L.-P. Schmidt

Universitätsklinikum Erlangen, Erlangen, Bavaria, Germany

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Publications (92)11.96 Total impact

  • C. Schildbach · L.-P. Schmidt
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    ABSTRACT: For focusing reflectors usually paraboloidal and ellipsoidal shapes are used, which are a first degree approximation to an optimal beam transformer. In this paper, the design of such an optimally shaped reflector is described, using basic numerical procedures and common CAD software. The complexity of the described procedure is not much higher than the design of paraboloidal or ellipsoidal reflectors. Measurement data is presented to confirm the functionality of the designed reflector at frequencies beyoned 200 GHz.
    No preview · Article · Jan 2015
  • M. Nezadal · J. Schur · L.-P. Schmidt
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    ABSTRACT: A full polarimetric imaging system for the nondestructive testing of glass fibre reinforced plastics in the W-Band (75 GHz to 110 GHz) is presented. It is capable of detecting defects in depths of up to 14.5mm, and 0.5mm near the backside of the samples. The full polarimtric information eases the defect detection, since it is not sensitive for the reflection from the backside.
    No preview · Article · Nov 2014
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    ABSTRACT: Frequency extender modules of vector network analyzers and signal generators, as well as front-end modules of semiconductor automatic test systems, make use of broadband resistive diode frequency multipliers. This paper presents the design and fabrication of innovative planar varistor frequency multipliers. Three frequency triplers (#1, #2, #3) and two frequency doublers (#4, #5), operating in the 60-110 GHz and 50-110 GHz frequency ranges, respectively, are designed. The hybrid architecture utilizes commercial gallium arsenide Schottky diodes from United Monolithic Semiconductors on thin-film processed high-permittivity alumina substrate. Synthesis is based on a co-simulation procedure between 3-D electromagnetic field and nonlinear harmonic balance circuit simulations. Scalar and spectral measurement data over the focused output frequency ranges are presented. Conversion loss values around 18 dB from 60 to 95 GHz and below 22 dB from 60 to 110 GHz are achieved with frequency tripler #1. Frequency doubler #5 achieves conversion loss values below 15 dB from 50 to 89 GHz and below 22 dB from 50 to 110 GHz. A comprehensive comparison of the presented work with reported frequency multipliers is included.
    No preview · Article · Dec 2013 · IEEE Transactions on Microwave Theory and Techniques
  • Philipp Quednau · Ralph Trommer · L.-P. Schmidt
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    ABSTRACT: This paper presents the development of a compact sized, low cost wide range tunable bandpass filter based on a novel RF structure. The proposed design offers a narrow passband with a relative bandwidth down to 3.9%, a wide tuning range from 700 MHz to 1150 MHz and the ability to adapt bandwidth and insertion loss during operation. Tuning is achieved by reverse biased varactor diodes with a low supply voltage of 5 V max. Design of the novel bandpass structure, integration and miniaturization to reduce its size down to approx. 6 cm2 is discussed. Measurement results over the whole tuning range are presented and the design of a miniaturized multi channel bias controller for easy frequency setting and temperature compensation is described.
    No preview · Conference Paper · Oct 2013
  • M. Schramm · M. Hrobak · J. Schur · L.-P. Schmidt
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    ABSTRACT: Single receiver vector network analyzers (VNA) are offering a cost efficient possibility to measure complex scattering parameters. One main drawback of this architecture is the larger required period of time to complete the measurement, due to the sequential capturing of the wave quantities. In order to reduce this handicap, a new switch correction scheme is detailed in this paper. The discussion includes a comparison to alternative methods based on measurements and simulations.
    No preview · Conference Paper · Jan 2013
  • M. Hrobak · M. Sterns · M. Schramm · W. Stein · L.-P. Schmidt
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    ABSTRACT: Schottky diode detectors are the method of choice for many scalar power measurement applications in the millimeter wave frequency range. Power monitoring of forward and backward travelling waves is especially important within signal generator frequency extension modules and front end modules of semiconductor automatic test systems (ATS). We present the synthesis and characterisation of a planar zero bias Schottky diode (ZBD) detector that covers an input frequency range of 60 GHz to 110 GHz. The planar design is based on thin-film processed Al2O3 substrate. The utilized gallium arsenide (GaAs) diodes are commercially available from Virginia Diodes, Inc. (VDI). The presented measurement data is compared to results from 3D electromagnetic field (EM) and nonlinear circuit simulations.
    No preview · Conference Paper · Jan 2013
  • M. Nezadal · J. Schur · L.-P. Schmidt
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    ABSTRACT: This paper presents investigations on impact damages on carbon and glass fibre reinforced plastics with a synthetic aperture radar in the frequency range of the W-Band (75 to 110 GHz) and J-Band (220 to 325 GHz). It was possible to detect the high energy impacts in the carbon fibre samples due to their phase delay in both bands. With the glass fibre samples it was also possible to detect changes in magnitude besides the phase delay. The three dimensional image reconstruction also revealed the damages beneath the surface.
    No preview · Conference Paper · Jan 2013
  • Julian Adametz · L.-P. Schmidt
