Rotated Antenna Research Articles

Low‐profile circular‐polarized fractal antenna design with reduced orbital angular momentum beam divergence

AbstractThe authors introduce a novel low‐profile circular‐polarized three‐layer fractal antenna design to reduce beam divergence in orbital angular momentum (OAM) applications at microwave frequencies. The top layer of the proposed design has a printed Koch fractal antenna that is coupled to a rotated rectangular patch antenna in the mid‐layer fed through a microstrip line. The bottom layer consists of a metallic ground plane to improve beam collimation. The antenna was developed from a new fractal geometry generated in Scilab™. Characteristic mode theory was used in the antenna design to obtain two orthogonal current modes in quadrature that generate circular polarization with OAM fields of order l = –1 at 5.88 GHz. The proposed fractal antenna system has good potential to improve the performance of microwave OAM systems.

A Versatile Shared-Aperture Antenna for Vehicle Communications

This communication introduces a versatile, multi-service, shared-aperture antenna system for multiple vehicle applications. The design comprises three antenna elements: a rotatable microstrip antenna for global positioning system (GPS) communication, a cross-dipole circularly polarized antenna for satellite communication in the S-band, and a pattern reconfigurable antenna for V2V (vehicle-to-vehicle) communication. These antennas collectively support GPS, satellite communication (Satcom), and V2V communication in a single, shared-aperture design. This shared-aperture antenna system offers cost savings and occupies less space compared to using separate antennas for each service. The microstrip antenna covers the 1575 MHz frequency band used for GPS communication. The cross-dipole circularly polarized antenna provides continuous wideband coverage for S-band satellite communication. The pattern reconfigurable antenna, tailored for the specific application scenario, covers the 5.9 GHz V2V working frequency band (5.855–5.925 GHz). Practical testing and simulation results confirm the effectiveness of this antenna system for the intended applications. In summary, the microstrip antenna has a bandwidth of 1.565–1.578 GHz and a realized gain of 7 dBi with radiation efficiency of 81%, the cross-dipole antenna has a bandwidth of 2.2–3.8 GHz (53.3%) and a realized gain of 8.3 dBi with radiation efficiency of 90%, and the pattern reconfigurable antenna has a 5.8–6 GHz bandwidth and a realized gain of 3.7 dBi with radiation efficiency of 85%, and the isolation between antennas with different frequencies is 25 dB, 20 dB, and 30 dB in three frequency bands.

Analysis and Design of Broadband OAM Array Antenna

This paper presents a Uniform Circular Array (UCA) antenna of crossed-dipole that can excite vortex waves in a wide frequency range from 3.5 GHz to 8.4 GHz. In the design process, the theoretical derivation of the influence on the Orbital Angular Momentum (OAM) when the antenna elements are arrayed in Co-directional Antenna Array (CAA) and Rotational Antenna Array (RAA) is given respectively. The fixed mode of the dipoles CAA is achieved by feeding each element with equal amplitude and 90∘ phase difference produced by the broadband feeding network. Furthermore, the proposed broadband OAM array antenna has been fabricated and measured to verify the predicted properties. The vortex electromagnetic wave with +1 mode could be excited in the bandwidth of 82.35%. Simulated and measured results are in good agreement. The proposed OAM array antenna is simple in design principle, compact in structure and low in profile, making this array antenna an excellent candidate for broadband OAM communication systems.

Privacy Preserving Contraband Detection Using a Millimeter-Wave Dynamic Antenna Array

We present a privacy preserving technique for contraband detection using a real-time 75 GHz rotational dynamic antenna array that samples only a reduced set of Fourier-domain information to prevent image reconstruction of the screened subject. Complex objects such as handguns have sharp edges that correspond to sharp spatial frequency features in the Fourier domain. These features are dependent on the orientation of the object and manifest at millimeter-wave frequencies through conditions such as being concealed under clothing. The technique combines a dynamically rotated active interferometer and simple arithmetic feature extraction approach supporting a threshold-based classifier to identify when a handgun is concealed under clothing. The active interferometer technique utilizes noise transmitters to illuminate the test subject to produce thermal-like radiation, enabling Fourier-domain signal sampling, while the rotational dynamics support sampling that spans a circle in the 2-D Fourier domain to retrieve sharp-edge responses induced by concealed objects. We experimentally demonstrate the detection of concealed objects under clothing in a laboratory environment using a 75 GHz dynamic antenna array based on simple heuristic features extracted from statistics of the measured responses. The classifier is evaluated based on processing one or more subsequent measurements, showing a classification accuracy of 0.908 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$F$</tex-math> </inline-formula> 1-score of 0.916 using four consecutive measurements.

