Conformal leaky wave antenna based on gap waveguide technology

The space mapping (SM) technique is applied to conformal antenna design for the first time. A planar microstrip antenna printed on a finite ground-plane with a coarse-mesh is solved as the coarse model and aligned with a conformal microstrip antenna placed on a platform's surface with a fine-mesh through space mapping. When some conformal antennas have the same planar configuration, being able to share a common coarse model is an important advantage of this technique in these conformal antenna optimizations. The S-parameters of conformal antennas are optimized. The function responses in this example are chosen as "e S11". The comparisons of efficiency and accuracy with the commercial software CST MWS 5.0 are made. The final results demonstrate that the SM technique can reduce the overall design process by an order of magnitude (10 times). Therefore, the proposed technique is particularly suitable for conformal antenna optimization. As a demonstration, examples of a planar broadband E-shape microstrip antenna placed on two different platform' surfaces are introduced in this communication.

The radiation characteristics of a conformal spiral antenna positioned on a finite-length conducting cylinder are numerically analyzed using the moment method. The effects of cylinder length on the radiation field are discussed. It is found that when the cylinder length is more than twice the free space wavelength, the current induced on the conducting cylinder is attenuated significantly near the end of the cylinder and the radiation field converges. It is also found that the current on the back side of the conducting cylinder affects the front-to-back (FB) ratio of the radiation field and the gain in the front direction. An FB ratio of 22 dB is obtained when the radius of the conducting cylinder is half of the wavelength. The front gain is 1 dB lower compared to the gain (8.7 dBi) of a planar spiral antenna on a planar conductor. The conformal spiral radiates a circularly polarized wave with an axial ratio of less than 3 dB over an 18% bandwidth. As an application, a conformal array antenna for omnidirectional radiation is realized by using seven spirals around the conducting cylinder. An axial ratio of less than 3 dB over all directions is obtained with a main polarization gain variation of less than 1.2 dB. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 83(5): 107–114, 2000

A compact and ultrathin conformal antenna is crimped on a polyimide substrate with an isochoric (equally fed) antenna array with a footprint of 30 mm $$\times $$ 26.6 mm $$\times $$ 0.4 mm is investigated. The proposed antenna employs three concentric rings (CRAs) with oval rings linked together. This work presents a conformal frequency reconfigurable antenna for automotive applications. The designed antenna consists of circular rings in the design to achieve the multiband operation. The proposed antenna is studied for frequency reconfigurable characteristics in the desired locations and obtained the reconfigurability in the 5.8 GHz region. Results describe that the antenna inside a radome is covering 1.58–2.33 GHz (GPS, PCS, GSM1800/1900), 3.22–3.7 GHz 28 (WiMAX), and 4.25–5.8 GHz (WLAN, DSRC, WAVE, V2X) bands for vehicular communications with various switching cases. The obtained gain varies from 3.2 to 4.1 dB in the boresight direction and 6.9–9.8 dB in the lateral directions of the vehicle with placement on the vehicle body. With the obtained results of both simulated and measured, this antenna is suitable for vehicular communication scenarios.

The realization of flexible and conformable antennas, suitable for IoT applications, is still a challenging activity. The traditional manufacturing techniques, mostly based on Silicon, rarely allow to realize such devices. Nevertheless, additive manufacturing technologies are good candidates to fulfill such a need, while enabling, in the meantime, the production of otherwise unrealizable geometries. In this paper a new design for a flexible, and conformable Rectangular Dielectric Resonator Antenna, working at 2.45 GHz, enabled by 3D printing, is proposed. Its feasibility is demonstrated by indicating how any part of the prototype could be properly manufactured. Eventually, simulated results proving the performance of the antenna in terms of stability, radiation efficiency, and gain (straight, concave, and convex) are reported and discussed.

