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The independent control of two orthogonal polarizations that possess dual functionalities is highly desirable in antenna and wireless communication technologies. Spin-decoupled metasurfaces with integrated dynamic and geometric phases have been proposed to generate two independent right-handed and left-handed circularly polarized (RCP and LCP, respectively) waves. However, the RCP and LCP phases are correlated by a linear equation of the dynamic and geometric phases. In this article, we propose a meta-atom in which the 1 b phase of two orthogonal polarizations can be controlled independently. Moreover, a high-gain broadband millimeter-wave multidimensional metasurface to generate an $x$ -polarized $l=0$ beam with a 10° beam deflection and a $y$ -polarized $l=+1$ beam independently is simulated, fabricated, and tested. The proposed metasurface operating over the frequency range of 16–28 GHz has the maximum gains of 28.7 and 23.8 dBi for the $l=0\,\,x$ -polarized waves and $l=+1\,\,y$ -polarized waves, respectively. Compared with spin-decoupled metasurfaces, the proposed metasurface provides a simpler design process to generate two independent vortex beams for the two orthogonal polarizations. The proposed vortex metasurface also has the advantages of dual polarization, high gain, wide relative bandwidth, and is broadband. The proposed metasurface has potential application in high-capacity communication systems. [ABSTRACT FROM AUTHOR]

A circularly-polarized (CP) traveling-wave endfire antenna featuring low profile, high gain, and simple feeding structure is presented in this communication. Offset parallel strips with proper dielectric loading are employed in a low-profile substrate to achieve two orthogonal electric field components with equal magnitude and 90° phase difference for CP endfire radiation. Meanwhile, periodic phase-loading technique is used to achieve a proper phase constant for high endfire gain. A prototype is designed and fabricated to verify the proposed method. Experimental results demonstrate CP endfire radiation within a frequency band of 9.78–10.09 GHz. The average endfire gain is 10.3 dBic with an average efficiency of 62.5%. [ABSTRACT FROM AUTHOR]

In this article, we propose a traveling-wave endfire antenna based on the first higher-order transmission line (TL) mode, and it features wide bandwidth, high gain, and large aperture efficiency. We propose two essential conditions for the realization of the proposed wideband endfire antenna. First, the dispersion curve of the first higher-order mode should be made close to that of the air line across a wide frequency band. Second, the fundamental mode should be suppressed to allow single higher-order mode operation across a wide frequency band. Following these principles, we provide a design for an endfire antenna based on a periodically slotted parallel stripline, where the periodic meandered slots suppress the fundamental mode and hence allow single higher-order mode radiation. To verify the proposed approach, a prototype has been designed and fabricated. The antenna can achieve endfire radiation within a 1:2 frequency band (8.5–17.5 GHz), with an average gain of 10.7 dBi, and large aperture efficiency up to 6.38 dBi/ $\lambda ^{2}_{0}$. [ABSTRACT FROM AUTHOR]

This article proposes a general design technique for high-gain traveling-wave endfire antennas using a periodic arbitrary-phase loading technique. This work extends the periodic phase-reversal techniques reported in previous work to application scenarios where phase reversals are difficult to realize (e.g., single-layer circuits). It also relaxes the substrate permittivity requirement in phase-reversal techniques. To verify the proposed technique and theory, two design examples using different phases other than π are provided. Double-side parallel stripline and coplanar stripline are employed to provide vertical and horizontal polarizations, respectively. Double-side parallel stripline antenna achieves a maximum endfire gain of 15.6 dBi with vertical polarization. The coplanar-stripline antenna exhibits a maximum endfire gain of 16.6 dBi with horizontal polarization. The experimental results of these two examples validate the proposed technique. [ABSTRACT FROM AUTHOR]

In this article, two configurations of novel dual-band half-mode substrate integrated waveguide (HMSIW) leaky-wave antennas are presented. The first proposed antenna radiates linearly polarized (LP) waves in the lower band and circularly polarized waves in the upper band when the unit cells are cascaded sequentially. The second antenna, where the sidewall via of the HMSIW unit cells is connected alternatingly, provides simultaneous dual beams with different polarization in the upper operational band in addition to the LP beam in the lower operational band. The unit cells of the two antennas are analyzed in terms of their dispersion behaviors. Finally, the performance of both the antennas is experimentally verified. [ABSTRACT FROM AUTHOR]

A phase-reversal technique is proposed in this article to overcome the gain-aperture tradeoff of endfire antennas. Such a tradeoff fundamentally forbids simultaneous high gain and small cross-section aperture. The phase-reversal technique breaks this tradeoff and hence allows one to design a high-gain endfire antenna with a small cross-section aperture. To illustrate the proposed phase-reversal technique, a crossover stripline structure is implemented. The antenna radiates into the endfire direction within 9.5–10.5 GHz and it achieves 13 dBi endfire radiation gain with only $0.047\lambda _{0}\,\,\times \,\,0.022\lambda _{0}$ cross-section aperture size. These results successfully validate the proposed phase-reversal technique. Such a high-gain and small-aperture endfire antenna is potentially useful for microwave imaging in lossy medium. [ABSTRACT FROM AUTHOR]

