Antenna Polarization Research Articles

Performance analysis of improved path loss models for millimeter-wave wireless network channels at 28 GHz and 38 GHz.

The importance of the path loss in millimeter wave channel propagation cannot be taken for granted in terms of deployment, design, performance assessment, and planning. The path loss helps to determine the network's geographic coverage. Although many path loss models, including statistical and empirical models based on measurement and linear regression, have been proposed by various researchers, high fidelity is required to determine the performance of the wireless network's channel. This research validates the improved version of the well-known close in (CI) and floating intercept (FI) path loss models at frequency bands of 28 and 38 GHz. The measurement surroundings comprised of an enclosed passageway with vertical-horizontal (V-H) and vertical-vertical (V-V) antenna polarizations. One of the key findings of this study is that the enhanced versions of these models typically perform better in terms of consistency than the standard models thereby justifying their high accuracy level. The improved versions of the CI and the FI models demonstrate a significant improvement for various antenna polarizations. The mean prediction error (MPE) and standard deviation error (SDE) also show how precisely and accurately the improved models predict the path loss. Additionally, the improved models provide the reasonable responsiveness and uniformity of the parameters with the change in the antenna polarization and lower the shadow fading's standard deviation in LOS as well as NLOS situations. The results confirm that the modified versions of CI and FI models predict path loss better in an enclosed environment for 5G networks.

Dual polarization and mutual coupling improvement of UWB MIMO antenna with cross shape decoupling structure

A simple, compact MIMO antenna that operates in the UWB frequency band is presented in this paper. The proposed antenna consists of four elements where the shape of the radiators derived from series modifications of a conventional rectangular patch antenna. Radiators are placed orthogonally to each other to achieve the dual polarization operation and cross shape Defected Ground Structure (DGS) is inserted in the ground plane to improve decoupling between the antenna elements. The designed model was fabricated on FR-4 substrate with dimensions of 48 × 44 × 1.6 mm3 and measurements were performed to validate the simulated results. The fractional bandwidth reaches 112% from 3.1 GHz to 11 GHz with reflection coefficient less than -10 dB and mutual coupling between antenna elements is less than -20 dB. The antenna has a stable radiation pattern, and low gain variation. In addition, the time domain characteristics and diversity performance indicators were evaluated and compared with the standard values. The miniaturized dimensioning of the antenna along with the good performance metrics indicates that the proposed antenna can be used in various UWB applications such as portable handheld devices.

High-gain reconfigurable polarization antenna based on metamaterial array for Terahertz applications

This paper suggestsproposes a high-gain reconfigurable polarization antenna using a metasurface polarizaer. The metasurface polarizer is a rectangular array that consists of similar 25 unit-cell elements. Each metamaterial (MM) unit-cell element consists of a circular copper patch attached to two copper arrow-shaped strips installed at its circumference. The circular patch and two arrows are installed between a rectangular superstrate at the top and a rectangular substrate at the bottom, which is backed with a perfect electric conductor with a relative permittivity of εsub = 3.38. The MM characteristics are obtained in a wide range of frequencies from 1.4 to 2.1 THz. The metasurface polarizer array is installed at an optimized height of 25 μm under a linear polarized dipole antenna that operates at 1.81 THz with a bandwidth (BW) of 0.2 THz from 1.75 to 1.95 THz (11.05%, − 10 dB BW) and gain of 2.27 dBi. The incident-plane wave from the antenna can be converted into a reconfigurable left- or right-hand circular polarization according to the directions of the arrow of the MM unit-cell element. Moreover, the operating − 10-dB BW of the dipole antenna increases to 30.93%, and the gain is enhanced to 6.18 dBi at the same operating frequency. A reconfigurable polarization conversion for the dipole antenna can be obtained over wide 3-dB axial ratio BW from 1.45 to 1.95 THz (33.3% BW).

