Design of a compact wideband CP metasurface antenna

In this article, a new compact metasurface circularly polarized (CP) antenna is presented, where the rotating 45° periodic ellipse patch is used to achieve polarization conversion from linearly polarized to CP. The meta‐surface is composed of 4 × 4 ellipse patches with 45° rotation, which are etched on the top layer of upper substrate. A slot ground plane and a coplanar waveguide structure are printed on both sides of bottom substrate, and the bottom substrate is directly connected to the upper substrate, which can make the antenna profile lower. As demonstrated in this article, the presented antennas have good characteristics of excellent 3‐dB axial ratio bandwidth of 17.4% (5.25‐6.25 GHz), and wide 10‐dB impedance bandwidth of 20.6% (5.0‐6.15 GHz).     

Design and implementation of a low profile polarization‐reconfigurable transmitarray with linear polarized feed

A novel polarization‐reconfigurable transmitarray with linear polarized feed is presented in this letter. Each element in the proposed transmitarray consists of two cascaded cross dipoles to achieve more than 310° of linear phase with transmission magnitude equal to or better than 0.8 dB. The proposed unit cell has a thickness of 0.22λ₀, which leads to a low profile transmitarray compared with those conventional designs. The element behavior of low transmission loss has resulted in higher antenna efficiency. By properly rotating the feed antenna around the center and selecting the x‐ and y‐dimension of each element, the proposed transmitarray can generate radiation patterns with different polarization states, including left‐handed circular polarization (LHCP), right‐handed circular polarization (RHCP), and linear polarization(LP). For the purpose of validation, a double‐layer center‐fed 11 × 11‐element transmitarray prototype is manufactured and tested at X‐band. Measurement results demonstrate the designed transmitarray realize both high gain performance and multiple polarization operation.     

A new broadband circularly polarized antenna with a single‐layer metasurface

In this article, a new low‐profile broadband circularly polarized antenna with a single‐layer metasurface is designed. The metasurface is composed of 4 × 4 rotated rectangle‐loops. Compared to single rotated rectangle, introducing inner‐cut rectangle slot can increase the design flexibilities by changing this slot size for wider circularly polarized operating bandwidth and reduce the size of the antenna in same frequency. The proposed antenna has the advantages of a wide 3‐dB axial ratio bandwidth from 5.4 to 6.05 GHz and an excellent 10‐dB impedance bandwidth from 5 to 6.05 GHz.     

A low scattering slot antenna based on broadband polarization conversion metasurface

An ultrawide band polarization conversion metasurface (PCM) is proposed to reduce the reflection of a slot antenna. The proposed PCM can convert a linearly polarized incident wave to the reflected wave with a 90° rotation. By arranging the PCM around the antenna symmetrically, an ideal phase cancelation is achieved. To verify the design, a metasurface‐slot antenna is simulated and measured to confirm the proposed PCM for a significant reduction of the reflection. Results show that the normal reflection of the proposed antenna at boresight is reduced more than 10 dB over an ultrawide band. In addition, 2 dB enhancement of the gain is achieved compared with a reference antenna which has the same dimensions. Meanwhile, the small influence is observed for the antenna radiation by introducing the PCM.     

Metasurface based pattern reconfigurable antenna for 2.45 GHz ISM band applications

In this article, a Z‐shaped antenna is designed for 2.45 GHz ISM band applications. The proposed antenna is surrounded by metasurface‐based unit cells. The unit cells are designed to reflect for the proposed frequency. Each of this unit cells are activated with the help of a diode. Unit cell is considered active by switching on the diode of respective unit cell. According to the activation of unit cell the pattern of the antenna will be reconfigured. The 2.45 GHz ISM band pattern reconfigurable microstrip antenna is presented. The radiation pattern of the antenna can be steered toward a desired direction by activating appropriate metasurface unit cell, minimizing the interference and optimizing medium usage. The proposed antenna performance is presented with the help of reflection coefficient and the pattern steerable capability by activating metasurface unit cells. The proposed antenna is having azimuth‐pattern reconfigurable capability around 360°.     

Broadband compact CPW‐fed metasurface antenna for SAR‐based portable imaging system

A broadband and compact coplanar waveguide (CPW) coupled‐fed metasurface (MS)‐based antenna for C‐band synthetic aperture radar (SAR) imaging application is proposed in this article, which is consisted of 16 uniform periodic square patches performed as radiators. The CPW feeding structure gives two following functions: (1) It excites an aperture coupling slot structure underneath the center of MS patch array. (2) It acts as a ground plane for the metasurface patch units. Different slots were investigated and eventually an hourglass‐shaped slot is applied to enhance bandwidth for imaging applications. A prototype with a dimension of 60 × 60 × 1.524 mm³ (1.1λ₀ × 1.1λ₀ × 0.03λ₀) operating at the center frequency 5.5 GHz (f₀) has been fabricated and measured to verify the design principle. This antenna has a measured impedance bandwidth of 12.4% from 5.14 to 5.82 GHz, a peak gain of 9.2 dBi and averaged gain of 7.2 dBi at broadside radiation. Microwave imaging experiments using the proposed antenna have been carried out and a good performance is achieved.     