A conformal microstrip antenna is highly integrated with the carrier profile, giving it the advantage of reduced carrier space. However, the processing technology for fabricating an antenna with a conformal surface is complicated and expensive owing to its irregular shape. Therefore, it is particularly important to find ways to reduce the difficulty in producing conformal conductive patterns. For the production of conformal microstrip antennas, a five-axes motion printing system is proposed to print conductive patterns on nonexpanded surfaces. The conductive pattern uses a new boundary-alignment-optimization algorithm in the printing process to improve the accuracy of the boundary of the conductive pattern by optimizing the ink-dropping points in the motion command. The short-time and low-temperature sintering of the conductive pattern by using a flash light enables it to exhibit conductive properties. This method is practically implemented to fabricate a conformal array microstrip antenna. The main and side lobes of the electric and magnetic fields in the directional pattern measured in the microwave darkroom have the same trend as in the simulation diagram. Thus, the effectiveness of this method was verified through simulation analysis and experimental results.

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.

ABSTRACT: A mathematically accurate method of analysis of a spheri - cal-disk antenna conformally printed on a dielectric-co ¤ ered metallicsphere is presented. The antenna is fed by a radial coaxial probesimulated by an electric dipole. The solution consists of reducing theboundary- ¤ alue problem to the dual-series equations, and further to aregularized infinite-matrix equation. This procedure is based on theanalytical in ¤ ersion of the static part of the problem of a disk in freespace, and results in a stable and fast algorithm with a guaranteedcon ¤ ergence. Numerical data on the basic antenna characteristics arepresented. Q 2000 John Wiley & Sons, Inc. Microwave Opt TechnolLett 26: 176]182, 2000. Key words: spherical disk; conformal antenna; dual-series equations;analytical regularization; directi ¤ ity 1. INTRODUCTION Metallic circular disks printed on dielectric substrates areused frequently in patch antenna technology. Conformalprinted antennas are necessary in automotive and airbornecommunications and radar due to their low profile and lightweight. In this paper, the problem of modeling of aspherical-disk conformal printed antenna is considered as-suming an excitation by a coaxial probe. The probe is mod-eled by a radial electric dipole RED located at the surface.of the metal sphere covered with dielectric. From a theoreti-cal point of view, such a geometry is a canonical one for awide class of conformal patch antennas. Previously, similarproblems have been analyzed by direct applications of themethod of moments 1, 2 . However, convergence of thesewxnumerical approximations is not uniformly guaranteed, espe-cially if narrow resonances are present 3 . Patch antennaswxare essentially resonant devices; hence, this must be kept inmind when developing an accurate simulation software. Wepropose an exact mathematical method based on the analyti-cal inversion of the free-space static problem for a sphericaldisk 4, 5 that has been used previously in the analysis ofwxcavity-backed apertures and reflector antennas 6wx]8 . Thismethod belongs to the broad family of techniques collectivelycalled the method of analytical regularization 9 that arewxremarkable for stable and fast numerical solutions.

In this paper, a novel wideband leaky wave antenna using a composite right-/left-handed transmission line for UHF band are proposed. The antenna is composed of a ladder network less than one wavelength. Transmission and radiation characteristics of the leaky wave antenna are measured. The fabricated leaky wave antenna has flat gain characteristics from 400 MHz to 700 MHz.

This study proposes a novel scheme based on the characteristics of leaky-wave antennas for the empirical design of broadband tapered microstrip leaky-wave antennas. This scheme can explain and approximately model the radiation characteristics of a linearly tapered leaky-wave microstrip antenna. A broadband feeding structure that uses the balanced and the inverted balanced microstrip lines to form a pair of broadband baluns is also presented. The measured return loss of the inverted balanced microstrip lines has a VSWR/spl les/2 from dc to 18.6 GHz and that of the back-to-back feeding structures has a VSWR/spl les/2 from 2.2 to 18.6 GHz. This feeding structure can be used to feed a broadband planar leaky-wave antenna with a fixed mainbeam that uses the tapered microstrip structure. The measured bandwidth of the antenna for a VSWR/spl les/2 exceeds 2.3:1.

