Stable Antenna Research Articles

Dual-Polarized Dipole Antenna with Wideband Stable Radiation Patterns Using Artificial Magnetic Conductor Reflector.

This paper presents a wideband dual-polarized dipole antenna structure operating at 1.7-3.8 GHz (76.4%). For a traditional 4G dipole antenna that covers the band 1.71-2.69 GHz, it is difficult to maintain the satisfactory impedance matching and normal stable radiation patterns within the 5G sub-6 GHz band 3.3-3.8 GHz, mainly due to the fixed antenna height no longer being a quarter-wavelength. To solve this, a connected-ring-shaped metasurface structure is proposed and deployed to operate as an artificial magnetic conductor (AMC). As a result, stable antenna radiation patterns are obtained within the whole band 1.7-3.8 GHz. For verification, this wideband dipole antenna using AMC is implemented and tested. The measured results show that the proposed antenna has an impedance bandwidth of 80.7% (1.7-4.0 GHz). It has an average measured in-band realized gain of 7.0±1.0 dBi and a stable 70±5 half power beam width (HPBW) within the 4G/5G-sub 6GHz bands 1.71-2.69 GHz and 3.3-3.8 GHz.

Broadband Miniaturized C-Band Stacked Antenna Design and Analysis Using TLM

This paper presents the design of broadband miniaturized C-band stacked antenna and its analysis using TLM . The proposed antenna operates at C-band and acquires 45% bandwidth with a peak gain of 8 dBi. The generalized transmission-line model, developed earlier for the analysis of multilayered stacked antennas (without slots), has been implemented and modified for the analysis of the proposed antenna (having a slot in the driven patch). The slot coupling effect is incorporated in the modified TLM model for the circuit-level simulation and analysis of the designed antenna. Circuit simulation results agree with EM simulation and measured results. The proposed antenna occupies an overall volume of 52 × 50 × 4.5 mm3, while volume of the radiating elements is 13 × 19.89 × 4.5 mm3, which makes the design quite compact. The proposed stable antenna has unidirectional radiation patterns throughout the band of operation and is thus suitable for applications such as remote sensing, target detection, and imaging.

Design of High-Gain Magneto-Electric Dipole Antenna by Loading a Magneto-Electric Dipole Director

A high-gain magneto-electric dipole (ME-Dipole) antenna has been designed by adding a ME-Dipole director on top of a conventional cavity-backed ME-Dipole antenna. The purpose of adding the ME-Dipole director is to significantly enhance the gain of the antenna. The proposed design has been both measured and simulated, with an average gain of 12.5 dBi and 12.4 dBi, respectively, demonstrating the design's high gain capabilities. Additionally, the measured and simulated impedance bandwidth (VSWR ≤ 2) are 29.21% (1.90 GHz - 2.55 GHz) and 30.70% (1.93 GHz - 2.63 GHz), respectively, confirming the wideband nature of the design. Other outstanding performance metrics, such as low cross-polarization of - 25 dB and the stable antenna gain of 11.8 ± 1.7 dBi as measured and 12.0 ± 1 dBi as simulated, have also been observed in the current design.

Stable High-Gain Linearly and Circularly Polarized Dielectric Resonator Antennas Based on Multiple High-Order Modes

Dielectric resonator antennas (DRAs) under high-order multiple-modes resonator (MMR) for stable high gain are proposed in this communication. The approach is to implement slot cuts on the surface of DR for reconstructing the electric field distribution of high-order resonance modes. In this way, the sidelobes are reduced and two high-order modes are reallocated to construct a continuous wide band. Various MMR configurations were proposed in this work. First, a DRA operating in TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {x}}_{031}$ </tex-math></inline-formula> and TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {x}}_{051}$ </tex-math></inline-formula> modes is proposed with a pair of loaded slots to realize a fractional bandwidth (FBW) of 26% and a stable gain as high as 8.3 dBi within the desired passband. Second, a DRA with TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {x}}_{051}$ </tex-math></inline-formula> and TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {x}}_{071}$ </tex-math></inline-formula> modes is developed by introducing two pairs of slots, and an impedance FBW of 12.8% and a stable gain as high as 11 dBi are achieved. Third, three pairs of slots are introduced to the DRA with TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {x}}_{091}$ </tex-math></inline-formula> and TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {x}}_{0,11,1}$ </tex-math></inline-formula> modes, and an impedance FBW of 6.4% and a stable antenna gain as high as 12.3 dBi are obtained. At last, a circularly polarized (CP) DRA array with four proposed linearly polarized (LP) DRA elements is designed with an impedance bandwidth of 51.8%, a 3 dB axial-ratio (AR) FBW of 32%, a peak gain of 13.89 dBic, and a 1 dB gain bandwidth of 19.9%.

