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This research article presents the design and realization of a flexible semi-circular shaped ultra-wideband (UWB) printed antenna based on metamaterial superstrate for medical applications. In this article, at first, the design of a semi-circle structured UWB patch antenna is performed which provides an ultra-wide impedance bandwidth [2.83–13.57] GHz and a peak gain of 5.17 dBi. In order to ameliorate the radiation performance, an array pattern of 5 × 5 metamaterial (MTM) unit cells are generated and placed over the proposed antenna. Also, both the antenna and the superstrate layer are printed on a flexible teflon material. The proposed design has an overall compact size of 32.1 × 34 × 0.6 mm3. Using the superstrate MTM unit cell, the measured operating bandwidth ranges from 4.03 GHz to 14 GHz and the experimental peak gain and radiation efficiency are 6.7 dBi and 97.26%, respectively. Moreover, the conformal analysis is investigated to verify the robustness and the applicability of the prescribed antenna over the curved surfaces. The suggested antenna presents magnificent performance by maintaining ultra-wide bandwidth and offering required radiation characteristics during various bending analysis. Furthermore, the reflection coefficient and specific absorption rate (SAR) of the proposed antenna have been analyzed by placing it on different human body parts such as the hand, arm and chest. The suggested antenna maintains UWB characteristics along with acceptable SAR values for 1 g and 10 g tissues for various on body analysis cases. Hence, this UWB antenna structure can be a convenient choice for implementing on curved surfaces in flexible/bending conditions and also for wearable applications. The prescribed antenna could be useful for portable medical devices within the UWB spectrum. [ABSTRACT FROM AUTHOR]

Blade antennas are used as transmitters in telemetry system of the sounding rocket RX-450 of Research Center for Rocket Technology - National Research and Innovation Agency to send rocket information to the ground station. For 360° coverage, the rocket needs two blade antennas connected with a splitter device which necessitates provision of additional power on the rocket payload. We designed a circular polarization conformal 2.4 GHz antenna to avoid both aerodynamic disturbances due to antenna shape and data transmission loss due to polarization loss with the ground station. The antenna material is Roger 6010LM and good antenna parameters were determined by simulation. The antenna bandwidth is 71 MHz (2412-2483 MHz). The maximum and minimum gain 7.8 dB at 2.43 GHz and 4.5 dB at 2.47 GHz respectively. Because of its conformal shape, we get an omnidirectional radiation pattern. Further, using the Hilbert curve method with a U-slot on the ground plane, circular polarization with an axial ratio = 2 dB is obtained. [ABSTRACT FROM AUTHOR]

This work deals with the design and development of a conformal series-fed antenna structure operating at the 60 GHz frequency. The proposed antenna operates from 57 GHz to 62 GHz with good return loss and radiation characteristics for 6G and beyond applications. The antenna is shown to give a good gain of more than 14.7 dBi with directional radiation beam in the hemispherical boresight direction. The fabricated prototype is verified with the simulated result, and it is found to be a good matching. The step-by-step antenna design process, parametric variation, and a detailed study are also reported. For a case study, this series-fed antenna conformal configuration is also embedded on a cylindrical structure. From this study, similar resonant and radiation performance characteristics are observed. Since the structure is compact, conformal, and gives better performance, it can be suitable for applications such as 6G, radar, guided missiles, body-centric medical imaging, etc.

This work deals with the design and development of a conformal series-fed antenna structure operating at the 60 GHz frequency. The proposed antenna operates from 57 GHz to 62 GHz with good return loss and radiation characteristics for 6G and beyond applications. The antenna is shown to give a good gain of more than 14.7 dBi with directional radiation beam in the hemispherical boresight direction. The fabricated prototype is verified with the simulated result, and it is found to be a good matching. The step-by-step antenna design process, parametric variation, and a detailed study are also reported. For a case study, this series-fed antenna conformal configuration is also embedded on a cylindrical structure. From this study, similar resonant and radiation performance characteristics are observed. Since the structure is compact, conformal, and gives better performance, it can be suitable for applications such as 6G, radar, guided missiles, body-centric medical imaging, etc. [ABSTRACT FROM AUTHOR]

A U-slot located symmetrically at the centre of the patch has been utilized to enhance the patch antenna's operating bandwidth compared to the standard conventional patch. The operating frequency range of the circumferential patch antenna is from 8.61 to 11.43 GHz, while the axial patch covers the frequency range 8.71 to 11.33 GHz (covering X band). The antenna shows excellent gain with minimal variation in both E and H-planes across the operating frequency range. Moreover, the antenna achieves less than −10 dB sidelobe levels in both E and H-planes across all frequencies and configurations. The co and cross-polarization plots are also depicted to show the excellent polarization purity of the antenna for the planar and cylindrical conformal configurations. The antenna may be suitable for airborne applications where the conformability to the Arial host body is of prime importance. [ABSTRACT FROM AUTHOR]

