Tri-polarized Antenna Research Articles

Design of a Wideband Tripolarized Antenna With High Isolation and Diverse Patterns

Design of a Wideband Tripolarized Antenna With High Isolation and Diverse Patterns

Wideband tripolarized circular patch antenna for fifth-generation access point applications

In this article, a wideband tripolarized antenna for fifth-generation access point applications is proposed. The proposed antenna consists of a circular patch and a square reflector. The antenna is excited by three ports that are separated by 120°. Each port is surrounded by a circular hook shaped slot to increase the bandwidth and isolation of the antenna. Further, the bandwidth is improved by using a shorting pin and a defective ground reflector. The proposed antenna design is examined in terms of the S-parameter, diversity gain, total active reflection coefficient (TARC), front-to-back ratio, radiation pattern and envelope correlation coefficient. The measured impedance bandwidth of the antenna is 46.9 % (3.1 GHz–5 GHz) and the peak isolation is −26 dB. The proposed antenna has a low envelope correlation coefficient of <0.01, a high diversity gain of >9.9 dB and a total active reflection coefficient TARC of −10 dB in the entire wideband range of operation, and a front-to-back ratio of greater than 34 dB. Additionally, the proposed antenna has a peak gain of 7.6 dBi.

Switching-Based Selection Techniques for Tripolar Antennas in Multihop IoT Networks

Adaptive multielement antennas can be leveraged to improve the reliability of wireless systems deployed in cluttered, depolarizing environments, such as those expected for Internet of Things (IoT) applications. While the performance improvement provided by such antennas has been well studied for individual links, multiple-hop networks have received little attention. In this work, we consider the problem of how devices in a multihop network should configure a three-element, tripolar antenna when deployed in a Rayleigh fading environment. We propose two switching-based antenna selection strategies: 1) Max-Sum and 2) Max–Min, each of which considers the channel conditions for communicating to nodes both higher and lower in the network hierarchy. We first derive the outage performance of the proposed schemes analytically and compare their performance with the well-known approaches of selection and switched diversity. Through simulations, which utilize empirical channel data from IoT devices equipped with a tripolar antenna, we show that the proposed Max-Sum and Max-Min schemes reduce antenna switching by over 80%, when compared to selection diversity. In addition, these two approaches lead to a median gain of 1.8 and 0.3 dB and a 1% diversity gain of 3.6 and 1.4 dB, respectively, relative to switched diversity.

A Wide-Angle and Fully Polarimetric Retrodirective Array Based on Tri-Polarized Antennas With Pattern Complementation

A wide-angle and fully polarimetric Van Atta retrodirective array (RDA) based on tri-polarized antennas is proposed in this article. By leveraging the pattern complementary and polarization orthogonality of three resonant modes including a TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> monopole-like mode and two orthogonal TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> microstrip patch modes, the RDA could better sense and retrodirect the incident wave with arbitrary polarization over a large field of view. A prototype of the RDA consisting of four tri-polarized antenna elements is designed and fabricated, which works at 5.8 GHz and has a low-profile planar structure with a compact volume of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.93\times 0.56\times 0.059\,\,\lambda _{0}^{3}$ </tex-math></inline-formula> . The simulated and measured monostatic radar cross-section (RCS) results show that, compared with the RDA composed of dual-polarized microstrip patches, this tri-polarized RDA has a significant improvement of the retrodirective angle range for the transverse-magnetic (TM) incident wave. Specifically, for the tri-polarized RDA, the −3 dB monostatic RCS beamwidth is 132°, and the −7 dB monostatic RCS beamwidth can reach 180°; while for the dual-polarized RDA, the −3 and −7 dB monostatic RCS beamwidths are only 52° and 73°, respectively.