A Wideband Differentially Driven Dual-Polarized Antenna by Using Integrated Six-Port Power Divider

A new method to design wideband differentially driven dual-polarized antenna with high common-mode suppression and high port isolation is presented. The presented antenna can be equivalent as a combination of a six-port power divider and four crossed folded dipoles. The six-port power divider is composed of two orthogonal input ports and four equal magnitude output ports. Detailed analysis illustrates that the six-port power divider can have wide bandwidth and high isolation under odd-mode excitation and high common-mode suppression under even-mode excitation. Therefore, based on the wideband and high even-mode suppressed six-port power divider, a wideband differentially driven dual-polarized antenna is developed with high common-mode suppression. To validate the design concept, the proposed antenna was designed, fabricated, and measured. The measured results prove that the antenna has a wide impedance bandwidth of 1.64–3.0 GHz (58.6%) for the return loss higher than 15 dB and isolation higher than 35.4 dB. In addition, very high common-mode suppression is achieved for the measured common-mode reflection coefficient higher than −0.87 dB over the entire bandwidth. With stable antenna gain and half-power beamwidth, the developed antenna is suitable for base station applications.

A Compact Wideband Dual-Polarized Antenna With Enhanced Upper Out-of-Band Suppression

A compact wideband dual-polarized antenna with enhanced upper out-of-band suppression is presented in this paper. The proposed antenna is an equivalent configuration of two electric dipoles and two magnetic dipoles using the crossed shunt loops. The incorporation of the electric and magnetic dipoles enables the antenna to achieve wide impedance bandwidth and a compact radiator size. In addition, four parasitic strips are inserted near the inner edge of the four loops to enhance the antenna upper out-of-band suppression at 3.5 GHz with improved impedance bandwidth. The antenna is fed by the crossed coaxial baluns with high isolation. A shorting sheet is introduced into the baluns to enhance the upper out-of-band suppression further and create another rejection at 4.9 GHz. To demonstrate the design method, the proposed antenna prototype was fabricated and measured. Measured results show that the proposed antenna has a wide impedance bandwidth of 1.625–3.05 GHz (61%) for ${S}_{11} dB with the isolation better than 38.3 dB. The upper out-of-band suppression of the antenna is also highly enhanced with measured ${S}_{11}>-2$ dB from 3.35 to 5.25 GHz. In addition, stable antenna gain and radiation patterns are achieved for base station applications.

A High Efficiency Gyrostabilizer Antenna Platform for Real-Time UAV Synthetic Aperture Radar (SAR) Motion Error Compensation

A gyro-stabilized antenna platform could implement a real-time motion compensation for a SAR system. Since motion errors reduce during the data acquisition process, post-processing load also reduces. Subsequently, production of well-focused, and high-resolution synthetic aperture radar (SAR) images is conceivable. The research is to design a gyro-stabilized SAR antenna platform that compensates motion in real time during data acquisition. This paper explains the study of undesired motion (error) for typical UAV SAR. The resulting angle ranges of yaw, pitch, and roll describe the magnitude of the motion errors. The design of a gimbal system as a stable antenna platform considers yaw, pitch and roll range parameters. IMU optimization (Complimentary Filter, and Madgwick Filter algorithms are tested and compared in order to decide the optimum optimization scheme for the antenna platform. The data fusion and gradient descent algorithm from Madgwick show significant performance. The implementation of the optimized IMU algorithm and control on a field programmable gate array (FPGA) has resulted in a very effective stable antenna platform.

Salinity tolerance of quinoa (Chenopodium quinoa Willd) as assessed by chloroplast ultrastructure and photosynthetic performance

