A Frequency Steerable Substrate-Integrated
Waveguide Slot Antenna for 77 GHz Radar
Application
Tim Martin Böbel, Matthias Rabel
The Industrial Radar Company
indurad GmbH
Aachen, Germany
tim.boebel@rwth-aachen.de
matthias.rabel@indurad.com
Thomas Dallmann, Dirk Heberling
Institute of High Frequency Technology
RWTH Aachen University
Aachen, Germany
{dallmann, heberling}@ihf.rwth-aachen.de
Abstract—For a low cost radar system a serially fed, linear and
equidistant waveguide slot antenna has been developed. A meander
shaped waveguide path allows a frequency steerable main lobe
without additional mechanical or electrical components. The
antenna design focused on a maximum steering angle of ±60°. In
order to further reduce the costs and simplify fabrication of the
antenna a Substrate-Integrated Waveguide (SIW) structure was
used. A new concept to reduce the parasitic coupling of these
structures has been investigated. To fulfill the requirements on the
radiation characteristics and matching of the antenna, a new slot
shape and a cavity based waveguide-SIW transition were designed.
Simulations and measurement results show that the antenna could
be realized successfully.
Keywords—radar antnnas; beam steering; linear antenna
array; planar array; broadband antennas; slot antennas;
I. INTRODUCTION
Radar systems with the ability to measure distances along
cross-range are interesting for industrial applications since they
allow the observation of entire areas with a single sensor
element. Compared to mechanically steerable antennas,
electrically steerable antennas are well suited for rough
environments due to reduced need of maintenance. Antennas
with electrically steerable main beam can be realized with
antenna elements connected in parallel and external phase
shifters. A low cost approach that can be used without
additional circuit components is a serially fed antenna array
with meander shaped transmission lines. If the frequency of
operation is changed also the electrical length of these
transmission lines changes and leads to phase differences Δφ
between the serially connected antenna elements according to
Fig. 1.
The antenna was designed to be operated in E-band. This
frequency range is rarely used by other services and offers a
Fig. 1. Serially fed antenna array with meander shaped transmission lines
high bandwidth for radar applications. The FMCW system
connected to this antenna uses the full bandwidth of 10 GHz to
resolve scatterers in the vicinity of the radar. Cross-range
resolution is realized by the frequency steering of the antenna.
Along range, scatterers are resolved by reusing the bandwidth
available while the scatterer is illuminated by the main beam.
This allows using the frequency bandwidth for resolving
scatterers both in range and cross-range.
Substrate-Integrated Waveguide structures are a relatively
new transmission line concept to realize low cost, highly
integrated waveguides with printed circuits [1]. Beside these
advantages the losses are studied in [2]. Several SIW antennas
without steerable main lobe or a steering angle of ±20° for
lower frequencies have been introduced in [3], [4] and [5].
To simplify the discussion in the following sections, the
concept of the proposed antenna is shown in Fig. 2.
II. REQUIREMENTS ON THE ANTENNA
The desired frequency band is the E-band with 77 GHz
center frequency and a maximum bandwidth of 10 GHz
(relative bandwidth of 13 %). The antenna has to fulfill
requirements like impedance matching to 50 Ω better than
-10 dB, a high sidelobe suppression and a high gain. In mass
production the cost of the antenna should be as low as possible.
Fig. 2. Antenna concept (does not agree with final design)
325ISBN 978-3-9812668-7-0 © IMATech e.V. • Ratingen, Germany
GeMiC 2016 • March 14–16, 2016, Bochum, Germany
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