This article presents the design of a flat Luneburg metalens antenna at V-band using gap waveguide (GW) technology. The metalens consists of a parallel plate waveguide (PPW) loaded with metallic pins whose height is modulated to get an effective refractive index that follows the Luneburg equation. A Groove GW (GGW) H-plane horn is used to illuminate the metalens, such that the rays are collimated and a planar wavefront is generated in the direction of propagation. Since the structure at hand is planar, it can be efficiently integrated on flat surfaces. Moreover, the fully metallic structure is mechanically robust and presents lower losses than lenses including dielectric substrates. A prototype has been fabricated and tested, simulations and experimental results are in very good agreement. The metalens yields an input reflection coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> ) below −10 dB from 45 to 70 GHz, whereas the −3 dB gain fractional bandwidth is 26.2% with respect to a center frequency of 60 GHz, with a peak of 22.5 dB at 61 GHz. These features make this design an interesting solution for millimeter-wave (MMW) applications.

Conformal antennas are required for next generation of wireless systems combining the use of high frequency bands (terahertz) with smart interconnected devices (the Internet of Things). Here, we study and demonstrate curved terahertz leaky-wave antennas. We also demonstrate data transmission using a multibeam conformal antenna.

In this paper, a novel method to decrease the sidelobe level (SLL) of conformal leaky-wave antennas (CLWAs) which are synthesized based on the holographic techniques is proposed. For this purpose, the holographic relation is modified by using the modulation index as a function of the spatial component corresponding to the propagation direction of the reference wave. In order to create a fascinating impedance matching between the launcher and the radiative metasurface, an initial phase is considered in the holographic formula. The designed one-dimensional (1D) sinusoidally modulated conformal antenna indicated a broadside fan beam at 18 GHz. At this frequency, about 3 dB SLL reduction was observed in the E-plane compared the traditinal holographic antenna. The measurement results indicated that the realized gain of the novel antenna at the design frequency was about 14.6dBi, and the SLL and the radiation efficiency of the antenna were −10.6 dB and 95%, respectively.

In this paper, the proximity of the body is included in the antenna design which leads to propose a novel antenna for on-body communication channel. As the initial stage, the behavior of a dipole parallel to the body surface is investigated. This study provides valuable information which is used in the novel surface wave antenna design. To evaluate the new antenna performance, a pair of antenna is put on two opposite sides of cylinder made of muscle tissue property and the path gain results are compared with a pair of parallel dipole and also monopole.

The manuscript reports phase compensation technique for improving the directionality and gain of a conformal phased array antenna on a cylindrical surface while steering the beam. The investigation reports two different components of phase compensation required for enhancing the directionality: (i) compensation required to mitigate the effect due to the vertical displacements of antenna elements on the conformal surface and (ii) additional phase shift required to align the broadside of each element in the direction of scan angle. It is highly effective in the restoration of the beam of a phased array mounted on conformal surfaces of a smaller radius causing significant deformation in the radiation pattern. The proposed formulation is implemented through Matlab and verified using CST for a 1-D circumferential phased array with 7 elements of a rectangular patch antenna of dimensions L = 8.72 mm and W = 14.52 mm designed for 10 GHz on a cylindrical surface of 10 cm radius. The model is also applicable to a Concave conformal phased array and can be extended to 2-D arrays. To the best of our knowledge, this is the first report on such a study and will find direct applications in the design and development of conformal phased arrays with high directionality and gain.

Copper is typically used for the conductor in most antenna designs and flexible materials can be useful to make a conformal antenna. Here, a CPW-fed conformal monopole antenna was designed on a flexible low-cost paper substrate, and flexible graphene-based conductive material was used as an alternative to copper. The antenna was designed for 3.6 GHz applications with a size of 24 mm × 6 mm. The design was simulated in HFSS, a full-wave simulation tool; a prototype was manufactured using a micro-cutter; and measured in a full anechoic chamber. Overall, it was shown that the S-parameter simulations agreed well with measurements, and that the electrical benefits of the flexible graphene-based conductor can be utilized to design a CPW-fed conformal monopole antenna.