Low profile antenna based on a fractal shaped metasurface for public safety applications

In this article, design and analysis of a fractal shaped metasurface (FSMS) antenna for public safety applications is presented. It comprises of two layers, upper layer and lower layer. The upper layer has the metasurface (MS) and lower layer has the fractal inspired monopole antenna. MS is made up of Sierpinski Knopp fractal shaped unit cell, which is arranged in 4 × 6 layout to achieve miniaturization. Ansys Electronic Desktop tool is utilized for analyzing the performance of the MS antenna. The projected FSMS antenna is fabricated using FR4 dielectric material and experimented with the help of an anechoic chamber and Vector Network Analyzer (VNA). Results show that the FSMS antenna exhibits a bandwidth of 200 MHz and a gain of 1.56 dBi at 4.89 GHz. The results obtained in simulation and measurement are in good agreement. Consequently, the proposed antenna with a low profile of 0.43λ₀ × 0.43λ₀ × 0.03λ₀, where λ₀ is the free space wavelength at 4.89 GHz is well fit for public safety applications.     

A multistate high gain antenna based on metasurface

A multi‐state high gain antenna based on metasurface is proposed. The antenna is composed of two stacking layers and a ground plane. The metasurface is constituted by two layers with the same size. And both of the two layers contain a copper patch array which is formed by 4 × 4 square copper cells uniformly distributed along x and y directions. The metasurface antenna is excited by the aperture coupled structure. The structure is consists of an anomaly microstrip line and a narrow slot etched in the ground plane. Genetic algorithm (GA) is adopted to optimize all the parameters and obtain the best performance of the metasurface antenna. By appropriately choosing the dimensions of the antenna, the proposed antenna can be achieved with the impedance bandwidth (RL≥10 dB) of about 340 MHz (7.8% at 4.36 GHz), 180 MHz (3.6% at 5.02 GHz), and 2800 MHz (41.1% at 6.81 GHz). The peak gain of the proposed antenna is 10.1dBi, 6.9 dBi, and 10.5dBi at 4.26 GHz, 5 GHz, and 7 GHz. In addition, the proposed metasurface antenna can work in multistate, which makes it an excellent candidate for practical applications.     

Smart monopole antenna with pattern and frequency reconfiguration characteristics based on programmable metasurface

Metasurfaces having ultrathin and planar structure with sub‐wavelength unit cell, have recently gained significant potential for use thanks to their control capabilities over the electromagnetic waves from microwave to the visible range. The structure and the dimensions of the sub‐wavelength elements determine the electromagnetic properties, capabilities, and functionalities of the metasurfaces providing a full control of the reflected and transmitted fields and these metasurfaces are referred to as analog metasurfaces. When adjustability is added to the unit cells, programmable or digital metasurfaces are obtained, allowing us to take multiple unique functionality advantages controlled by external stimuli. In this study, we propose a metasurface structure, also known as 1‐bit coding metasurface, which is controlled depending on the “On/Off” state. The “On/Off” state is controlled by a computer program using genetical algorithm. Depending on the operating state, electromagnetic waves can be manipulated and different functionalities of the metasurfaces can be realized. The contribution and innovation of the study is the demonstration of the beam rotation, resonance frequency shift and radiation pattern reconfiguration properties of a simple monopole antenna by using controllable metasurface composed of T shaped resonator and circular patch with an operating frequency between 4.3 and 5.6 GHz.     

Broadband and high-aperture-efficiency metasurface antenna using multi-mode radiator

A high-aperture efficiency and broadband metasurface antenna array with multi-mode radiator is put forward in this article. The abnormal slot is etched at the center of the ground plane and fed to the antenna via a microstrip line. Resonant along the slot line, and in the electric field, two short horizontal lines with uniform gaps are symmetrically added near zero. Additional radiation modes have been introduced. Then, broadband slot antenna with two resonances is obtained by combining full-wavelengths provided by the first slot. Working bandwidth increased from 7.6% to 21.1%. By introducing a ring slot, the antenna gain is increased by 0.9 dBi. At the same time, the aperture efficiency is modified by 12.9%. A 2 × 2 array was made to verify the design, with an overall size of 2.01λ₀× 2.01λ₀ × 0.07λ₀. The simulation and measurement results show that the operating bandwidth is 38.9% with maximum gain is 15.8 dBi.     