Quinoa has been widely used as a model crop for understanding salt-tolerance in halophyte plants. However, a salt tolerance mechanism regarding the photosynthetic activity is poorly evaluated. Here we report the effects of salt stress on photosynthesis of the halophyte Chenopodium quinoa cultivated under different NaCl concentrations (0, 100, and 300 mM). Our results revealed no apparent effect of moderate salinity (100 mM NaCl) on plant growth while, a reduction of plant biomass production was detected under 300 mM NaCl without any symptom of toxicity. No significant effect on the chloroplasts ultrastructure was observed under moderate salinity. Some morphological deformations of chloroplasts such as swelling of thylakoids, disruption of envelope, accumulation of starch grains and plastoglobuli were observed following prolonged exposure to severe stress. Under moderate salinity, no considerable change was detected on the rate of primary photochemistry (fluorescence O-J phase) and the reduction of the PQ pool (J-I phase), no apparent effects on the minimal (F0), the maximal fluorescence (Fm) and the maximal photochemical efficiency (Fv/Fm) showing a high stability of PSII. The high PSII efficiency was also confirmed by the donor side intactness (constant Fk/Fj ratio) and stable antenna size. The high stability of PSII efficiency was also demonstrated by enhanced communication between antenna complex and PSII reaction centre and the stability of OEC complex (PsbQ and PsbO proteins). However, high salinity (300 mM NaCl) results in a swelling of thylakoids and disappearance of grana and in a decrease of Fm and (Fv/Fm) leading to the down-regulation of PSII activity. In addition, a significant increase in F0 occurred and could be associated to the presence of some QA− in darkness in equilibrium with a partially reduced PQ pool. High salt treatment could be responsible for the thermal phase which induced an increase in chl a fluorescence (JIP rise with oxidized PQ pool).

A Filtering Patch Antenna With Reconfigurable Frequency and Bandwidth Using F-Shaped Probe

A wideband filtering patch antenna is investigated in this paper. The patch antenna is fed by an F-shaped probe, which consists of one upper and two lower horizontal arms, as well as a vertical arm that connects them. Owing to the novel excitation scheme, two probe modes along with a patch mode are simultaneously excited within the passband, producing a wide bandwidth of 21.3% with stable antenna gains and radiation patterns. Meanwhile, cross-coupling is constructed in the antenna, generating two symmetrical radiation nulls right at the two sides of the passband. Consequently, a compact filtering antenna with bandpass response and high selectivity is obtained, without utilizing any extra filtering circuit. This design is also extended to realize a reconfigurable filtering antenna. Two varactor diodes are embedded in the F-shaped probe to continuously tune the frequency of the operating band from 2.05 to 2.52 GHz. The antenna bandwidth can be flexibly tuned from 2.2% to 21.3%, and simultaneously good filtering performance is kept during the tuning of different states.

A Simple Design of Compact Dual-Wideband Square Slot Antenna With Dual-Sense Circularly Polarized Radiation for WLAN/Wi-Fi Communications

A novel compact dual-wideband, dual-sense, circularly polarized (CP), square slot antenna with the simple structure is presented in this communication. The right-hand circular polarization in the +z-direction for the lower frequency is mainly realized by an inverted L-shaped strip, and the left-hand circular polarization in the +z-direction for the upper frequency is mainly achieved by an offset feed structure. A parasitic matching stub is helpful to improve the input impedance matching. The overall dimension of the prototype is only $50 \times 50 \times 1~\text{mm}^{3}$ . An optimized antenna is fabricated and measured. The measured 10 dB return loss bandwidth is 111% (1.82–6.36 GHz). Its measured 3 dB axial-ratio bandwidths in the broadside direction are 55% (1.91–3.36 GHz) at lower band and 29.3% (4.78–6.41 GHz) at upper band, which can fully cover all the wireless local area network and wireless fidelity bands. What is more, this antenna has stable antenna gain and good radiation patterns within these two CP bands.

Development of an ultra-wideband, stable and high-directive monopole disc antenna for radar-based microwave imaging of breast cancer

ABSTRACTRadar-based ultra-wideband (UWB) microwave imaging (MI) system has recently attracted considerable attention for detection of breast cancer at early stage. A key component of the system is the sensor (antenna) that is used to radiate and receive the UWB pulses. In this study, a compact-size, UWB, directive, and microstrip-fed planar circular disc monopole antenna (PCDMA) with modified L-shaped ground plane for the radar-based UWB MI system is developed. Analysis and the performance optimization of the proposed antenna are performed by HFSS software. In the development process of the antenna design, some modifications such as adjusting feed point, adding parasitic element, slot, notches are made on the conventional PCDMA to improve the bandwidth, directivity and half-power beamwidth (HPBW) of the antenna. After obtaining the optimum parameters, the proposed antenna is fabricated and then tested by using Vector Network Analyser. Impedance bandwidth of the designed antenna covers the broad frequency range of 3–10 GHz (108%) for Return Loss < –10 dB. The good stability of the directional radiation patterns is obtained in the 3–10 GHz. The direction of the maximum radiation moves from 32° to 54° and HPBW decreases from 56° to 30° through the frequency band. The directivity changes between 6.2 and 9.4 dB in the 3–10 GHz. Results confirm that the proposed antenna is suitable for using in radar-based UWB MI of the breast cancer.

