Electrical Downtilt Research Articles

A Miniaturized Wideband Dual-Polarized Antenna Based on Mode-Control Principle for Base-Station Applications

In this paper, a miniaturized wideband dual-polarized antenna and its array are proposed and demonstrated for practical base-station applications. “Mode-control” principle is employed to facilitate both miniaturization and bandwidth-enhancement of the proposed antenna element. To be more specific, by inserting meander lines into a traditional crossed loop-dipole antenna, its first resonant mode can be shifted to a lower frequency without increasing the aperture size, implying that a total size reduction can be achieved. Meanwhile, by embedding a pair of crossed straight strips into the coupling region of the crossed loop-dipole antenna, its second resonant mode can be moved to a higher frequency with a good impedance matching, thereby improving the impedance bandwidth significantly. A prototype of the proposed antenna with a small radiator size of only 0.33λ x 0.33λ (λ is the wavelength at the center frequency of 2.2 GHz) is designed, fabricated and measured. Measurements show that in the target frequency band from 1.71 GHz to 2.69 GHz, i.e., 2G/3G/4G bands, a relatively good impedance matching with the VSWR of less than 1.65 and a high isolation of greater than 28 dB are obtained by the proposed antenna element. Also, a stable gain of 8.7±0.5 dBi and a stable 3-dB beamwidth of 64.8±2.7° at the H -plane are respectively achieved. A multiple-input-multiple-output (MIMO) antenna array consisting of two subarrays with electrical down-tilt is further developed for practical base-station applications. Each subarray is composed of ten antenna elements. The overall width of the array is only 260 mm, which is much narrower than that of typical industrial products (~305 mm). Measured results show that the antenna array has also achieved good performances such as wide impedance bandwidth, high isolations among different ports, and stable radiations over the 2G/3G/4G bands.

Performance Analysis and Evaluation for Active Antenna Arrays Under Three-Dimensional Wireless Channel Model

In this paper, we establish a full 3-D channel model to support the performance analysis and evaluation of active antenna array (AAA)-based wireless communication systems. We analyze and compare the impact of three different downtilt methods employed in AAA antennas, electrical downtilt (ET), mechanical downtilt (MT), hybrid downtilt (the combination of ET and MT), on the antenna patterns, which would notably impact the performance of mobile wireless communication systems. We compare the performances of the wireless communication system throughput based on the 2-D and 3-D wireless channel models using passive antenna arrays. We also investigate the system performance in terms of the capacity and coverage with different AAAs under the 3-D channel. After the performance analysis and evaluation, we have observed that the downtilt optimization may introduce significant gains in coverage and capacity for individual antennas with smaller beamwidth of the vertical patterns, but may not lead to notable gains for individual antennas with relative larger beamwidth of the vertical patterns.

A Miniaturized Base Station Antenna With Novel Phase Shifter for 3G/LTE Applications

This paper presents a new type of miniaturized base station antenna array, which consists of a metal reflector, six upper-band dipoles, and a couple of ladder sidewalls, operating over 1.71–2.69 GHz (DCS/PCS/UMTS/LTE). Meanwhile, this paper also proposes a novel miniaturized phase shifter with one input and five outputs to enable the antenna array to achieve electrical downtilt (0°–10°) in the operating frequency band. Three different sidewalls are applied in the proposed antenna array to compare their performance. Simulated results demonstrate that the antenna array with ladder sidewalls can achieve an excellent performance, and this proposed phase shifter also has good electrical properties to help the proposed antenna array realize downtilt. The proposed antenna array and phase shifter are fabricated and measured, and the measured results show that the antenna array has good radiation characteristics, including low-voltage standing wave ratio ( 31 dB), low third-order passive intermodulation (3 30 dB), and high cross-polarization discrimination at ±60° azimuth (>11.5 dB) in all frequency bands and electrical downtilt angles. The proposed antenna array exhibits an acceptable gain of 15 ± 1.1 dBi across the operational frequency band.

A Novel Dual-Broadband Dual-Polarized Electrical Downtilt Base Station Antenna for 2G/3G Applications

A novel dual-broadband dual-polarized base station antenna array with compact structure and low profile is proposed in this paper for the existing mobile communication system operating over 0.79–0.96 GHz (European Digital Dividend/CDMA/GSM) and 1.71–2.17 GHz (DCS/PCS/UMTS). The antenna array is mainly composed of five lower-band elements, ten upper-band elements, some U-shaped metal baffles, and a metal reflector with specific shape. In order to reduce the overall size of the antenna array, lower-band element is designed as octagon aperture shape that upper-band elements can be embedded in it. Two kinds of radiation elements (five for each kind of element) are applied in the antenna array as upper-band elements to achieve better radiation performance. The proposed antenna array achieves electrical downtilt (0°–14° and 0°–10° at lower frequency band and upper frequency band, respectively) by adjusting input amplitude and phase of each array element. Measured results demonstrate that the antenna array has good broadside radiation characteristics, including low voltage standing wave ratio (VSWR 28 dB), low backlobe level (>25 dB), high cross-polarization discrimination (>20 dB), and stable radiation pattern with horizontal half-power beamwidth (HPBW) 65° ± 5° at both frequency bands and all electrical downtilt angles. The peak gains of 15.1 and 17.3 dBi are obtained at lower and upper bands respectively. Owing to these advantages, the antenna array is suitable for existing 2G/3G applications in modern mobile communication systems.