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    ABSTRACT: In this paper, an approach to differentiate between various dielectric threat objects in security applications is investigated. The scattering information in form of the Sinclair matrix of relevant scenarios is gained from a fully polarimetric, monostatic synthetic aperture radar (SAR). A possible polarimetric calibration procedure is presented. The radar data are processed with the H - α decomposition algorithm. The H - α scattering characteristics of threat objects are analyzed in terms of a weighted averaging. It is shown that an object classification is possible even for threat objects conceiled under thick layers of clothing. Measurement results are presented to illustrate the topic.
    No preview · Conference Paper · Jan 2013
  • M. Hrobak · M. Sterns · M. Schramm · W. Stein · F. Poprawa · A. Ziroff · J. Schur · L.-P. Schmidt
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    ABSTRACT: To extend the frequency range of existing short-range radar modules for industrial applications, millimeter-wave frequency multipliers based on cost-effective PCB technology are required. This paper describes a zero-bias D-band frequency doubler and Y-band frequency tripler based on pure PTFE material and the commercially available DBES105a diode from United Monolithic Semiconductors (UMS). At an input drive level range of 16 dBm to 18 dBm the multipliers deliver output power levels POUT ∈ [5, -5] dBm from 100 GHz to 160 GHz and POUT ∈ [-11, -20] dBm from 180 GHz to 230 GHz.
    No preview · Conference Paper · Jan 2013
  • C. Schildbach · J. Schur · L.-P. Schmidt
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    ABSTRACT: A field coupled detector is presented including planar antenna design as well as the video amplifier topology. The compact antenna design is suitable for application in dense antenna arrays. Particularly an array concept is shown that suits for holographic imaging at frequencies beyond 200 GHz. For this purpose a broadband planar antenna is designed for frequencies from 230 GHz to 325 GHz, allowing for high depth resolution in an imaging system. Optimization methods utilized to improve the antenna perfomance are discussed. The presented transimpedance amplifier design offers a low noise figure and a protection for the diode, as it regulates the diode voltage to zero. An optimal diode impedance for this amplifier topology is derived. Simulation and measurement results are presented.
    No preview · Conference Paper · Jan 2013
  • R. Trommer · P. Quednau · L.-P. Schmidt
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    ABSTRACT: Secondary surveillance radar is an important part of air traffic control nowadays. Modern receivers use an antenna array to estimate the direction of the arriving signal in order to increase the reliability of the received aircraft positions. In this paper a versatile multi-channel signal generator for testing these receivers is presented. The requirements for such a system are explained followed by the description of the hardware and software design and the automatic self calibration process. Finally the measurement results of the output signals are presented.
    No preview · Conference Paper · Jan 2013
  • M. Hrobak · M. Sterns · E. Seler · M. Schramm · L.-P. Schmidt
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    ABSTRACT: In this study the design and construction of an ultrawideband backward wave directional coupler is presented. The symmetric, non-uniform coupler covers the frequency range from 2 to 50 GHz with an average coupling of 16.6 2.4 dB while establishing directivity values greater than 10 dB from 10 MHz to 33.8 GHz and 8 dB up to 48.4 GHz. The design is based on coupled microstrip lines suitable for integration into planar front end modules of modern measurement systems. To account for the dispersive behaviour of such waveguides, wiggly-line technique is utilised. Accurate extraction of the waveguide frequency-dependent distributed equivalent circuit parameters is done by 2D finite element electromagnetic field (EM) simulation. To balance out the remaining mistuning appropriate scaling parameters are introduced. The influence of common manufacturing and assembly tolerances on the device performance is analysed. Measurement results of the synthesised coupler with planar matched isolated port are presented.
    No preview · Article · Jun 2012 · IET Microwaves Antennas & Propagation
  • M. Schramm · M. Hrobak · J. Schur · L.-P. Schmidt
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    ABSTRACT: Scattering parameter measurements in the presence of crosstalk is a well documented problem. The available calibration methods, suited for the general 16-term error model, capable of taking the crosstalk into account, suffer from the required Thru-Standard, which has to be perfectly known. This information is hard to acquire in some cases. An approach which makes the advantage of the 7-term SOLR (Short-Open-Load-Reciprocal) accessible to the 16-term error model is discussed in this article. The mathematical description, the feasibility for multiport applications, measurement results and a brief sensitivity analysis will be presented.
    No preview · Conference Paper · Jan 2012
  • M. Hrobak · W. Stein · M. Sterns · M. Schramm · L.-P. Schmidt
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    ABSTRACT: Triple balanced mixers (TBM) are ideally suited for use in heterodyne transceivers with great signal bandwidths. The design and construction of a hybrid broadband TBM based on commercial silicon crossed quad diodes is presented. Broadband planar baluns and the use of balanced edge and broadside coupled striplines allow for covering an RF / LO frequency range of 1 GHz to 35 GHz and at least 10 GHz IF bandwidth, if we claim for up- and downconversion loss values below 15 dB. This is achieved with local oscillator power levels PLO ∈ [10,14] dBm and an input 1 dB compression point of 6 dBm. The paper includes spectral measurement data which are in reasonable agreement with the simulation results that are based on a co-simulation procedure between 3D electromagnetic field (EM) simulations and nonlinear harmonic balance circuit simulations.