Characteristic mode analysis of a compact circularly polarized rotated square slot antenna

AbstractPresented in this paper is a circularly polarized (CP) wide 45° rotated slot antenna with a broad bandwidth. Characteristic mode analysis is initially carried out to show that, by simply rotating a square slot, CP waves can be radiated if it is properly excited. A simple 50 Ω feedline is then designed to excite the slot for the generation of broadband CP waves. The antenna has a total volume of 30 × 30 × 1.6 mm3. Measurement results indicate a broad S11 ≤ −10 dB impedance bandwidth of 85.7% (3.2–8 GHz), a broadband 3 dB axial ratio bandwidth of 57.1% (3.5–6.3 GHz) and a peak gain of 3.6 dBi are obtained by the antenna. The proposed antenna possesses stable radiation patterns as well as relatively flat gain over its operational bandwidth in addition to being compact. It can thus be used for wireless technologies such as WiMAX 3.5 and 5.5 GHz, WLAN 5.2 and 5.8 GHz in addition to Industrial, Scientific, and Medical 5.8 GHz.

Localizing RFIDs in Pixel Dimensions

Radio Frequency IDentification (RFID) is emerging as a vital technology of the Internet of Things (IoT). Billions of RFID tags have been deployed to locate daily objects such as equipment, pharmaceuticals, vehicles, and so on. Unlike previous solutions that focus on localizing tagged objects in the world coordinate system in reference to reader antennas, this work exploits a system, called RFCamera, that can identify and locate RFID-tagged objects in images with pixel dimensions. Our core insight is that an image is a visual AoA profile in terms of lights, which is resulted from the pinhole camera model. Similarly, we generate an RF image derived from the AoA profile of a tag using the same pinhole model as the camera. Consequently, the locations of visual entities corresponding to tagged objects are highlighted by comparing two types of images. To this end, we customized a camera system equipped with a pair of rotatable reader antennas. Our experimental evaluation demonstrates that RFCamera enables a mean error of 5.7∘ and 2.9∘ at azimuth and elevation angle estimation, respectively. It can locate a visual entity with a mean error of 51 pixels (i.e., ≈1.3 cm at 96 dpi) in a 640× 480 image.

Virtual Antenna Array With Directional Antennas for Millimeter-Wave Channel Characterization

Millimeter-wave (mm-Wave) band channel modeling and characterization are essential for system design and analysis in the fifth generation (5G) and future communication systems. Reliable channel sounding in the deployment scenarios is required for accurate and realistic channel modeling and characterization. In the state of the art, directional scanning sounding (DSS) and virtual antenna array (VAA) sounding are two popular methods due to their simplicity and cost-effectiveness. The DSS and the VAA methods are typically based on mechanically rotatable directional antennas and mechanically movable omnidirectional antennas, respectively. However, the spatial resolution is limited by the directivity and high sidelobes of the directional antennas used in the DSS method. The conventional VAA method also has limitations in terms of the low signal-to-noise ratio (SNR) and the unavailability of suitable omnidirectional antennas that support mmWave (above 60 GHz) band measurements and wideband horizontal polarization measurements. In this article, a novel directional antenna-based VAA framework in combination with the associated beamforming algorithm is proposed. Compared to the state-of-the-art methods, the proposed framework can achieve high angular resolution and high SNR for mm-Wave channel measurements without introducing additional cost and measurement time. Furthermore, it is a generic solution that can be applicable for arbitrary frequency bands and polarizations, unlike the conventional VAA method. To validate the effectiveness and robustness of the proposed method, experiments in two scenarios (a clean anechoic chamber and a realistic indoor meeting room) were conducted over 28–30 GHz with two types of directional antennas (i.e., a horn antenna and a corrugated antenna). Besides, the advantages of the proposed method are highlighted with a comparison to the conventional VAA and DSS methods.

