Dual-polarized Dipole Research Articles

Broadband dual‐polarized crossed‐dipole antenna with tapered integrated balun for base‐station applications

A ± 45° dual-polarized dipole antenna with low profile and stable radiation pattern over a wide operating band for base station is proposed. The antenna is formed by two polygon-shaped dipoles and a shaped metallic reflector. Two baluns with tapered structure are used to excite the dipoles for dual-polarized radiation and enhancing the impedance matching and bandwidth, while the shaped-reflector is used to obtain stable radiation pattern in the horizontal plane during a wide frequency band. The design principles of crossed dipoles, baluns and reflector is described in detail. The proposed antenna achieves wide impedance bandwidth of 67% for VSWR<1.5, and high-isolation better than 31 dB over the operating band. In addition, the 3 dB beamwidth in the horizontal plane of the antenna is stabilized within the range of 66.3° ± 2.8°. These performances make the presented antenna applicable for mobile communications.

Sensitivity of a low-frequency polarimetric radio interferometer

Context.The sensitivity of a radio interferometer is a key figure of merit (FoM) for a radio telescope. The sensitivity of a single polarized interferometer is typically given as an antenna effective area over a system temperature,Ae/Tsys, assuming an unpolarized source. For a dual-polarized polarimetric interferometer intended to observe sources of unknown polarization, the state of polarization must not be assumed a priori. Furthermore, in contrast to the narrow field of view (FoV) of dish-based interferometers, the sensitivity of a polarimetric low-frequency radio interferometer warrants a careful review because of the very wide FoV of the dual-polarized antennas. A revision of this key FoM is particularly needed in the context of the Low-Frequency Square Kilometre Array (SKA-Low) where the sensitivity requirements are currently stated usingAe/Tsysfor a single-polarized antenna system, which produces ambiguity for off-zenith angles.Aims.This paper aims to derive an expression for the sensitivity of a polarimetric radio interferometer that is valid for all-sky observations of arbitrarily polarized sources, with neither a restriction on FoV nor with any a priori assumption regarding the polarization state of the source. We verify the resulting formula with an all-sky observation using the Murchison Widefield Array telescope.Methods.The sensitivity expression was developed from first principles by applying the concept of system equivalent flux density (SEFD) to a polarimetric radio interferometer (not by computingAe/Tsys). The SEFD was calculated from the standard deviation of the noisy flux density estimate for a target source due to system noise.Results.The SEFD for a polarimetric radio interferometer is generally not 1/√2 of a single-polarized interferometer as is often assumed for narrow FoV. This assumption can lead to significant errors for a dual-polarized dipole based system, which is common in low-frequency radio astronomy: up to ∼15% for a zenith angle with a coverage of 45° and up to ∼45% for 60° coverage. The worst case errors occur in the diagonal planes of the dipole for very wide FoV. This is demonstrated through theory, simulation, and observations. Furthermore, using the resulting formulation, the calculation of the off-zenith sensitivity is straightforward and unambiguous.Conclusions.For wide FoV observations pertinent to a low-frequency radio interferometer such as SKA-Low, the narrow FoV and the single-polarized sensitivity expressions are not correct and should be replaced by the formula derived in this paper.

Design and Analysis of High Gain Dual-polarized Dipole Antenna Based on Partially Reflective Metasurface

A partially reflective metasurface (PRMS) structure is proposed for dual-polarized dipole antenna with a high gain and wide broadband. Stable radiation patterns are realized by using quadrilateral bottom reflector. The phase bandwidth of PRMS structure reflection presented in this paper matches well with the antenna operating bandwidth. The gain of the dualpolarized antenna is improved to 10.2dBi at 1.8GHz by adjusting the size and height of PRMS structure. Meanwhile, the bandwidth is expanded (61.2%). Measured result demonstrates that the antenna has a stable beamwidth which is desirable in base station applications. Furthermore, the designed antenna can be used for communication in complex environment because of its excellent performance.

