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Microwave Tech

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Microwave Tech

Microwave Tech

Antenna layout: a solution using FEKO simulation
2021-07-08
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Author:Dag

FEKO helps a large number of OEM manufacturers and their suppliers in the industrial field to solve the EMC problems they encounter in the process of product design, analysis and test verification. By using FEKO and other simulation tools, the number of trial samples and the number of tests are reduced, and the traditional test driven development process is transformed into simulation driven design. The important applications of FEKO in the field of EMC / EMI include electromagnetic radiation, electromagnetic anti-interference, lightning effect, high intensity radiation field (HIRF), electromagnetic pulse (EMP), electromagnetic shielding, electromagnetic radiation hazards and antenna coupling.


Antenna layout

In free space, there are many technologies to choose. In practical applications, such an antenna is installed on the solid structure, which seriously affects the free space radiation characteristics of the antenna. For the antenna installed on a large platform, it is very difficult to measure its radiation characteristics, sometimes even impossible to measure. Therefore, the challenge of accurate simulation is the interaction between antenna and large electronic environment. Over the years, FEKO has gained a good reputation in antenna layout, becoming a standard EMC/EMI simulation tool for antenna layout in vehicles, aircraft, satellites, ships, cellular base stations, towers, buildings and other places. The mlfmm, the progressive Solver (PO, rl-go and UTD) in FEKO and the model decomposition work together to make FEKO an ideal tool for solving antenna layout and co location interference problems on large or super large electronic platforms.

Antenna layout on fighters and ships (surface current shown).jpg

Antenna layout on fighters and ships (surface current shown)

FEKO simulation

The isolation between multiple antennas on the platform (Figure 1) is one of the issues that FEKO is best at dealing with. The aircraft model is a test model presented at the EMC Computational Electromagnetics (CEMEMC) Symposium. It is a modified version of EV55 (belonging to the HIRF-SE FP7 EU project, EVEKTOR, spol.s r.o. and the HIRF SE Alliance have its copyright). The user only needs to select one of the solvers in FEKO for calculation according to the type of problem to be solved, the electrical size and complexity, etc. One way to quickly calculate mutual coupling between antennas in FEKO is through S-parameters. Users can visually display the effect of changes in antenna load on the coupling between antennas through a calculation without repeatedly starting the solver, and visually display the effect of a large number of antenna ports. Coupling and plotting the co-site interference matrix to identify and analyze the level of coupling strength. In addition, FEKO's model decomposition technology combined with antenna equivalent and EMC equivalent disturbance sources can reduce the demand for computing resources.

By FEKO simulation, the distribution of magnetic field intensity inside and outside the aircraft at 1GHz is obtained.jpg

By FEKO simulation, the distribution of magnetic field intensity inside and outside the aircraft at 1GHz is obtained

EMI design challenges

There are many cases of using FEKO to solve EMI problems. For example, the radiation field from the vehicle cable bundle is coupled to the windshield antenna (and to other forms of antenna), which is also related to the CISPR-25 EMC test standard of the automotive industry (CISPR is the International Special Committee for Radio Interference, and is also an international radio station. International Special Committee). Noise signals will propagate through different cables in the vehicle, and the radiation fields of these cables will be coupled to different antennas, thereby reducing the performance of analog or digital broadcasting systems. To solve this problem, FEKO includes a complete comprehensive cable modeling tool to analyze cable radiation (and anti-interference). This tool and the windshield antenna modeling and solution technology developed specifically for real windshield antenna applications are suitable for analyzing and solving these challenges (Figure 2). Figure 2b shows the radiated electric field at two positions 10 meters away from the left and right sides of the car. Each position point includes the vertical and horizontal polarization field strength values obtained by simulation.

Simulation model of car model with windshield antenna.jpg

Figure 2: simulation results of vehicle model with wind window antenna, equivalent source of wire harness and engine control unit (ECU) (a) and near-field electric field intensity at 10m around the vehicle and simulation model based on measurement system (b)

Unique performance

FEKO is easy to use, and has a comprehensive, accurate, reliable, fully parallelized set of solvers that support true hybrid solving, including the method of moments (MoM), multi-layer fast multipole (MLFMM), finite element (FEM), and time Finite difference domain (FDTD), physical optics/large surface element physical optics method (PO/LE-PO), ray geometric optics (RL-GO) and uniform diffraction theory (UTD), etc. These solvers have been widely used in the simulation of antenna design and antenna layout, EMC, radar cross section (RCS), bio-electromagnetics, radome, and radio frequency devices. According to the electrical size of the problem to be solved and the complexity of the problem, you only need to choose to use this one or the other solver. FEKO's comprehensive cable modeling tool solves EMC problems involving complex cables. The special algorithm used by FEKO for cable analysis is the multi-conductor transmission line method (MTL) and the MoM/MTL hybrid method. The latter is suitable for analysis scenarios when the ground below the cable is discontinuous. As part of the Altair HyperWorks computer-aided engineering platform, FEKO brings a series of additional differentiated functions. Thanks to Altair's unique authorization system, these functions can be used without additional cost. With the help of the industry's most famous finite element analysis pre-processor module HyperMesh, it can reduce the time of complex CAD model cleaning (including automatic cleaning) and meshing; using HyperStudy, FEKO users can use the design of experiments method (Design of Experiments) to Optimize design, including analysis of other physical characteristics; use activate to design and analyze circuits (such as DC/DC converters).