Angular momenta in fields from a rotational mechanical antenna‡ ‡JPCO-102088.R3, Submitted to J. Phys. D: Appl. Phys. on 13th May, transferred to J. Phys. Commun. 3rd August, revised 17th Nov. and 5th Dec., accepted 8th Dec. 2021.

Mechanic antennas provide opportunities for human portable, VLF communications, where a rotational dipole emits EM signals with angular momenta. In this paper we analytically derive the electromagnetic fields from a rotational electric dipole using Fourier transform method, and find that the radiated fields from the rotational electric dipole carries nonzero energy flow density in both orbital and spin angular momentum (AM) parts by their flux tensors. Intuitively, a dipole circulating on the transverse plane induces a longitudinal orbital angular momentum and a longitudinal spin angular momentum. And the binding force for the rotational electric dipole is then shown to result mainly from the Coulomb fields. We believe that our work will contributes to novel communication designs for portable mechanic antennas.

Bandwidth Enhancement of a Microstrip-Line-Fed Printed Rotated Wide-Slot Antenna Based on Self-Shape Blending Algorithm

This paper proposes a self-shape blending algorithm to improve antenna bandwidth. A printed antenna is designed for bandwidth enhancement based on the proposed algorithm; this approach can also be used to enhance bandwidth in other applications. The antenna completely covers WLAN bands and WiMAX bands after the proposed algorithm is applied. The shape of the rotating slot and the parasitic patch also changes, which excites additional resonance and improves the impedance matching at high frequencies. Test results show that the proposed antenna can work from 2.07 GHz to 5.94 GHz with S 11 ≤ − 10 dB . Compared to a slot antenna without the self-shape blending algorithm, the bandwidth increases by more than 0.7 GHz.

An one-drive-four wireless high voltage high speed controller system used in 100°/8 ms MEMS rotary actuator for antenna array

In order to support rapid beamforming, this paper presents an one-drive-four wireless high voltage high speed controller for micro-electromechanical system (MEMS) rotary actuator antenna array. The target antenna array consists of 225 rotatable antennas with controller and achieves >25.0 dBi gain with below −20 dB side lobe and below −20 dB cross polarization in simulation. Each rotatable antenna, which is called actuator, can rotate from 0° to 100° depending on the voltage it received from 1 to 150 V respectively. The correspondingly high voltage is provided by the wireless high voltage high speed controller. To facilitate array installation, it is preferred to control each rotatable antennas wirelessly and reduce controller’s number. Therefore, this paper proposes a wireless multiplexing control scheme to support control voltages from 1 to 150 V to each rotatable antenna in a less than 8 ms settling time. To prove the concept, the proposed MEMS rotary actuator antennas is processed and the one-drive-four wireless high voltage controller has been designed and fabricated with a size of 15 × 10 × 15 mm3 to control four independent antennas simultaneously by ‘time division multiplexing’ method. Measurement results suggest that the MEMS rotary actuator achieves 100°/8 ms settling time with the equally high speed wireless voltage controller. The control voltage accuracy for the rotation at 150 V is less than 8‰, which greatly support rapid beamforming.

A study of uplink and downlink channel spatial characteristics in an urban micro scenario at 28 GHz

This paper presents an empirical study of the uplink and downlink azimuth angle of arrival (AoA) in an urban micro (UMi) scenario at 28 GHz. At present, most UMi measurements are conducted in the downlink and then the uplink situation is inferred assuming channel reciprocity. Although the channel correlation coefficient of the uplink and downlink can be as high as 0.8, this does not mean that they are the same. Only a real uplink measurement can accurately describe its channel conditions, and this is what this study does. A receiver equipped with a rotatable horn antenna is mounted at the base station and the user terminal, respectively, in simulating the uplink and downlink. To improve the angular resolution, we extract the multipath components (MPCs) using the space-alternating generalized expectation-maximization algorithm. Also, a spatial lobe approach is used to cluster the MPCs in the power angular spectrum. By matching MPCs with objects in the environment, we find that direct propagation and first-order reflections are dominant in line-of-sight and non-line-of-sight cases. By comparing our measurement with those in standard channel models, we verify that the AoA of clusters follows a Gaussian distribution in the uplink and downlink. In addition, a two-dimensional Gaussian distribution for ray AoA and power is established to reflect their correlation.