In order to meet the demands of dual-band and integrated conformal antenna for UAV (Unmanned Aerial Vehicle) swarm communication systems, an integrated wing conformal antenna is designed and fabricated. The antenna is realized by combining a broadband dipole antenna and a low pass and high-pass LC combiner. The antenna element is realized by three pairs of open branch lines to achieve effective choking characteristics and broad- band omnidirectional radiation. The combiner consists of K-m LC filters, which are used to realize dual - band operation with low insertion loss and high rejection. The measured Voltage Standing Wave Ratio(VSWR) of antenna is less than 2, the measured gain is more than 0 dBi, and the isolation is better than 30 dBc between L and S frequency band. By mounting only one wing conformal antenna, a dual-band simultaneous operation can be realized which meets the need of UAV swarm data link system for high communication rate. The proposed antenna is whole arranged in the tail wing of UAV to enhance the integration capability of the UAV swarm, and can be widely used in UAV field. [ABSTRACT FROM AUTHOR]

In this article, a compact super-wideband flexible textile antenna is proposed. It operates over an extremely broad frequency range from 3.16 to 50 GHz. The proposed design is characterized by its simple geometry, consisting of an offset rectangular patch, which is incorporated with three slots to enhance its performance, while a circular parasitic patch is positioned on the opposite side of the substrate. The proposed antenna prototype is fabricated on a footprint of 30 mm × 25 mm × 1 mm, which measures an electrical dimension of 0.31λ0 × 0.26λ0 × 0.012λ0 at 3.16 GHz. As per measurements, a wide bandwidth of 15.82:1 from 3.16 to 50 GHz is achieved with a peak gain of 7.70 dBi at 23.05 GHz. Furthermore, the ADS software is employed to create and analyze the equivalent circuit model of the designed antenna whose simulation studies are executed using CST software. The suggested antenna's overall performance is described by investigating the effects of structural bending and also proximity to the human body. Moreover, it provides acceptable values of specific absorption rate, ensuring lower absorption, which are under the safety standard limits for RF exposure. The measured results correlate with simulated results. Owing to its simple topology, compact size, super-wideband behavior, and high gain, endorse its suitability for low-power requirement applications in the real world. [ABSTRACT FROM AUTHOR]

In this paper, a four unit cell micron-sized magnetic particles embedded composite right/left-handed (CRLH) transmission line metamaterial phase shifter is proposed. The variable phases are achieved by activating the micron-sized magnetic particles along the length of stub transmission lines of the CRLH transmission line structure. This causes to effectively change the inductance of stub transmission lines, which changes the phase of the RF signal. These structures can be activated in a symmetric or asymmetrical manner to obtain wide range of phase shifts. A prototype of cascaded four unit cell CRLH transmission line phase shifter with embedded silver-coated ferrites (magnetic particles) is designed, fabricated and tested for phase shifters applications. The measured phase response of the proposed phase shifter is in close agreement with the simulated phase response. Next, for the performance analysis of proposed phase shifter, a 1 x 4 conformal curved-shaped phased array operating at 5.8 GHz is fed with the four unit cell cascaded phase shifter in CST full-wave simulator. The conformal phased array with proposed integrated phase shifters was simulated for broadside pattern correction and main beam scanning at 20 degree on curved-shaped surface with different bend angles. The radiation pattern results obtained with the proposed integrated phase shifters are in close agreement with those obtained with direct excitation of the array. [ABSTRACT FROM AUTHOR]

A low-profile Wi-Fi 6E antenna for laptop applications is proposed in this paper. The proposed antenna is electrically small covering 2.4/5/6 GHz Wi-Fi 6E frequency bands. A planar geometry is first introduced that is later conformed for achieving minimal area in the horizontal plane (x–y plane). A total size of 4 mm × 10.7 mm × 3.7 mm is obtained for conformal topology. A thin and flexible polyimide substrate of thickness 0.15 mm is used for attaining conformity. Regarding the antenna structure, it consists of a shorted and meandered monopole strip connected with a rectangular-shaped loop that is capacitively coupled by a Г-shaped driven trace. The meandered strip and the loop structure aid in the excitation of the fundamental 0.25-λ monopole mode and also 0.25-λ loop mode at 2.4/5 GHz, respectively. Moreover, the Г-shaped coupling strip produces the 0.25-λ monopole mode in the 6 GHz frequency band. The proposed antenna conforms to the Chu–Harrington limit with ka value of < 0.78 implying that the antenna is electrically small. In addition, the implementation of the antenna inside a commercial laptop is also illustrated. [ABSTRACT FROM AUTHOR]

