Scientific Publications

Journal Papers

Driver assistance systems based on millimeter-wave radar sensor technology are starting to be integrated into the full range of newly introduced car models. This paper gives some background on the state of the art of millimeter-wave technology used in current automotive radar sensors and introduces new developments for future generations.
Transactions of Microwave Theory and Techniques, March 2012
This paper describes the first fundamental frequency single-chip transceiver operating at D-Band. The low-IF, monostatic transceiver integrates on a single-chip two 120-GHz VCOs, a 120-GHz divide-by-64 chain, two IQ receivers with phase calibration circuitry, a variable gain transmit amplifier, an antenna directional coupler, a patch antenna, bias circuitry, a transmit power detector, and a temperature sensor. A quartz antenna resonator with 6 dBi gain and simulated 50% efficiency is placed directly above the on-chip patch to transmit and receive the 120-GHz signals. The circuit with the above-IC antenna occupies an area of 2.2 mm x 2.6 mm, consumes 900 mW from 1.2 V and 1.8 V supplies and was wirebonded in an open lid 7 mm x 7 mm QFN package. Some transceiver performance parameters were characterized on the packaged chip, mounted on an evaluation board, while others, such as receiver noise figure and VCO phase noise at the 120-GHz output were measured on circuit breakouts. The AMOS- varactor VCOs have a typical phase noise of -100 dBc/Hz at 1 MHz offset and a tuning range of 115.2-123.9 GHz. The receiver gain, and the transmitter output power are each adjustable over a range of 15 dB, with the transmitter output power, above the antenna, measured to be at least -6.2 dBm. The receiver IQ phase difference, measured at the IF outputs of the packaged transceiver, is adjustable from 70 to 110 degrees while the amplitude imbalance remains less than 1 dB. The receiver breakout gain and double-sideband noise figure are 10.5-13 dB and 10.5-11.5 dB, respectively, with an input compression point of -20.5 dBm. Several experiments were conducted through the air over distances of up to 2.1 m with a focusing lens placed above the packaged chip.
IEEE Transactions of Microwave Theory and Techniques, March 2012
A study of SiGe signal sources in the 220–330 GHz range
This paper investigates fundamental and push-push SiGe HBT voltage-controlled-oscillator topologies with and without doublers, as possible solutions for efficient milliwatt-level, low-noise signal sources at sub-millimeter wave frequencies. A fundamental frequency Colpitts VCO covers the 218-246 GHz range (the highest for SiGe HBTs) with up to -3.6 dBm output power and 0.8% efficiency. A Colpitts-Clapp VCO-doubler shows -1.7 dBm output power around 290 GHz, a record -101 dBc/Hz phase noise at 10 MHz offset, 7.5% tuning range and 0.4% efficiency. These efficiency numbers are 2-4 times higher than those of recently reported 300-GHz SiGe or CMOS sources based on multipliers or free-space power combining.
IEEE Journal of Solid State Circuits
Compact Topside Millimeter-Wave Waveguide to Microstrip Line Transitions
This letter presents two different waveguide-to-microstrip transition designs for the 76-81 GHz frequency band. Both transitions are fabricated on a grounded single layer substrate using a standard printed circuit board (PCB) fabrication process. A coplanar patch antenna and a feed technique at the non-radiating edge are used for the impedance transformation. In the first design, a conventional WR-10 waveguide is connected. In the second design, a WR-10 waveguide flange with an additional inductive waveguide iris is employed to improve the bandwidth. Both designs were developed for the integration of multi-channel array systems allowing an element spacing of λ0/2 or less. Measurement results of the first transition without the iris show a bandwidth of 8.5 GHz (11%) for 10 dB return loss and a minimum insertion loss (IL) of 0.35 dB. The transition using the iris increases the bandwidth to 12 GHz (15%) for 10 dB return loss and shows a minimum insertion loss of 0.6 dB at 77 GHz.
Microwave and Guided Wave Letters
A Novel Millimeter-Wave Dual-Fed Phased Array for Beam Steering
A novel beam steering approach is presented, based on the superposition of two squinted antenna beams. The two antenna beams are generated by exciting the opposite feeds of a dual-fed array antenna. A change in phase difference and amplitude ratio between the fed-in signals, possibly using only one phase shifter and one variable gain amplifier, steers the main beam in different directions. Additionally, sum and difference patterns can be obtained using this concept, allowing monopulse operation with a broad peak or a deep null at broadside. Using this approach, beam nulls can also be moved to a desired direction, while keeping the shape and direction of the main beam unchanged. To demonstrate the concept, a 77GHz demonstrator using a linear patch array antenna and MMIC I-Q modulators has been designed and fabricated. The measurement results show a beam scanning range of 16◦, well in agreement with the simulation results.
