Hermann Schumacher | Universität Ulm (original) (raw)

Papers by Hermann Schumacher

2016 Global Symposium on Millimeter Waves (GSMM) & ESA Workshop on Millimetre-Wave Technology and Applications, 2016

In this paper, a novel differential microstrip patch antenna (DMPA) is designed and used to feed ... more In this paper, a novel differential microstrip patch antenna (DMPA) is designed and used to feed a lens antenna for short range F-band MIMO radars. The DMPA is fed differentially by a pair of coupled lines. The antenna is connected via a differential impedance matching network to the differential output of the modules, eliminating this way the need of a balun in the RF frontend. The simulated antenna gain is about 8 dBi and bandwidth (S11 <-10 dB) is between 125-137 GHz. Preliminary experimental measurements are shown using Transmit/Receive modules in 0.13 m SiGe:C BiCMOS technology, hybrid connected using wirebonding to off chip DMPAs. It is shown by the transmission link evaluation that the gain is increased by about 15 dBi adding a 10 mm radius 3D printed polyamide lens in the near field of the DMPA. Index Terms-millimeter wave (mm-wave), differential microstrip patch antenna (DMPA), 3D printing, polyamide lens. I.

Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2015

In this paper we present a prototype for a spectrum sensing node for a cognitive radio sensing ne... more In this paper we present a prototype for a spectrum sensing node for a cognitive radio sensing network. Our prototype consists of a custom down-conversion front-end with an RF input frequency range from 300 MHz to 3 GHz and a Power Spectral Density (PSD) estimation algorithm implemented on a Virtex-6 Field Programmable Gate Array (FPGA). The base-band processing part is capable of calculating the PSD for a bandwidth upto 245.76 MHz achieving a resolution of 60 kHz and an online variable averaging functionality with a maximum of 32767 averages. We show the arithmetic optimization techniques used for the PSD evaluation to optimize FPGA resource usage. Real time performance and calculation of the PSD for real world signals in the GSM downlink, DECT and the UHF DVB-T bands are demonstrated.

2017 IEEE 30th Conference on Software Engineering Education and Training (CSEE&T), 2017

Educational approaches for computer science proposing the use of complete online courses or tradi... more Educational approaches for computer science proposing the use of complete online courses or traditional courses employing some kind of online material have received much attention recently. The integration of online materials into traditional courses or the replacement of entire courses offer huge possibilities, including increased teaching quality and better study and work alignment. However, researchers and teachers also identified some drawbacks of using online material, including the lack of interaction between students and teachers, and the need to discuss and provide feedback of the students' exercise results. A solution for providing such feedback are automated assessment tools which can generate feedback. However, these tools are not applicable in all situations, e.g. for providing feedback to conceptual modeling exercises. In this paper, we report on the design and implementation of an online course for teaching conceptual modeling. In this course, we use explicitly ambiguous exercises and sketch multiple solutions in brief whiteboard-style videos, thus enabling students to assess their own solutions. Evaluation results show that the proposed approach is able to fulfill students' educational needs.

Proceedings of the 1996 BIPOLAR/BiCMOS Circuits and Technology Meeting

2016 IEEE MTT-S International Microwave Symposium (IMS), 2016

This paper presents a VCO that utilizes the analog capacitive tuning properties of a MEMS varacto... more This paper presents a VCO that utilizes the analog capacitive tuning properties of a MEMS varactor for continuous frequency tuning. The MEMS based VCO achieves a tuning range from 3.37 to 3.58 GHz and a superior phase noise performance of -134.5 dBc/Hz at a 500 kHz offset from the carrier. This work shows the potential of MEMS varactors as attractive alternative to standard varactor solutions for frequency tuning of high performance VCOs.

