode substrate integrated waveguide (HMSIW) with open stop-band suppression is proposed. The modified cross-slot is etched on the top of HMSIW as the radiating element. The folded and unfolded ground plane designs of the proposed HMSIW LWA are compared and analyzed w.r.t their bloch impedance characteristics and it is found that further miniaturization and gain improvement at broadside by ~ 2dBi are achieved for folded ground plane design. The proposed LWA scans a region from -40° to +24° as the frequency range increases from 12 to 17 GHz with broadside at 15.5 GHz. The HMSIW LWA with folded ground plane is fabricated and its performance is experimentally measured showing the close agreement between the simulation and the measured results.

A new sub-THz leaky wave antenna based on grounded silicon substrate for chip to chip communication applications is presented. The proposed leaky wave antenna is based on sinusoidally modulated surface reactance. This surface reactance is implemented by using varying width strips on the top of a grounded silicon substrate. Two approaches for developing these strips are studied. These two approaches are based on either highly doped silicon strips or gold strips. Both the doped silicon and the gold are presented by using their corresponding Drude models at the proposed operating frequency. Comparisons between the properties of these two approaches are presented to show the applicability of each one.

An approximate circuit model to analyze microstrip rampart line in open-stopband (OSB) suppressing is presented. The proposed antenna consists of periodically orthogonally bending microstrip transmission line, and the widths of two transversal lines are adjusted to match the input impedance of the unit cell to the characteristic impedance of the transmission line. The approximate circuit model is presented to analyze the behavior of the PLWA. The prototype antenna shows a seamless frequency scanning from 3.7 to 6.8 GHz with a scanning range of 118° from the backward to forward quadrant. The simulation and measured results have demonstrated that the OSB is successfully suppressed in the improved case.

In this paper, a pattern and frequency reconfigurable leaky wave X-band antenna based on liquid crystal is designed. The frequency sweep characteristics of traditional leaky wave antennas are replaced by electrical properties of liquid crystal materials. Through the liquid crystal tuning, the main lobe pattern is deflected by 25 degrees at a frequency shift of 1GHz, where the liquid crystal tuning is saturated at 20V bias voltage. The relative frequency reconfigurable bandwidth is 19%, the relative pattern reconfigurable bandwidth is 9.3% and the maximum gain is 10dBi. Moreover, the pattern and frequency response are well preserved during the tuning.

In this study, miniaturization of composite right-left handed (CRLH) transmission line (TL) antennas using via structure is proposed. The proposed CRLH TL antenna replaces the planar interdigital capacitor structure of the conventional CRLH TL antenna using vias in the printed circuit board multilayer structure. Via structure derives series capacitance values by replacing the finger-shaped patterned parts that comprise the conventional interdigital capacitor. The proposed model reduces the increased length of 8.34 mm to 2.66 mm for every one-cell increase based on an operating frequency of 2.9 GHz. Unlike the three-cell conventional model that utilizes 5.17 dBi at a size of 47.79 mm, the proposed four-cell model utilizes 5.35 dBi at a size of 33.41 mm. [ABSTRACT FROM AUTHOR]

This 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. [ABSTRACT FROM AUTHOR]

The application of high impedance layer (HIL) in (Bi)CMOS millimeter wave on-chip antennas is studied. The HIL consists of grounded two-dimensional periodic dogbone-shaped elements that use a metal layer of the CMOS structure. Two different mechanisms that take advantage of the HIL in on-chip antenna design are investigated. First, we implant the HIL below the on-chip dipole antenna to act as an artificial magnetic conductor (AMC), which enhances the radiation of the dipole. We have obtained 1.2 dB realized gain for a dipole antenna placed above a 45 dogbone array at 90 GHz. The second use of the HIL is directly as a radiating antenna, without the need of the dipole antenna on top. In this case we have obtained 2dB accepted gain from a HIL made of 55 dogbone array, fed by two microstrip lines having 180 phase difference. The results are obtained by full-wave simulation. © 2011 IEEE.

The application of high impedance layer (HIL) in (Bi)CMOS millimeter wave on-chip antennas is studied. The HIL consists of grounded two-dimensional periodic dogbone-shaped elements that use a metal layer of the CMOS structure. Two different mechanisms that take advantage of the HIL in on-chip antenna design are investigated. First, we implant the HIL below the on-chip dipole antenna to act as an artificial magnetic conductor (AMC), which enhances the radiation of the dipole. We have obtained 1.2 dB realized gain for a dipole antenna placed above a 45 dogbone array at 90 GHz. The second use of the HIL is directly as a radiating antenna, without the need of the dipole antenna on top. In this case we have obtained 2dB accepted gain from a HIL made of 55 dogbone array, fed by two microstrip lines having 180 phase difference. The results are obtained by full-wave simulation. © 2011 IEEE.

A planar asymmetric substrate integrated wave¬guide leaky wave antenna is proposed with open stop band suppression and radiation efficiency equalization through broadside for the Ku-band. The stop-band behavior exhib¬ited at broadside in the 1-D periodic structure is signifi¬cantly reduced using reflection cancellation technique by placing the two slots at a quarter distance within the unit cell. Furthermore, asymmetric technique is applied. The asymmetry is introduced with respect to both axial and transversal axis of the structure so as to match the at-broadside Bloch impedance and off-broadside Bloch im¬pedance. This provides total open stop band suppression and radiation efficiency improvement as well as equaliza-tion through broadside. The problem is analyzed with the help of Bloch impedance behavior. For illustration of the above techniques; single slot, double slot and asymmetric designs are developed for the proposed leaky wave an¬tenna. The final asymmetric design after optimization is fabricated. Measured results are almost consistent with the simulation results with complete suppression of open stop band, efficiency improvement and equalization through broadside providing continuous beam scanning from –32° to +27° with constant gain of ~12.5 dBi.

A surface waveguide (SWG) leaky-wave antenna featuring directional single-side beam scanning capability is presented. A novelty of the design is that transition design utilizes the spoof surface plasmon (SSP) as an intermedia to feed the SWG, which realizes an efficient SWG transition from the conventional coplanar waveguide. In addition, a novel spatial profile is modulated on the SWG to produce leaky-wave radiation. Because the transmission modes in SSP and SWG are similar, the transition exhibits low loss and broadband performance. Both the transition and the leaky-wave antenna are demonstrated using simulations and experiments. It is shown that the transition has an average loss of 0.61 dB across the frequency range 5–13 GHz, which is an improvement on other feeding techniques reported. It is also shown that the leaky-wave antenna produces a single-side scanning beam of 8.7 dB gain with an overall efficiency of 75%. The beam scans through a 43.5-degree range over the frequency 10–13 GHz.