Tripolarizated MIMO: Experimental Analysis and Modeling of Channel Properties in Both Indoor and Outdoor Scenarios

The tripolarized MIMO system can provide one more degree of freedom and have a more compacted size over a dual-polarized MIMO system, which is attractive for high-capacity wireless communication systems. In this paper, we analyze and model channel properties for tripolarized MIMO systems based on experimental channel measurements in typical indoor and outdoor scenarios. Firstly, channel measurement campaigns in the laboratory and the Urban Micro (UMi) scenarios on sub-6 GHz bands are presented. Then, based on measured data, path loss, delay spread (DS), and cross-polarization discrimination (XPD) for 9 polarization combinations are analyzed and modeled in a statistical way. Statistical results of these channel properties are also given. It is observed that channel properties of both large-scale fading and small-scale fading depend strongly on the polarization direction. Furthermore, we evaluate the performance of tripolarized MIMO systems by analyzing the Demmel condition number and channel capacity gain (CG). For both the indoor and the outdoor scenarios, it is found that colocated tripolarized antenna can bring a nearly threefold CG with respect to the unipolarized one. These results can give good insights into the design and evaluation of tripolarized MIMO systems.

Compact and Low-Coupled Tripolarized Microstrip MIMO Antenna Based on Parasitic Patch Loading

A miniaturized and low-coupled tripolarized microstrip multiple-input multiple-output (MIMO) antenna working at 3.5 GHz is proposed. This antenna includes a main circular radiating patch, which is shorted to the ground plane by an outer layer of vias, and a parasitic patch inside the cavity, which is connected to the main patch by an inner layer of vias. Through the selection of suitable number of the outer layer vias and the loading of the parasitic patch, the resonant frequencies of modes TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> can be reduced, individually. The design procedure of this antenna is demonstrated and a transmission-line model for TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> mode is presented, which can give a good explanation for the frequency reducing by the capacitance introduced by parasitic patch loading. This design can not only downsize the diameter of the unloaded antenna from 0.7λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> to 0.485λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , with the same height of 0.035λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , but also can reduce the interport coupling from -13 to -18 dB. The measured and simulated S-parameters and radiation patterns are in good agreements. Fine MIMO performance of the proposed tripolarized antenna in terms of large capacity and low correlation coefficients has been verified by some propagation measurements in a real-world office.

Low-Profile Metasurface-Based Antenna With Tripolarization for 5G Applications

This article develops a novel low-profile meta-surface-based tripolarized antenna with complementary patterns for fifth-generation (5G) application. A shared aperture metasurface-based structure is first proposed, which is carefully studied by equivalent circuit models and field distribution. Then, to realize multiple polarization operation, the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> , antiphase TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> , and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> modes are used and excited by suitable feeding networks. For horizontal polarization, wideband response is realized by coupling and combining the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> /TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> dual modes. An inductance-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> mode is displayed by loading the shorting vias on the metasurface, which is used to implement vertical polarization. Finally, a metasurface-based tripolarized antenna with a low profile of 0.04λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ( λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free space wavelength at 3.30 GHz) is fabricated. The overlapped 10-dB bandwidths for all excitations are from 3.26 to 3.84 GHz (16.3%) with isolation greater than 22 dB, which well covers the 5G-N78 band. The measured peak gain and radiation efficiency are larger than 10.3 dBi and -0.42 dB (90.8%), respectively. The results indicate that the proposed antenna with a low profile, a simple and low-cost configuration, multipolarization, good bandwidth, high radiation efficiency, and gain performance could be widely used in sub-6 GHz 5G communication systems.

A Tri-Polarized Antenna With Diverse Radiation Characteristics for 5G and V2X Communications

A tri-polarized antenna with diverse radiation characteristics is proposed in this paper. This design mainly consists of two pairs of loop radiating dipoles and an omnidirectional monopole antenna element, which are used for the fifth generation (5G) and vehicle to everything (V2X) communications, respectively. By adding eight pairs of inverted L-shaped patches with unequal sizes around the proposed dipoles, wide beamwidths in both E- and H-planes can be obtained across the desired lower and upper frequency bands. Furthermore, by employing eight fork-shaped microstrip stubs to combine the circular monopole antenna element and the L-shaped patches, the flare angle of the conical beam can be increased to 180°, which results in gain enhancement in the azimuth plane. Finally, the proposed loop radiating dipoles are excited by a pair of symmetrical differentially-fed feeding lines. Consequently, high port isolation for the proposed loop radiating dipoles as well as low gain variations for the monopole antenna element can be achieved. Measured results show that the impedance bandwidths of 32.84% (2.8-3.9 GHz) and 18.18% (4.5-5.4 GHz) can be achieved for the 5G communications. Wide half power beamwidths (HPBW) of larger than 103° in E-plane and 91° in H-plane can be achieved across the operating bands. In addition, a bandwidth of 5.5% (5.82-6.15 GHz) with gain of 2.47 ± 0.69 dBi in the azimuth plane can also be obtained for V2X communications.