IEEE Transactions on Circuits and Systems I: Regular Papers, 2017

Analog multipliers are employed in many applications. In conventional RF front ends, for example,... more Analog multipliers are employed in many applications. In conventional RF front ends, for example, they are widely used for frequency conversion tasks. In noncoherent energy detectors or autocorrelation receivers, they multiply the (broadband) input signal by itself to achieve a down-conversion. Unfortunately, there exist no ideal hardware realizations of such devices, hence multipliers inevitably create undesired signal content at their output. To be able to deal with these effects or correct for them, we need to be able to model and identify realistic RF multipliers. This paper proposes and validates a multiple-input single-output Wiener-Hammerstein model for ultra-wideband (UWB) analog multipliers. The structure of the proposed model gives insight in the distortions created. It thus provides the possibility to study the realistic behavior of systems involving those multipliers, e.g., the influence of undesired nonlinear signal content onto noncoherent UWB receivers. A comparison of the model performance is shown with respect to measurements and circuit simulations.

2016 IEEE MTT-S International Microwave Symposium (IMS), 2016

Heterodyne and direct detection radiometer receivers at 94 GHz have been realized in a 130 nm Si/... more Heterodyne and direct detection radiometer receivers at 94 GHz have been realized in a 130 nm Si/SiGe BiCMOS process. They have been assembled into fully self-contained metal housings with a waveguide flange for the antenna connection. The receivers, which employ a SiGe LNA with below 4 dB noise figure, show overall responsivities of 620 μV/K and 380 μV/K respectively.

Microwave and Optical Technology Letters, 2015

ABSTRACT

International Technical Digest on Electron Devices

Electronics Letters, 2003

For the first time the fabrication of a distributed amplifier based on n-type Si=SiGe-MODFETs is ... more For the first time the fabrication of a distributed amplifier based on n-type Si=SiGe-MODFETs is presented. The realised amplifier consists of six identical stages and has a gain of 5.5 dB. The bandwidth of this amplifier is 32 GHz. The gain ripple up to this frequency is AE 0.8 dB. The return losses at the input and output are better than 10 dB. Using a coplanar waveguide layout for the amplifier no via-holes and backside processing is needed. The MMIC has a size of 0.9 Â 3.2 mm 2 .

gaasmantech.com

In this paper several existing industrial GaAs MIM-capacitor processes were evaluated regarding t... more In this paper several existing industrial GaAs MIM-capacitor processes were evaluated regarding their suitability for use with high-voltage GaN MMIC technologies. These processes were tested using different time domain voltage stress methods from which lifetime estimations based on the linear field model were calculated. In addition the influence of electrode geometries and dielectric thicknesses on capacitor performance was investigated. Furthermore early device failures were correlated with defects detected on ...

Abstract—Tunable microstrip filters, phase shifting elements, and switches in the GHz range were ... more Abstract—Tunable microstrip filters, phase shifting elements, and switches in the GHz range were previously realized in a low complexity technology. This paper now presents time dependent measurements of the RF-signal to evaluate the switching behavior of this technology. The measured switching time for a 300µm long cantilever in air is below 75µs. It depends on the amplitude and the sign of the DC actuation due to semiconductor effects in the actuation path that lead to a delay of 60µs before the cantilever starts to move down. ...

Nachhaltigkeit in der wissenschaftlichen Weiterbildung, 2017

Heterogene Zielgruppen erfordern im Vergleich zu herkömmlichen Studierenden flexiblere Organisati... more Heterogene Zielgruppen erfordern im Vergleich zu herkömmlichen Studierenden flexiblere Organisationsformen. Hochschulintern ist hierfür oft ein Paradigmenwechsel notwendig. Daher sind grundsätzliche strategische und strukturelle Entscheidungen zu treffen. Eine Tandem-Struktur, wie sie an der Universität Ulm realisiert wurde, bietet hierzu einen Lösungsansatz.

Online courses and incorporation of e-learning elements in traditional courses are becoming incre... more Online courses and incorporation of e-learning elements in traditional courses are becoming increasingly popular. Switching to an online format is often seen as beneficial to students and educators alike. However, online courses often struggle with teaching complex topics where solutions are not either correct or incorrect but come in different degrees of appropriateness. While models created for model-based engineering must fulfill various rules to be considered suitable, usually various, often equally well suited alternatives exist. In this talk we report our experience from creating and teaching an online course for model based engineering and explain how we handled the need for individualized feedback to modeling exercises.