A compact co-planar waveguide (CPW) based triple-band printed conformal antenna for on-body applications is presented in this research. In order to accomplish impedance matching, a coplanar structure is employed with the ground on the same plane, and this is printed on the top layer of a polyimide substrate of 0.6 mm thickness. The proposed conformal antenna consists of two identical patch elements. The radiating element is made up of two split ring resonators positioned on the top of the feeding element. The suggested on-body antenna has an overall miniaturized size of only 35 37.5 mm², making it ideal for use in the biomedical field. The designed antenna is capable to cover various spectrum spanning from 2.387-2.618 GHz, 4.2-4.64 GHz, and 6.23-6.56 GHz with a 2:1 voltage standing wave ratio. The designed antenna is fabricated and antenna parameters are measured which is correlated with simulated results. The antenna achieves a total gain of around 5 dBi with radiation efficiency of up to 95 % over the various operating spectrums. To validate the conformality over curved surfaces, the fabricated prototype of the proposed antenna is bent at 30°, 45, 90° angles and the measured results are compared with simulation results of the bending analysis. Furthermore, to validate the on-body performance of the antenna Specific Absorption Rate has been calculated through simulation and it is found to be lower than 1 W/Kg over all three bands of spectrums which proves that the proposed bio-medical antenna could be a viable candidate for microwave imaging applications. [ABSTRACT FROM AUTHOR]

Conformal metasurface antenna embedded on the platform with an arbitrary shape is of great significance for communication systems in practical applications. Herein, a convenient design strategy for conformal transmissive metasurface antenna with arbitrary cylinder surface is presented. First, a novel‐phase compensation concept for curved surface is inspired by ray‐tracing technique. Then, by using arc differentiation and numerical integration, the meta‐atoms' coordinates calculation method is analyzed for arbitrary cylindrical surface. Next, the electromagnetic responses of planar and curved transmissive meta‐atoms are discussed, and conformal metasurfaces in single‐quadratic surfaces are simulated to validate the feasibility of the design strategy. Finally, for potential applications, three combined quadratics conformal metasurface antennas with capabilities of beam focusing, beam deflecting, and vortex generation are designed and measured. It is indicated in the results that the three conformal metasurface antennas with combined quadratic cylinder surfaces can transform the spherical wave efficiently into the plane wave, deflected beam, and vortex beam, respectively, verifying the validity of the designs. The convenient strategy has good generality and flexibility because it is applicable to arbitrary cylindrical metasurface with a specific alignment function, which has promising perspective in practical applications, and offers a novel approach to design conformal antennas without changing aerodynamic shapes of platforms. [ABSTRACT FROM AUTHOR]

A smart antenna system suitable for micro base stations is proposed, which consists of three left-handed circularly polarized designs operating at 3.5 GHz. The first one is an eight-port cylindrical conformal antenna with both omnidirectional and directional modes. Its maximum omnidirectional realized gain is 5.0 dBic, and its maximum single/dual beam realized gain under the directional mode on the horizontal plane is 9.4/6.9 dBic. In addition, it can achieve elevational scan from 70° to 110°. The second one is based on the first one with a feeding network, therefore reducing the number of ports to four, achieving a maximum omnidirectional and directional realized gain of 4.2 and 7.9 dBic. The third one is also based on the first one, but with two additional omnidirectional antennas added, making it a hybrid system with enhanced omnidirectional radiation. It has a maximum omnidirectional and directional realized gain of 6.4 and 8.2 dBic. To validate the proposed concept, three prototype arrays are designed, fabricated, and measured, showing that the proposed antenna system can achieve the desired radiation patterns according to different targeted applications. [ABSTRACT FROM AUTHOR]

The 700 MHz public safety spectrum is released for commercial wireless and safety communication wearable applications (CWSC-WA). However, the 700 MHz band need a larger aperture for an efficient radiation due to a larger wavelength. In this paper, we have systematically developed a novel miniature omnidirectional 700 MHz antenna for the CWSC-WA. Over 40% miniaturization is realized by truncating the ground plane and a meander line inspired radiator compared to a conventional rectangular patch antenna. The truncation of the ground plane also yields a perfect omnidirectional radiation pattern desired for the CWSCA. Considering current and future demands of wearable electronics and virtual reality, the antenna is made on a flexible substrate and conformity analysis is also performed. The prototype of the antenna is developed and simulated results are verified in planar as well as conformal configurations.