A Tripolarized Antenna With Ultrawide Operational Bandwidth

In multiscattering environment, the channel capacity can be enhanced by employing dual-polarized antennas, and more significantly, using tripolarized antennas. Aiming at providing a wide coverage of both existing wireless communication systems and the new 5G sub-6 GHz band, this article presents a compact ultrawideband tripolarized antenna. The proposed design consists of a monopole-equivalent structure for vertically linearly polarized (LP) omnidirectional radiation and two orthogonal stepped dipoles for ±45° LP broadside radiation. Several important design features are proposed and implemented. The dipoles act as parasitic elements for the monopole structure, which broadens the monopole bandwidth and reduces the mutual coupling. Furthermore, the port isolation is improved by inserting two metallic posts between the crossed dipoles and the ground plane. The measured results indicate that the fabricated prototype achieves an overlapped bandwidth of 84.73% (1.68–4.15 GHz) for <−10 dB reflection coefficient and coupling value of <−30 dB among all ports. Tripolarized radiation is verified with pattern measurement, showing peak realized gains of 8.4 and 9.4 dBi in monopole and two broadside modes, respectively.

Coordinating Three-Branch Diversity Switching Using a Hidden Markov Model

Multielement antenna systems have been shown to provide improved performance over single-element antennas in harsh, depolarizing propagation environments. However, how best to leverage these systems is still a challenge for low-cost implementations, e.g., for the Internet of Things (IoT) devices. In this article, we present a three-branch switched diversity scheme that models the transition between the elements of a tripolar antenna by means of a hidden Markov model (HMM), parameterized from the measurement data. The proposed technique determines antenna polarization before each transmission using the received signal strength indication (RSSI) values, their probabilistic relationship with antenna elements, and transition probabilities among the diversity branches. The simulation and experimental results show that in high multipath environments, similar to those expected for many IoT networks, selection of the most likely antenna element before every transmission using the HMM approach leads to a median gain of 0.4 and −0.9 dB and a 1% diversity gain of 2.4 and −6.8 dB over conventional switched diversity and selection diversity, respectively, with no additional hardware costs. In addition, a hardware implementation demonstrates that the proposed method can reduce power drain from the battery by at least 15% as compared with the selection and switched diversity techniques, with no degradation in packet delivery rates.

Capacity optimization of multi-input/multi-output relay channel by SADDE algorithm

In this paper, we use self-adaptive dynamic differential evolution (SADDE) to search for multi-input/multi-output (MIMO) relay locations and transmitter locations to reduce the outage probability in the indoor ultra-wideband (UWB) environment. Amplify-and-forward (AF) MIMO relay is chosen to improve the performance of the environment. We use the shooting and bouncing ray/image (SBR/image) method to compute the frequency response, which is used to compute capacity. The channel capacities for the linear antenna with 1 × 1 antenna, 3 3 spaced linear antennas, and 3 × 3 tri-polarized antennas are compared. First, we deploy the relay and transmitter at the equipartition area. It is found that there are some outage receiving points. Thus, the SADDE is employed to optimize the position of the relay and transmitter in order to reduce the outage probability. Numerical results show that the outage probability for the relay and transmitter location is reduced by SADDE. Moreover, it is found that the channel capacity for the tri-polarized antennas has increased when comparing to 3 × 3 spaced linear antennas. For the zero outage probability requirement, the signal to noise for the tri-polarized antennas is lower 6 dB than that for 3 × 3 spaced linear antennas.

