Research Internship / Master Thesis: Sidelobe Level Reduction of an 8x8 mmWave Antenna Array via Amplitude Tapering
23.01., Studentische Hilfskräfte, Praktikantenstellen, Studienarbeiten
This work focuses on simulating, implementing experimentally, and validating the efficacy of the two most promising amplitude weighting methods.
Microstrip antennas have been widely adopted due to their low production cost and easy integration into PCB circuits. They have the disadvantage of offering low antenna gain, which is normally compensated by arranging multiple microstrip antennas into an array, whose combined radiation pattern benefits from a beamforming gain. As a side effect, high sidelobes are also induced, which leaks radiation in unwanted directions. Reducing such sidelobes is the focus of this research internship/master thesis.
There are several motivations for eliminating sidelobe radiation. In the context of physical layer security, a legimite transmitter using an array antenna with a beam-based radiation pattern exhibiting high sidelobes increases the attack surface of a passive eavesdropper and compromises the message confidentiality in the communication. In the context of cellular communications, sidelobes account for increased interference in adjancent cells.
In order to counter the sidelobe effects, amplitude tampering techniques are long known in the literature. The most interesting ones for practical implementations due to their good compromise between sidelobe level and half-power bandwidth include the Dolph-Tschebyscheff, Kaiser, Blackman and Hausdorff designs.
We will start with a literature review of the state of the art on amplitude tampering methods for rectangular antenna arrays, which may shed light on additional suitable amplitude weighting techniques. Two of them will be finally chosen for implementation based on an analytical performance comparison using the results reported in the scientific papers.
Next, the radiation pattern of a 4x4 microstrip antenna array for mmWave communications will be simulated using Matlab. The dimensions of the antenna array will be based on the TMYTEK BBox One 5G 4x4 beamformer, which will be later used for measurements. The simulated radiation pattern will be compared against the actual one, which was measured in our anechoic chamber. Adjustments in the simulation parameters may be needed to fine-tune the simulations with the measurements. These two will be served as our baseline.
Then, the sidelobe level reduction using the two aforementioned weighting techniques will be quantized using Matlab simulations and used as a baseline for comparison with the measurements in the anechoic chamber.
Experimental verification of the reduced sidelobes will be performed in our anechoic chamber. For this purpose, a 3D model of the antenna holder for the TMYTEK BBox One 5G will be first designed in Blender and printed out using our Ultimaker S3 3D printer before conducting the radiation pattern measurements.
The TMYTEK beamformer will be positioned in the antenna holder specifically designed for it and ° radiation pattern measurements will be performed, applying the two tampering methods to each of the 16 microstip antennas sequentially. C++ knowledge is needed for performing the measurements. The sidelobe level reduction will be compared against the corresponding simulations, as well as to the initial radiation pattern measurement without using the tampering methods.
The final results will be summarized in a report using an IEEE two-column format. A 20-minute presentation will be hold in front of the chair by the end of the research internship.