Dual Channels for Polarization-Insensitive Microwave Energy and Data Co-Delivery Through Shared Aperture of Dual-Linearly Polarized Antennas

To guarantee aligned polarization between transmitting (TX) and receiving (RX) antennas, dual isolated channels can be established through shared aperture of TX and RX dual-linearly polarized (DLP) antennas. Under excitations of microwave energy and data individually at vertically and horizontally polarized (VP/HP) ports of TX DLP antenna, it enables both balanced RF-to-dc rectification and differential data demodulation insensitive to tilts of RX DLP antenna polarization with employment of a hybrid coupler and two identical sub-rectifiers. All circuits are fabricated on a 20-mil low-loss substrate, Rogers RO4350B (tan <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta = 0.0037$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r} = 3.66$ </tex-math></inline-formula> ). Selected polarization tilts ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varphi $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0\sim 90^{\circ }$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \varphi = 30^{\circ }$ </tex-math></inline-formula> ) are conducted as experimental measurements, which along with theory analysis validate its robustness of dual channels for polarization-insensitive microwave energy and data co-delivery.

A Broadband Circularly Polarized Antenna with Stable Gain Based on Square Slotted Ground

In this paper, a circularly polarized (CP) low cost, low profile antenna with broadband stable gain is proposed. The antenna consists of a grounded square slot with two inverted-L shaped microstrips, an asymmetrical Y-shaped microstrip radiator with a stub, and several fine tuning elements. The CP radiation is first realized by using the Y-shaped microstrip line, which incorporates a stub is to realize better impedance matching. Next, by utilizing two Inverted-L microstrips into the corners of the grounded slot, the axial ratio (AR) characteristic can be further improved. A wider AR bandwidth (ARBW) can be achieved by utilizing four rectangular strips as fine tuning elements. Simulation results show the proposed antenna demonstrates a radiation with a CP bandwidth of 50% and a stable gain with average value of 5.18 dBi.

Polarization and Frequency Reconfigurable Antenna using Metasurface: Analysis, Review and Proposal

Wireless communication technology experienced drastic developments during the last few decades. Meanwhile the reconfigurable antenna had attracted more researchers because of its growing needs in various applications. Reconfiguration was performed to replace numerous antennas with single reconfigurable antenna which is capable of changing the Frequency, Polarization, Radiation Pattern etc. Antenna reconfigurability is attained by deploying several switching mechanisms among them electronic switching mechanisms are commonly used because of its simple integration, reliability, and efficiency. In this paper, review of various implementation techniques for antenna reconfiguration using meta surface are studied. Some of the reviewed factors are: Meta surface is the distribution of electrically small scatters called two-dimensional metamaterial. Metamaterial is an artificially built periodic array structure which consists of subwavelength cells. Some of the reviewed challenges in reconfiguration of the antenna are modeling of reconfigurable reflectarray, low-profile, high gain, unidirectional radiation pattern etc. Finally, some of the features, parameters and fundamental properties for designing reconfigurable antenna were investigated. Based on the study conducted, reconfigurable structure for 5 G application using meta surface is proposed.

Conceptual Design of a Semi-Dual Polarized Monopulse Antenna by Computer Simulation

Presented in this paper is a conceptual design by computer simulation of a monopulse reflector antenna with dual-circularly polarized sum patterns and linearly polarized azimuth and elevation difference patterns, which can be called a semi-dual polarized antenna. The proposed antenna consists of a five-element monopulse feed and a prime-focus parabolic reflector. The novelty of the proposed antenna is a monopulse feed consisting of a dual-circularly polarized square waveguide sum channel radiator and linearly polarized rectangular waveguide azimuth and elevation difference channel radiators. The separation of dual circular polarization is realized by a septum polarizer. The difference pattern is obtained by feeding two rectangular waveguides in opposite directions using a coaxial probe. The proposed monopulse feed geometry requires only two power combiners for a monopulse comparator network while providing dual-polarized performance comparable to the full dual-polarized sum and difference channel monopulse scheme. The concept of the proposed antenna is shown in a conceptual design by computer simulation. The monopulse feed is designed first, and then combined with a parabolic reflector. The designed monopulse reflector antenna operates at 14.5–16.0 GHz, and shows excellent sum and difference pattern characteristics: 36.1–36.7 dBc sum channel directivity with 0.65 dB boresight axial ratio and 32.6–32.9 dBi difference channel directivity with 1.56–1.66° crossover angle.

