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Antennas are an important part of mobile communication systems. With the development of mobile communication technology, antenna forms are becoming more and more diversified, and the technology is becoming more and more complex. Entering the 5G era, massive MIMO and beamforming have become key technologies, which promote the evolution of antennas in the direction of activation and complexity. Antenna design methods also need to keep pace with the times, adopt advanced simulation methods to respond to complex design requirements, and meet the ever-increasing performance requirements of antennas in the 5G era.
5G and phased array
The 5G era will be extremely rich in applications. 5G networks need to adapt to scenarios such as large bandwidth, high reliability, low latency, and large connections. This requires 5G antennas to support more channels, flexible real-time beam adjustment, and support high-frequency communications., Its key evolution direction is the massive MIMO active antenna. Compared with traditional MIMO, massive MIMO can effectively improve the performance of the core is based on phased array technology.
The so-called phased array refers to a type of array antenna that changes the beam direction of the directional pattern by controlling the feed phase of the radiating element in the array antenna.
The main purpose of the phased array is to realize the spatial scanning of the array beam, the so-called electrical scanning. The phased array was mainly used in the military in the early days-phased array radar. Due to its fast scanning speed and strong multi-task capability, phased array radar has been widely used in the field of military radar and has become one of the symbols of military strength.
In addition, phased array technology is also widely used in civil fields such as weather forecasting.
Picture contains sky, outdoor, building description has been automatically generated Picture contains building, sky, outdoor, dome description has been automatically generated
The picture comes from the Internet. The left picture is a strategic early warning radar, the right picture is a weather radar
Looking back at the development history of mobile communications, it can also be seen from the evolution trend of base station antennas that phased array technology is an inevitable choice for improving system capacity and spectrum utilization, reducing interference, and enhancing coverage in the 5G era:
First of all, from passive antennas to active antenna systems, this means that antennas may be intelligent, miniaturized (co-designed), and customized. In the future, the network will become more and more detailed, and it will be necessary to customize the design according to the surrounding scenes. For example, the deployment of stations in urban areas will be more refined, rather than simple coverage. 5G communication will use high frequency bands, and obstacles will have a great impact on communication. Customized antennas can provide better network quality.
Second, the systemization and complexity of antenna design, such as beam arrays (to achieve space division multiplexing), multi-beams, and multiple/high frequency bands. These all put forward high requirements on the antenna, which will involve the entire system and compatibility issues. In this case, the antenna technology has surpassed the concept of components and gradually entered the design of the system.
Phased Array Simulation Design
The design of phased array can be divided into two parts: antenna array and beamforming network.
Antenna array design
The antenna array design needs to determine the form and pattern characteristics of the radiating element, the arrangement of the array and its feed form, etc. The array design directly determines the radiation characteristics of the phased array, such as antenna gain, lobe width and maximum scanning range And so on, is one of the key points of phased array design.
1. Design and optimization of radiating unit
Because the phased array antenna has beam scanning characteristics, the selection of its radiating unit has certain requirements and restrictions. There are two types of antennas that are generally suitable as phased array radiating elements:
Aperture antennas, such as open waveguide, waveguide slot antenna, microstrip patch antenna, etc.;
Monopole or symmetrical dipole evolution, such as printed symmetrical vibrator, tapered slot antenna, etc.
In the 5G era, in order to obtain higher channel capacity, a large number of new spectrum resources have been introduced, which has higher requirements for the broadband characteristics of the radiating unit. In addition to the addition of a new frequency band in the Sub 6GHz frequency band, a high-frequency millimeter wave frequency band has also been added, which has more stringent requirements on the form and processing technology of the radiating unit. In addition, under the trend of integration, miniaturization and light weight have become the basic requirements of antenna design. In summary, the form of the radiating element is mostly microstrip patch and half-wave dipole, and the process is mainly in the form of PCB and plastic vibrator.
For the simulation design of the radiating unit, it is particularly critical to accurately solve the performance in the working frequency band. The complex materials and geometric characteristics of the 5G antenna radiating unit, as well as the characteristics of ultra-wideband and multi-frequency bands, have brought great challenges to the simulation design of the radiating unit.
The unique automatic adaptive meshing technology (Adaptive Meshing) in ANSYS HFSS, combined with broadband meshing technology (BAM), can efficiently and accurately obtain the mesh in the whole frequency band, thereby obtaining an accurate response in the whole frequency band.
It is very important to quickly find the optimal design of the radiating element during the simulation design process.
ANSYS HFSS can perform derivative fast tuning and sensitivity analysis based on the parameterized model.
Quickly find the correct variable value, better understand how the variable affects performance, and shorten the development time;
Clarify the most influential parameter categories and focus on highly sensitive design parameters to make the design robust.
After the Derivatives analysis, based on the tuning results, the key variables can be screened out, and the radiating unit can be automatically optimized in HFSS to obtain the optimal S-parameters, antenna pattern, electromagnetic field distribution and other result indicators.
The rapid optimization in the state of large parameter space and multi-parameter space has always been a great challenge for designers. The DoE (numerical experiment) analysis method is an advanced technology to solve this kind of problems. The DoE tool DesignXplorer in HFSS can help accelerate the process of array element design optimization. Before optimization, the design space should be fully explored and optimized to reduce the number of simulations. Quickly determine the feasibility of the design.
In addition, HFSS's latest fast mode can provide fast simulation results of design trends for the early stages of the product design cycle without significantly reducing the accuracy of the solution. As the design is nearing completion, the HFSS quasi-precision function is used for high-precision verification through simple slider settings.
2. Fast analysis of element method array
Phased array unit selection and design optimization are key aspects of phased array design. This process involves the selection and optimization of many schemes and parameters. Therefore, rapid analysis and related optimization analysis are particularly important. For example, the phased array unit spacing is one of the important parameters that affect the radiation characteristics of the phased array antenna.
If the distance between the units is too small, the mutual coupling effect between the units will increase, which is not conducive to accurately configuring the feed amplitude and phase of the phased array elements, so that part of the energy will be stored in the near-field area of the front and cannot be effectively radiated; in addition, the units The pattern in the array will also be distorted, and scanning blind spots will appear when the array antenna is scanned at a large angle.
When the unit spacing is too large, harmful grating lobes will appear in the physically visible space of the phase-scan antenna. Since the grating lobe level is equivalent to the main lobe level, the beam energy of the phased array antenna in the main radiation direction will be greatly reduced.
Therefore, the design and optimization of the array arrangement are particularly critical. When designing the front, engineers need a simulation method that can quickly iteratively optimize repeatedly to obtain the appropriate cell spacing.
The element method in ANSYS HFSS can help engineers quickly evaluate the element spacing and the performance of the elements in the array at the early stage of antenna array design.