IEEE Transactions of Microwave Theory and Techniques, 2013

Conference Papers

Efficient transmission of high power microwaves and their launching can be achieved in corrugated waveguides by particular mixtures of hybrid modes. The optimum coupling of a free space Gaussian beam into a corrugated waveguide as well as forming of suitable launch patterns for diverse applications are investigated. There are many different schemes for mode conversion in corrugated waveguides to meet the specific requirements of different users. This paper reports on three different principles, a calculation method and a new type of mode converter based on varying the wall impedance, without inner diameter change.
Conference on Infrared and Millimeter Waves 2002, San Diego
Silicon based monolithic Impatt diodes are investigated. The Impatt diodes are integrated in coplanar waveguides with aluminum metallization. S-parameter measurements are performed from 75 GHz up to 110 GHz measuring the reflection coefficient S11. The diodes show a negative real- and imaginary part of the impedance.
Asia Pacific Microwave Conference 2002 in Kyoto, Japan
In this paper monolithically integrated IMPATT diodes are presented. To prove the concept of completely monolithic integration, no special heatsinks or other constructions to optimize cooling were used. The diodes were grown with molecular beam epitaxy on a high resistivity silicon substrate. S-Parameter measurements were performed from 85 GHz up to 110 GHz, showing high negative impedances above the avalanche frequency. Oscillations at a frequency near 93 GHz were observed with the designed resonator circuit.
European Microwave Conference 2003 in Munich, Germany
Bandwidth and antenna aperture size considerations drive radar applications into ever higher frequency ranges. Yet increasing the operating frequency has its advantages, allowing the integration of distributed circuit elements on silicon, utilizing highly sophisticated microelectronic structuring processes. Using high resistivity silicon and an advanced micromaching technology, millimeter wave circuit components with low loss and small tolerances are presented.
European Microwave Conference 2003 in Munich, Germany
Fully monolithic integration of a millimeter wave system on silicon requires low loss passive circuitry. Transmission line elements are needed to interconnect active devices and to realize distributed passive components. Using bulk micromachining and high resistivity silicon on insulator (SOI) wafers, well defined thin silicon membranes can be manufactured. This allows the use of microstrip circuits on silicon substrate at frequencies beyond 100 GHz. Full wave simulation results accompanied by measurements are presented for coplanar to microstrip transitions, microstrip lines and two simple test circuits.
Silicon Monolithic Integrated Circuits 2004 in Atlanta
A rectangular microstrip patch antenna realized as silicon based monolithic millimeter-wave integrated circuit (SIMMWIC) is presented. The antenna was designed for an operating frequency of 122 GHz and manufactured on micromachined high resistivity silicon on insulator (SOI) substrate. Since direct measurements of the far field pattern of an integrated antenna element are difficult at this frequency, a scaled version of the antenna was also manufactured. Far field measurements were performed, to determine the antenna performance and compare with numerical results.
Silicon Monolithic Integrated Circuits 2004 in Atlanta
Designing oscillators in a fully monolithically integrated technology requires accurate characterization of the active element, as well as the surrounding passive circuitry. Based upon S parameter measurements of Impatt diodes, millimeter wave oscillators up to 124 GHz have been designed,manufactured and measured.
Silicon Monolithic Integrated Circuits 2006 in San Diego
A system simulation approach to model conducted emissions of a gearbox electronic control unit (ECU) is investigated. The system is partitioned in ECU, cable harness and load. The ECU itself is modeled using 3D electromagnetic simulation, for the cable harness and loads analytic models are employed. Coupling effects inside the ECU housing are investigated and basic design rules for positioning critical subassemblies on the printed circuit board inside the ECU are derived.
EMC Europe 2008 in Hamburg
Various microstrip coupler structures have been realized using high resistivity silicon on insulator (SOI) wafers. By applying an anisotropic etching process, membranes with a thickness of 50 mum are achieved. Thereby it is possible to realize low-loss microstrip circuits for millimeter-wave applications in F- band. This paper presents a side-coupled filter structure, a 10 dB directional coupler, a branch-line coupler, a rat-race coupler and a Wilkinson divider. The circuits are designed for the 122 GHz ISM band. The measured characteristics of the circuits agree well with the results achieved by momentum simulation.
