This invention relates to an hourglass-shaped with wedge magneto-electric dipole antenna. In particular, the operating frequency of the antenna has a wider bandwidth by adding two pairs of wedges. The antenna is mechanically designed and easy to fabricate with die-casting, thus saving cost since only a single die is required for mass fabrication with low errors and large quantities.
The outstanding features of 5G technology (5th Generation—fifth-generation wireless mobile network technology) compared to previous technologies are its superior transmission speed and the rapid response of wireless networks. Not only inheriting outstanding technologies of the previous 4G technology, but 5G technology also applies new technologies such as Massive MIMO (multiple input multiple output) with up to 64 receiver/transmitter ports or beamforming to increase the number of concurrent users; and other technologies to increase link diversity, enhancing message reliability and latency.
To expand bandwidth, 5G technology has been researched and developed at higher frequency bands, including two main bands, the sub-6 GHz frequency band, and the 20 GHz to 60 GHz frequency band called Millimeterwave-mmW. Operating at higher frequencies makes the bandwidth expandable from 100 MHz at 4G up to 400 MHz at the sub-6 GHz band and 2 GHz at the mmW band. In Vietnam, two licensed n41 2.6 GHz and n77 3.7 GHz bands are allowed for 5G. Therefore, the dual-polarization, high isolation, and wideband antenna (covering all frequencies of 3G/4G/5G at sub-6 GHz) are required for base station application. This antenna structure must be suitable for mass production with low error and stable operation and low cost.
There are different configurations of wideband, dual-polarized antennas designed for base stations in recent years, such as patch antennas, electromagnetic dipole antennas, folding electric dipole antennas, and electric cross-dipole antennas. Patch antennas are the most popular as are compact and low cost but have narrow bandwidths. Other antenna structures such as folding electric dipole and cross dipole have a wide bandwidth, good isolation, and XPD (Cross-Polar Discrimination), but their structures are complex and often designed in the form of microstrips, thus the performance will not be stable under the cold and hot weather conditions. Despite noteworthy advantages, these antennas have intricate designs and are often 3-D printed circuit antennas, thus they generally require extra strengthened frames, making them less suitable for industrial mass manufacturing. This problem may be solved by using mechanical antennas since they can operate well in adverse weather conditions, have fewer fabrication errors, and are ideal for mass production because they do not require healing. One of the antenna structures being widely used in the array of base stations is the magneto-electric dipole antenna with characteristics that ensure wideband as well as dual-polarization requirements. Its-dual polarization has a stable radiation pattern over a wide frequency range.
Most magneto-electric dipole antenna structures are microstrip. Although their structures are simple, low weight and easy to manufacture but it is prone to errors during welding and mounting, making them unsuitable for industrial production. Casting technology is currently very popular for antenna fabrication because it is easy to produce in mass, has high mechanical strength, can work well in bad weather conditions, and so on. It is also compatible with microstrip technology, making it a good candidate for element base station antenna. However, mechanical construction has limitations in mold making or design that prevent the antenna from reaching the electric requirements because the impedance matching structures are not too flexible. Therefore, it is necessary to master an analysis method like characteristic mode to understand the radiation part of the antenna so that it can be optimized in the antenna design in a short time.
This invention provides the design of a mechanical dual-polarized magneto-electric dipole antenna, optimally designed for mass production. The proposed antenna structure achieves wide bandwidth, high gain, and high isolation, which can ensure stable multi-band operation at the sub-6 GHz frequency band. In addition, the authors have also proposed the method to add two wedges on each radiator element using the characteristic mode to adjust the operating frequency of the antenna so that the antenna can exhibit optimal performance at a desired frequency. This design can also be easily adjusted to operate at different frequency ranges without having to design a new antenna structure.
The purpose of the invention is to propose a mechanical antenna structure with good isolation, a wide bandwidth that can cover most of the frequency range of 5G technology with a high gain at the operating bands. This antenna gives an economic benefit, and flexibility in hardware deployment for telecommunication infrastructure. The antenna is mechanically and easy to fabricate with die-casting, thus saving cost since only a single die is required for mass fabrication with little error and easy assembly in the industry where a large quantity is required.
To achieve the above purposes, the antenna consists of two magneto-electric dipoles placed orthogonal to each other to create ±45 degree of the dual-polarization, the main antenna structure includes:
The antenna uses two pairs of Γ-shaped feeds to simultaneously excite two magneto-electric dipoles placed orthogonal to each other, creating ±45 degree linear polarizations. The electric dipole is designed using the characteristic mode analysis, the antenna achieves a wide bandwidth, high peak gain, low back lobe, and side lobe level, which can easily be tuned to suitable frequency for sub-6 GHz bands of all the operators in Vietnam.
a-c shows the simulated radiation patterns results of each mode (a) current mode J1, (b) current mode J2, (c) current mode J3;
Details of the invention The structure of the proposed 3G/4G/5G radio base station antenna in the invention is shown in
In general, the proposed antenna is developed from a basic magneto-electric dipole antenna (
The electric dipole (1-1) is designed in an hourglass shape to obtain a wideband. The resonant frequency of the conventional electric dipole depends on its length (that corresponds with the wavelength at the operating frequency), while the hourglass shape electric dipole does not only depends on the length but also depends on the angle θ. Therefore, it can resonate at different frequencies corresponding with the values of length and opening angle. The dimensions of the electric dipole (1-1) include the length of the dipole Ld and the angle θ (
where, Df is calculated by
Meanwhile, the angle value θ is directly related to the bandwidth of the antenna.