Radio-Frequency Energy Harvesting Using Rapid 3D Plastronics Protoyping Approach: A Case Study

Harvesting of ambient radio-frequency energy is largely covered in the literature. The RF energy harvester is considered most of the time as a standalone board. There is an interest to add the RF harvesting function on an already-designed object. Polymer objects are considered here, manufactured through an additive process and the paper focuses on the rapid prototyping of the harvester using a plastronic approach. An array of four antennas is considered for circular polarization with high self-isolation. The RF circuit is obtained using an electroless copper metallization of the surface of a 3D substrate fabricated using stereolithography printing. The RF properties of the polymer resin are not optimal; thus, the interest of this work is to investigate the potential capabilities of such an implementation, particularly in terms of freedom of 3D design and ease of fabrication. The electromagnetic properties of the substrate are characterized over a band of 0.5–2.5 GHz applying the two-transmission-line method. A circular polarization antenna is experimented as a rapid prototyping vehicle and yields a gain of 1.26 dB. A lab-scale prototype of the rectifier and power management unit are experimented with discrete components. The cold start-up circuit accepts a minimum voltage of 180 mV. The main DC/DC converter operates under 1.4 V but is able to compensate losses for an input DC voltage as low as 100 mV (10 μW). The rectifier alone is capable of 3.5% efficiency at −30 dBm input RF power. The global system of circularly polarized antenna, rectifier, and voltage conversion features a global experimental efficiency of 14.7% at an input power of −13.5 dBm. The possible application of such results is discussed.

Experimental and Computational Analysis of Broadband THz Photoconductive Antennas

The work presents the fabrication and measurements of four LT-GaAs photoconductive terahertz (THz) antennas with different geometries of metallic electrodes. The goal is to analyze the overall bandwidth of the antennas through a comparison between the spectra of the generated photocurrent in the antenna gap, the radiated electric field THz pulse, and the S11 parameter of the metallic electrodes. The photocurrent density and the S11 parameters are computed using COMSOL multiphysics, while the generated THz pulse was experimentally measured using a time-domain spectroscopy system. The polarizations of the photoconductive antennas are experimentally measured, using x-cut quartz crystal halfwave plates, showing polarization in the direction of the electrode’s long axis. Pinholes are used to verify system alignment and quality of the radiated signal spectra. The results show that the spectra of the radiated THz pulses in all four antennas considered in this work are dominated by the behavior of the S11 parameter at the lower part of the frequency band, but with the decreasing photocurrent dominating the spectra at higher frequencies.

Design and Analysis of Circular Polarized Two-Port MIMO Antennas with Various Antenna Element Orientations

This article presents the circularly polarized antenna operating over 28 GHz mm-wave applications. The suggested antenna has compact size, simple geometry, wideband, high gain, and offers circular polarization. Afterward, two-port MIMO antenna are designed to get Left Hand Circular Polarization (LHCP) and Right-Hand Circular Polarization (RHCP). Four different cases are adopted to construct two-port MIMO antenna of suggested antenna. In case 1, both of the elements are placed parallel to each other; in the second case, the element is parallel but the radiating patch of second antenna element are rotated by 180°. In the third case, the second antenna element is placed orthogonally to the first antenna element. In the final case, the antenna is parallel but placed in the opposite end of substrate material. The S-parameters, axial ratio bandwidth (ARBW) gain, and radiation efficiency are studied and compared in all these cases. The two MIMO systems of all cases are designed by using Roger RT/Duroid 6002 with thickness of 0.79 mm. The overall size of two-port MIMO antennas is 20.5 mm × 12 mm × 0.79 mm. The MIMO configuration of the suggested CP antenna offers wideband, low mutual coupling, wide ARBW, high gain, and high radiation efficiency. The hardware prototype of all cases is fabricated to verify the predicated results. Moreover, the comparison of suggested two-port MIMO antenna is also performed with already published work, which show the quality of suggested work in terms of various performance parameters over them.