A Balun Bandpass Filter to Facilitate the Design of Dual-Polarized Dipole Antenna

A dipole antenna based on a balun bandpass filter (BPF) is developed in this paper. The balun BPF employs two U-shaped resonators settled on the left side of the open-circuited transmission line and two L-shaped stubs to produce signals with equal amplitude and inverse phase. In this way, the volume of the balun BPF is reduced by half, and the distance between two output ports is dramatically decreased. Then, the balun BPF is integrated with a dipole. Instead of the traditional Γ-shaped line with a wide balun ground, two thin microstrip lines with width of 1 mm are adopted to connect the dipole and the balun BPF. The antenna bandwidth is further extended due to the fusion of the resonance of the dipole and balun BPF. As a result, the proposed antenna can operate from 4350 to 5025 MHz (covering the n79 band of 5G NR, 4400 MHz–5000 MHz), yielding a good filtering performance in the stopband. The measured half-power beamwidth is ranging from 61° to 63° and the measured gain is ranging from 7.95 to 8.5 dBi in the passband. This new balun BPF and the dual-polarized dipole based on it have great potential to be applied in 5G MIMO systems.

Wideband Wide Beamwidth Full-Wavelength Sectorial Dipole Antenna Under Dual-Mode Resonance

In this article, a novel design approach to wide beamwidth dual-resonant, wideband sectorial dipole antennas is advanced. At first, a 1-D, full-wavelength dipole is evolved into a 2-D, sectorial dipole, so as to determine its two usable resonant modes. Then, both wideband and wide beamwidth characteristics are simultaneously attained under dual-mode resonance. Next, dual-resonant sectorial dipole antennas with flared angle of 270° and 240° are designed and studied. As experimentally validated, the proposed antenna exhibits an omnidirectional pattern with its impedance bandwidth over 70.4%. A few prototypes mounted above a ground plane are further investigated, so as to achieve a broad H-plane half-power beamwidth (HPBW) to over 120°. In addition, the antennas exhibit stable gain frequency response with fluctuation less than 2.2 dB within the entire impedance bandwidth. Thus, the advanced design approach based on 2-D dual-resonant, full- wavelength dipole leads to the formulation of novel wide beamwidth antennas with low frequency dispersion and simple configuration within a wide radiation bandwidth over 53.3%. Finally, a dual-polarized dipole antenna with port-to-port isolation higher than 34.5 dB and available radiation bandwidth of over 49% is implemented to further validate its potential for practical applications.

Design and Fabrication of Wideband Dual-Polarized Dipole Array for 5G Wireless Systems

This paper presents simulation and measurement results of a wideband planar phased array for 5G. The desired wideband operation is achieved using a tightly coupled dipole array (TCDA). The proposed array consists of tightly coupled dipole units in dual-polarized configuration, and two thin parasitic layers separated apart by air gap for wide-angle impedance matching (WAIM). The top matching layer is loaded with a metasurface composed of sub-wavelength split-ring resonators (SRRs) to improve the scanning performance of array. The infinite array achieved a bandwidth from 23.5 to 29.5 GHz, with voltage standing wave ratio (VSWR) $0.144\lambda _{l}$ , and it exhibits high gains, high efficiency >71% (largest scan angle) and good cross-polarization. The simulations are validated by fabrication and measurement of an array prototype, which indicates agreement to simulated values. The proposed dual-polarized antenna array can be deployed in the future beam scanning applications for 5G.

Simple Triple-Mode Dual-Polarized Dipole Antenna With Small Frequency Separation Ratio

A triple-mode dual-polarized dipole antenna topology with a very small frequency separation ratio is proposed. The antenna has a simple structure with a very low manufacturing cost while maintaining a good performance. A conventional dipole is fed by a feeding network also acting as a radiator to generate a second resonant mode. A shorted conductor loaded to the dipole is used to excite a third resonant mode. It is shown that the three modes can be tuned in order to cover different sets of applications. By fusing the two higher resonances, an antenna with a lower band and a very wide higher band can be obtained. Two orthogonal linear polarizations are achieved by integrating two of the aforementioned topologies. The conceptual structure is prototyped and measured. The realized antenna has a lower band of 2.38–2.54 GHz and a higher band of 3.11–4.15 GHz. Its electrical size is 0.8 × 0.8 λ2, with a profile of 0.27 λ ( λ is the wavelength in free space at 2.4 GHz). The mutual coupling between the two ports is below -20 dB, which is quite beneficial for the diversity performance in multiple-input–multiple-output (MIMO) systems.