The length of the δ2 feeding for the second antenna includes Lf2+Df+Lf21 and is calculated by
The difference of the length between the two feeding sections ensures the isolation between the two antennas. Where:
After calculation and simulation, the antenna will be analyzed using characteristic mode analysis to improve antenna performance as well as to adjust the resonant frequency if the resonant frequency does not match the design requirement. This is the new point of the antenna design in this invention. The characteristic mode analysis helps the designer to deeply understand the radiation characteristics and current distribution on the surface of the structure, then the designers propose a suitable adjustment to improve antenna quality such as the resonant frequency, expanding the bandwidth, increasing the quality factor of the antenna and proposing the new antenna structures.
The characteristic mode analysis method describes the radiation structures according to each characteristic mode instead of calculating and simulating the Full-wave method as traditional. The equation describes the properties of the structure is shown in the following equation:
X(Jn)=λnR(Jn) (4)
where:
R (Jn) is the resistance matrix of the structure with the current mode Jn,
X(Jn) is the reactance matrix of the structure with the currents mode Jn,
Jn is the current mode representing for the surface of the conductor, dependent on its shape and size, and independent on the excitation source.
The value λn indicates the resonance level of each mode. The larger the magnitude of λn is, the more power is stored in the mode. The sign of λn indicates the mode-related the power storage pattern. The mode is inductive when λn is positive, and the mode is capacitive when λn is negative. The resonance mode on the structure is at that frequency when λn=0 then. In a simple way, λn expresses the resonant level of a mode through Modal Signaling (MS) as following equation:
The MS parameter also indicates the radiation level of the mode. When MS=1, it implies that the mode is in resonant state and radiates with maximum efficiency (for example, the MS parameter in
A radiator structure is analyzed to a linear of a finite number of characteristic modal currents, each one excites its own characteristic mode, independent with other currents. Therefore, this property can be applied to analyze the structure according to the properties of each mode and the excitation of the mode of interest, allowing adjust the desired frequency. This is the idea that the authors developed the antenna structure in the invention.
The authors have studied and calculated the resonant frequencies f1 and f2 using the characteristic mode, which includes three resonance modes. In which, the first and the second mode determinate the resonant frequency f1 and the third mode affect the resonant frequency f2 as shown in
As seen from
The authors conducted an implemented a wideband antenna for the 64T64R base station application that can work well at two frequency bands: n41: 2.496 GHz-2.69 GHz (center frequency is 2.6 GHz) and n77: 3.6 GHz-3.8 GHz (center frequency is 3.7 GHz) according to the international 3GPP standard. In which, the main frequency bands at 2.6 GHz and 3.7 GHz frequencies are considered in the design, it is licensed for 5G purpose in Vietnam.
The main required specification of an antenna element for a 5G base station are listed in Table 1:
From the requirement above, the authors have designed a mechanical magneto-electric hourglass-shaped antenna with four wedges, this antenna has ±45 degree linearly polarization and the peak gain more than 7 dBi.
The detail of designed antenna with all parameters as presented as follows:
The parameters of the proposed antenna is described in the following Table 2 and Table 3, where λ1 and λ2 is wavelengths at 2.6 GHz and 3.7 GHz:
The results of the proposed antenna are shown in
Characteristic mode analysis is used to analyze the antenna structure as the authors are presented. Simulation results of MS values of the structure are shown in
As shown in
The adding wedges using the characteristic mode analysis changes the resonant frequency from 2.46 GHz to 3.7 GHz and improves the radiating efficiency. The proposed antenna with a bandwidth from 2.42 GHz to 4.2 GHz covers most of the sub-6 GHz frequency bands for 5G technology. Table 4 and
This invention presents a wideband dual-polarized hourglass-shaped with wedges antenna for 3G/4G/5G base station. This magneto-electric antenna element consists of two wideband hourglass-shaped electric dipoles combined with a bent magnetic dipole to obtain ±45-degree dual-polarization. The balun feeding is designed using a basic Γ-shape structure. A highlight of the antenna structure is adding four wedges at the outmost of the two electric hourglass-shaped electric dipoles to adjusts the resonant frequency and therefore improve antenna efficiency at the frequency bands of interest. The antenna element has a stable radiation pattern and a peak gain of 8.3±0.3 dBi over the entire frequency range. The fully mechanical antenna is easy to fabricate with die-casting and is suitable for mass production with low installation cost and errors, requiring low correction cost.
While a preferred embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appended claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.
Number | Date | Country | Kind |
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1-2021-04084 | Jul 2021 | VN | national |