A Wideband Dual-Polarized Antenna With Two Independently Controllable Resonant Modes and Its Array for Base-Station Applications

A wideband dual-polarized antenna with two independently controllable resonant modes for 2G/3G/4G bands is proposed. Its radiator mainly consists of two crossed stepped-width loop dipoles loaded with two crossed straight dipoles. Two approaches are adopted to design the proposed antenna with large freedom. First, by replacing the traditional uniform-width loop dipole with a stepped-width one, the first resonant mode can be adjusted independently by controlling the width ratio of the loop. Second, a pair of crossed straight dipoles are embedded into the gap of the crossed loop dipoles, and the second resonant mode can be controlled independently by altering the length or position of the straight dipoles. Measurements show that the antenna achieves an impedance bandwidth of 54.5% with VSWR< 1.5 (1.68–2.94 GHz) and isolation of greater than 28.5 dB within the bandwidth. Also, an antenna array with ten elements is developed with electrical downtilt from 0° to 8° for practical base-station applications.

Energy Saving Scheme for Multicarrier HSPA + Under Realistic Traffic Fluctuation

In the near future, an increase in cellular network density is expected to be one of the main enablers to boost the system capacity. This development will lead to an increase in the network energy consumption. In this context, we propose an energy efficient dynamic scheme for HSDPA + (High Speed Downlink Packet Access-Advanced) systems aggregating several carriers and which adapts dynamically to the network traffic. The scheme evaluates whether node-B deactivation is feasible without compromising the user flow throughput. Furthermore, instead of progressive de-activation of carriers and/or node-B switch-off, we evaluate the approach where feasible combination of inter-site distance and number of carriers is searched to obtain best savings. This is done by also considering the effect of transition delays between network configuration changes. The solution exploits the fact that re-activation of carriers might permit turning off other BSs earlier at relatively higher load than existing policies. Remote electrical downtilt is also considered as a means to maximize the utilization of higher modulation and coding schemes in the extended cells. This approach promises significant energy savings when compared with existing policies - not only for low traffic hours but also for medium load scenarios.

Vertical sectorization in self-organizing LTE-advanced networks

Cellular radio networks continuously evolve to respond the exponential growth in data traffic volume in mobile communications. Active antenna technology contributes to this evolution by introducing vertical sectorization, which splits the horizontal sector into two subsectors with respect to the elevation plane and doubles the number of cells that can be deployed. However, in order to guarantee a reliable and near-optimal operation of vertical sectorization in a system that applies universal frequency reuse, such as LTE-advanced, co-channel interference mitigation is essentially needed. In this article we propose a decentralized self-optimization method that can be used to mitigate the undesirable inter-cell interference by self-tuning the electrical antenna downtilt toward the optimal antenna elevation angle. The performance evaluations for the proposed self-optimization method are carried out for both coordinated and uncoordinated subsector transmission scenarios within the LTE-advanced framework using a dynamic LTE-advanced compliant system level SON simulator. Based on the extensive performance evaluations carried out for a realistic urban scenario, it is found that self-optimization improves the vertical sectorization performance 25 % in terms of virtual load. Furthermore, the performance gain reaches up to 30 % when vertical vectorization is provided with dynamic point selection and muting feature. Therefore, the article concludes that in LTE-advanced networks vertical sectorization can largely benefit from the antenna self-optimization and outperform the traditional horizontal sectorization approach with low algorithmic complexity .

Metrocell Antennas: The Positive Impact of a Narrow Vertical Beamwidth and Electrical Downtilt

This article discusses the positive impact that metrocell antennas with a narrow vertical beamwidth and electrical downtilt can have on heterogeneous cellular networks. Using a model of random cell placement based on a Poisson distribution, along with an innovative three-dimensional (3-D) building model that quantifies blockage due to shadowing, it is demonstrated that the network spectral efficiency and average user through-put both increase as the vertical beamwidth decreases and downtilt is applied to metrocell transmission. Moreover, the network becomes more energy efficient. Importantly, these additional gains in network performance can be achieved without any cooperation or exchange of information between macrocell base stations (BSs) and metrocells.

Impact of Electrical and Mechanical Antenna Downtilt on the Uplink of a WiMAX System with Soft Frequency Reuse

Impact of Electrical and Mechanical Antenna Downtilt on the Uplink of a WiMAX System with Soft Frequency Reuse

Optimum Antenna Downtilt Angles for Macrocellular WCDMA Network

The impact of antenna downtilt on the performance of cellular WCDMA network has been studied by using a radio network planning tool. An optimum downtilt angle has been evaluated for numerous practical macrocellular site and antenna configurations for electrical and mechanical antenna downtilt concepts. The aim of this massive simulation campaign was expected to provide an answer to two questions: firstly, how to select the downtilt angle of a macrocellular base station antenna? Secondly, what is the impact of antenna downtilt on system capacity and network coverage? Optimum downtilt angles were observed to vary between – depending on the network configuration. Moreover, the corresponding downlink capacity gains varied between – . Antenna vertical beamwidth affects clearly the required optimum downtilt angle the most. On the other hand, with wider antenna vertical beamwidth, the impact of downtilt on system performance is not such imposing. In addition, antenna height together with the size of the dominance area affect the required downtilt angle. Finally, the simulation results revealed how the importance of the antenna downtilt becomes more significant in dense networks, where the capacity requirements are typically also higher.

The Influence of Downtilt of Antennae Directional Diagrams on the Formation of Mobile Network Cells and Estimation of Electromagnetic Field Intensity

The possibility of making use of antennas with continually adjustable mechanical and electrical downtilt of directional diagrams in the formation of mobile network cells has been presented in the paper. The quantitative evaluation of the changes in the intensity parameters of the electromagnetic fields generated by the antenna in the near environment has been made using mechanical and electrical downtilt of directional diagrams. Analytical EMF calculation method errors occurring due to inaccurate evaluation of antennas diagrams and their tilting on the vertical plane have been analysed. Ill.7, bibl.6 (in Lithuanian; summaries in Lithuanian, English and Russian).