A first SiGe bipolar heterojunction phototransistor developed in a commercial available SiGe/Si t... more A first SiGe bipolar heterojunction phototransistor developed in a commercial available SiGe/Si technology is presented.Emphasis on the development of a complete numerical model for the simulation of strained- SiGe based devices is given.The SiGe HPT exhibits a dc opto-microwave power gain of 3.46dB,i.e.a responsivity with 50Ohms loads of 1.49A/W,and a –3dB bandwidth of 0.4GHz at 940nm.Power budgets are drawn with the use of the opto-microwave power gain 's monogram chart.

A new, analytic large-signal model for N-channel SiGe Modulation Doped Field Ef-fect Transistors ... more A new, analytic large-signal model for N-channel SiGe Modulation Doped Field Ef-fect Transistors (MODFETs) is presented. The model is based on a non-linear equivalent circuit and can be employed to fit the characteristics in the sub-threshold, linear and saturation operating region from DC to high frequencies. In addition to the non-linear I ds current source, gate/drain-and gate/source capacitance elements, it contains a dispersion model to account for the observed low-frequency dispersion effects in the devices. This contribution focuses on the reliable pre-diction of large-signal characteristics such as gain compression and third order intercept points by ex-tending the covered gate-source and drain-source voltage regimes of the model. Device characterisa-tion has been carried out up to 50GHz and allows for the extension of the model's valid frequency range well beyond the device's measured transit frequency of around 40GHz.

An original approach based on a physical model is used to evaluate opto-microwave performances of... more An original approach based on a physical model is used to evaluate opto-microwave performances of avertically illuminated single strained layer SiGe HPT. Analysis of optomicrowave performance is presented at 940nm. The contribution of each regionon the dynamic performances is studied. Frequency response enhancement is shown for base optical detection first and also by wavelength analysis while maintaining whole component detection. Increases up to a 9. 8 factor for the transition optical frequency (fTopt)in phototransistor mode are presented, reaching respectively 19.7 GHz and 15.3 GHz.

This paper deals with an Integrated Circuits (ICs) compatible MEMS technology, which is used to e... more This paper deals with an Integrated Circuits (ICs) compatible MEMS technology, which is used to elaborate an ultra compact RF communication module centered at 24GHz. This technology uses conventional equipments and is in adequation with millimeterwave applications. A compatibility test protocol has consequently been defined in order to check that each technological step does not degrade the SiGe circuits' performances. Finally, the realized demonstrator present a total surface of only 9mm².

33rd European Microwave Conference, 2003, 2003

The authors present the first SiGe HEMT mixer integrated circuit. The active mixer stage, operati... more The authors present the first SiGe HEMT mixer integrated circuit. The active mixer stage, operating up to 10GHz RF, has been designed and realized using a 0.1µ µ µ µm gate length transistor technology. The design is based on a new large-signal simulation model developed for the SiGe HEMT. Good agreement between simulation and measurement is reached. The mixer exhibits 4.0dB and 4.7dB conversion loss when down-converting 3.0GHz and 6.0GHz signals, respectively, to an intermediate frequency of 500MHz using high-side injection of 5dBm local oscillator power. Conversion loss is less than 8dB for RF frequencies up to 10GHz with a mixer linearity of-8.8dBm input related 1dB compression point.

Journal of Signal Processing Systems, 2016

Despite the progress made in digital signal processing during the last decades, the constraints i... more Despite the progress made in digital signal processing during the last decades, the constraints imposed by high data rate communications are becoming ever more stringent. Moreover mobile communications raised the importance of power consumption for sophisticated algorithms, such as channel equalization or decoding. The strong link existing between computational speed and power consumption suggests an investigation of signal processing with energy efficiency as a prominent design choice. In this work we revisit the topic of signal processing with analog circuits and its potential to increase the energy efficiency. Channel equalization is chosen as an application of nonlinear signal processing, and a vector equalizer based on a recurrent neural network structure is taken as an example to demonstrate what can be achieved with state of the art in VLSI design. We provide an analysis of the equalizer, including the analog circuit design, system-level simulations, and comparisons with the theoretical algorithm.