European Microwave Conference 2007 in Munich
A novel ultrawideband (UWB) tapered slot antenna with high directivity is presented. It operates in the frequency range from 2.2 GHz up to 8.5 GHz. The antenna consists of three parts. As feed, a tapered slot on a PCB is used. Additional corrugations at the lateral metallic borders of the tapered structure lead to reduced side lobe levels and a flat gain in the main direction. The PCB is inserted into a cylindrical dielectric rod to increase the directivity. Finally a metallic reflector is added at the back of the antenna structure to reduce the backward radiation. With this design, a mean gain of 9 dBi and a stable main beam direction with a nearly constant 3 dB beam width, both in the E- and H-plane, were achieved. The antenna shows excellent time domain behavior with a high and sharp peak as well as low ringing of the impulse response.
ICUWB 2008 in Hannover
This work has developed an ultrawideband tapered slot antenna in the frequency range from 2.2 GHz to 8.5 GHz. High directivity is achieved by using a dielectric rod as a waveguide and a metallic reflector. The antenna exhibits a stable main beam direction over the band of operation and a measured mean gain of 8.1 dBi. At 5.5 GHz, a 3 dB opening angle of 42deg and a front-to-back ratio better than 14 dB were realized.
Antennas and Propagation Society International Symposium 2008 in San Diego
Ultra Broadband Dipole based Near Field Probe with Integrated Amplifier
An ultra broadband near field probe operating in the frequency range from 2GHz to 11GHz was developed. The high bandwidth of the active probe allows to measure the electrical near field of UWB antennas. Due to its small size of 7.6mm x 56mm the probe can be set up easily in a near field measurement system and has little effect on the electromagnetic field distribution of the antenna under test. To protect the probe, a Teflon housing was designed. The components on the PCB of the probe are shielded. So, there is reduced influence from external fields which can couple into the stripline based matching network. A broadband differential amplifier with a measured onwafer gain of about 15.5 dB in the frequency range of interest is used to transform the output voltage of the dipole into an unsymmetrical signal. The output port of the amplifier is matched to 50 Ohm by using striplines. Only one single RF cable connected to the mounted SMP plug is required to supply the amplifier with +5V DC and to carry the probe signal. In the frequency band from 2GHz to 9GHz, the reflection coefficient of the prototype is better than -8 dB and the conversion factor is nearly constant. The probe reaches a decoupling of the electrical field components of 10 dB at 2.5GHz increasing up to more than 20 dB at 10GHz. The measured common mode rejection of the dipole with its feeding lines is higher than 10 dB at 7GHz.
EuCap 2009 in Berlin
A complete radar transceiver for 77 GHz with two integrated antenna elements is presented. Based on a previously published design, two of the transmit and receive channels of the transceiver are supplemented with integrated antenna elements. The antennas exhibit a well defined antenna pattern with an efficiency of better than 50%.
German Microwave Conference 2010, Berlin
Deterministic radio channel simulations for large and complex environments at very high frequencies are a challenging task. In this paper an approach is presented in which the computational complexity is significantly reduced by using scattering center models for the most complex objects. The scattering centers are described in form of directional, bistatic scattering intensities and can be computed for the isolated complex object in advance without considering the complete environment. Thus, the simulation performance benefit is due to a significant reduction of the complexity of the geometrical representation of the scene. The parameterization of the scattering centers itself is based on an efficient high frequency asymptotic field prediction tool incorporating Geometrical Optics and other techniques. The models are designed to study deterministically the wave propagation for vehicle based radar systems operating near 80 GHz. An example for a bistatic three-dimensional parameterization is given. Furthermore, a fast Inverse Synthetic Aperture Radar (ISAR) imaging technique is applied that can be used to find the most relevant scattering center positions on the objects.
German Microwave Conference 2010, Berlin
A single chip, dual-functionality radio and FMCW radar transceiver, operating at 140 GHz is described. Doppler, loop-back, and 4Gb/s NLOS radio link demos, over the air and distances exceeding one meter, are demonstrated. The second part of the paper presents novel, sub-1.8 V circuit topologies intended for a low power, high resolution 120 GHz radar transceiver with self-calibration capabilities. The measured receiver noise figure, gain, and phase noise are 7.5 dB, 20 dB, and -100 dBc/Hz@1MHz offset, respectively.