In this paper, a patch antenna with compact, flexible, and transparent properties is presented to support Wi-Fi 6E (2.4 GHz/6 GHz) applications. This antenna design was formulated based on a transparent metal mesh film (MMF), for which the average optical transparency (OTav) is 69% and the sheet resistance (Rs) is 0.1Ω/sq. The measurement results on frequency bands of 2.4–2.51 GHz and 5.87–7.04 GHz show that the average gain exceeds 5.4 dBi and 6.3 dBi with corresponding radiation efficiency rates as high as 67.8% and 70%. In addition, for the purpose of integration into aesthetic devices for smart home applications, the antenna conformed to foam and a lamp. All research outcomes here indicate that the proposed antenna maintains a directional radiation pattern, as well as transparency and flexibility, making it a potential candidate for transparent Internet of Things (IoT) applications.

The conformal antenna is a precision device installed on the wing of an aircraft, and its components are distributed on a curved surface. Quality detection is required after assembly. In solving the path planning problem for conformal antenna surface detection, the traditional genetic algorithm faces problems such as slow convergence and easily falling into a local optimal solution. To solve this problem, an improved genetic algorithm combining the historical optimal population (CHOP-IGA) is proposed. First, the algorithm uses the probability-based four-nearest-neighbor method to construct an initial population. Subsequently, the probabilities of the crossover and mutation operators are dynamically adjusted. Next, the algorithm applies the crossover and mutation operators to the population and performs mutation operations on each individual of the historical optimal population. Then, the fitness value is calculated and the next generation of individuals is selected from the parent, offspring, and historical optimal populations according to the elite selection strategy. Finally, the current best fitness is checked to determine whether updating the historical optimal population is necessary. When the termination condition is satisfied, the algorithm outputs the optimal result. Experiments showed that the algorithm satisfactorily solved the path planning problem for conformal antenna surface detection, with a 48.44% improvement in detection efficiency. [ABSTRACT FROM AUTHOR]

A compact sized ingestible antenna is presented at 3.3 GHz for lower ultra-wide band (UWB) wireless capsule endoscope system, by taking the stomach part of human body model presence into consideration. The proposed novel design is based on microstrip feed model and consists of three unique strip lines at center, The tuning of strip lines length and gaps between them achieved the intended frequency band of operation. This unique design helped in reducing the size of the antenna significantly and can maintain the operational band in flexible condition which proves advantage while integrating the antenna inside the capsule. The dimension of the antenna excluding the superstrate are 5.4 mm × 7 mm × 0.36 mm. The size is compact enough to be placed in cap part of capsule to avoid overlapping and coupling losses with surrounding circuitry. Initially the ingestible antenna along with circuitry and capsule were designed and placed inside homogenous stomach box using Ansys HFSS tool for the analysis, later the capsule system is placed inside different parts of the realistic virtual human phantom model and the comparative analysis is presented using the reflection coefficient curves and specific absorption rate (SAR). The SAR analysis is carried as per the Federal Communications Commission (FCC) over 1 g volume tissue, and it is 0.74 W/Kg for the proposed ingestible antenna for input power of 1 mW. The proposed antenna maintained its operational band with good impedance matching and S11 below − 10 dB making to robust and insensitive towards the variation of tissues dielectric properties in gastrointestinal tract (GI). The presented coupling strength analysis from endoscopy antenna to outside antenna proved its ability to communicate. The link budget analysis for the GI tissues proved that the margin between the actual link and the required strength is good for up to 5 m distance between the Tx and Rx antennas. Moreover, the fabricated model is measured under minced pork condition and compared analysis between the simulated and measured showed that proposed antenna-maintained impedance matching below − 10 dB in the operational band from almost 2.7 to 3.8 GHz showing significant agreement for without circuit case. The overall measured bandwidth is 1100 MHz, at operating frequency 3.3 GHz the measured return loss is − 18 dB. [ABSTRACT FROM AUTHOR]

The processing of the three-dimensional circuit on the surface of conformal antennas is mainly performed via manual processing. At present, there is no automatic intelligent equipment for the processing of a similar small-sized circuit with variable curvature in China. Therefore, a high-precision, automated, full-process manufacturing method for three-dimensional circuits with flexible surfaces on conformal antennas of radar equipment has been proposed to improve processing quality and manufacturing efficiency. The processing relationship between solder paste spraying, resistor mounting, and laser welding in the flexible three-dimensional circuit manufacturing process was analyzed. The structure of the new conformal antenna three-dimensional circuit intelligent manufacturing equipment was determined, and simulation verification of the three-dimensional circuit processing was performed using Vericut. The optimal processing parameters were selected based on solid experiments. This method meets the electronic assembly requirements of radar equipment and fills the domestic gap. [ABSTRACT FROM AUTHOR]

Vertically polarized omnidirectional antenna system (VPOAS) and horizontally polarized omnidirectional antenna system (HPOAS) are designed and theoretically analyzed at 2.2 GHz for NAG-Missile telemetry. Theoretical formulations of far-zone field patterns are derived using the cavity model in conjunction with array theory, equivalence theorem, and image theory. The derived radiation patterns are plotted using MATLAB software. The proposed antenna is simulated using CST software and fabricated to validate the derived results. The proposed antenna systems are resonating at 2.22 GHz with 32 MHz impedance bandwidth and peak gain of 4.15 and 5.37 dBi for VPOAS and HPOAS, respectively. [ABSTRACT FROM AUTHOR]

