Descripció del projecte
Introduction
Plastic injection molding is a high yield manufacturing process that allows low-cost mass-production of complex objects. The deployment of 5G antenna infrastructure and the mandatory adoption of anti-collision radars in automobiles will require large amount of antennas operating in the millimeter and sub-millimeter wavelength. These antennas are arrays and the possibility to manufacture the antenna array including the feeding network and the radiating element as an injection molded piece, eliminating the need to use (Printed Circuit Boards) PCB on expensive dielectric substrates, can be an interesting manufacturing technology.
In addition, waveguide-based distribution networks exhibit smaller losses than their planar transmission line (microstrip) counterparts [1][2].
On the other hand, to enable Autonomous Driving, high resolution sensors both in azimuth and elevation are needed. Therefore, large arrays are required in order to implement imaging radar. Moreover, space in the vehicle is a precious resource. By integrating the radiating element into the injection molded part, antennas are closer to the vehicle outer surface and the Field of View will be unobstructed and free from other elements which can distort radiation and increase reflections towards the sensor. Sensors are today integrated behind large radius (front grill) and small radius (vehicles corners) plastic parts, so curvature in both horizontal and vertical planes can be taken into account to design conformal antennas that better exploit the vehicle surface characteristics with improved radiation performance.
Challenges of this technology are to achieve the required accuracy in the injection molding process and the need to apply additional process, such as metal coating, to achieve the desired performance.
Scope of the thesis
Study the design of antenna arrays based on distribution networks on Gap Waveguides (GW). GWs hold their operation principle on a parallel-plate waveguide, where one of the plates is replaced by a high-impedance surface to create a cutoff condition. For that, the gap between the two plates must be less than a quarter-wavelength. Commonly, the high-impedance condition is achieved through a bed of nails, a quarter-wavelength in height at the center frequency. There are already commercial proposals to use Gap Waveguides in building commercial antennas for automotive radar and 5G applications [3].
It has already been shown that this type of antennas can be effectively built by 3D printing with plastic and posterior metallization [4]. In consequence it is possible to envisage mass production of this type of structures by injection molding.
The main focus will be on automotive radar antennas in the 76 GHz band and its potential integration with decorated radome. Nevertheless, 5G spectrum and the 120-140 GHz will also be studied.
The performance of 3D GW over flexible substrates for low small curvature radii surfaces will also be one of the key points to be analyzed. The use of optically transparent metallization layers will also be a point of interest during the development of the thesis.
Major challenges are to identify those geometries that are more insensitive to manufacturing tolerances and assess different metallization options to achieve the desired result.
References
[1] Z. Ahmad and J. Hesselbarth, “High-Efficiency 3-D Antenna for 60-GHz Band,” in IEEE Transactions on Antennas and Propagation, vol. 65, no. 12, pp. 6274-6281, Dec. 2017.
doi: 10.1109/TAP.2017.2708123
[2] M. Ferrando-Rocher, A. Valero-Nogueira, J. I. Herranz and J. Teniente, “60-GHz Single-Layer Slot-Array Antenna fed by Groove Gap Waveguide,” in IEEE Antennas and Wireless Propagation Letters.
doi: 10.1109/LAWP.2019.2903475
[3] https://www.gapwaves.com/
[4] M. Ferrando-Rocher, J. I. Herranz-Herruzo, A. Valero-Nogueira and B. Bernardo-Clemente, “Performance Assessment of Gap-Waveguide Array Antennas: CNC Milling Versus Three-Dimensional Printing,” in IEEE Antennas and Wireless Propagation Letters, vol. 17, no. 11, pp. 2056-2060, Nov. 2018. doi: 10.1109/LAWP.2018.2833740