Antenna design

FEKO is widely used in the analysis and design of antennas in the industry, and is suitable for radio and TV broadcasting, wireless systems, cellular mobile communication systems, remote keyless unlocking systems, tire pressure monitoring systems, satellite positioning and communications, radar, RFID and other fields. The FEKO method of moments (MoM) solver is widely used in antenna design. In addition, because this software not only has the function of model decomposition (generating and using equivalent sources), it also combines multi-layer fast multipole algorithm (MLFMM) and other comprehensive functions. Wave acceleration method, or physical optics (PO), ray tracing geometric optics (RL-GO) or uniform diffraction theory (UTD) and other asymptotic methods, so it can efficiently align reflector antennas, radar antennas and equipped antennas Cover the antenna for analysis. FEKO also has functions such as the Domain Green's Function Method (DGFM) suitable for large finite arrays, so it can analyze antenna arrays accurately and efficiently.

Current on a 1.5 GHz 2x2 microstrip patch antenna array.jpg

Current on a 1.5 GHz 2x2 microstrip patch antenna array

Electromagnetic compatibility 

Electromagnetic compatibility (EMC) has become a hot topic of OEM and its suppliers in many industries. It is very important to integrate components and equipment into the system without electromagnetic problems. It is also important to comply with EMC regulations. For many years, FEKO has been used in EMC to simulate electromagnetic interference (EMI) and electromagnetic sensitivity or immunity (EMS). FEKO includes a complete cable modeling tool to analyze the radiation generated between the cable and other cables, antennas or equipment, which can cause the formation of interference voltage and current, and cause system failure. FEKO is also used to simulate the radiation emission, shielding effectiveness, radiation hazard analysis, electromagnetic pulse (EMP), illumination effect and high intensity radiation field (HIRF) of electronic control unit (ECU) in the system.

Cable modeling interface in FEKO

Cable modeling interface in FEKO

Scattering and RCS

When the object is exposed to the incident electromagnetic field, the scattering characteristics of the object are related to the spatial distribution of the scattering energy. Two typical cases in which scattering is very important: when designing a system to detect objects, such as collision detection system; And designing objects to increase or decrease the detection capability of the transmitter, such as the design of stealth aircraft. Various digital methods of FEKO, including mlfmm, rl-go and Po, and post-processing function, can efficiently and accurately solve the scattering and radar effective cross section (RCS) problems.

RCS strength view of helicopter.jpg

RCS strength view of helicopter

Waveguide components and microstrip circuits

Since the first realization of space communication, waveguides have been widely used in national defense, aerospace, navigation and communication industries, such as couplers, filters, circulators, isolators, amplifiers and attenuators. FEKO can be used in the simulation of waveguide components, usually using waveguide port excitation, FEKO's mom and finite element method (FEM) solver.

Microstrip technology is used to design planar circuits, such as couplers, resonators and filters. When the trace length of the circuit can be compared with the wavelength, full wave 3D EM analysis is used. The plane layered Green's function and the surface equivalent principle (SEP) formula in FEKO are very suitable for the analysis of printed microwave circuits.

Simulation of wr-90 magic-T coupler driven by waveguide Delta.jpg

Simulation of wr-90 magic-T coupler driven by waveguide Delta

Bioelectromagnetics

EM simulation plays an important role in the development of biomedical technology. Simulation can provide valuable reference for the interaction of electromagnetic fields in or near human body. Due to the nature of tissue loss, emitter design usually focuses on ensuring that enough signal is emitted and the signal is not lost in the anatomic load, while meeting the rules of limiting the specific absorption rate and maximum temperature increment in the human body. Typical applications are related to mobile and wireless devices, RF fields in cars, hearing aids, human antenna, MRI, implants, and hypothermia. FEM, FDTD and mom / FEM in FEKO are very suitable for these applications. FEKO includes a database of different mannequins.

SAR calculation for the model of wearing a pocket radio in a car

SAR calculation for the model of wearing a pocket radio in a car

Design of matching circuit

An important task for antenna design engineers is to ensure that the bandwidth and efficiency meet the technical specifications. It can be realized by changing the physical structure of the antenna or using matching circuits. Optenni lab is developed by optenni Ltd. and can be purchased through Altair sales channel. The tool provides automatic matching circuit generation and optimization program. Users only need to specify the required frequency range and the number of components in the matching circuit, and then optenni lab provides the topology selection for optimizing the matching circuit. Optenni lab uses accurate inductor and capacitor models from major component manufacturers, and conducts rapid tolerance analysis to ensure that the matching circuit produced meets the design standards, making it an ideal supplement to FEKO.


Antenna synthesis tool

Antenna magus is an antenna synthesis tool from magus (Pty) Limited, which can be purchased through Altair sales channel. It provides a large number of searchable antennas, in which we can find and design antennas that meet user specifications. The FEKO model that can run immediately can be exported, making antenna magus an ideal tool to complement FEKO.