Phase Compensation for Decoupling of Large-Scale Staggered Dual-Polarized Dipole Array Antennas

Staggered array antenna is a common array configuration for large-scale array antennas due to its favorable radiation characteristics and relatively large element spacing. In developing a compact staggered dipole array, the most challenging issue is how to simultaneously reduce the four mutual couplings taking place between adjacent co-polarized antenna elements with diversified phase laggings. A large difference in the phase of different mutual couplings makes simultaneous reduction of all the mutual couplings by applying the recently developed array-antenna decoupling surface (ADS) technique difficult. In this article, a phase compensation method by using a staple-shaped probe for alleviating the largest phase offset is proposed conceptually and verified experimentally. With the proposed phase compensation method, the ADS technique can be effectively applied to a compact staggered dipole array with a wideband simultaneous decoupling. The design guideline for the phase compensation probe is presented by EM simulation and a parametric study. Two practical design examples of dual polarized staggered dipole arrays are given to demonstrate the effectiveness of the proposed phase compensation method in conjunction with ADS, showing a promising potential for wideband simultaneous decoupling of a large-scale dual polarized staggered dipole array-antenna.

Broadband dual-polarized dipole antenna for LTE/5G base station applications

ABSTRACTThis article presents a broadband dual-polarized dipole antenna for LTE/5G base station, which consists of loop dipoles, T-shaped cross-feeding lines, L-shaped parasitic elements, and metallic cylinders. As a result, the test results show good achievement of wide band (48.6%, 2.21–3.63 GHz), stable gain (8.3 dBi) and high port-to-port isolation (>30 dB). In addition, good cross-polarization discrimination (XPD) (>30 dB) and stable radiation pattern () on horizontal plane are realized over the band by employing a rectangular box-shaped reflector. Furthermore, with simple structure, this antenna can provide partial reference for the design of LTE/5G base station antennas.

Dual-polarized dipole radiation elements for the modern base station antennas

Two improved designs of wideband dual polarization antennas for base station. The first design is the crossed dipoles for the frequency bands 1695–2695 MHz. The presented shape of crossed dipole provides a low level of crosspolarization, VSWR better than 1.4, the isolation between polarizations is better than –33 dB and the beam width in the horizontal plane is 65±4 degrees. The second design is the square dipole in the frequency range 690–960 MHz provides the beam width in the horizontal plane 60±5 degrees, E-plane 58±3 degrees, H-plane 64±3 degrees, the isolation between polarizations better than –35dB.

Compact Broadband Dual-Polarized Filtering Dipole Antenna With High Selectivity for Base-Station Applications

This paper presents a broadband dual-polarized filtering dipole antenna for base-station application, which has a compact size of 50 $\text {mm} \times 50\,\,\text {mm} \times 31.8$ mm. The antenna consists of four parts: main radiator, feeding baluns, reflector, and two parasitic loops. Without using complex filtering circuits, the dual-polarized dipole antenna realizes satisfactory filtering performance and enhanced bandwidth by employing only two parasitic loops. Two specific radiation nulls are thus generated and individually controlled by the two parasitic loops. To further improve the upper stopband selectivity and bandwidth, a simple open-ended stub is added to the arms of the dipole. As a result, the bandwidth can be tuned from 7.4% to 47.6%, and the realized gain is decreased dramatically from 8.6 dBi at 2.7 GHz (in-band) to −10 dBi at 2.9 GHz (out-of-band). For demonstration, a broadband dual-polarized dipole antenna is implemented. Measured results show that the proposed antenna has more than 34 dB port isolation over 48.7% (1.66–2.73 GHz) impendence bandwidth (VSWR < 1.5). The measured in-band gain is about 8.15 dBi with stable 3 dB beamwidth 65.4°±2.4° in the horizontal plane, whereas the out-of-band radiation suppression is more than 17 dB.