Conformal metasurface antenna embedded on the platform with an arbitrary shape is of great significance for communication systems in practical applications. Herein, a convenient design strategy for conformal transmissive metasurface antenna with arbitrary cylinder surface is presented. First, a novel‐phase compensation concept for curved surface is inspired by ray‐tracing technique. Then, by using arc differentiation and numerical integration, the meta‐atoms’ coordinates calculation method is analyzed for arbitrary cylindrical surface. Next, the electromagnetic responses of planar and curved transmissive meta‐atoms are discussed, and conformal metasurfaces in single‐quadratic surfaces are simulated to validate the feasibility of the design strategy. Finally, for potential applications, three combined quadratics conformal metasurface antennas with capabilities of beam focusing, beam deflecting, and vortex generation are designed and measured. It is indicated in the results that the three conformal metasurface antennas with combined quadratic cylinder surfaces can transform the spherical wave efficiently into the plane wave, deflected beam, and vortex beam, respectively, verifying the validity of the designs. The convenient strategy has good generality and flexibility because it is applicable to arbitrary cylindrical metasurface with a specific alignment function, which has promising perspective in practical applications, and offers a novel approach to design conformal antennas without changing aerodynamic shapes of platforms.

This work is proposed a single layer wideband conformal microstrip patch antenna with low profile suitable for airbone application. Semicircular shape slots located at the corners of the patch and center of the length of the patch along with a partially cut ground plane are utilized to improve the impedance bandwidth of the patch antenna over the standard rectangular patch. The antenna exhibits passband characteristics across multiple bands with fractional impedance bandwidth (VSWR < 2) of about more than 113% with an operating range 4.31–15.691 GHz for the proposed planar and 114% bandwidth with frequency range 4.37–16 GHz for the cylindrical antenna configuration (covering C, X, and Ku bands). Radiation characteristics of both planar and the cylindrical conformed versions of the antenna in both E and H planes are also presented for the corresponding resonant frequencies within the operating frequency range. The effect of the radius of curvature on the resonance curve is also analyzed for the cylindrical conformal patch antenna. [ABSTRACT FROM AUTHOR]

In this paper, a patch antenna with compact, flexible, and transparent properties is presented to support Wi-Fi 6E (2.4 GHz/6 GHz) applications. This antenna design was formulated based on a transparent metal mesh film (MMF), for which the average optical transparency (OTav) is 69% and the sheet resistance (Rs) is 0.1 O/sq. The measurement results on frequency bands of 2.4-2.51 GHz and 5.87-7.04 GHz show that the average gain exceeds 5.4 dBi and 6.3 dBi with corresponding radiation efficiency rates as high as 67.8% and 70%. In addition, for the purpose of integration into aesthetic devices for smart home applications, the antenna conformed to foam and a lamp. All research outcomes here indicate that the proposed antenna maintains a directional radiation pattern, as well as transparency and flexibility, making it a potential candidate for transparent Internet-of-Things applications. [ABSTRACT FROM AUTHOR]

In this work, a dual-band linear polarized C/X conformal shared aperture antenna (SAA) for spaceborne SAR applications is presented. The proposed single layer SAA is designed with a square-shaped patch in linear polarization and arranged as four elements ( $2\times 2$ ) array with corporate feeding to allow for efficient signal transmission. The design of that operates at C-band (5.35 GHz) and X-band (9.65 GHz). Most spaceborne applications, such satellite radar and weather forecasting, employ the C-band antenna. On the other hand, X-band antennas are used for surveillance, reconnaissance, air traffic control, and weather monitoring. A prototype is built, and its s-parameters are tested to confirm the antenna. With the suggested design, we were able to obtain a bandwidth of 65 MHz for C-band and 354 MHz for X-band, as well as gains of 13.2 dBi for the C-band and 10.6 dBi for the X-band, and isolation of more than 40 dB. The total size of the SAA size is $130\times 80\times0.8$ mm. According to this study, dual band antennas operating future SAR spacecraft on a same aperture is a practical solution to satisfy user demands.

