Dual-band Base Station Antenna Research Articles

Differentially Fed Dual-Band Base Station Antenna With Multimode Resonance and High Selectivity for 5G Applications

Differentially Fed Dual-Band Base Station Antenna With Multimode Resonance and High Selectivity for 5G Applications

Broadband Suppression of Common-Mode Current Interference in Dual-Band Base Station Antenna Arrays by Loading an LC Circuit

Broadband Suppression of Common-Mode Current Interference in Dual-Band Base Station Antenna Arrays by Loading an LC Circuit

Dual-Band Base Station Antenna Array With Cross-Band Scattering and In-Band Coupling Suppression

Dual-band base station antenna array mainly suffers from the drawbacks of cross-band scattering and in-band coupling, which will disturb the radiation performances of the antennas, especially for the high-band (HB) antennas. In this paper, a dual-band base station antenna array with cross-band scattering and in-band coupling suppression is proposed. It contains a low scattering low-band (LB) crisscross-shaped dipole antenna codesigned with four square rings and four patches and a 2×2 HB antenna array. The crisscross-shaped dipole antenna is fed by four L-shaped strips, and a photonic bandgap (PBG) cell is loaded in the middle of each arm of the LB antenna to achieve HB-induced current scattering suppression without affecting the LB antenna, so the radiation patterns distortion from the cross-band scattering can be avoided. As the LB antenna employs crisscross structure, the four rings and patches can be integrated together with the LB antenna on the same substrate, which not only help to broaden the bandwidth, but also act as the array-antenna decoupling surface (ADS). With the codesign of LB antenna and ADS, no extra substrates are required for in-band decoupling. A dual-band base station antenna array prototype is fabricated and measured, showing good performances in LB and HB.

In-Band Mutual Coupling Suppression in Dual-Band Shared-Aperture Base Station Arrays Using Dielectric Block Loading

Dual-band base station antenna (BSA) arrays with shared aperture have attracted considerable attention for the fifth-generation (5G) communication. The focus is mainly on decoupling between lower band (LB) and higher band (HB) antennas (i.e., cross-band decoupling). The in-band BSA decoupling techniques are usually not applicable to broadband dual-band shared-aperture BSA arrays. HB BSAs’ elements usually are separated by more than half-wavelength to reduce the in-band mutual coupling, which increases the array aperture and causes grating lobes for beam steering. Here, a novel decoupling technique of dielectric blocks is proposed to suppress the in-band couplings in dual-band shared-aperture BSA arrays. The dielectric blocks are placed above the HB elements to neutralize the original coupling by creating partially reflected waves (an addition wave path). A compact interleaved dual-band BSA array with dielectric blocks is designed and manufactured. The LB operates between 1.9 and 2.5 GHz, and the HB covers the 5G band from 3.3 to 3.9 GHz. The HB coupling is effectively reduced below −25 dB, while the impedance matching and radiation performance of the HB and LB elements are maintained. Moreover, the dielectric blocks are implemented for stacked and interleaved dual-band BSA arrays with suppressed cross-band interference. The proposed decoupling method has simple structures, easy to design and fabricate, and is compatible with the existing cross-band decoupling techniques for different dual-band BSA array configurations.

Self-Decoupled Dual-Band Shared-Aperture Base Station Antenna Array

A new decoupling concept for dual-band shared-aperture base station antenna arrays is proposed. By loading arrow-shaped decoupling structures in the hollowed regions of the low-band (LB) loop dipole arms, the LB antenna can yield partial reflection to the high-band (HB) antennas, canceling the HB-coupled wave. A dual-band base station antenna array is designed, fabricated, and measured based on this decoupling concept. With decoupling, the HB radiation patterns are restored. The copolarized in-band couplings between the HB antennas are reduced by about 9 dB, reaching >26.9 dB. The proposed antenna array possesses both cross-band and in-band decoupling abilities, without extra decoupling layer.

Dual-Band Base Station Antenna Array Using the Low-Band Antenna as Parasitic Decoupler

In this letter, a dual-band interleaved base station antenna array with self-decoupling characteristic is studied. The low-band antenna radiator along with its feeding baluns can be considered as compensation and partition structures for the high-band (HB) antennas. The measured co- and cross-polarized in-band isolations between the HB subarrays are enhanced to > 24.6 dB and > 29.3 dB, respectively, without introducing extra decoupling layer. The HB radiation performances are recovered, exhibiting good capability of crossband scattering suppression. The decoupling principles are analyzed and explained.

