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Dr.-Ing. Franz Röhrl

Fakultät Elektrotechnik und Medientechnik

Lehrbeauftragte

Lehrbeauftragter

  • Schaltungstechnik 2
  • Fachbeirat der Fakultät Elektrotechnik und Medientechnik

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Zeitschriftenartikel

  • Felix Sepaintner
  • M. Schmalzbauer
  • K. Lobbicke
  • Johannes Jakob
  • Andreas Scharl
  • Franz Xaver Röhrl
  • Roman Sammer
  • Werner Bogner
  • Stefan Zorn

Characterization of Additively Produced RF-Structures on Low-Cost PCB Materials Based on Inkjet Technology for Industrial Applications up to 80 GHz

In: IEEE Transactions on Components, Packaging and Manufacturing Technology vol. 11 pg. 1-11.

  • (2021)

DOI: 10.1109/TCPMT.2021.3118720

Usually, the printed circuit board industry has to use special subtractive manufacturing methods, if small line and space dimensions down to 50 μm are desired. This drastically raises production effort and costs. In this paper a method is shown, how the inkjet technology can be used to produce passive RF structures with minimum line and space dimensions of 25 μm. For the first time, this is possible over complete panels of low-cost PCB substrates, which have a relatively high surface roughness compared to ceramic or glass carriers. To ensure process reliability, printed lines must also be plated with an additional electroless copper layer to overcome the surface roughness with conductive layers and to lower insertion loss in the two-digit GHz range. Additionally, a surface impedance model is developed, which allows broadband first time right simulations. Finally, additively produced, passive RF filters are compared to their subtractive counterparts to show their benefits regarding production costs and electrical performance up to 80 GHz.
  • TC Teisnach Optik
  • Elektrotechnik und Medientechnik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • M. Schmalzbauer
  • Johannes Jakob
  • Andreas Scharl
  • Felix Sepaintner
  • K. Löbbicke
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Reliability Investigations of Additive Manufactured RF-Structures on Low-Cost PCB Materials Based on Inkjet Technology

  • (2021)
  • Elektrotechnik und Medientechnik
  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Felix Sepaintner
  • M. Schmalzbauer
  • Johannes Jakob
  • Andreas Scharl
  • G. Weber
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Comparison of an Inkjet Fabrication Method on Low-Cost PCB Substrates With Semi Additive And Subtractive Technologies Regarding RF-Performance

pg. 266-268.

  • (2021)

DOI: 10.1109/IMWS-AMP53428.2021.9643887

  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Andreas Scharl
  • Felix Sepaintner
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

A Cost-Effective Method for Extracting the Complex Permittivity of Inner Layer Dielectric PCB Materials

  • (2021)
  • TC Teisnach Optik
  • Elektrotechnik und Medientechnik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Felix Sepaintner
  • M. Schmalzbauer
  • Johannes Jakob
  • Andreas Scharl
  • G. Weber
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Comparison of an Inkjet Fabrication Method on Low Cost PCB Substrates With Semi Additive And Subtractive Technologies Regarding RF-Performance

  • (2021)
  • Elektrotechnik und Medientechnik
  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Felix Sepaintner
  • Andreas Scharl
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Extracting Complex PCB Substrate Permittivity from a Transmission Line using the Finite Difference Integral Method from 10 GHz - 100 GHz . [Invited Talk]

  • (2020)

DOI: 10.1109/IMWS-AMP49156.2020.9199738

This paper presents a new numerical method to deduce the complex permittivity εr of PCB (printed circuit board) substrates. First, the attenuation and phase of an on board transmission line are measured with a vector network analyzer (VNA). The transmission line is then simulated with the finite difference integral method (FDI) with the substrate substituted by air. The measured and simulated phases are used, to calculate the effective permittivity and the real part of the complex permittivity εr ' . With known εr ' , the electromagnetic field distribution can be calculated, which is necessary to deduce the imaginary part of the permittivity. The shown algorithms can be used for frequencies up to 100 GHz and without any iterative processes.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Monographie

  • Franz Xaver Röhrl

Ein flexibles Leiterplatten-Technologiekonzept für Anwendungen im Millimeterwellenbereich . Dissertationsschrift