Signal-to-Noise Ratio Improvement by Vortex Wave Detection With a Rotational Antenna

This article investigates whether a vortex wave detection method with a rotational antenna can improve the receiving signal-to-noise ratio (SNR) of stealth targets. To be specific, a vortex wave detection system with a rotational antenna is established. Considering both bistatic and monostatic models, it demonstrates that the vortex wave can be efficiently synthesized by applying the fast Fourier transformation algorithm to all receiving pulses. The SNR of synthetic orbital angular momentum (OAM) is compared with that of circular synthetic aperture radar (SAR) because the synthetic OAM and circular SAR systems have similar architectures and are described by similar mathematical models. Experiments confirm that the synthetic OAM method can improve the receiving SNR of a specific complex target with different polarizations. The SNR improvement by OAM for general complex targets is then demonstrated in simulations. Furthermore, the detection probability and the quality of 2-D detection results can also be improved by the proposed synthetic OAM method.

Wideband Compact Triangle-Slot Antenna With Out-of-Band Rejection

A wideband and compact triangle-slot antenna with out-of-band rejection is proposed. The antenna covers the whole C-band (4–8 GHz) including the 5.8 GHz ISM and sub-6 GHz band of 5G. First, a right-angled triangle-slot antenna is developed from a rotated square-slot antenna with a 50% size miniaturization. Then, a defected ground slot (DGS) and a thin microstrip line section are integrated into the antenna to improve the out-of-band rejection. This prevents the noise and unwanted interference to the receiver and effectively suppresses the high-order harmonics from the transmitter. Importantly, the added DGS and thin microstrip line increases the bandwidth up to 5.51 GHz (82.7% fractional bandwidth) and reduces the antenna size. Finally, by adding matching elements using stacked rectangular slot principle, the antenna size is reduced furthermore, leading to a total 60% reduction in size. The final ground size is 32 × 32 mm, which is suitable to be integrated into portable devices. The return loss is measured up to the third harmonic of the highest working frequency and compared with the reference triangle-slot antenna to validate the rejection concept. The out-of-band return loss remains smaller than 1.2 dB up to 26.5 GHz. The maximum improvement of return loss is 33.3 dB at 26.4 GHz, from 34.4 dB of the reference antenna to 1.1 dB of the proposed antenna.

Circularly Polarized Microstrip Antenna Using SLPD Electromagnetic Band Gap Structure

AbstractIn this article, a new structure comprising of a novel compact slot loaded polarization dependent Electromagnetic Band Gap structure (SLPDEBG), which enhances the performance of circularly polarized rotated square patch antenna by placing SLPDEBG unit cells around it, has been designed. The proposed antenna, having dimensions 0.640 λo x 0.640 λ x 0.0128 λo (λo stands for the free space wavelength at 2.39 GHz), shows that the measured impedance bandwidth and AR bandwidth is 120 MHz and 50 MHz, respectively, with a peak gain of 3.52 dB. Some prominent features of the proposed structure are: front to back ratio of 64, 3 db, beamwidth of 92° at xz-plane and 74° at yz-plane. This prototype antenna finds its application in wireless communication of ISM band. Good performance of the proposed antenna is verified by the close agreement between the simulated and measured results.