A Low-Profile Wideband Tripolarized Antenna

As a combination of three orthogonal dipoles, the tripolarized antenna has been demonstrated to significantly improve signal quality in scattering environment. In this communication, we propose a low-profile tripolarized antenna with wideband characteristics. The tristate includes 0° and 90° linear polarizations (LP) with the main beam at broadside and a vertically LP with omnidirectional pattern in the azimuth plane. The design consists of a monopolar patch and two orthogonal dipoles. The wideband performance for the monopolar patch is obtained from two nearly overlapped radiating modes controlled by an array of shorting wires. For the two orthogonal dipoles, the antenna profile is reduced with the effect of parasitic patches. One of the key design features is to utilize the shorting wire in the monopolar patch to feed the dipoles, allowing a simple design and avoiding any feeding network. The concept is experimentally verified with a prototype exhibiting an overlapped bandwidth of 14% with a low profile of 0.09λ, where λ is the free-space wavelength at the lowest operating frequency. The measured peak gain in two broadside modes and in monopolar mode are 10 and 7.5 dBi, respectively. Measured isolation between any port is better than 31 dB in the whole frequency range.

Design of a Low-Profile Tripolarized Antenna With Wide Bandwidth

In this paper, a low-profile tripolarized antenna with the wideband operation is presented. It includes a monopolar patch element for vertically linear polarization (LP) omnidirectional radiation in the horizontal plane and two orthogonal dipoles for ${x}$ - and ${y}$ -direction LP broadside radiations. In order to achieve the wideband, nevertheless keeping the low-profile, the monopolar patch antenna is coupled with an annular ring, while the two orthogonal dipoles are incorporated with a metasurface. Optimized design with a profile of $0.09\lambda _{\min}$ ( $\lambda _{\min}$ is the free space wavelength referring to the lowest operational frequency) has been fabricated and measured. The measurements result in an overlapped bandwidth of 24.45% (2.19–2.80 GHz) for reflection coefficient < −10 dB and coupling coefficients of < −30 dB among the three ports. In addition, the antenna yields measured peak gains of 8.4 and 9.5 dBi in monopolar mode and two broadside modes, respectively.

On Random and Multidimensional Channel Effects in Cluttered Environments

Machine-to-machine devices have the potential to be placed in environments that are less than ideal for wireless propagation, such as factory floors or within metallic enclosures. In this letter, we illustrate that such environments not only produce the expected multipath, but can also depolarize the signal across all three spatial dimensions. Furthermore, we show that these effects are multidimensional in which they are highly sensitive to extremely small changes in user placement and frequency of operation. That is, these channels exhibit randomness based on a user's action. These effects motivate new channel characterization approaches and metrics along with the development of tripolar antenna designs. This letter concludes by presenting the efficacy of such a prototype antenna.

Radiation Characteristics Analysis of Tri-Polarized Dipole Antenna

Dual-polarized antenna involves polarization purity degradation and power gain loss when scanning at wide angles. Aiming at mitigating the above limitations, we exploit a tri-polarized antenna for better radiation characteristics in this letter. We formulate the beampattern synthesis problem of a single tri-polarized dipole antenna in a convex form, and solve it with the Lagrange multiplier method. When circular polarization is synthesized, we show that degree-of-freedom increase improves the polarization purity and power gain of the multipolarized antenna, especially at wide scan angles. We further find that, using the infinite current sheet model, the radiation pattern synthesized by tri-polarized antenna is the same with the optimally oriented dual-polarized antenna - the dual-polarized antenna is mechanically rotated to be oriented normally to the scanning direction. We discuss the situation when linear polarization is synthesized. We show that the power gain is increased corresponding to scan angle, while the polarization purity is not improved obviously.

