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