Dual‐band stacked base station antenna array with high isolation

A high-isolation dual-band base station antenna array is proposed. At first, a 5-element high-band (HB) dipole antenna array with inter-element distance of 0.4 λH0 (the free-space wavelength at the center frequency of the HB) is decoupled. With the main antenna decoupling surface (ADS), metal baffles and auxiliary ADS, the E-plane and H-plane couplings can be reduced to <−23.1 dB (<−11.4 dB without decoupling) and <−22.6 dB (<−14.8 dB without decoupling), respectively. The dual-layer ADS design successfully resolves the contradiction between decoupling performance and matching. The ground plane of the 5-element array is then exploited as the low-band patch radiator, forming the proposed dual-band antenna array. Measured results show that satisfactory cross-band isolation (>33.1 dB), in-band isolation (>22.2 dB) and polarization isolation (>30 dB) are obtained. Stable unidirectional radiation patterns are also acquired.

Shared-Radiator Design of Dual-Band Coplanar Base Station Antenna Array Using Cavity-Backed Slots

In this communication, we propose a shared-radiator design concept for dual-band base station antenna arrays. To realize the concept, novel differentially fed dual-polarized slot antenna is devised to be the high-band (HB, 3.4–3.6 GHz) radiator, while the large slot ground can be reused as the radiating arm of the low-band (LB, 0.69–0.96 GHz) crossed dipole. Reflective cavities are introduced to back the HB antennas, building clear and independent radiating environments for the two operating bands. A dual-band base station antenna array with one LB dipole antenna and four HB slot antennas is designed, by adopting the proposed integration concept. Good impedance matching (voltage standing wave ratio <1.5) and high port isolation (>29.5 dB in the LB and >26.6 dB in the HB) are obtained. Stable radiation patterns are also achieved in the two bands.

A Dual-Band Base Station Antenna with a Split Ring for Sub-6 GHz Communication

A dual-band base station antenna is introduced in this paper. The proposed antenna is composed of baluns, bowtie patches, and a split ring. The two pairs of bowtie patches excited by the two orthogonal balun structures can achieve dual polarization. The split ring is used to yield two additional resonances to broaden the impedance bandwidth. In this way, a compact dual-band base station antenna is obtained with the size of 0.41 λc × 0.41 λc × 0.13 λc (λc is the wavelength in the free space at the lowest operating frequency band) and the average gain of 8.2 dBi. Moreover, the operating frequency bands of the proposed antenna cover 2515–2675 MHz, 3400–3600 MHz, and 4800–5000 MHz, which can function as an element for macro- or microcells in sub-6 GHz communications.

Suppression of Cross-Band Scattering in Interleaved Dual-Band Cellular Base-Station Antenna Arrays

In this article, novel techniques to suppress cross-band scattering in interleaved dual-band base station antenna arrays are presented. Firstly, the detrimental effect of high-band (HB) elements on low-band (LB) radiation performance is theoretically analyzed. With a thorough analysis, a capacitance-loaded HB element is innovated to solve the issue and restore the LB patterns. Secondly, to eliminate the reverse HB scattering caused by the LB element while enhancing the bandwidth of the LB element, a novel double-arm choked cross-dipole configuration is proposed. A compact array section is built with these innovated elements. The experimental results of the array show a largely suppressed cross-band scattering with stable radiation performance across the well-matched bands, demonstrating the effectiveness of the presented techniques.

A Low-Profile Coplanar Dual-Polarized and Dual-Band Base Station Antenna Array

This paper presents a low-profile coplanar dual-polarized dual-band base station antenna array. A slotted patch antenna operating from 0.82 to 0.99 GHz with four shorting strips is proposed and analyzed. The four shorting strips are employed not only to improve the impedance matching in the lower band but also to remove the center part of the patch, thus making room for higher band dipoles operating from 1.68 to 2.86 GHz. The height of the proposed array is nearly half of the conventional base station array while other performances are guaranteed. The measured results show that the proposed antenna array has wide impedance bandwidths of 18.7% (0.82–0.99 GHz) and 57.9% (1.68–2.86 GHz) (VSWR $0.109\lambda _{0}$ at 820 MHz). The measured gains are 13.8±0.5 dB and 16.7 ± 1 dB in lower and upper bands. Large front-to-back ratio (>24.6 dB) and high isolations (>30 and >25 dB in lower and upper bands, respectively) are achieved. The proposed antenna can be easily built with printed circuit board fabrication technique and applied in low profile multiband base stations for 2G/3G/4G and the next-generation systems.

Particle Swarm Optimization as Applied to Electromagnetic Design Problems

Particle swarm optimization (PSO) is a swarm intelligence algorithm inspired by the social behavior of birds flocking and fish schooling. Numerous PSO variants have been proposed in the literature for addressing different problem types. In this article, the authors apply different PSO variants to common design problems in electromagnetics. They apply the Inertia Weight PSO (IWPSO), the Constriction Factor PSO (CFPSO), and the Comprehensive Learning Particle Swarm Optimization (CLPSO) algorithms to real-valued optimization problems, i.e. microwave absorber design, and linear array synthesis. Moreover, the authors use discrete PSO optimizers such as the binary PSO (binPSO) and the Boolean PSO with a velocity mutation (BPSO-vm) in order to solve discrete-valued optimization problems, i.e. patch antenna design. Additionally, the authors apply and compare binPSO with different transfer functions to thinning array design problems. In the case of a multi-objective optimization problem, they apply two multi-objective PSO variants to dual-band base station antenna optimization for mobile communications. Namely, these are the Multi-Objective PSO (MOPSO) and the Multi-Objective PSO with Fitness Sharing (MOPSO-fs) algorithms. Finally, the authors conclude the paper by providing a discussion on future trends and the conclusion.