Safety for all - Automotive Radar R&D at Bosch
Automotive radar sensors workshop WFF01, European Microwave Conference 2010, Paris
A 77 GHz FMCW Radar Sensor using a Single-Chip Transceiver with Integrated Antennas
Automotive radar sensors workshop WFF01, European Microwave Conference 2010, Paris
Automotive Radar Operation Considerations and Concepts at Frequencies Beyond 100 GHz
Influence of Weather; Material Characterization; Influence of Radome Deposits; Digital Beamforming Sensor; Semiconductor technology; Packaging; Feasibility study using system simulation; Frequency Regulation.
Automotive radar sensors workshop WFF01, European Microwave Conference 2010, Paris
A Dual Polarized Low Profile UWB Antenna for Building Material Analysis
A compact directive dual linear polarized ultra-wideband (UWB) antenna designed for building material analysis (BMA) devices in the frequency range from 2.6 GHz to 4 GHz is proposed. The antenna has a total size of 61 mm2 and a height of 18 mm. The radiation patterns for both polarization directions are symmetrical over a wide bandwidth and radiate perpendicular to the antenna surface. The wave propagation behavior into the wall is investigated and measurement results with different antenna to wall surface distances are presented. The principle of the antenna is described and experimental results show a good performance for building material analysis.
European Conference on Antennas and Propagation 2011, Rome
77GHz Automotive Radar Sensor in low-cost PCB Technology
An automotive radar sensor operating in the 77GHz band is presented. The sensor is realized using lowcost PCB technology,directly integrating all millimeter-wave components including the antenna feed on a SiGe integrated circuit transceiver. The construction of the radar sensor frontend is described and the sensor performance is evaluated.
European Microwave Conference 2011, Manchester
A System Simulation of a 77GHz Phased Array Radar Sensor
In this paper, a novel MATLAB-implemented millimeter-wave radar system simulation tool is described, allowing simulations of a radar sensor including the electromagnetic propagation channel. A phased array module, implemented into this simulator, is introduced. A complete simulation is performed for a specific scenario employing a steerable antenna system to show its contribution to the overall performance of a 77GHz FMCW radar sensor.
International Radar Symposium 2011, Dresden
Workshop WFL: Low-Cost, Surface-Mountable Millimeter-Wave Radar Sensor
This workshop covers the complete design and development process of a low-cost, surface-mountable millimeter-wave Radar sensor, starting from a system perspective, covering the MMIC design including innovative methods for Built-in-Self-Test and System-in-Package-Testing, and treating a low-cost package design with integrated antennas. New research results from both academia and industry are included into the workshop, among them SiGe MMIC designs of receivers, transmitters and complete on-chip Radars above 100 GHz, as well as measurements and prototypes of 122 GHz integrated off-chip and on-chip antennas. The workshop not only covers the sensor design, but also explains the extremely challenging testing and measurements of the MMICs, the antennas, and the complete system.
International Microwave Symposium 2012, Montreal
A Study of SiGe Signal Sources in the 220-330 GHz Range
This paper investigates fundamental and push-push SiGe HBT voltage-controlled-oscillator topologies with and without doublers, as possible solutions for efficient milliwatt-level, low-noise signal sources at sub-millimeter wave frequencies. A fundamental frequency Colpitts VCO covers the 218-246 GHz range (the highest for SiGe HBTs) with up to -3.6 dBm output power and 0.8% efficiency. A Colpitts-Clapp VCO-doubler shows -1.7 dBm output power around 290 GHz, a record -101 dBc/Hz phase noise at 10 MHz offset, 7.5% tuning range and 0.4% efficiency. These efficiency numbers are 2-4 times higher than those of recently reported 300-GHz SiGe or CMOS sources based on multipliers or free-space power combining.
A Fundamental Frequency 143-152 GHz Radar Transceiver with Built-in Calibration and Self-Test
2012 IEEE Compound Semiconductor IC Symposium, San Diego, California
122 GHz Radar Sensor based on a Monostatic SiGe-BiCMOS IC with an On-Chip Antenna
2012 European Radar Conference, Amsterdamm, Netherlands
A Low-Cost Miniature 120 Ghz SiP FMCW/CW Radar Sensor with Software Linearization and Millimeter Wave BIST
This paper presents an integrated mixed-signal 120GHz FMCW/CW radar chipset in a 130nm SiGe BiCMOS technology. It features on-chip MMW built-in-self-test (BIST) circuits, a harmonic transceiver, software linearization (SWL) circuits and a digital interface. This chipset has been tested in a low-cost package, where the antennas are integrated. Above 100GHz, our transceiver has achieved the highest integration level and receiver linearity, and the lowest DC power so far.
