![]() ![]() This tendency is also reflected in the 3D simulation plot. In the 2D polar plot, with the radiation directed toward the lumped port, we can see a slight variation in the pattern’s directionality as the frequency increases. The next set of plots depicts the far-field radiation pattern. ![]() Smith plot displaying the impedance matching properties. The frequency-swept impedance normalized by 50 Ω is plotted near the point shifted from the middle of the plot (approximately 68 Ω). To visualize the impedance matching properties, a Smith plot is generated, with the different colors representing different frequencies. Further, with parameterized geometry parts, it is easy to build the repeated pattern for the radiating structure. Note that the length of the dipole rods decreases gradually with a ratio that is constant to the lumped port. The model itself is housed in a spherical domain enclosed by perfectly matched layers (PMLs) that absorb any outgoing radiation. To terminate the electric field, a 300-Ω resistor is added to the other end of the gap, where a longer pair of rods is located. The antenna is excited via a lumped port that is placed between two body frames at the end of one gap, where a shorter pair of rods is located. The configuration of the log-periodic antenna. Note that the interior portion of the antenna’s body is excluded from the modeling domain, including frames and rods where wave propagation is not anticipated. These frames and the metallic dipole rods are modeled with perfect electric conductor (PEC) boundary conditions, as surface loss is negligible for the relative frequency range. To help our log-periodic antenna take shape, we fit a coplanar diode array through a few metallic body frames. A log-periodic antenna achieves a wider frequency response (bandwidth) through a coplanar array, while a Yagi-Uda antenna achieves a higher gain (directionality) through a driven element and multiple passive elements. ![]() However, the way these two antennas work is quite different. When looking at a log-periodic antenna, you may notice that its shape is similar to a Yagi-Uda type of antenna. Using RF Modeling to Analyze the Design of a Log-Periodic Antenna The COMSOL Multiphysics® software and the RF Module can be used to optimize these designs. Krallis, via Wikimedia Commons.īefore these antennas are ready to obtain EMC/EMI measurements, it is important that their designs are analyzed to ensure accuracy. (We discussed one of the other well-known types, a biconical antenna, a little while back.) The coplanar dipole array type - a popular form of this wideband antenna - is often placed inside an anechoic or reverberation chamber and used to obtain antenna measurements in the UHF range.Īn example of a log-periodic antenna. Log-periodic antennas are one of three well-known test antennas used for this purpose. Running EMC/EMI tests requires specific equipment. By achieving immunity, devices can function as normal when encountering unwanted emissions. In the case of susceptibility, testing shows how devices react in the presence of radio frequency waves, where there is a tendency for breakdown to occur. On the emissions front, tests point out unwanted emissions and potential countermeasures that could reduce the electromagnetic energy that is generated. When thinking about EMC/EMI testing, we can divide its focus into two classes: emissions and susceptibility. Licensed under CC BY-SA 3.0 IGO, via Flickr Creative Commons. This question is at the heart of EMC/EMI testing, and finding the answer helps us modify operations as needed.Ī spacecraft undergoes EMC/EMI testing. ![]() To showcase this, we’ll look at a well-known equipment choice in EMC/EMI testing…ĭoes an electronic or electrical device operate as it should in a common electromagnetic environment? Before such a product is of the quality and safety to bring to market, this is an important question to address. RF modeling is a useful approach to analyzing and optimizing such devices, generating greater confidence in the measurements they obtain. This testing equipment must be designed so that it delivers precise measurements that are reflective of real-world performance. Just as important as these tests is the equipment used to perform them. Compliance testing is used to ensure that various products, processes, and systems meet standard requirements. ![]()
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