A glide-symmetry Goubau line leaky-wave antenna for achieving both high scanning rate and wide scanning angle range is introduced. The novelty of the design is its combination of glide symmetry and a single-layer Goubau line. This combination leads to performance enhancement in both scanning rate and scanning angle range. Utilizing a corrugated Goubau line in a glide-symmetry fashion closes its stopband at the cutoff frequency while slowing down its group velocity. As the dispersion around the closed stopband is shifted to the fast-wave region by periodic profile modulation, the space harmonics exhibit high-scanning-rate radiation. In conjunction with this, the single-layer nature of the Goubau line allows the beam to scan from nearly endfire to backfire directions, leading to a wide scanning angle range. Numerical examples and experimental validation are provided to validate the proposed design. These show that the proposed antenna exhibits dual-band operation, where one band scans 152° within 2.2 GHz (corresponding to scanning rate of 69°/GHz) with 67% efficiency, while the second band scans 145° within 0.7 GHz (corresponding to scanning rate of 207°/GHz) with 26% efficiency. A tradeoff between scanning rate and efficiency always exists in high-scanning-rate leaky-wave antennas. One is able to freely choose the preferred scanning rate in this single antenna. A comparison with other related works shows that the proposed antenna exhibits the best performance. [ABSTRACT FROM AUTHOR]

We systematically analyze and describe a new type of traveling-wave endfire antenna based on an asymmetrically corrugated Goubau line that exhibits high efficiency and has a low profile. By proving that asymmetry is a necessary condition in addition to the Hanson–Woodyard condition for traveling-wave endfire radiation, we study the effect of asymmetric corrugation on the mode guide and coupling. We subsequently show that two different waves are independently guided along the two corrugated edges, whose phase difference leads to a transversally polarized dipole moment radiating in the endfire direction. A closed-form expression for the radiation pattern is derived based on the proposed analysis to approximately predict the antennas’ optimum length. To verify the proposed analysis and design principles, results from an experimental prototype operating at 13–15 GHz are also provided. The experimental results show that the antenna design has an average gain of 9.9 dBi and an average efficiency of 82%. The agreement between the predicted results and the final optimized results validates the proposed analysis. [ABSTRACT FROM AUTHOR]

Abstract: This article proposes model analysis of a microstrip leaky‐wave antenna for forward and backward scanning. Mode coupling and dual scan concept is introduced in this article with an inverted V‐section leaky‐wave antenna. The proposed design concept has been implemented on microstrip planar structure. An inverted V‐section has been therefore implemented which resulted in frequency scanning in forward and backward directions in the right‐hand (RH) region. The phenomenon has been observed within same frequency bandwidth of leaky‐wave region which is normally difficult to see in conventional leaky‐wave antennas. The article has also provided a circuit model analysis and design implementation explained by mode coupling theory. The proposed dual scanning leaky‐wave antenna (DSLWA) design is providing a wide impedance bandwidth in the Ku‐band and K‐band with high gain, reduced side lobe levels and high radiation efficiency. [ABSTRACT FROM AUTHOR]

A physically transient (PT) antenna changes its properties over a predefined lifespan due to its time-varying dimension and shape. The PT antenna technology has attracted much attention in the areas of biomedical, environmental, and military applications. It is also a fundamental building block of transient communications, where certain components of the communication link are degradable. In this paper, we revisit the classical antenna figures-of-merit such as resonant frequency and input impedance, and propose a novel immersion-time-dependent description framework to characterize this class of antennas, taking into account their PT nature. Subsequently, we present the notions of average and outage antenna characteristics over all realizations of the random antenna degeneration process occurring in a solvent. To the best of our knowledge, this is the first attempt in the open literature to quantify stochastically the properties of a PT antenna. Finally, we look into the specific application scenario of a degradable circular patch to demonstrate the principles and applicability of the proposed methodology. The analytical approach may also find important applications in the design and evaluation of other PT wireless devices and systems. [ABSTRACT FROM PUBLISHER]

This article proposes a simple and low profile planar Goubau line based end‐fire antenna. End‐fire radiation is achieved by modifying the Goubau line into inverted periodic arrangement of V‐shaped unit cells. Designed prototype is simulated and verified experimentally. Both the simulated and measured results are in good agreement. Proposed antenna radiates toward end‐fire direction between 7.8 and 8.3 GHz. The maximum gain of the antenna is obtained around 7.2 dBi. The average efficiency is observed 70% over the entire operating bandwidth. Proposed end‐fire antenna has a single metallic layer with simple configuration which is easy to fabricate and also easy to integrate with other electronics circuits. The proposed antenna can be used for satellite and RADAR applications. [ABSTRACT FROM AUTHOR]

• 3-D LM composite with high electrical conductivity of 105–106 S/m is fabricated. • Soft antennas with ultimate strain of 300% are achieved based on 3-D LM composite. • The antenna presents a strain-independent reflection coefficient of around −30 dB. • The antenna exhibits stretch-tuned resonant frequency over wide frequencies. • Both softness of LM and protection from stiff layer contribute to the performance. We develop a class of stretchable dipole antennas based on embedding three-dimensional liquid metal network into an elastically soft elastomer as conductive branches, which can be highly stretched up to a strain of 300% while presenting high-quality reflection coefficient around −30 dB and a wide range of tunable resonant frequency from 1.55 to 0.45 GHz simultaneously. Neither mechanical damage nor performance degradation was observed during 100 stretch-release cycles under 100% strain for the antennas. The high electrical conductivity and deformation reversibility of the liquid metal, super stretchability of the soft elastomer and protection from the rigid layer are responsible for such a unique performance, enabling potential application for wireless strain sensors. [ABSTRACT FROM AUTHOR]