2013 ISSCC, San Fransisco, California
Integrated radar sensors for short range distance and motion measurement
2013 International Microwave Symposium, Seattle
122GHz Bistatic SiGe-BiCMOS Short Range Radar Sensor with System-in-Package (SiP) Solution
In this paper, a short range bistatic radar sensor operating at 122 GHz is presented. The goal is to show the feasiblity of a SiP solution in a low-cost SMD(Surface Mounted Device) like package. The millimeter-wave frontend, including 2- Antenna-in-Packages (AiP), is based on an integrated circuit realized in SiGe-BiCMOS technology which offers an fT of 280 GHz and fmax of 300 GHz. The setup of the radar sensor is introduced and measurement results for frequency modulated contineous wave (FMCW) modulation demonstrate the performance of the radar frontend. The targeted application areas are a short range distance and speed measurements, which gains an advantage for high resolution measurements because of the short wave length at mm-wave frequency.
2013 EuMW, Nürnberg, Germany
Overview: Technologies for Practical Deployment of mm-Wave Radar
2013 EuMW, Nürnberg, Germany
Miniaturized 122 GHz Short Range Radar Sensor with Antenna-in-Package (AiP) and Dielectric Lens
Invited Paper
2014 EuCap, The Hague, Netherlands
Chip-to-Rectangular Waveguide Transition Realized in embedded Wafer Level Ball Grid Array (eWLB) Package
Conference Paper
2014 WAMICON, Tampa Bay
Performance Degradation in Cooperative Radar Sensor Systems due to Uncorrelated Phase Noise
Conference Paper
2014 EuMW, Rome
122 GHz Single-Chip Dual-Channel SMD Radar Sensor with Integrated Antennas for Distance and Angle Measurements
Conference Paper
2014 EuMW, Rome

PhD Dissertation

This work investigates the fully monolithic integration of active and passive millimeter wave components on high resistivity silicon, using Silicon Millimeter Wave Integrated Circuit (SIMMWIC)-Technology. Employing standard process technology from microelectronics and microsystem technology, key components for the realization of a millimeter wave radar sensor were investigated. Realizing the millimeter wave part of a radar sensor as a monolithically integrated element has a number of advantages compared to a traditional assembly using discrete components. The main advantages are lower cost, higher reliability and smaller component size. Because the size of resonant transmission line structures is only a fraction of a millimeter in size on silicon, an efficient realization as a monolithically integrated circuit, in terms of required area, is feasible. Using a suitable process technology, passive circuits, antennas and active components can be integrated on a silicon chip. This allows creating a fully integrated millimeter wave radar frontend as a single chip component. Such an integrated approach also allows the use of a simple packaging technology, because only low frequency signals need to be transferred on or off chip. In this work, a standard microelectronics process is employed for structuring passive components like signal traces, resonant circuits and the antenna. Utilizing an anisotropic etch process (the so called Bosch-Process), the wafer backside is structured to include thin membranes. Such membranes allow the realization of low loss microstrip components for frequencies up to and above 100 GHz. The expected favorable properties of microstrip components are demonstrated by realizing microstrip transmission lines with less than 0,3 dB mm loss and radial stubs with a Q factor of more than 40 in the frequency range above 100 GHz. Another key component of the integration concept is the antenna structure. It needs to provide sufficient bandwidth and a well defined radiation pattern. Using a microstrip patch as radiating element an antenna was realized, despite the high permittivity of the silicon substrate. The antenna efficiency was determined to be about 50%. To monolithically integrate active components, Molecular Beam Epitaxy is used. This allows creating semiconducting layers with a well defined thickness and doping profile. In this work, by stacking several semiconducting layers and selectively etching the layers, Impatt diodes have been created. The realized diodes are shown to exhibit avalanche frequencies of up to 110 GHz. Using scattering parameter measurements, the Impatt diodes have been characterized up to 140 GHz. Based on the measured small signal parameters, coplanar waveguide Impatt oscillators with oscillation frequencies up to 124 GHz at 1 dBm output power have been realized. The maximum output power of 11.4 dBm was achieved for a 104 GHz oscillator. Finally, a transceiver circuit was designed and realized, containing micromachined passive components and and Impatt diode as active component.