Multiband Sub-THz Double Angular Characterization in Indoor Scenario

In this article, we present a multiband channel characterization at sub-THz. Three measurement campaigns were conducted in an indoor environment, for different frequency ranges: 125–155, 235–265, and 270–300 GHz, by exploiting a single (vertical) polarization antenna and performing only the azimuth plane. Line-of-sight (LOS) and nonline-of-sight (NLOS), given by human body obstructions and walls, are considered. From directional measurements, the omnidirectional power angular delay profile was extracted. Modeling of large-scale parameters and cluster study are presented.

A Compact Quadruple-Band Circular Polarized MIMO Antenna With Low Mutual Coupling

This brief presents a compact multiband multiple input multiple output (MIMO) antenna, where two robot-character-shaped patches are closely positioned on the top of the substrate for circular polarization. The dimensions of the proposed MIMO antenna are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.34\lambda \times 0.13\lambda \times 0.01\lambda $ </tex-math></inline-formula> at 4 GHz and the distance between two symmetrical elements is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.05\lambda $ </tex-math></inline-formula> mm. The robot-character-shaped patch generates four different frequency bands of 3.85-4.25 GHz, 4.95-5.1 GHz, 6.94-7.35 GHz, and 8-8.3 GHz. The simulation and measurement results show that the designed antenna has better S-parameters <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$|S_{11}| \le -$ </tex-math></inline-formula> 10 dB, and an isolation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$|S_{12}| \le -$ </tex-math></inline-formula> 25 dB resulting from the irregular parasitic element to reduce mutual coupling, an axial ratio (AR) of no more than 3 dB, radiation pattern, total gain, and efficiency over all operating bands when compared to the existing two-port MIMO antennas. MIMO antennas diversity characteristics are also calculated to evaluate the proposed antennas performance. The proposed antenna is a good contender for 5G pioneer band, 5 GHz WLAN band, and satellite communication applications concomitantly.

X-Band Microstrip Array Antenna for UAV Onboard Full Circularly Polarized Synthetic Aperture Radar

Recently, unmanned aerial vehicles onboard synthetic aperture radar (UAV-SAR) have been developed by many institutions to provide high-resolution, real-time data acquisition and local emergency observation. The SAR system remains the issue to realize the system with the high resolution, lightweight, minimalized payload, power efficiency, high altitude operation, extreme environment, long-duration flight, and full polarimetric mode. For this purpose, our research group plans to develop the X-band circularly polarized UAV-SAR for disaster and environmental monitoring using the 25 kg payload of the UAV. The SAR system requires a broadband antenna and full circular polarization for precise observations. The antenna for the SAR systems requires a small size, lightweight, high gain, broadband for chirp pulse, and good antenna isolation and axial ratio (AR). For this purpose, we proposed the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times4$ </tex-math></inline-formula> ax-shaped radiator array antenna. The proposed antenna was simulated, fabricated, and measured in an anechoic chamber. Furthermore, the indoor polarimetric scattering SAR experiment was conducted using canonical targets to investigate the polarimetric SAR capability of the system with the proposed antenna. The result proves the performance of circularly polarized SAR.

A Wideband Circularly Polarized Antenna Based on Anisotropic Metamaterial

This article presents a novel circularly polarized (CP) antenna based on an anisotropic metamaterial. The antenna is capable of performing linear-to-circular polarization conversion over a wideband of frequencies in the X-band (8–12 GHz). The proposed antenna was constructed from a metamaterial-based polarizer mounted above the aperture of a rectangular waveguide. The polarizer was oriented at 45° to E-plane of the waveguide. The proposed polarizer is composed of multiple metamaterial layers. The unit cell of the proposed polarizer consists of a single dielectric slab incorporating a series of rectangular split ring resonators that are printed on both sides of the slab. Impedance matching layers (IML) are introduced to enhance the axial-ratio (AR) bandwidth. The polarizer has a low profile in terms of electrical length (thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.41 \lambda _{0}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at 10.5 GHz). A full-wave electromagnetic simulator was used to verify the anisotropic characteristics of the unit cell. This was achieved by showing that the metamaterial exhibits two different refractive indices along the orthogonal components of the incident electric field. The prototype of the proposed design is fabricated and measured to validate the performance. The measured results agree with the simulated ones and demonstrated a wide impedance bandwidth of 62.4% ranging from 7.08 to 13.5 GHz with a 3 dB AR bandwidth of 29.9% (9.25–12.5 GHz).