Multilayered substrate-integrated magnetoelectric dipole antenna with low profile and wideband

In this article, a multilayered substrate-integrated magnetoelectric dipole antenna with low profile and wideband is proposed. Based on the multilayered printed circuit board technology, the magnetoelectric dipole antenna is composed of four layers of substrate. By adopting rectangular window techniques, the impedance matching at the low-frequency band is improved and a low profile of 0.08λ₀ (where λ₀ is the free space wavelength of the center frequency) in height is achieved. A Γ-shaped meandering unit is also adopted to guide the electric current through the rectangular window and enhance the boresight radiation. Additionally, the antenna is fed by a 1/4 wavelength microstrip line on bottom plane to easily integrate to the front-side planar circuit. The transverse size of the proposed antenna is 100 mm*50 mm (0.8λ₀*0.4λ₀). Through simulation and optimization, the wideband, low profile, and unidirectional radiation characteristics are obtained simultaneously. The tested impedance bandwidth ranges from 1.92 to 3.15 GHz (48.5%) for voltage standing wave ratio (VSWR) < 2. The radiation property is also validated and the boresight mean gain is 5.1 dBi. Cross polarization level at boresight is lower than ?25.15 dB. Both simulated and tested results agree well with each other.     

新的面向低功耗聚芯片上系统可重构技术

针对聚芯SoC的结构特点,提出了一种适用于聚芯SoC的面向低功耗的可重构技术。概述了可重构技术的相关研究,提出了针对聚芯SoC中片上cache的可重构技术,并详细叙述了软硬件两种实现方法,给出了与传统方法功耗比较的实验结果。实验表明,对于Qsort程序,该方法相对传统方法可以降低35.3%的功耗,对于Dijkstra程序,该方法相对传统方法也可以降低46%的功耗。     

Wideband printed slot antenna using Koch fractal metasurface structure

A novel wideband slot antenna with Koch fractal metasurface structure is presented in this letter. Using Koch metasurface as a slot edge, the proposed antenna obtains excellent performance in bandwidth. For optimal bandwidth, optimization is done for both iteration angle (IA) and iteration factor (IF) at each iteration order (IO). The measured results show that the impedance bandwidth of the optimized antenna can reach about 1.75 octaves (1.45‐4.86 GHz) for VSWR ≤ 2. In addition, stable radiation patterns are observed over the whole operating band of the proposed antenna.     

A multi to wideband frequency reconfigurable antenna

A frequency reconfigurable antenna with a simple design structure and biasing circuit is presented. The antenna is able to configure its frequencies to operate either in multiband or wideband modes. The antenna is fed by a coplanar waveguide transmission line. The reconfiguration characteristics of the antenna is achieved by using PIN diode switches. The operating frequencies of the multiband mode are designed within the wideband mode operating range, from 2 to 6 GHz. Both simulated and measured results of S₁₁, radiation pattern and realized gains are verified. The antenna allows a degree of freedom in providing the frequency reconfiguration from multiband to wideband mode and vice versa.     

Wideband beam‐steerable configuration of metasurface loaded slot antenna

In this article, a wideband two dimensional (2D) beam‐steerable antenna structure is presented. The proposed structure is based on a radially gradient hybrid metasurface (RGHMS) illuminated through a slot antenna. The half aperture of the RGHMS comprises of a gradient phase profile topology, while its other half aperture consists of a constant phase profile configuration. The slot antenna possessing the bidirectional radiation pattern is printed on a relatively thin substrate, which operates over a wide bandwidth of 1420 MHz (15.10%). The placement of RGHMS tilts the main beam of slot antenna by 15° away from normal direction. Further, in‐plane movement of MS provides beam steering in both elevation and azimuth planes, with a conical region of an apex angle of 30°. Apart from the beam steering capability, the placement of RGHMS in front of slot antenna also enhances the overall bandwidth and gain by 360 MHz and 5 dB, respectively. Thus, a wide band beam steering configuration with the impedance bandwidth of 1780 MHz (18.85%) is obtained. In order to investigate the frequency dependent beam tilting capability of the RGHMS in the elevation plane, a detailed analysis is carried out using the principle of refraction.     

A high gain wideband circularly polarized antenna with asymmetric metasurface

An asymmetric‐metasurface based wideband circularly polarized (CP) microstrip antenna using a coaxial probe is proposed for L‐band applications. The antenna involves a stacked asymmetric‐metasurface, a radiating rectangular‐patch and a coaxial feed. An asymmetric‐metasurface is designed using rectangular unit cells and smaller size unit cells along one of the diagonal lines. The asymmetric‐metasurface is placed above a radiating rectangular‐patch with support of foam layer to achieve a wideband CP radiation. The measured performance of the prototype antenna achieves an impedance bandwidth (?10 dB return loss bandwidth) of 15.7% (1.58‐1.85 GHz) with CP bandwidth (3‐dB axial ratio) of 13% (1.58‐1.80 GHz) and gain of ≥9 dBic.     