A Wideband Dual-Polarized Dipole Antenna With Folded Metallic Plates

A wideband dual-polarized dipole antenna with fourfolded metallic plates is proposed in this letter. The folded metallic plates are vertically placed on the ground plane, under the dipole arms. Owing to the coupling with the nearby dipoles, an additional resonance beside the original impedance passband of the dipole antenna can be generated by the parasitic plates, leading to a very wide operating bandwidth. A prototype was fabricated and tested to verify the design. The measured results show that the prototype has a −10 dB impedance bandwidth of about 92%, a port isolation of over 20 dB, and an average gain of 6.2 dBi within the operating band.

A Low-Profile Dual-Polarized Dipole Antenna Using Wideband AMC Reflector

A low-profile dual-polarized dipole antenna using wideband artificial magnetic conductor (AMC) reflector with stable radiation pattern for use in 2G/3G/4G base stations operating from 1.7 to 2.7 GHz is presented. The antenna consists of a pair of crossed-dipoles and a wideband AMC reflector which consists of an AMC surface, a metallic ground plane, and the air substrate between them. The AMC is designed to operate with 90° reflection-phase bandwidth of 1.64–2.88 GHz (54.8%). Compared with using perfect electric conductor reflector, the profile height of the dual-polarized dipole antenna using AMC reflector is reduced by half from 36 to 18 mm, resulting in the lowest-profile 2G/3G/4G base station antenna. Six metallic ground walls are used to stabilize the radiation pattern, and the resulted half-power beamwidths are around 68±3° and 81±3° in the H- and V-planes, respectively, across the operating band. More measured results show that wide impedance bandwidths of 1.67–2.98 and 1.64–3.05 GHz for the two input ports, isolation of more than 25 dB, and cross-polarization of less than −20 dB are achieved.

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 Low-Profile Dual-Polarized High-Isolation MIMO Antenna Arrays for Wideband Base-Station Applications

A low-profile dual-polarized high-isolation multiple input multiple output (MIMO) antenna array for wideband base-station applications is presented in this paper. The proposed dual-polarized antenna element has the advantage of lower profile ( $0.067\lambda $ ) by utilizing artificial magnetic conductor structure. The antenna array consisting of four elements is working within the frequency band from 2.4 to 3 GHz. Furthermore, decoupling branches among the elements are introduced to improve the isolation by about 10 dB. Both simulation and measured results indicate that the proposed dual-polarized antenna element has a good isolation over 28 dB. Moreover, the beamwidth of the antenna array can be effectively broadened by the adjustment of phase distributions of corresponding artificial material plane. Finally, a larger MIMO system is also investigated, and the simulation and measured results prove that dual-polarized dipole antenna MIMO array has good system performance.

A dual polarized antenna on a novel broadband multilayer Artificial Magnetic Conductor backed surface for LTE/CDMA/GSM base station applications

The paper presents a low profile dual polarized dipole antenna topology backed by a novel broadband multilayer Artificial Magnetic Conductor (AMC) based reflecting surface. The antenna consists of a pair of square loop shaped dipoles with T-shaped feed structures arranged orthogonally to provide dual slant polarizations at ±45°. The antenna structure is backed by a novel multilayered AMC structure consisting of stacked square patches with via connected at middle and an air filled ground plane at the bottom. Experimental results show that the proposed antenna operates from 700 to 1000MHz with bandwidth of 35% and an average gain of 8.5dBi over the bandwidth. The Simulated and measured results of the antenna structure indicate the antenna to be suitable for interoperable Long Term Evolution (LTE), Code Division Multiple Access (CDMA) and Global System for mobile communications (GSM) applications.