In: Elektrotechnik

Verlag Dr. Hut München

  • (2020)
Die vorliegende Arbeit beschreibt ein Konzept zum Betrieb von millimeterwellentauglichen Schaltungen auf konventionellen Leiterplatten. Dazu werden neben den technologischen Grundlagen und neuen Leiterplattentechnologien auch konkrete Realisierungen von Schaltungen vorgestellt. Der Fokus liegt dabei auf einer toleranzarmen, fertigungstechnisch prozesssicheren Umsetzung. Die entwickelten Fertigungsverfahren und Optimierungen erlauben die Herstellung von bisher nicht realisierbaren Feinstleiter-Strukturen auf Außenlagen und ermöglichen dadurch auch eine breitbandige dämpfungsarme Signalführung. Ein großer Vorteil der hier vorgestellten Umsetzung ist, dass die Verfahren zum Großteil mit konventionellen Leiterplattenprozessen umgesetzt werden können und auch eine beliebige Kombination mit bestehenden Leiterplattenprozessen zulässig ist. Es wird versucht möglichst viele Funktionen und Herausforderungen direkt auf der kostengünstigen Leiterplatte zu lösen. Das Konzept beinhaltet zudem eine breite Auswahl an Möglichkeiten zur reflexionsarmen Kontaktierung der Leiterplatte von Signalen im Millimeterwellenbereich. Außerdem wird die Anbindung von aktiven Bausteinen und anderen Schaltungsträgern detailliert behandelt. Die Ergebnisse werden sowohl mit dem aktuellen Stand der Leiterplattentechnologie als auch mit alternativen Fertigungstechnologien verglichen und bewertet.
  • TC Teisnach Optik
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
Vortrag

  • Felix Sepaintner
  • Andreas Scharl
  • Florian Keck
  • Kevin Kunze
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Cost-Effective Implementation of Air-Filled Waveguides on Printed Circuit Boards . Invited Talk

In: IEEE Conference on Electrical Performance of Electronic Packaging and Systems (EPEPS)

Institute of Electrical and Electronics Engineers Inc. San José, CA, USA

  • 05.10.2020 (2020)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
  • NACHHALTIG
Vortrag

  • Felix Sepaintner
  • Andreas Scharl
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Extracting Complex PCB Substrate Permittivity from a Transmission Line using the Finite Difference Integral Method from 10 GHz - 100 GHz . Invited Talk

In: 2020 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP)

Institute of Electrical and Electronics Engineers Inc. Suzhou, China

  • 29.07.2020 (2020)
  • TC Teisnach Optik
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
  • NACHHALTIG
Zeitschriftenartikel

  • Felix Sepaintner
  • Andreas Scharl
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Characterization and Production of PCB Structures With Increased Ratio of Electromagnetic Field in Air

In: IEEE Transactions on Microwave Theory and Techniques vol. 68 pg. 2134-2143.

  • (2020)

DOI: 10.1109/TMTT.2020.2983934

Producing passive printed circuit board (PCB) structures in the millimeter-wave range includes some fundamental challenges, such as low manufacturing costs and high fabrication accuracy. These aspects, in general, have to be combined with low signal attenuation, precise simulation models, and a reliable producibility. This article shows a new method to manufacture different kinds of passive RF waveguides with reduced attenuation and decreased electrical length on low-cost PCB substrates. First, the complex material parameters of the used substrate and the used copper foil are extracted from 10 to 100 GHz to have accurate simulation models in CST Microwave Studio. This is necessary because the parameters provided by the manufacturer are often no longer generally valid in this frequency range. In addition, PCB materials have a significantly higher surface roughness compared with conventional materials for millimeter-wave applications. Therefore, the correct determination and the correct modeling of surface roughness is particularly important. Next, laminate is removed partially on the outer layer of the PCB to increase the electromagnetic field ratio in air. The undesired substrate is removed by a CO2 laser drilling machine by setting narrow drills sequentially. The RF performance of these waveguides is compared with those manufactured in conventional PCB technology according to attenuation and producibility.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Andreas Scharl
  • Felix Sepaintner
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Design and Comparison of Filter Structures in the Millimetre Wave Frequency Range on Outer- and Inner-Layers of Organic Circuits Boards . [Invited Talk]

  • (2020)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Vortrag

  • Andreas Scharl
  • Felix Sepaintner
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Simulation and Measurement of PCB Crossover Structures from DC up to 70 GHz . Invited Talk

In: 2020 German Microwave Conference (GeMiC)

Cottbus

  • 09.03.2020 (2020)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • NACHHALTIG
  • DIGITAL
Zeitschriftenartikel

  • E. Hassan
  • B. Scheiner
  • F. Michler
  • M. Berggren
  • E. Wadbro
  • Franz Xaver Röhrl
  • Stefan Zorn
  • R. Weigel
  • F. Lurz

Multi-Layer Topology Optimization of Wideband SIW-to-Waveguide Transitions

In: IEEE Transactions on Microwave Theory and Techniques vol. 68 pg. 1326-1339.