Two-dimensional broadband and wide angle scanning multi-beam antenna based on leaky-wave metasurface

In this article, a novel two-dimensional multi-beam antenna with a broad band and a wide angle scanning range is proposed. It is composed a leaky-wave metasurface (MTS) and a four-port feeding network with high isolation. The leaky-wave MTS formed by T-shaped slots is displayed as radiator and divided into four angular sectors, each one devoted to the formation of a beam in a given elevation plane. At every fixed frequency, the antenna can radiate multi beam in azimuth plane through exciting different ports. Also, multi-beam radiation with a broad band and a wide angle scanning range in the elevation plane is realized when fixed port is excited at different frequency. The antenna with overall size of 207 mm by 207 mm by 2.0 mm is fabricated on FR-4 substrate. The measured and simulated results show that the ?10 dB relative bandwidth is 30% (from 9.44 to 12.77 GHz). When different ports are excited at the same frequency, the azimuth of radiation beam is steered to 0°, 90°, 180°, and 270°. In addition, the beam-scanning range of the prototyped antenna is from 29° to 75° when the frequency sweeps in the range of 9.5–12.0 GHz. Also, the maximum radiation efficiency reaches to 31.1% and the measured peak gain within the scanning range is 12.29 dBi.     

A low‐profile antenna with circularly polarized reconfigurable and omnidirectional radiation patterns

A low profile circularly polarized (CP) antenna with reconfigurable polarization is designed and presented, which can radiate omnidirectional patterns that can be switched between left‐hand circularly polarized (LHCP) and right‐hand circularly polarized (RHCP). A pair of arc‐shaped complementary dipoles is acted as reconfigurable elements by bridging four pin diodes at the dipole arced arms. A meander phase shift line is employed to connected the arc dipole arms and plate cavity to adjust the phase relationship of two sources. The proposed antenna exhibits the omnidirectional radiation pattern by combining six identical elements placed in a circular array configuration. 24 p‐i‐n diodes are exploited to six elements, by manipulating the dc bias voltage across the diodes, the polarization state of the antenna can be switched. The patterns of the antenna are similar to that of a dipole, but its size is only about Φ0.87 × 0.029λ₀ at 5.8 GHz. The overlapped bandwidth of measured 3‐dB axial ratio (AR) and 10‐dB return loss is 5.724‐5.87 and 5.738‐5.91 GHz for two polarization states, which are right on the target of ISM band. It can be well adapted to medical diagnosis systems.     

A compact configuration of semicircular metasurface loaded slot antenna for beam steering application

In this article, a compact beam steering antenna configuration is presented. The proposed structure comprises a semicircular radially gradient metasurface (SCRGM) and a slot antenna. This metasurface (MS) with the dimensions of 3.17λ₀² covers only half of the antenna aperture by placing it at a height of 0.16λ₀ from the slot antenna. The SCRGM is made up of four different semicircular regions, which introduce progressive phase delay to the impinging spherical electromagnetic waves from the slot antenna. The placement of the SCRGM tilts the main beam by 30° away from the normal direction. Furthermore, in‐plane movement (rotation and translation) of the SCRGM facilitates beam steering in the elevation plane (E‐plane) with the total scanning range of 60°. Moreover, in simulation, two SCRGMs are placed at both sides of antenna aperture to independently control the beam directions in both upper and lower hemispheres of the slot antenna. Due to the symmetry of the slot antenna, only one SCRGM is tested during the measurement process and the same outcome is expected for the other MS. Considerably small volume (0.50λ₀³) of the structure revealed compact antenna configuration. Moreover, independent control of the beam directions in both of the hemispheres makes proposed antenna a suitable candidate for various applications.     

Wideband and low profile polarization conversion meatasurface‐based circularly polarized slot antenna

The purpose of this study is to investigate the application of a polarization conversion meatasurface for constructing a low profile, wideband circularly polarized slot antenna, which consists of a new Polarization conversion metasurface (PCM)‐based square‐corner‐cut artificial magnetic conductor cell structure and a feeding slot antenna. PCM possesses two frequency points of polarization rotation (PR), produced by appropriately adjusting width between the two triangular metallic patches. A 39.3% (4.7‐7 GHz) of big PR band was realized through the combination of two neighboring PR frequency points. The impedance bandwidth of PCM based patch antenna was measured to be 43.5% (4.5‐7 GHz), with 17.2% (5.3‐6.3 GHz) of 3 dB axial ratio (AR) bandwidth and 0.045λ₀ of profile. It also generated 7.3 dBic of high broadside gain in operational bandwidth.