A Dual-Broadband Dual-Polarized Fylfot-Shaped Antenna for Mobile Base Stations Using MIMO Over-Lapped Antenna Subarrays

This paper proposes a novel design of a dual-broadband dual-polarized antenna for mobile communication base stations. The proposed antenna is Fylfot-shaped and covers 0.7–0.96 and 1.7–2.7 GHz simultaneously (with S11 ≤ −10 dB), which are the two common frequency bands for mobile communication systems. Three resonant frequencies are produced in the proposed design where two of them are independently controlled to achieve the dual-broadband performance. A prototype of the proposed antenna has been developed and tested. The results demonstrate that the antenna has high isolation between its ports, high polarization purity, and stable radiation patterns across both the frequency bands. A new linear array is proposed and implemented. Unlike reported dual-band base station antenna arrays, the proposed array uses a novel technique of two MIMO overlapped subarrays with shared radiating antenna elements. The overlapped subarrays have excellent frequency diversity performance with low envelope correlation coefficients. The array has been found to have the same performance as a standard conventional base station antenna but with 25% less number of antenna elements, which leads to a smaller size and lower cost. The simple antenna structure and the novel smart MIMO overlapped antenna subarrays technique give the design the privilege to be an ideal candidate for a low-cost directive base station antenna.

Dual-Band Base Station Array Using Filtering Antenna Elements for Mutual Coupling Suppression

This paper presents a novel dual-band base station antenna array using filtering antenna elements for size miniaturization. It consists of two $1 \times 6$ subarrays arranged side by side, which are designed for Digital Cellular System (DCS: 1710–1880 MHz) and Wideband Code Division Multiple Access (WCDMA: 1920–2170 MHz) applications. The two subarrays are composed of filtering antenna elements with high in-band radiation efficiency and out-of-band radiation rejection levels. The radiation of the DCS subarray is suppressed in the WCDMA band and vice versa. Mutual coupling between the two subarrays, therefore, can be suppressed and high isolation can be obtained with reduced subarray spacing. For demonstration, a dual-band filtering antenna array is designed and fabricated. The overall width of the array is only 206 mm, which is much narrower than that of typical industrial products ( $\sim 290$ mm). An isolation of 35 dB is obtained between the two subarrays without any decoupling network. The measured antenna gains are about 14.2 and 14.5 dBi for DCS and WCDMA bands, respectively, and the 3-dB beamwidths of the horizontal radiation patterns are 65° ± 5°. In addition, null filling below the main beam in the vertical radiation patterns is realized by elaborately designing a feed network to manipulate the output magnitude and phase of each array element. The proposed array is suitable for potential base station applications.

A Dual-Band High-Gain Base-Station Antenna for WLAN and WiMAX Applications

A dual-band base-station antenna with high gain is proposed in this letter. The antenna consists of a pair of planar patches and vertical shorted patches. Each of the two planar patches is composed of three U-shaped slots that differ in size. The bigger U-shaped slots that are connected to vertical patches operate at high frequency (3.5 GHz), and the smaller ones work at low frequency (2.4 GHz), which can be applied to wireless local area network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) operations. This antenna also exhibits high gains of near 8.0 and 11.0 dBi at the low and high working frequencies, respectively. Good cross-polarization performance is also verified by measured results. It is also demonstrated that the two working bands can be flexibly controlled by suitable changes of corresponding parameters of U-shaped arms.

Pareto Optimal Design of Dual-Band Base Station Antenna Arrays Using Multi-Objective Particle Swarm Optimization With Fitness Sharing

The design of dual-band base station antennas under constraints for mobile communications is addressed in this paper. Given the antenna geometry, the method of moments (MoM) is used to compute the antenna characteristics. Two distinct multi-objective evolutionary algorithms are applied in order to find the Pareto front of the feasible solutions that satisfy the design constraints. In the present work, the Multi-Objective Particle Swarm Optimization with fitness sharing (MOPSO-fs) is compared with the Nondominated Sorting Genetic Algorithm-II (NSGA-II) in order to optimize the antenna geometry. Two design cases are presented. The first case is a five-element array operating in GSM1800/UMTS frequency bands. The second base station antenna array consists of six elements operating in UMTS/WLAN (2.4 GHz) frequency bands.