2016 Global Symposium on Millimeter Waves (GSMM) & ESA Workshop on Millimetre-Wave Technology and Applications, 2016

In this paper, a novel differential microstrip patch antenna (DMPA) is designed and used to feed ... more In this paper, a novel differential microstrip patch antenna (DMPA) is designed and used to feed a lens antenna for short range F-band MIMO radars. The DMPA is fed differentially by a pair of coupled lines. The antenna is connected via a differential impedance matching network to the differential output of the modules, eliminating this way the need of a balun in the RF frontend. The simulated antenna gain is about 8 dBi and bandwidth (S11 <-10 dB) is between 125-137 GHz. Preliminary experimental measurements are shown using Transmit/Receive modules in 0.13 m SiGe:C BiCMOS technology, hybrid connected using wirebonding to off chip DMPAs. It is shown by the transmission link evaluation that the gain is increased by about 15 dBi adding a 10 mm radius 3D printed polyamide lens in the near field of the DMPA. Index Terms-millimeter wave (mm-wave), differential microstrip patch antenna (DMPA), 3D printing, polyamide lens. I.

Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2015

In this paper we present a prototype for a spectrum sensing node for a cognitive radio sensing ne... more In this paper we present a prototype for a spectrum sensing node for a cognitive radio sensing network. Our prototype consists of a custom down-conversion front-end with an RF input frequency range from 300 MHz to 3 GHz and a Power Spectral Density (PSD) estimation algorithm implemented on a Virtex-6 Field Programmable Gate Array (FPGA). The base-band processing part is capable of calculating the PSD for a bandwidth upto 245.76 MHz achieving a resolution of 60 kHz and an online variable averaging functionality with a maximum of 32767 averages. We show the arithmetic optimization techniques used for the PSD evaluation to optimize FPGA resource usage. Real time performance and calculation of the PSD for real world signals in the GSM downlink, DECT and the UHF DVB-T bands are demonstrated.

2017 IEEE 30th Conference on Software Engineering Education and Training (CSEE&T), 2017

Educational approaches for computer science proposing the use of complete online courses or tradi... more Educational approaches for computer science proposing the use of complete online courses or traditional courses employing some kind of online material have received much attention recently. The integration of online materials into traditional courses or the replacement of entire courses offer huge possibilities, including increased teaching quality and better study and work alignment. However, researchers and teachers also identified some drawbacks of using online material, including the lack of interaction between students and teachers, and the need to discuss and provide feedback of the students' exercise results. A solution for providing such feedback are automated assessment tools which can generate feedback. However, these tools are not applicable in all situations, e.g. for providing feedback to conceptual modeling exercises. In this paper, we report on the design and implementation of an online course for teaching conceptual modeling. In this course, we use explicitly ambiguous exercises and sketch multiple solutions in brief whiteboard-style videos, thus enabling students to assess their own solutions. Evaluation results show that the proposed approach is able to fulfill students' educational needs.

Proceedings of the 1996 BIPOLAR/BiCMOS Circuits and Technology Meeting

2016 IEEE MTT-S International Microwave Symposium (IMS), 2016

This paper presents a VCO that utilizes the analog capacitive tuning properties of a MEMS varacto... more This paper presents a VCO that utilizes the analog capacitive tuning properties of a MEMS varactor for continuous frequency tuning. The MEMS based VCO achieves a tuning range from 3.37 to 3.58 GHz and a superior phase noise performance of -134.5 dBc/Hz at a 500 kHz offset from the carrier. This work shows the potential of MEMS varactors as attractive alternative to standard varactor solutions for frequency tuning of high performance VCOs.