Tri-polarized MIMO systems in real-world channels: Channel investigation and performance analysis

Polarized multi-antenna systems are an effective solution for reducing inter-antenna spacing while still maintaining low inter-antenna correlation. Traditionally, only dual-polarized antenna systems are used for polarized transceivers. In this paper, tri-polarized antenna systems are investigated. Starting from the polarization mechanisms in the wireless propagation channel, it is shown that dual-polarized MIMO systems show high sensitivity to the transmitter and receiver orientation, which may be very critical in practical applications. Tri-polarized MIMO systems are introduced as a solution to obtain a robust MIMO performances, which are independent of the transmitter and receiver orientation. The performances of dual- and tri-polarized MIMO systems are evaluated on real-world measured channels, and the limits of each of these systems is highlighted.

A Compact Eighteen-Port Antenna Cube for MIMO Systems

An 18-port compact antenna cube is proposed in this paper. The cube, which has a volume of 0.76 × 0.76 × 0.76 λ03, provides 18 individual channels and is ideal for multiple-input multiple-output (MIMO) wireless communications. On each of the total six faces of the cube, a three-port tri-polarization antenna is installed. All antennas adopt a metal backing configuration, so the ground of all antennas forms a well shield Faraday cage, in which other functional circuits can be installed. Experimental measurements were carried out to evaluate the performance of the antenna cube in different MIMO scenarios. The results show that MIMO systems with the proposed compact antenna cube outperform those with dipole antennas which occupy the same number of RF channels but with much larger space. When a vertical 3-dipole array, a horizontal 3-dipole array and a dual polarization antenna are used in the user end (UE), respectively, the capacity of the global selected MIMO systems with antenna cube is about 2.7, 4.6, and 2.9 bits/s/Hz more than the full MIMO systems with a vertical 3-dipole array as the access point (AP) antennas. It is 1.9, 3.9, and 2.0 bits/s/Hz more than the full MIMO systems with a vertical 5-dipole array as AP antennas. The performance differences between the MIMO systems using global and simplified selection circuits are small.

Diversity Measurements for On-Body Channels Using a Tri-Polarization Antenna at 2.45 GHz

Characteristics and diversity performance for on-body communication systems using a tri-polarization antenna are investigated based on measurements at 2.45 GHz. A disk-loaded monopole has been used as a transmitter, and a low-profile planar tri-polarization antenna as a three-branch receiver. Measurements were conducted for six typical on-body scenarios, where standing and sitting postures are considered. Envelope correlation and cross-polar discrimination (XPD) are calculated from measurement data. The tri-polarization diversity performance is evaluated by diversity gain, when different signal combing techniques are employed. Diversity gain is high for the non-line-of-sight scenarios and increases with increasing mobility. Tri-polarization diversity outperforms dual-polarization diversity in terms of up to 16.33 dB higher path gain due to the full utilization of polarization resource of electromagnetic wave and the avoidance of polarization mismatch for the dynamic on-body channels.

Low-Profile Planar Tripolarization Antenna for WLAN Communications

A tripolarization and low-profile planar antenna is designed, prototyped, and tested for WLAN application. The developed three-port antenna provides three orthogonal polarization radiations. Two slot-coupled microstrip antennas and a disk-loaded monopole are integrated into one structure. The total height of the antenna is 5.8 mm. Obtained gain for the two slot-coupled directive elements at 2.42 GHz is 7 dBi, while the gain for the monopole omnidirectional element is 2.5 dBi. The bandwidths of the three elements are 2.352.52, 2.32.54, and 2.382.49 GHz, respectively. Simulation results of the radiation patterns are presented and validated by experimental measurements.

Evaluation of True Polarization Diversity for MIMO Systems

MIMO systems where multipath fading is only partially correlated could use polarization diversity to provide a higher diversity gain. Recent letters have proposed the use of tri-polarized antennas and a novel true polarization diversity (TPD) scheme. In this paper, the full potential of TPD is evaluated with both simulations and measurements and compared to conventional orthogonal polarization diversity (OPD). MIMO system performance with respect to capacity and diversity gain is obtained through the use of multimode-stirred chambers for both isotropic and non-isotropic environments. Simulated and measured results in over 591 different MIMO systems show that TPD outperforms conventional OPD for reduced volumes. Likewise, it has been demonstrated that TPD can be effectively combined with spatial diversity to nearly double the diversity gain and MIMO capacity for the same available handset volume.