Abstract
Antennnas for automotive radar sensors at 79GHz
In this thesis low-cost planar antennas for 79GHz automotive radar systems are
investigated. Considering state of the art antennas in current radar systems, two
different antenna concepts are studied.
First, substrate integrated waveguide slot antennas using a synthetic waveguide
formed in a laminate are researched. An equivalent circuit model using precomputed
full-wave simulation data is used to precisely control the exhibited radiation
pattern in order to meet the automotive radar specifications for short-, mid- and
long-range mode. Arrays for these ranges are manufactured using low-cost substrates
in a standard PCB-process. Measurements carried out in an anechoic chamber
show a high agreement with full-wave simulations. Finally, the manufactured
antennas are integrated within a demonstration sensor to test their effectiveness
in a real world scenario. It is concluded that this type of antenna can be used for
different radar ranges and offers sufficient performance.
As the second antenna type, grid array antennas are investigated. These antennas
are composed of perpendicular microstrip lines forming a mesh on a substrate
with continous back metallization. By shaping this mesh the aperture is formed
and thus the resulting beam can be controlled. Full-wave simulations and a simple
equivalent circuit model are used to develop grid antennas on a low-permittivity
substrate. Single-ended and a newly differential feeding technique are studied.
The differential feed is using a two-layer substrate stack with the feeding enclosed
in a synthetic waveguide in the lower layer in order to avoid spurious radation.
Measurements of the fabricated antennas show a good performance in the 79GHz
range. An array of grid antennas with incorporated feeding network is developed
for integration into the demonstration sensor.