A Miniaturized Wideband Directional Circularly Polarized Antenna Based on Bent Vivaldi Antenna Structure

This letter describes the design of compact broadband circularly polarized (CP) array antenna based on the Vivaldi element. Four sequentially rotated Vivaldi antenna elements are bent into the antenna aperture for miniaturization and are fed by a 1-to-4 integrated feeding network with identical amplitude and orthogonal phase. A coupling metal patch is mounted on the top of the antenna to enhance the impedance, circular polarization, and gain characteristics. A prototype is fabricated and measured for demonstration purposes, the results show a 10 dB impedance bandwidth (IBW) of 57.8% (1.6–2.9 GHz) and a 3 dB axial ratio bandwidth (ARBW) of 50.7% (1.65–2.77 GHz). Furthermore, the antenna has outstanding radiation performance, with a peak gain of 5.6 dBic across the entire operating bandwidth. The antenna, in particular, is highly miniaturized in comparison to other similar antennas, with an overall size of 0.26 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\lambda }_{l}$</tex-math></inline-formula> × 0.26 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\lambda }_{l}$</tex-math></inline-formula> × 0.12 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\lambda }_{l}$</tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\lambda }_{l}$</tex-math></inline-formula> is the free-space wavelength at 1.6 GHz).

A dual‐band dual‐sense circularly polarized antenna based on chiral structure

AbstractA millimeter‐wave (MMW) dual‐band dual‐sense (DBDS) circular polarization (CP) antenna based on a chiral structure is presented. An arc parasitic patch is loaded around a circular patch to have chiral characteristics. This structure exhibits bi‐isotropy to the electromagnetic wave. The linear polarization (LP) wave passes through the chiral structure and excites the orthogonal left‐handed (LH) and right‐handed (RH) CP waves. The antenna is fabricated and measured. The LHCP radiation is achieved in the range between 23.75 and 24.25 GHz, and the RHCP radiation is between 27.75 and 28.25 GHz. The realized gains reach 6.9 dBic at 24 GHz and reach 7.1 dBic at 28 GHz. The proposed antenna has a profile of 1.044 mm (0.08 λ) and occupies an area of 0.54 λ × 0.54 λ, λ is the free‐space wavelength at the lower frequency and is convenient for array design.

Detection Probability of Polarimetric GNSS-R Signals

Polarimetric Global Navigation Satellite System-Reflectometry (GNSS-R) is the next natural step for land monitoring using GNSS signals. The Soil Moisture Active Passive (SMAP) radar receiver has been retrieving polarimetric GNSS-R data using two orthogonal linearly polarized antennas since 2015, enabling the study of the polarimetric signature of GNSS-R signals on different Earth’s surfaces. Currently, new instruments and missions are using circularly polarized antennas to retrieve polarimetric GNSS-R information. In this manuscript, synthetic right and left-hand circularly polarized signals are reconstructed using the Stokes parameters of the SMAP L2C GNSS-R data. The signal-to-noise ratio (SNR) of the SMAP-R data at the equivalent RHCP, LHCP, H, and V polarization antennas is retrieved, and normalized to an arbitrary receiver with a noise figure of 2 dB. Appling the Albersheim model, we analyze the probability of detecting a reflection in a 0.5° Lat/Lon box. Results are presented for different configurations of coherent and incoherent integration times and antenna gains, for each possible antenna polarization. We present different receiver configurations capable of detecting more than 70% and 90% GNSS reflections over land. Results show that with a 10-dB antenna and a receiver with a coherent integration time of 4 ms, and an incoherent integration time of 1000 ms would suffice to detect 19.4%, 92.3%, 83.5%, and 79.4% for RHCP, LHCP, H-polarized, and V-polarized antenna, respectively. Detectability improves up to 57.4%, 99.3%, 96.3%, and 96.6% using a 14-dB antenna. Results are then generalized to L1 C/A GNSS-R signals.