    No preview · Conference Paper · Jan 2012
  • Amir Cenanovic · Marcus Schramm · L. P. Schmidt
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    ABSTRACT: A non-destructive microwave measurement setup for broadband complex permittivity determination of solid materials over a frequency band from 0.05 GHz to 6 GHz is presented. The setup design was optimized for measurements of glass materials with planar and convex surfaces, but works with other dielectric materials as well. The measurement method is based on the near field coupling of two open-ended coaxial probes through the material under test (MUT). A theoretical modeling of this measurement configuration was performed, using a 3D full-wave electromagnetic field simulator. Two identical coaxial probes and an equivalent calibration kit, in order to perform a TRL calibration of the proposed setup, were designed. The calibration procedure of the measurement setup is explained and experimental results are presented.
    No preview · Article · Jun 2011 · IEEE MTT-S International Microwave Symposium digest. IEEE MTT-S International Microwave Symposium
  • A. Ćenanović · S. Martius · A. Kilian · J. Schür · L.-P. Schmidt
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    ABSTRACT: A nondestructive microwave measurement setup for complex permittivity determination of glass material with planar and convex surfaces over a frequency range of 75 MHz to 6 GHz is presented. The measurement method is based on an open-ended coaxial probe technique. Two coaxial probes were constructed and their design was optimized in order to meet two contradictory requirements. On the one hand a large probe aperture is needed for sufficient measurement sensitivity at desired frequency range, on the other hand a small probe aperture is better suited for contacting non planar surfaces and avoiding air gaps. The calibration procedure of the measurement setup is explained and experimental results for planar and curved glass material are presented.
    No preview · Conference Paper · Apr 2011
  • Julian Adametz · Frank Gumbmann · L.-P. Schmidt
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    ABSTRACT: In the classical indirect holographic setup, a wave emitted by the measurement object is superimposed with a reference wave at the aperture of the imaging system. The resulting interference pattern can be recorded with a simple intensity detection. However, the complex object field can be obtained from the plane wave spectrum (PWS) of the interference pattern. Dedicated methods can be used to calculate the field distribution at the object position, which is equivalent to the object properties and to an image of the object, respectively. This paper shows that the resolution of the created image is restricted due to the fact that the bandwidth of the extracted field is limited by the extraction process. A relation between the maximum possible bandwidth and the geometrical dimensions of the imager setup is deduced. Furthermore, a formula for the minimum achievable resolution is derived. Experimental results are presented to illustrate the issue.
    No preview · Conference Paper · Apr 2011
  • C. Reck · U. Berold · L.-P. Schmidt
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    ABSTRACT: Methods to estimate Directions of Arrival (DOA) on radio signals are susceptible to hardware and signal deficiencies. In the following, the robustness of four algorithms is evaluated by numerical and experimental tests. The focus lies thereby on Secondary Surveillance Radar (SSR) signals, but the algorithms can generally be used on any kind of radio signal. It will be shown that variants of the ESPRIT algorithm provide highly accurate DOA estimates on SSR signals even without calibration.
    No preview · Conference Paper · Feb 2011
  • C. Reck · U. Berold · L.-P. Schmidt
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    ABSTRACT: Multipath propagation is a serious problem with Secondary Surveillance Radar (SSR) systems at airport apron and taxiway areas. In this approach, effective suppression of interference (garbling) by multipath components, using a multichannel receiver is presented. Thereby the SSR header format is exploited to detect multipath components, which are then eliminated by subspace based signal suppression. Extensive tests at Frankfurt international airport show the potential of the proposed approach to significantly improve reception at problematic sites.
    No preview · Conference Paper · Jan 2011
  • C. Reck · R. Trommer · L.-P. Schmidt
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    ABSTRACT: The focus of this work is the construction of a bandpass filter fully electronically tunable in bandwidth and center frequency by combining modified combline and split ring resonator structures loaded by varactor diodes. It is shown how separate tuning of the assembled varactors can be used to significantly alter filter bandwidths. A design with large tuning range from 800 to 1300 MHz in combination with moderate insertion loss is presented.
    No preview · Conference Paper · Jan 2011

Publication Stats

289 Citations
11.96 Total Impact Points

Institutions

  • 2001-2013
    • Universitätsklinikum Erlangen
      Erlangen, Bavaria, Germany
  • 1999-2013
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      Erlangen, Bavaria, Germany
  • 2006
    • Nuremberg University of Music
      Nuremberg, Bavaria, Germany
  • 2005
    • Technical University Darmstadt
      • Institute of Microwave Engineering and Photonics
      Darmstadt, Hesse, Germany
  • 2004
    • University of Freiburg
      Freiburg, Baden-Württemberg, Germany