A Wideband Dual-Polarized Antenna Using Shorted Dipoles

A novel design method of a wideband dual-polarized antenna is presented by using shorted dipoles, integrated baluns, and crossed feed lines. Simulation and equivalent circuit analysis of the antenna are given. To validate the design method, an antenna prototype is designed, optimized, fabricated, and measured. Measured results verify that the proposed antenna has an impedance bandwidth of 74.5% (from 1.69 to 3.7 GHz) for VSWR < 1.5 at both ports, and the isolation between the two ports is over 30 dB. Stable gain of 8–8.7 dBi and half-power beamwidth (HPBW) of 65°–70° are obtained for 2G/3G/4G base station frequency bands (1.7–2.7 GHz). Compared to the other reported dual-polarized dipole antennas, the presented antenna achieves wide impedance bandwidth, high port isolation, stable antenna gain, and HPBW with a simple structure and compact size.

A Sparse Bayesian Learning Approach for Through-Wall Radar Imaging of Stationary Targets

Through-the-wall radar (TWR) imaging is an emerging technology that enables detection and localization of targets behind walls. In practical operations, TWR sensing faces several technical difficulties including strong wall clutter and missing data measurements. This paper proposes a sparse Bayesian learning (SBL) approach for wall-clutter mitigation and scene reconstruction from compressed data measurements. In the proposed approach, SBL is used to model both the intraantenna signal sparsity and interantenna signal correlation for estimating the antenna signals jointly. Here, the Bayesian framework provides a learning paradigm for sharing measurements among spatial positions, leading to accurate and stable antenna signal estimation. Furthermore, the task of wall-clutter mitigation is formulated as a probabilistic inference problem, where the wall-clutter subspace and its dimension are learned automatically using the mechanism of automatic relevant determination. Automatic discrimination between targets and clutter allows an effective target image formation, which is performed using Bayesian approximation. Experimental results with both real and simulated TWR data demonstrate the effectiveness of the SBL approach in indoor target detection and localization.

A Wideband Differentially Fed Dual-Polarized Antenna with Stable Radiation Pattern for Base Stations

A new wideband differentially fed dual-polarized antenna with stable radiation pattern for base stations is proposed and studied. A cross-shaped feeding structure is specially designed to fit the differentially fed scheme and four parasitic loop elements are employed to achieve a wide impedance bandwidth. A stable antenna gain and a stable radiation pattern are realized by using a rectangular cavity-shaped reflector instead of a planar one. A detailed parametric study was performed to optimize the antenna’s performances. After that, a prototype was fabricated and tested. Measured results show that the antenna achieves a wide impedance bandwidth of 52% with differential standing-wave ratio $\approx 8$ dBi) and a stable radiation pattern with 3-dB beamwidth of 65° ±5° were also found over the operating frequencies. Moreover, the proposed antenna can be easily built by using printed circuit board fabrication technique due to its compact and planar structure.

Capability Study of Ti, Cr, W, Ta and Pt as Seed Layers for Electrodeposited Platinum Films on γ-Al₂O₃ for High Temperature and Harsh Environment Applications.

High temperature surface acoustic wave sensors based on radio frequency identification technology require adequate antennas of high efficiency and thermal stability for the signal transmission. Platinum is well known and frequently used as a material of choice for high temperature and harsh environment applications because of the high melting point and its chemical stability. Therefore, one way to realize high temperature stable antennas is the combination of a Pt metallization on an AlO substrate. As a cost-effective technique, the Pt film is deposited via electrochemical deposition. For this growth procedure, a pre-deposited metallization on the AlO layer is required. This paper analyzes the influence of various seed layers (Ta, Ti, W, Cr, Pt) on the morphology, stability and electrical properties of the electrochemically-grown Pt thick film after heat treatments up to 1000 C in air. We find an oxidation of all adhesion layers except for Pt, for which the best electrical properties were measured. Although significant areas of the films delaminate from the substrate, individual anchor structures retain a stable connection between the Pt layer and the rough AlO substrate.