A Polarization and Frequency Reconfigurable Microstrip Antenna for Vehicular Communication System Application

To face a complex wireless communication scenario, a flexible and tunable multi-functional antenna system should be employed to guarantee system quality. This paper presents a polarization and frequency reconfigurable microstrip patch antenna with a wide 3-dB axial ratio beam-width for vehicle communication systems. By controlling the p-i-n diodes, the proposed design can achieve four operating states: linear polarization (LP) in lower frequency bands between 1.45 and 1.47 GHz, and LP, left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP) in higher frequency bands between 1.50 and 1.53 GHz. The proposed antenna has an exceptionally low profile (0.02 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> at 1.5 GHz) and a simple structure, consisting of a single-layer square patch with two annular ring slots and four switches placed at appropriate locations in the slots. P-i-n diodes, as the switchs, change the current distribution on the radiating patch to achieve the antenna's polarization and frequency reconfigurability. The proposed antenna was fabricated and tested, and the observed results are identical to those predicted by the simulation. The antenna has outstanding reconfigurable capabilities independent of frequency or polarization in the operational frequency range. Therefore, it can be well used for vehicular communication systems because of its multi-reconfigurability and stable mechanical property.

A High Angular Stability, Single-Layer Transmission Linear-to-Circular Polarization Converter for Dual ISM-Band Operation

This paper presents a planar metasurface structure for linear to circular polarization (CP) conversion at the industrial, scientific, and medical bands of 2.4 GHz and 5.8 GHz. The new unit-cell structure consists of two loaded symmetric cross-shaped stubs with a size of 0.26 λ × 0.26 λ in a single thin substrate with a thickness of 0.0064 λ. The design process and parametric study are presented to clarify the operating mechanism for each frequency. The unit-cell element is analyzed and simulated, which exhibits an axial ratio (AR) bandwidth of 15.8% and 12.6% at a 3-dB criterion with the same polarization mode at 2.4 GHz and 5.8 GHz, respectively. The proposed LP-to-CP converter achieves a stable AR bandwidth with an oblique incident angle up to 45°. Moreover, a dual-band linear polarization (LP) antenna is combined with an array of 4 × 4 unit cells to validate the polarization converting ability of the proposed metasurface. The LP-to-CP converter and the antenna are fabricated and measured. The measurement results show that the antenna obtains a good impedance matching and CP waves radiation at 2.33–2.51 GHz and 5.55–5.89 GHz. The integrated antenna with dual-band CP waves radiation is suitable for improving the transmission efficiency in communication and wireless power transfer applications.

A HIGH GAIN CIRCULARLY POLARIZED (CP) ANTENNA ARRAY USING SEQUENTIAL PHASE (SP) ROTATION TECHNIQUE FOR WLAN APPLICATIONS

This paper designs and investigates a high gain circularly polarized 2 &amp;times; 2 antenna array for wireless applications using the sequential phase rotation technique. The feed network utilizes four rectangular lines of equal width and three 90&amp;deg; arcs. The length of all elements is equal to &amp;lambda;&lt;sub&gt;g&lt;/sub&gt;/4 to provide 0&amp;deg;, 90&amp;deg;, 180&amp;deg;, and 270&amp;deg; phase differences at the four outputs of feed network to increase the axial ratio(AR) bandwidth and purity. Four corner truncated patch elements are connected to the feed network to fulfill the 2 &amp;times; 2 antenna array design. The proposed design operates with an impedance bandwidth of 1.1 GHz from 4.9 GHz to 6 GHz bandwith and an AR bandwidth of 0.8 GHz from 5 GHz to 5.8 GHz band. The maximum measured gain of the antenna array is observed as 8.9 dBic in the operating band. The antenna array was prototyped and tested to validate its performance. This array is well suitable for high gain WLAN applications.