RCS promotion in orbital angular momentum imaging radar with rotational antenna

The azimuthal imaging can be acquired by the orbital angular momentum (OAM) wave. In addition, a large-scale OAM mode number is necessarily required for high azimuthal resolution. To reduce the required OAM mode number, an azimuthal imaging method based on compressed sensing and OAM mode selection is presented. To be specific, the system architecture and the mathematical model of the OAM imaging radar are established. Meanwhile, an efficient OAM generation method with rotational antenna is proposed. Moreover, experiments show that different radar cross sections (RCSs) of a specific complex target can be obtained by different OAM waves, which are generated by the proposed method. It is a delight to find that the signal-to-noise ratio gain can be achieved due to the appropriate OAM mode selection in the experiment. Since different OAM waves lead to different RCSs of complex target, the OAM modes corresponding to high RCSs are selected to measure the azimuth for low complexity. Furthermore, simulations are conducted to evaluate the performance of the proposed azimuthal imaging method for the general complex target. Using Monte Carlo simulations, it is found that the accuracy of azimuthal imaging can be guaranteed by the proposed azimuthal imaging method with only approximately 6% selected OAM modes.

A New Frequency Reconfigurable Antenna Using Proximity Fed Technique for Wireless Applications

This electronic paper presents an innovative technology for efficient use of the radio spectrum. This new frequency reconfigurable rotatable antenna is intended for wireless applications such as WLAN, WiMAX and Bluetooth mobile applications. The working principle of this proposed work is to print square patches mounted on the same circular dielectric substrate feed by a proximity coupling to eliminate the noise signal transmission and problems related to interference. The three positions correspond to an operating frequency controlled by a bipolar step-by-step engine. An optimization of the structure using the FEM finite element method as well as a comparison with other structures recently realized are detailed in this paper. The final numerical simulation results are: WLAN 4.95-5.53 GHz (BW = 11%) Gain = 6.06 dBi, WiMAX 3.35-3.75 GHz (BW = 11.2%) Gain = 7.48 dBi and Bluetooth 2.3-2.51 GHz (BW = 8.7%) Gain = 17.78 dBi.

Design and Performance Comparison of Rotated Y-Shaped Antenna Using Different Metamaterial Surfaces for 5G Mobile Devices

In this paper, a rotated Y-shaped antenna is designed and compared in terms of performance using a conventional and EBG ground planes for future Fifth Generation (5G) cellular communication system. The rotated Y-shaped antenn... | Find, read and cite all the research you need on Tech Science Press

Channel Characterization for Wideband Large-Scale Antenna Systems Based on a Low-Complexity Maximum Likelihood Estimator

Wideband large-scale array systems operating at millimeter-wave bands are expected to play a key role in future communication systems. It is recommended by standardization groups to use spherical-wave models (SWMs) to characterize the channel in near-field cases because of the large array apertures and the small cell size. However, this feature is not widely reflected in channel models yet, mainly due to the high computational complexity of SWMs compared to that of the conventional plane-wave model (PWM), especially when ultrawideband signals are considered. In this paper, a maximum likelihood estimator of low computational complexity is implemented with an SWM for ultrawideband signals. The measurement data obtained from an ultrawideband large-scale antenna array system at 28–30 GHz are processed with the proposed algorithm. The power azimuth-delay profiles estimated from the SWM and the PWM are compared to those obtained from rotational horn antenna measurement, respectively. It shows that the multipath components (MPCs) are well-estimated with the proposed algorithm, and significant improvement in estimation performance is achieved with the SWM compared to the PWM. Moreover, the physical interpretation of the estimated MPCs is also given along with the estimated scatterers.

Targeting Wideband Circular Polarization: An Efficient 2×2 Sequentially-Phase-Fed Rotated Array Antenna

Targeting Wideband Circular Polarization: An Efficient 2×2 Sequentially-Phase-Fed Rotated Array Antenna

Planar miniaturized CP antenna with coaxial feeding

AbstractA planar and miniaturized circularly polarized antenna is presented in this article. The antenna configuration is a sequential rotated antenna array with four monopole antennas bended for miniaturization purpose. A meandered microstrip series power divider is used to feed the four antennas through a coaxial feeding. The antenna is fabricated on a single layer 0.4 mm thickness FR‐4 dielectric substrate to work in the ultrahigh frequency (UHF) bandwidth, and measurement results confirm the goodness of the proposed design method.