ObjectivesIn order to meet the different performance requirements of ship-based integrated RF antennae for next-generation surface warships, such as high performance, low scattering and hull conformance, an optimization method for a conformal antenna combining the electromagnetic simulation and intelligent optimization methods is presented and applied in the design of an embedded array with a specific frequency band.MethodsBy improving the traditional particle swarm optimization (PSO) algorithm asynchronously and incrementally, discrete variables and continuous variables are processed at the same time, effectively accelerating the convergence speed of the PSO. Aiming at a VHF antenna on a surface ship, the objective function of the multi-dimensional parameter optimization of the complex antenna structure is constructed, and the semi-embedded installation forms of the synchronous optimization of multi-objective characteristics such as antenna gain, standing wave ratio and radar cross section （RCS） are obtained. ResultsAfter several rounds of simulation and iterative optimization, the antenna gain is increased by about 1 dB, the standing wave ratio is slightly improved and the RCS peak point reduction of the typical azimuth reaches 32 dB.ConclusionsThis method can provide references for the conformal ship mounting design of RF antennae for ships and the integrated design of complex large-scale systems.

This paper presents the design of a planar inverted F antenna with a miniature or tiny shape at the frequency of 2.4 GHz. The antenna uses a spiral design to reduce the dimension of the antenna with conformal shape for a suitable prosthetic arm. Usually, the antenna design uses long experimental steps, namely trial and error. It can be summarized using the DOE (design of experiment) method. The DOE is a method to streamline the experimental steps to get the best design. The DOE method uses a tuning reference at the design parameter variation of 5 % of the nominal value. Four tuning steps can get the best results from S11, bandwidth, and gain. The designed antenna works at the resonant frequency of 2.431 GHz with the value of S11 is -22.634 dB, bandwidth of 37.1 MHz, and gain of -7.596 dBi.

A conformal cylindrical phased array antenna excited with composite right/left-handed (CRLH) phase shifters is proposed. The phase tuning of the CRLH phase shifter is achieved by embedding novel magneto-static field-responsive micron-sized particles in its structure. It is shown that through the tiny magnet activation of these novel magneto-static particles at appropriate locations along the length of CRLH stub and inter-digital fingers, variable phase shifts are obtained. The proposed particle-based CRLH phase shifter operates in C-band (5–6) GHz with a low insertion loss and phase error. The 1 × 4 cylindrical phased array is excited with the four unit cells of the proposed particle-embedded CRLH transmission line phase shifters to scan the main beam at desired scan angles. A prototype of a 1 × 4 cylindrical phased array excited with the particle-based CRLH phase shifters was fabricated, and the results show that the simulated results are in close agreement with the measured results. The conformal cylindrical array with the proposed particle-based CRLH phase shifters has great potential for use in printed and flexible electronics design where commercially available phase shifters have a definite drawback. [ABSTRACT FROM AUTHOR]

Summary: This work presents a compact and conformal frequency reconfigurable antenna for automotive applications. The antenna is designed on a liquid crystal polymer substrate of footprint 40 × 30 × 0.1 mm3. The proposed antenna is having coplanar waveguide feeding with a circular ring radiating element and a pair of parasitic circular elements to obtain the multiband operation. The proposed antenna is studied for frequency reconfigurable characteristics by placing the PIN diodes as switching elements in the desired locations and obtained the reconfigurability in the 4.5–6.5 GHz region. Further, the bending effects of the antenna with respect to its operating bands and the conformal effects with PIN diodes for the reconfigurable performance make this study a trailblazing work. The simulated and measured results describe that the on‐glass conformal antenna is covering 1.58–2.33 (GPS, PCS, GSM1800/1900), 3.22–3.7 (WiMAX), and 4.25–6.8 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 to 9.8 dB in the lateral directions of the vehicle with placement on the vehicle body. As per the obtained results, the antenna is suitable to use for conformal usage on the windshield glass of the vehicle for connected driving scenarios. [ABSTRACT FROM AUTHOR]

This paper explains the novel conformal antenna design that achieves better Bandwidth (0.53 GHz) and Gain (9 dB) with slim and flexible substrate suitable for aircraft fuselage mounting. The achieved Bandwidth of 10.2% around the operating frequency of 5.2 GHz helps in improving the cross-range resolution of Synthetic Aperture Radar (SAR). The obtained gain increases the cross-range coverage and reduces the aerodynamic drag. The parametric study of the structure is presented along with the explanation to provide the physical insight of each parameter with the help of transmission line model and surface current analysis. Already available prominent design techniques, to improve the bandwidth, are also discussed along with its limitations to use it in aircraft applications. The RT Duroid 5880 is selected for its low loss, high gain and conformability nature. [ABSTRACT FROM AUTHOR]