Closed-Form Jones Matrix of Dual-Polarized Inverted-Vee Dipole Antennas Over Lossy Ground

This paper presents a closed-form expression for the Jones matrix of a dual-polarized inverted-vee dipole antenna based on the Lorentz reciprocity theorem and the basic rules of electromagnetic refraction. The expression is used to determine the intrinsic cross-polarization ratio (IXR) as a function of droop angle, position of the source in the sky, antenna height, frequency, and reflection coefficient of the underlying ground. The expression is verified using full-wave simulations with a method-of-moments solver, showing very good agreement. It explains the increase in the IXR when the antenna is placed over a perfect electric ground plane. This result is used to explain the polarization properties of the Square Kilometre Array Log-periodic Antenna. Through the LOw-Frequency ARray Low-Band Antenna (LOFAR-LBA), the importance of the size of the ground plane is explained. Finally, design consideration for high polarization purity antennas is discussed.

Broadband Dual-Polarized Dipole Antenna with Metallic Cylinder for Base Station

ABSTRACTIn this article, a broadband dual-polarized dipole antenna for mobile communication systems is proposed. The design is based on improvements to conventional bowtie dipole antennas, thereby simultaneously achieving wider bandwidth and a more compact size. The antenna consists of a metallic plate reflector and a pair of orthogonal planar dipoles with U-shaped slots, which are separately excited by T-shaped feeding lines. The application of U-shaped slots and T-shaped feeding lines effectively extends the impedance bandwidth. Additionally, using a new approach of adding metallic cylinders to each dipole improved impedance matching. Experimental results indicated that the designed dual-polarized antenna achieved a notably wide bandwidth (1.58–2.82 GHz). Further, the measured isolation between the two ports was better than 30 dB and cross-polarization level was less than –25 dB on the axis. Moreover, the antenna had stable radiation patterns with half-power beam width of 65° ± 5° on the horizontal plane and an average gain of 8.2 dBi over the operating band. Importantly, these parameters collectively meet current telecommunications industry standards.

Design and realization of a novel nonplanar dual-polarized log-periodic dipole array for 1-13 GHz

A feasible and low cost approach to implement a nonplanar dual-polarized log-periodic dipole array antenna using printed circuit board (PCB) technology is proposed. The proposed antenna utilizes a very short transition from a coaxial cable to a balanced twin-lead transmission line to realize an ultrawide bandwidth balun, and has two distinct scaling factor values for high and low frequency elements. A prototype of the antenna operating over the frequency range of 1–13 GHz was designed, fabricated, and tested. An average gain of 7 dBi is obtained. Measured VSWR, cross-polarization and front-to-back ratio are better than 2.6, −16 dB, and 22 dB, respectively.

Study of the Colocated Dual-Polarized MIMO Capacity Composed of Dipole and Loop Antennas

The colocated dual-polarized dipole (DPD) and dual-polarized loop (DPL) MIMO channel performances are compared. Computation results show that, for the ideal electric and magnetic dipoles, the dual-polarized MIMO systems have identical channel capacity. But the contour plots of the capacity gain of the realistic DPD and DPL are different, due to the difference in antenna patterns. The cumulative distribution function (CDF) of the capacity gain in the two-mirror (TM) channel shows that, for small distance, the capacity gain obtained by the DPD is obviously smaller than that of the DPL, but, with the increase of the distance, the difference gets smaller. A DPL with low mutual coupling is fabricated. Measured results show that high MIMO capacities can be obtained by this DPL in both the anechoic chamber (AC) and the realistic office room. The capacity gain of the DPL antenna is 1.5–1.99, which basically coincides with the theoretical and numerical results. Furthermore, the capacity of the virtual DPL antenna with no mutual couplings is also investigated. It is shown that, in the AC, the mutual coupling will generally decrease the dual-polarized MIMO capacity; however, in the office room, the effect of mutual coupling is not always negative.