79GHz Automotive Short Range Radar Sensor
based on Single-Chip SiGe-Transceivers
Volker Winkler
#1
, Reinhard Feger
∗2
, Linus Maurer
#3
#
DICE GmbH & Co KG
Freistaedterstr. 400, 4040 Linz,Austria
1
volker.winkler@mytum.de,
3
linus.maurer@infineon.com
∗
Christian Doppler Laboratory for Integrated Radar Sensors
Johannes Kepler University Linz
Altenberger Strasse 69, 4040 Linz, Austria
2
r.feger@icie.jku.at
Abstract— Today automotive short range radar sensors are
only available for the 24 GHz band. But in the EU the production
of ultra-wideband sensors is limited to 2013 for the 24 GHz band,
after 2013 the 79 GHz range must be used. This was the impact
to develop a single-chip SiGe RF-transceiver for the 79 GHz-
band on Infineon’s B7HF200-Process with transition frequencies
above 200 GHz. The power spectral density limit of -9
dBm
/MHz
for the 79 GHz-band is much higher than the -41.3
dBm
/MHz limit
for 24 GHz. Therefore the built prototype is a FMCW radar
and no pulse radar in order to achieve a higher Signal-to-Noise
Ratio. The required frequency ramp generation according to the
FMCW-Principle is realized without a Phase Locked Loop(PLL),
but by controlling digitally the tuning voltage of the VCO with
help of a D/A-converter. The non-linearity of the VCO tuning law
is compensated by measuring the frequency of the divider signal.
Two bistatic transceiver variants have been realized: ATRX2 has
one transmit and three receive channels, while ATRX3 has two
switchable transmitters and two receivers. An RF-board has been
designed for each chip, where low-cost patch antennas have been
applied, optimized for a short range system. In the following
the configuration for both chips is explained and measurement
results are presented in order to demonstrate the angle detection
capabilities.
I. SENSOR HARDWARE
On the left side of fig. 1 a photo of the ATRX3 radar module
is shown, where the transmitter antenna is on the right side.
The two receiver antennas are on the left side and placed
symmetrically around their middle axis so that the feeding
network is looking outwards. The space between the center of
the antennas could therefore be realized with 1.85 mm. The
angle is detected according to the phase monopulse principle.
So the space between the antennas shouldn’t exceed λ/2 to
cover an unambiguous angle range of ±90
◦
. Fig. 2 is the
corresponding block diagram. In order to perform a phase
calibration the second TX output can be turned on and a
pilot tone is fed into the two receive channels by directional
couplers along a delayline. The phase difference of the pilot
signal in the two r eceive channels is determined in a wideband
sweep. The resulting IF-frequency of the pilot signal is given
by the length of the delayline. The directional couplers are
terminated by spirals covered with absorber paint. All e lements
are placed symmetrically around the antennas and the lengths
Fig. 1. ATRX3(2TX-2RX) and ATRX2(1TX-3RX) 79 GHz Radar Modules
from the antennas to the chip are minimized to avoid losses.
The SiGe-bare dies are bonded to a Taconic TLE-95-RF-
Substrate with a dielectric constant of
r
=2.95 and a height
of 0.13 mm. Because of the differential circuit design the
RF transitions are carried out as differential wedge bonds
so that a balun on the RF board is required. Compared to
single ended transitions this is also advantageous, because the
silicon substrate in the B7HF200-Process is not conductive and
therefore additional ground bonds for single-ended transitions
are needed. The ATRX2-Module is similar, but instead of
the calibration TX output a third receive channel has been
realized. On both chips one TX-Output provides around 8 d Bm
of output power and the mixers have a gain of 14 dB and a
noise figure of 12 dB(on-wafer measurement). The spacing be-
tween the antennas has been chosen according to the Chinese
Remainder Theroem(CRT) and will be further described in
a subsequent section. For the three mixers three IF-channels
are used in parallel. The IF-outputs of the mixers are also
differential, they are amplified by variable gain amplifiers, that
are located on a motherboard stacked onto the RF-Modules.
In order to attenuate the strong signals from close targets,
978-2-87487-006-4 © 2008 EuMA October 2008, Amsterdam, The Netherlands
Proceedings of the 38th European Microwave Conference
1616