High-performance miniaturized antennas are one of the goals that have been pursued in the design of wireless communication systems for implantable medical devices. In this article, a 915 MHz novel-shape loop antenna conforming to the inner wall of the capsule is developed by comprehensively adopting meander and symmetrical structure patch, folding technique, and vector current reversal technique. Through electromagnetic simulation, testing, and experimentation, the antenna shows good characteristics such as small size, ultra-wideband, circular polarization, strong robustness, and safety. Specific performances include the following: 1) the size of the developed miniaturized loop conformal antenna is only 30.5 mm $\times $ 4.6 mm $\times $ 0.05 mm and the maximum gain is −21.5 dBi at 915 MHz, which solves the problem of low gain due to the small antenna radiation area; 2) the antenna has a 4.5 GHz ultra-wideband impedance matching bandwidth ($\vert S_{11}\vert < -10$ dB) from 0.5 to 5 GHz. Even if the parameters such as the implantation depth and the thickness of the capsule shell change, or there exists a wireless power transfer system, the antenna can still cover the required frequency band with strong robustness; and 3) the specific absorption rate (SAR) of human tissues radiated by the antenna is far lower than the safety limit in IEEE standards and ICNIRP guidelines. The experimental platform using pork to simulate human tissues was built for antenna performance testing and communication testing. The measurement results verified the good resonance performance, radiation characteristics, and omnidirectionality of the developed antenna. The antenna link loss model is also given, which has been used in wireless communication and localization. [ABSTRACT FROM AUTHOR]

This letter presents an omnidirectional conformal array microstrip patch antenna at 3.5 GHz band. The array of 1 × $\times $ 2 elements are used as a radiating element and placed on the planar face of a regular six‐faced hexagonal structure connected with six faced feeding network. The feeding network consists of one three‐way power divider and two two‐way power dividers. These power dividers are serially connected to each other and form a six‐faced regular structure with 12 output ports. The response of the conformal antenna is verified experimentally. A measured reflection coefficient is well below <−10 $\lt -10$ dB and isolation between the output ports are −20 dB. The proposed omnidirectional conformal antenna is low‐cost, easy to fabricate, and suitable for an omnidirectional radiation pattern for 5G applications. [ABSTRACT FROM AUTHOR]

Transmitarray (TA) antenna has great research value based on its unique advantages of low profile, high gain, and flexible performance, especially in the field of spaceborne, airborne, and unmanned aerial vehicles. Unfortunately, traditional TA antennas are usually of flat structures, which lack conformal flexibility and installation simplicity in certain complex application scenarios. In this letter, a broadband bifocal conformal TA antenna is proposed based on a designed concave‐cylindrical‐shaped triple‐layer TA surface with phase modulation capability. The broadband bifocal conformal TA antenna is simulated, fabricated, and measured by assembling the TA surface with a dual‐mode conical horn as a feed antenna. To better demonstrate the beam scanning stability of the bifocal TA antenna, a monofocal TA antenna is designed and simulated as a comparison. Simulation and experimental results confirm that the proposed bifocal conformal TA antenna can achieve a high gain of 24.4 dBi at 30 GHz and a 3‐dB gain bandwidth of 13.3% (27.4–31.3 GHz) under normal incidence. Antenna peak gain fluctuation is less than 1 dB with a maximum beam scanning range of ±30∘ $\pm 3{0}^{\circ }$, which is much more stable than that of the monofocal TA antenna (3.6 dB). The proposed design can be a promising candidate in many military and civilian application scenarios. [ABSTRACT FROM AUTHOR]

This article presents a conformal multiple input multiple output (MIMO) antenna array for wireless avionics intra‐communications (WAIC) system application. The MIMO array consists of five probe‐fed rectangular patch antennas, which are conformal with a hemispherical platform. Each antenna element of the antenna array radiates toward different angles, forming a wide signal coverage in aircraft cabin. To further enhance isolation between close‐spacing antenna elements and improve MIMO performance, metallic slots are included in the ground plane. The MIMO array is analyzed with design details and a prototype is fabricated for verification. Experimental results show that the MIMO array has good isolation and radiation characteristics in the WAIC band of 4.2–4.4 GHz. The low‐cost and conformal configuration with compact size of the designed MIMO array make it a promising candidate for future WAIC applications. [ABSTRACT FROM AUTHOR]

The conformal antenna is a precision device installed on the wing of an aircraft, and its components are distributed on a curved surface. Quality detection is required after assembly. In solving the path planning problem for conformal antenna surface detection, the traditional genetic algorithm faces problems such as slow convergence and easily falling into a local optimal solution. To solve this problem, an improved genetic algorithm combining the historical optimal population (CHOP-IGA) is proposed. First, the algorithm uses the probability-based four-nearest-neighbor method to construct an initial population. Subsequently, the probabilities of the crossover and mutation operators are dynamically adjusted. Next, the algorithm applies the crossover and mutation operators to the population and performs mutation operations on each individual of the historical optimal population. Then, the fitness value is calculated and the next generation of individuals is selected from the parent, offspring, and historical optimal populations according to the elite selection strategy. Finally, the current best fitness is checked to determine whether updating the historical optimal population is necessary. When the termination condition is satisfied, the algorithm outputs the optimal result. Experiments showed that the algorithm satisfactorily solved the path planning problem for conformal antenna surface detection, with a 48.44% improvement in detection efficiency.