  • (2020)

DOI: 10.1109/TMTT.2019.2959759

This article utilizes a topology optimization approach to design planar multilayer transitions between substrate integrated waveguides (SIWs) and rectangular waveguides (RWGs). The optimization problem is formulated based on the modal field analyses and Maxwell's equations in the time domain solved by the finite-difference time-domain (FDTD) method. We present a time-domain boundary condition based on the Klein-Gordon equation to split traveling waves at homogeneous waveguide ports. We employ the boundary condition to compute portal quantities and to devise an adjoint-field system that enabled an efficient computation of the objective function gradient. We solve design problems that include more than 105 000 design variables by using less than 400 solutions of Maxwell's equations. Moreover, a new formulation that effectively combats the development of in-band resonances in the design is presented. The transition configuration allows the direct mount of conventional RWG sections on the circuit board and aims to cover the entire K-band. The guiding structure of the optimized transition requires blind vias, which is realized by a simple and cost-efficient technique. In addition, the transition is optimized for three different setups that can be used to provide different field polarizations. The proposed transitions show less than 1-dB insertion loss and around 15-dB return loss over the frequency interval 18-28 GHz. Several prototypes are fabricated with an excellent match between the simulation and measurement results.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Felix Sepaintner
  • Andreas Scharl
  • Florian Keck
  • Kevin Kunze
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Cost-Effective Implementation of Air-Filled Waveguides on Printed Circuit Boards . [Invited Talk]

  • (2020)

DOI: 10.1109/EPEPS48591.2020.9231382

This paper presents a new cost-effective method to produce air-filled waveguides out of a printed circuit board (PCB) with a milling machine and how to implement them with standard PCB technology. For this purpose, low cost substrates like FR-4 are used. For the baseboard to waveguide transition in the E-Band (60-90GHz) a WR12 waveguide connector [1] was used. The WR12 waveguide was manufactured and analyzed on mechanical deviations. The RF performance in the E-Band was measured and compared to common PCB waveguides like microstrip lines (MS) and grounded coplanar waveguides (GCPW).
  • TC Teisnach Optik
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Andreas Scharl
  • Felix Sepaintner
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Simulation and Measurement of PCB Crossover Structures from DC up to 70 GHz . [Invited Talk]

  • (2020)

In this paper, 4 different crossover structures in a 6-layered printed circuit board (PCB) for high operation frequencies are presented. The design for all structures is based on grounded coplanar waveguide (GCPW). Two fully planar structures, a quasi-coaxial transition and coaxial transition are realized and have a measured bandwidth from DC to 50 GHz and DC to 60 GHz, respectively. Moreover, two structures are designed in submount technology. Especially the connection between baseboard and package (solder junction) plays an important role to guarantee best signal integrity. Therefore, the quality of the solder junction is analysed in detail with TDR (time domain reflectometry) measurement as well as with X-ray images. The submount transitions show good radio frequency (RF) characteristics from DC to 70 GHz.
  • TC Teisnach Optik
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
Vortrag

  • Andreas Scharl
  • Felix Sepaintner
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Design and Comparison of Filter Structures in the Millimetre Wave Frequency Range on Outer- and Inner-Layers of Organic Circuits Boards

In: 2020 50th European Microwave Conference (EuMC)

Institute of Electrical and Electronics Engineers Inc. Utrecht, The Netherlands

  • 15.09.2020 (2020)
  • TC Teisnach Optik
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
  • NACHHALTIG
Zeitschriftenartikel

  • Franz Xaver Röhrl
  • Johannes Jakob
  • Werner Bogner
  • R. Weigel
  • Stefan Zorn

Bare die connections via aerosol jet technology for millimeter wave applications

In: International Journal of Microwave and Wireless Technologies vol. 11 pg. 441-446.

  • (2019)

DOI: 10.1017/S1759078719000114

This paper presents a comparison of chip connections using aerosol jet (AJ) and bond technology on low-cost printed circuit board (PCB) substrates. First, the behavior of the used gap filler material and the used silver ink for AJ technology on PCBs are characterized. In addition to comparing the radio frequency (RF) performance (DC to 67 GHz) of the two technologies, the mechanical stability is also compared. While the AJ technology transitions score above all for their RF performance and the lower requirements (surface finish, pad size, and adhesion) on the PCB, the bonding technology has clear advantages, especially with a different coefficient of thermal expansion values of the substrates to be connected. Finally, the measurement results of a complete package are shown, whereby the chip connection is realized once by means of AJ and once by bonding wires.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Bericht/Report

  • Franz Xaver Röhrl
  • Siegfried Hildebrand
  • Johannes Jakob
  • Stefan Zorn
  • Werner Bogner

Projekt NePUMuk (Neue digitale Produktions- und Mikrostrukturierungstechnologien für Anwendungen bis 80 GHz) . Abschlussbericht

Technische Hochschule Deggendorf (THD)/Technologie Campus Teisnach

  • 2019 (2019)
  • TC Teisnach Optik
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Johannes Jakob
  • R. Sammer
  • Franz Xaver Röhrl
  • Stefan Zorn
  • Werner Bogner

WR12 to planar transmission line transition on organic substrate

  • (2019)

