Antenna array design for retrodirective wireless power transmission and radar
Hilario Re, Pascual D.
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This thesis presents antenna array design and the integration of microwave circuit systems for retrodirective wireless power transmission and radar. Wireless power transmission (WPT) and automotive radar are emerging topics which have attracted a lot of interest in the past few years. The development of these systems usually brings high associated costs if competitive performance is required. The ﬁrst part of the thesis is concerned with the development of a new retrodirective antenna array (RDA) system for WPT which uses sub-arrays in transmit to save costs, however, losing tracking in one plane. Nevertheless, depending on the application, the proposed system might be an alternative solution to existing approaches as similar performances are achieved, but at generally a lower cost for the proposed RDA design as compared to the conventional solution. The proposed system has been designed to work in the ISM band (2.5 GHz for receiving and 2.4 GHz for transmitting) which exhibits an 80◦ 3-dB half-power beamwidth for the monostatic pattern. Additionally, it has been demonstrated that the system is able to work in the near-ﬁeld region, being able to achieve wireless charging of a handeld electronic device at a 50 cm distance. The power for the beacon signal sent by the device to be charged by the system (for tracking purposes) is 6.6 dBm, whereas the received RF power from the RDA is in excess of 27 dBm, which means that the device is receiving a hundred times the power sent for battery charging. On the other hand, the second part of the thesis relates to the development of two important elements within a frequency-modulated-continuous-wave (FMCW) auto motive radar working at 24 GHz: a substrate integrated waveguide (SIW) butler matrix antenna array as the transmitter and a new post-processing technique called Pwr+. These two in combination bring some interesting advantages in terms of angular resolution improvements when compared to conventional single-input-multiple output (SIMO) radars. For example, the proposed system is able to distinguish two targets which are 2 degrees apart as well as a higher ﬁeld-of-view (FOV) thanks to the beamforming network that generates 4 individual beams covering a wide FOV. The newly developed radar system is also comparable to multiple-input-multiple output (MIMO) radars but with the added value of having a shorter processing time, which for automotive radar applications is a crucial characteristic to be minimized, and could, therefore, avoid potential road accidents. It should also be mentioned that this thesis was supported by the Samsung Advanced Institute of Technology.