Our Fields of Research

Future Automotive Radar Sensors

With the availability of highly integrated 77 GHz circuits in SiGe (for example from Infineon with a bipolar technology or from Freescale in BiCMOS) 77 GHz radar sensors have become a lot more affordable than in the past. Now, driver assistance systems such as Adaptive Cruise Control in a speed range of 0 - 160 km/h or Automatic Emergency Braking up to 30 km/h are already available in the middle-class car Volkswagen Golf VII (see for example http://www.youtube.com/watch?v=Vthgb2BFrpY or http://www.youtube.com/watch?v=AJFhpspMDmk). In future, more and more vehicles will be equipped with a radar cocoon consisting of multiple sensors in the front as well as in the rear. The new Mercedes S class will use one long range radar (LRR) and two short range radar sensors (SRR) in the front to allow ACC Stop & Go and Automatic Emergency Braking (AEB), both supported by a stereo camara behind the windshield. One medium range radar (MRR) and two SRR sensors will be used in the rear for Blind Spot Detection (BSD) and Lane Change Assistance (LCA). Wheras the LRR and MRR sensors operate at 76-77 GHz, the SRR sensors use the ultra wide band (UWB) frequency range 24.25 - 26.65 GHz that was recently agreed on by the European Commission with a sunset date of 2018/2022. That fits well in the UWB range in North America (24-29 GHz, FCC 2nd Report and Order 04-285 from 2004).  

Our research group is contributing to the development of future automotive radar systems. Within the German funded projects Kokon and RoCC, we investigated new packaging and integration concepts and Antenna in Package (AiP) approaches. See for example our recent journal paper

M. Alhenawy, M. Schneider, "Antenna-in-package (AiP) in mm-wave band," International Journal of Microwave and Wireless Technologies, Cambridge University Press, Vol. 5, pp. 55-64, 2013. (More papers can be found in our publication list.)

Within these investigations, we designed dipole and loop antennas that are directly integrated together with a SiGe MMIC into a plastic package based on Infineon's eWLB technology. Fig. 1 shows a half wavelength dipole in an 8x8 mm2 package which transmits/receives through the plastic package into/from the boresight direction. Here, the dipole has a length of about 1.1 mm. Such a BGA (ball grid array) package can directly be soldered on a cheap PCB board such as FR4 (see Fig. 1b); an RF substrate is no longer needed in such AiP concepts.

Fig. 1 eWLB package with integrated 77 GHz dipole antenna


a) 77 GHz planar dipole at the bottom side of the package

  b) Soldered eWLB package with integrated 77 GHz
  dipole antenna (dipole not visible)

Planar Antennas for 60 GHz WLAN

For wireless Gb/s transmission over short distances of a few meters, the 60 GHz band is well suited because of a nearly worldwide availability of several GHz bandwidth on a license-exempt basis. In addition to the available bandwidth, the attractive form factor of high-gain planar patch arrays at millimeter wavelengths eases a low-profile integration of such antennas into smartphones or laptop computers which opens a huge market. Our group investigates planar antennas such as patch arrays and surface integrated waveguide (SIW) antennas on low cost dielectric substrates. Fig. 2a shows an 8x8 array with a corporate feeding network; its return loss measurement on our wafer prober station is shown in Fig. 2b. The mounting in the anechoic chamber is shown in Fig. 2c for measuring the radiation pattern and the antenna gain by the Three-Antenna-Method.

Fig. 2 Planar patch array for 60 GHz WLAN applications


a) 60 GHz 8x8 array (3cm x 3cm)

  b) Return loss measurement on our wafer prober

c) Antennameasurement in our anechoic chamber

Direction of Arrival (DoA) Estimation with Circular Antenna Arrays


Currently we are investigating DoA estimation techniques based on a circular array that is operated at 2.5 GHz. Our main motivation in this field is the realization of DoA estimation with only one receiver chain in contrast to the widely adopted concept to provide one receiver chain per receive antenna being operated synchronously. A prototype of such a sequentially scanned receive array was realized in our lab. The PCB was milled on our LPKF S103 milling station, all IC's and lumped elements were mounted with our manual placer, and finally the board was soldered in our reflow soldering oven. Fig. 3 shows this prototype with eight monopole receive antennas placed in the outer periphery of the PCB. The receiver IC's and the SPMT switch are on the backside of the PCB. Our latest results will be presented during the next European Microwave Week in Nuremberg, Germany, in session EuMC58:

Fig. 3 Circular antenna array with eight monopole antennas being sequentially processed for DoA estimation


M. Stefer, CH. Schmedt, M. Schneider, "DoA Estimation Combining Iniform Circular Array and Sequential Array Processing", European Microwave Week EuMW 2013, Nuremberg, Germany (accepted for publication).

Brain Implants with a High-Speed Wireless Data Link


Within a joint research project at the University of Bremen, we are closely cooperating with biologists, physicists, and microelectronics and microsystems engineers to realize wireless brain implants for recording neural activity. Our laboratory is contributing by the development of extremely miniaturized antennas being operated in the MICS band around 400 MHz. Within these activities numerical simulation algorithms are being developed that allow precise calculation of external and internal inductances of the involved transmission structures. Fig. 4 shows one of our antennas that has a diameter of just 5 mm allowing data transmisson over a distance of a few centimeters.

Fig. 4  Loop antenna with a 5 mm diameter for date transmission in the MICS band (400 MHz)