A High-Temperature Stable Antenna Array for the Satellite Navigation System

This letter presents a high-temperature stable antenna array applied to an adaptive anti-jamming system in satellite navigation. The main features of the antenna are: owing to the titanium alloy and thermal stable ceramic material, the antenna works stably at 400 °C and demonstrates excellent heat-resisting property; no welding is used during the assembly to ensure the reliability of the electric connection under high temperature impact; metal walls are adopted to improve the radiation; the center shorting pillar is designed to reduce the inductance of the feed probe and obtain excellent impedance matching characteristics. During the simulation and experiments, the designed antenna array exhibits excellent performance and proves its suitability for high-temperature application. From 20 °C to 400 °C, the right-hand circular polarization gain is larger than 4 dBi and the operation frequency covers the L1 band of global positioning system and B1 band of BeiDou II.

Differential enhanced broadband dual‐polarized printed dipole antenna for base stations

ABSTRACTA simple differential enhanced broadband dual‐polarized printed dipole antenna for 2G/3G/LTE base station applications is presented. The proposed antenna contains two orthogonal square‐shaped dipoles and a novel square‐shaped feeding structure to achieve a wide bandwidth, and a planar reflector to shape radiation patterns. Due to adopting the differential feeding and ideally symmetrical structure, the antenna can achieve low cross‐polarization level and high port‐to‐port isolation, respectively. Measured results show that the proposed antenna achieves a bandwidth of 67.5% for SWR &lt; 1.5, differential port‐to‐port isolation better than −40 dB, stable half‐power beam width (HPBW) 68.7° ± 4.2° at E‐plane and 68.3° ± 4.9° at H‐plane, and a stable antenna gain of 7.8 ± 1 dBi from 1.65 to 3.33 GHz. The cross‐polarization ratio within the main lobe remains over than −25 dB, and the front‐to‐back ratios keep higher than 31 dB over the operating bandwidth. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2864–2868, 2016

Spaceborne GPS receiver antenna phase center offset and variation estimation for the Shiyan 3 satellite

In determining the orbits of low Earth orbit (LEO) satellites using spaceborne GPS, the errors caused by receiver antenna phase center offset (PCO) and phase center variations (PCVs) are gradually becoming a major limiting factor for continued improvements to accuracy. Shiyan 3, a small satellite mission for space technology experimentation and climate exploration, was developed by China and launched on November 5, 2008. The dual-frequency GPS receiver payload delivers 1Hz data and provides the basis for precise orbit determination within the range of a few centimeters. The antenna PCO and PCV error characteristics and the principles influencing orbit determination are analyzed. The feasibility of PCO and PCV estimation and compensation in different directions is demonstrated through simulation and in-flight tests. The values of receiver antenna PCO and PCVs for Gravity Recovery and Climate Experiment (GRACE) and Shiyan 3 satellites are estimated from one month of data. A large and stable antenna PCO error, reaching up to 10.34cm in the z-direction, is found with the Shiyan 3 satellite. The PCVs on the Shiyan 3 satellite are estimated and reach up to 3.0cm, which is slightly larger than that of GRACE satellites. Orbit validation clearly improved with independent k-band ranging (KBR) and satellite laser ranging (SLR) measurements. For GRACE satellites, the average root mean square (RMS) of KBR residuals improved from 1.01cm to 0.88cm. For the Shiyan 3 satellite, the average RMS of SLR residuals improved from 4.95cm to 4.06cm.

Low-profile UHF RFID reader antenna with CP radiation and coupled feeding technique

A low profile annular-ring patch antenna with circularly polarized (CP) radiation for radio frequency identification (RFID) reader applications in the ultra-high frequency (UHF) band (922-928 MHz) is presented in this article. Perturbation method is applied by loading a pair of triangular open-notch into the outer circumference of ring patch, and good impedance matching can be determined by using the coupled feeding technique. The overall size of this proposed antenna is 150 mm × 150 mm × 10.4 mm. The measured results show desirable 10-dB impedance bandwidth and 3-dB axial ratio (AR) bandwidth of 3.5% (908-941 MHz) and 0.65% (922-928 MHz), respectively. Stable antenna peak gain and efficiency of 7.2 dBic and 87% are also exhibited, respectively.

Broadband omnidirectional distributed antenna for indoor wireless communication systems

A broadband omnidirectional distributed antenna is studied theoretically and experimentally. By loading three shorted coupling patches over the top of the radiation patches and a circular sleeve on the ground plane, the bandwidth of the antenna which is excited by a truncated cone feeding structure is significantly enhanced. Results show that an impedance bandwidth of 152% ranging from 0.97 to 7.09 GHz is achieved. Omnidirectional radiation patterns in the horizontal plane, low cross polarisation level, and stable antenna gain ranging from 2.1 to 7.3 dBi are realised over the operating band, which suggests the distributed antenna can be widely used in indoor wireless communication systems.