IEEE Transactions on Circuits and Systems I: Regular Papers, 2017

Analog multipliers are employed in many applications. In conventional RF front ends, for example,... more Analog multipliers are employed in many applications. In conventional RF front ends, for example, they are widely used for frequency conversion tasks. In noncoherent energy detectors or autocorrelation receivers, they multiply the (broadband) input signal by itself to achieve a down-conversion. Unfortunately, there exist no ideal hardware realizations of such devices, hence multipliers inevitably create undesired signal content at their output. To be able to deal with these effects or correct for them, we need to be able to model and identify realistic RF multipliers. This paper proposes and validates a multiple-input single-output Wiener-Hammerstein model for ultra-wideband (UWB) analog multipliers. The structure of the proposed model gives insight in the distortions created. It thus provides the possibility to study the realistic behavior of systems involving those multipliers, e.g., the influence of undesired nonlinear signal content onto noncoherent UWB receivers. A comparison of the model performance is shown with respect to measurements and circuit simulations.

2016 IEEE MTT-S International Microwave Symposium (IMS), 2016

Heterodyne and direct detection radiometer receivers at 94 GHz have been realized in a 130 nm Si/... more Heterodyne and direct detection radiometer receivers at 94 GHz have been realized in a 130 nm Si/SiGe BiCMOS process. They have been assembled into fully self-contained metal housings with a waveguide flange for the antenna connection. The receivers, which employ a SiGe LNA with below 4 dB noise figure, show overall responsivities of 620 μV/K and 380 μV/K respectively.

Microwave and Optical Technology Letters, 2015

ABSTRACT

International Technical Digest on Electron Devices

Electronics Letters, 2003

For the first time the fabrication of a distributed amplifier based on n-type Si=SiGe-MODFETs is ... more For the first time the fabrication of a distributed amplifier based on n-type Si=SiGe-MODFETs is presented. The realised amplifier consists of six identical stages and has a gain of 5.5 dB. The bandwidth of this amplifier is 32 GHz. The gain ripple up to this frequency is AE 0.8 dB. The return losses at the input and output are better than 10 dB. Using a coplanar waveguide layout for the amplifier no via-holes and backside processing is needed. The MMIC has a size of 0.9 Â 3.2 mm 2 .

gaasmantech.com

In this paper several existing industrial GaAs MIM-capacitor processes were evaluated regarding t... more In this paper several existing industrial GaAs MIM-capacitor processes were evaluated regarding their suitability for use with high-voltage GaN MMIC technologies. These processes were tested using different time domain voltage stress methods from which lifetime estimations based on the linear field model were calculated. In addition the influence of electrode geometries and dielectric thicknesses on capacitor performance was investigated. Furthermore early device failures were correlated with defects detected on ...

Abstract—Tunable microstrip filters, phase shifting elements, and switches in the GHz range were ... more Abstract—Tunable microstrip filters, phase shifting elements, and switches in the GHz range were previously realized in a low complexity technology. This paper now presents time dependent measurements of the RF-signal to evaluate the switching behavior of this technology. The measured switching time for a 300µm long cantilever in air is below 75µs. It depends on the amplitude and the sign of the DC actuation due to semiconductor effects in the actuation path that lead to a delay of 60µs before the cantilever starts to move down. ...

Nachhaltigkeit in der wissenschaftlichen Weiterbildung, 2017

Heterogene Zielgruppen erfordern im Vergleich zu herkömmlichen Studierenden flexiblere Organisati... more Heterogene Zielgruppen erfordern im Vergleich zu herkömmlichen Studierenden flexiblere Organisationsformen. Hochschulintern ist hierfür oft ein Paradigmenwechsel notwendig. Daher sind grundsätzliche strategische und strukturelle Entscheidungen zu treffen. Eine Tandem-Struktur, wie sie an der Universität Ulm realisiert wurde, bietet hierzu einen Lösungsansatz.

Online courses and incorporation of e-learning elements in traditional courses are becoming incre... more Online courses and incorporation of e-learning elements in traditional courses are becoming increasingly popular. Switching to an online format is often seen as beneficial to students and educators alike. However, online courses often struggle with teaching complex topics where solutions are not either correct or incorrect but come in different degrees of appropriateness. While models created for model-based engineering must fulfill various rules to be considered suitable, usually various, often equally well suited alternatives exist. In this talk we report our experience from creating and teaching an online course for model based engineering and explain how we handled the need for individualized feedback to modeling exercises.