DOI: 10.23919/EuMC.2019.8910843

Transitions for planar transmission lines on printed circuit boards to rectangular waveguide are challenging to design and manufacture. This paper introduces two transitions, the first one is a broadband transition from WR12 (60-90 GHz) waveguide to a stripline (SL) and the second is a narrowband transition to a grounded coplanar waveguide (GCPW). The focus at the first transition is based on the fact that signals can be transmitted in the complete E-Band. In the process, many manufacturing possibilities were exploited. For the second transition, the focus was on manufacturability in order to achieve the most cost effective transition possible. Design, simulated and measured results will be presented.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Vortrag

  • Felix Sepaintner
  • Andreas Scharl
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Simulation and Manufacturing of Low Loss PCB Structures with Additional Electromagnetic Field in Air . Invited Talk

In: IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes (IMWS-AMP)

Bochum

  • 16.-18.07.2019 (2019)
  • TC Teisnach Optik
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Felix Sepaintner
  • Andreas Scharl
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

Simulation and Manufacturing of Low Loss PCB Structures with Additional Electromagnetic Field in Air

  • (2019)

DOI: 10.1109/IMWS-AMP.2019.8880079

This paper presents a new method to produce different kinds of RF waveguides with reduced attenuation on low cost PCB substrates. First, microstrip (MS) and grounded coplanar waveguides (GCPW) are characterized by considering rough conductors in CST Microwave Studio. Next, laminate is partially removed, to increase the electromagnetic field ratio in air. Accordingly, the dielectric losses are reduced and the electrical length is decreased. These conductors are produced by using a CO 2 laserdrilling machine to remove the undesired substrate. The RF performance (DC to 100 GHz) of these waveguides is compared to transmission lines manufactured in conventional PCB technology. Finally, different kinds of simulated and produced microstrip filters are shown and fabrication tolerances are compared to those produced in standard technology.
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Vortrag

  • Johannes Jakob
  • R. Sammer
  • Franz Xaver Röhrl
  • Werner Bogner
  • Stefan Zorn

WR12 to planar transmission line transition on organic substrate . Invited Talk

In: 49th European Microwave Conference (EuMC)

Paris, Frankreich

  • 29.09.-04.10.2019 (2019)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Franz Xaver Röhrl
  • Johannes Jakob
  • Werner Bogner
  • R. Weigel
  • Stefan Zorn

Bare Die Connections via Aerosol Jet Technology for Millimeter Wave Applications

  • (2018)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • TC Teisnach Optik
  • DIGITAL
Bericht/Report

  • Franz Xaver Röhrl
  • Siegfried Hildebrand
  • Johannes Jakob
  • Stefan Zorn
  • Werner Bogner

Projekt NePUMuk (Neue digitale Produktions- und Mikrostrukturierungstechnologien für Anwendungen bis 80 GHz) . Projektbericht

Technische Hochschule Deggendorf/Technologie Campus Teisnach

  • 2017 (2017)
  • TC Teisnach Optik
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Franz Xaver Röhrl
  • Roman Sammer
  • Johannes Jakob
  • Werner Bogner
  • R. Weigel
  • U. Hassel
  • Stefan Zorn

Cost-Effective SIW Band-Pass Filters for Millimeter Wave Applications

  • (2017)

DOI: 10.23919/EuMC.2017.8230878

  • Elektrotechnik und Medientechnik
  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Franz Xaver Röhrl
  • Johannes Jakob
  • Werner Bogner
  • D. Hageneder
  • Stefan Zorn

Differential Wideband Interconnects for Organic Millimeter Wave Chip Packages . An effort to design an all-purpose RF chip package

pg. 536-539.

  • (2016)
  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Franz Xaver Röhrl
  • Johannes Jakob
  • Werner Bogner
  • D. Hageneder
  • Stefan Zorn

Differential Wideband Interconnects for Organic Millimeter Wave Chip Packages . An effort to design an all-purpose RF chip package

pg. 1465-1468.

  • (2016)
  • TC Teisnach Optik
  • Elektrotechnik und Medientechnik
  • DIGITAL
Zeitschriftenartikel

  • T. Dietl
  • Franz Xaver Röhrl

Thermisches Management für Leiterplatten-basierte Hochfrequenz-Packages

In: PLUS - Fachzeitschrift für Aufbau und Verbindungstechnik in der Elektronik: Produktion von Leiterplatten und Systemen

  • (2015)
  • TC Teisnach Optik
  • DIGITAL
Beitrag in Sammelwerk/Tagungsband

  • Franz Xaver Röhrl
  • Johannes Jakob
  • Werner Bogner
  • D. Hageneder

Wideband RF interconnects for organic chip packages comparison of single ended and differential transitions . An effort to design an all-purpose RF chip package

pg. 781-784.

  • (2015)
  • Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen
  • DIGITAL