The processing of the three-dimensional circuit on the surface of conformal antennas is mainly performed via manual processing. At present, there is no automatic intelligent equipment for the processing of a similar small-sized circuit with variable curvature in China. Therefore, a high-precision, automated, full-process manufacturing method for three-dimensional circuits with flexible surfaces on conformal antennas of radar equipment has been proposed to improve processing quality and manufacturing efficiency. The processing relationship between solder paste spraying, resistor mounting, and laser welding in the flexible three-dimensional circuit manufacturing process was analyzed. The structure of the new conformal antenna three-dimensional circuit intelligent manufacturing equipment was determined, and simulation verification of the three-dimensional circuit processing was performed using Vericut. The optimal processing parameters were selected based on solid experiments. This method meets the electronic assembly requirements of radar equipment and fills the domestic gap.

A dipole with four branches, fed by Marchand balun, is designed to be conformal with wing of an unmanned aerial vehicle. With the help of branches, the proposed dipole element achieves a better impedance matching performance. Meanwhile, the metallic coupled strip is added to move the scanning blindness out of the operating frequency band, without deterioration at broadside radiation. Besides, the beamwidth in the vertical plane, i.e., the H-plane of the dipole, can be effectively compressed by loading three metallic strip directors, and the element gain increases as well. Based on the dipole element, a 12-element linear phased array is designed and simulated. The simulated results show that the array achieves ±60° scanning range in the horizontal plane, with the voltage standing wave ratio lower than 2.5 in the operating band of 2.4∼3 GHz. Moreover, the 3 dB beamwidth in the H-plane is 81° at the center frequency of 2.7 GHz. The measured results of the fabricated antenna prototype agree reasonably well with the simulated ones, which verify the feasibility of the wing-conformal linear phased array design. [ABSTRACT FROM AUTHOR]

Applications for conformal, wearable antennas are growing for consumer electronics. Hence, it is important to assess to what degree antenna performance can be tolerant to in situ deformations that can take the form of bending, crumpling, and twisting and combinations of these effects. However, generating geometries of arbitrary antenna deformations such as bending, crumpling, and twisting, which can be processed by standard electromagnetic (EM) software, is a major challenge that significantly complicates full assessment of in situ antenna performance. Constructive solid geometry methods of generating geometries is difficult to robustly apply to nonconformal antennas and more flexible techniques required to progress the antenna studies further. To address this challenge, this article investigates the utility of the green coordinate (GC) method for spatial manipulation of 3-D objects. First, calibration of a straightforward application of the GC method against a reference case of a patch antenna bent over a cylindrical surface, which can also be generated exactly, is undertaken. This article shows that systemic scaling distortions are introduced by the GC method and introduces a compensation method that can overcome these distortions. Subsequently, the compensated method is used to obtain new predictions of the EM performance of patch antennas with deformations. [ABSTRACT FROM AUTHOR]

We present a systematic design method for a cylindrical conformal array of rectangular waveguide-fed metasurfaces. The conformal metasurface consists of multiple curved rectangular waveguides loaded with metamaterial elements—electrically small apertures—inserted into the upper conducting walls of the waveguides. Each element radiates energy into free space to contribute to an overall radiation pattern. Thus, the geometry or electrical configuration of each of the elements needs to be tailored to generate a desired pattern. Generally, due to difficulties in modeling the effect of curvature, the design of conformal metasurface arrays has relied on full-wave simulations or experiments. In this study, we propose a design method utilizing the semianalytical model of a planar metasurface accounting for metamaterial elements’ locations and orientations over a curved surface. Although approximate, we demonstrate that the alteration along with the framework of dipolar modeling of planar elements can be used for the analysis of conformal arrays with small curvature. We then design a conformal array metasurface using the method combined with the covariance matrix adaptation evolution strategy (CMA-ES) optimizer. Through numerical simulations, we confirm the validity of the proposed design method. Applications include the design of metasurfaces for radar, communications, and imaging systems for mobile platforms. [ABSTRACT FROM AUTHOR]

Crack detection of metal structures is an important procedure to ensure the safe operation of metal structures. In this work, a metal crack sensor based on a highly conductive flexible graphene film is proposed. The sensor is designed based on conformal microstrip antenna composed of a flexible graphene film radiation patch and a flexible dielectric substrate. The prepared sensor exhibited a detection sensitivity of 36.82 MHz/mm demonstrated by both experimental and simulation results. Moreover, benefiting from the flexible nature of the graphene film, the proposed sensor shows good conformality which makes up the shortcoming of the traditional rigid crack detection device. [ABSTRACT FROM AUTHOR]