A first SiGe bipolar heterojunction phototransistor developed in a commercial available SiGe/Si t... more A first SiGe bipolar heterojunction phototransistor developed in a commercial available SiGe/Si technology is presented.Emphasis on the development of a complete numerical model for the simulation of strained- SiGe based devices is given.The SiGe HPT exhibits a dc opto-microwave power gain of 3.46dB,i.e.a responsivity with 50Ohms loads of 1.49A/W,and a –3dB bandwidth of 0.4GHz at 940nm.Power budgets are drawn with the use of the opto-microwave power gain 's monogram chart.

A new, analytic large-signal model for N-channel SiGe Modulation Doped Field Ef-fect Transistors ... more A new, analytic large-signal model for N-channel SiGe Modulation Doped Field Ef-fect Transistors (MODFETs) is presented. The model is based on a non-linear equivalent circuit and can be employed to fit the characteristics in the sub-threshold, linear and saturation operating region from DC to high frequencies. In addition to the non-linear I ds current source, gate/drain-and gate/source capacitance elements, it contains a dispersion model to account for the observed low-frequency dispersion effects in the devices. This contribution focuses on the reliable pre-diction of large-signal characteristics such as gain compression and third order intercept points by ex-tending the covered gate-source and drain-source voltage regimes of the model. Device characterisa-tion has been carried out up to 50GHz and allows for the extension of the model's valid frequency range well beyond the device's measured transit frequency of around 40GHz.

An original approach based on a physical model is used to evaluate opto-microwave performances of... more An original approach based on a physical model is used to evaluate opto-microwave performances of avertically illuminated single strained layer SiGe HPT. Analysis of optomicrowave performance is presented at 940nm. The contribution of each regionon the dynamic performances is studied. Frequency response enhancement is shown for base optical detection first and also by wavelength analysis while maintaining whole component detection. Increases up to a 9. 8 factor for the transition optical frequency (fTopt)in phototransistor mode are presented, reaching respectively 19.7 GHz and 15.3 GHz.

This paper deals with an Integrated Circuits (ICs) compatible MEMS technology, which is used to e... more This paper deals with an Integrated Circuits (ICs) compatible MEMS technology, which is used to elaborate an ultra compact RF communication module centered at 24GHz. This technology uses conventional equipments and is in adequation with millimeterwave applications. A compatibility test protocol has consequently been defined in order to check that each technological step does not degrade the SiGe circuits' performances. Finally, the realized demonstrator present a total surface of only 9mm².

33rd European Microwave Conference, 2003, 2003

The authors present the first SiGe HEMT mixer integrated circuit. The active mixer stage, operati... more The authors present the first SiGe HEMT mixer integrated circuit. The active mixer stage, operating up to 10GHz RF, has been designed and realized using a 0.1µ µ µ µm gate length transistor technology. The design is based on a new large-signal simulation model developed for the SiGe HEMT. Good agreement between simulation and measurement is reached. The mixer exhibits 4.0dB and 4.7dB conversion loss when down-converting 3.0GHz and 6.0GHz signals, respectively, to an intermediate frequency of 500MHz using high-side injection of 5dBm local oscillator power. Conversion loss is less than 8dB for RF frequencies up to 10GHz with a mixer linearity of-8.8dBm input related 1dB compression point.

Journal of Signal Processing Systems, 2016

Despite the progress made in digital signal processing during the last decades, the constraints i... more Despite the progress made in digital signal processing during the last decades, the constraints imposed by high data rate communications are becoming ever more stringent. Moreover mobile communications raised the importance of power consumption for sophisticated algorithms, such as channel equalization or decoding. The strong link existing between computational speed and power consumption suggests an investigation of signal processing with energy efficiency as a prominent design choice. In this work we revisit the topic of signal processing with analog circuits and its potential to increase the energy efficiency. Channel equalization is chosen as an application of nonlinear signal processing, and a vector equalizer based on a recurrent neural network structure is taken as an example to demonstrate what can be achieved with state of the art in VLSI design. We provide an analysis of the equalizer, including the analog circuit design, system-level simulations, and comparisons with the theoretical algorithm.