L.-P. Schmidt

Universitätsklinikum Erlangen, Erlangen, Bavaria, Germany

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Publications (98)18.9 Total impact

  • A. Cenanovic, T. Koppel, J. Ringel, L.-P. Schmidt
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    ABSTRACT: In this work a broadband waveguide orthomode transducer (OMT) operating at the entire WR12 band is presented. The compact size OMT is fabricated in split-block technique. It exhibits an insertion loss below 0.6 dB and return loss values for the horizontal polarization greater than 20 dB and for the vertical polarization greater than 17 dB at 69 - 90 GHz. The simulated isolation between the orthogonal polarization ports is better than - 65 dB across the 60 - 90 GHz band.
    Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013 38th International Conference on; 01/2013
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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.
    Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013 38th International Conference on; 01/2013
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    ABSTRACT: If, for practical reasons, there is a need to bend a differential waveguide, the bend has to be compensated to avoid mode conversion into the common mode which can lead to unwanted resonance effects. This paper deals with two possible compensating structures for a 45° bend in a differential waveguide exciting a hybrid antenna. The hybrid antenna in turn is part of a large array used in a security scanner for people screening. Simulations show antenna behavior with and without compensation with respect to matching, mode conversion, gain, and suppression of the cross polarization.
    Microwave Conference (EuMC), 2013 European; 01/2013
  • S. Methfessel, L.-P. Schmidt
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    ABSTRACT: Size and feed structure are some of the important constraints for using antenna-elements in multi-element two-dimensional arrays, where easy planar integration with transceiver chips is essential. This applies especially when differential signaling and adaptable polarization is required. Based on a balanced-fed patch-excited cavity-backed horn antenna (hybrid antenna), feeding concepts and approaches to reduce size are discussed and evaluated in this paper. The influence of the substrate integrated cavity is analyzed and methods to overcome the restrictions are presented, together with simulated and measured results. The optimized antennas achieve a relative bandwidth of more than 17% for 10 dB return loss, a gain of more than 5 dBi as well as symmetric and homogeneous radiation patterns in amplitude and phase with low cross-polarization.
    Radar Conference (EuRAD), 2013 European; 01/2013
  • 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.
    Microwave Conference (EuMC), 2013 European; 01/2013
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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.
    IEEE Transactions on Microwave Theory and Techniques 01/2013; 61(12):4442-4460. · 2.23 Impact Factor
  • J. 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.
    Radar Conference (EuRAD), 2013 European; 01/2013
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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.
    Microwave Conference (EuMC), 2013 European; 01/2013
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    ABSTRACT: Target movement during illumination causes reliability issues in imaging systems, particularly in applications where time efficiency is needed. A technique is proposed in order to reduce measurement time and as a consequence also motion blur effects. With the use of OFDM waveforms, a decrease in measurement time by a factor of 1.6 is achieved with minimal hardware costs. Measurement time for increasing numbers of carriers is predicted. A hardware realization is investigated with respect to hardware imperfections. Influence of intermodulation distortion and phase noise on dynamic range is discussed. Afterwards, imaging results are presented.
    Radar Conference (EuRAD), 2013 European; 01/2013
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    ABSTRACT: Current digital-beamforming multistatic mm-wave array designs show superior near field imaging performance. Therefore, mm-wave imaging systems based on these concepts are suitable for a variety of security, medical and industrial applications. The theoretically achieved array performance can be degraded by noise and unwanted signals within the actually implemented systems. In this work, the sensitivity of such systems on certain types of systematic errors within its signal processing chain including the system error correction mechanism is discussed and analyzed. Effects of errors within the reconstructed images are demonstrated, and methods to reduce the effects of some dominant error signals are proposed.
    Radar Conference (EuRAD), 2013 European; 01/2013
  • M. Kohler, J. Schur, L. Schmidt
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    ABSTRACT: Current Automotive Radar sensors operate in a frequency range up to 81 GHz to provide distance, velocity and angle information about traffic objects. For detecting weakly reflecting objects in presence of a nearby strong reflector (e.g. a person standing close to a van) there are high demands on a radar systems angular resolution. A possibility to improve the angular resolution is increasing the operation frequency. In this paper an antenna concept at 150 GHz is presented showing the benefits of high resolution radar for cars.
    Radio and Wireless Symposium (RWS), 2013 IEEE; 01/2013
  • 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.
    Microwave Conference (EuMC), 2013 European; 01/2013
  • 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.
    Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013 38th International Conference on; 01/2013
  • A. Cenanovic, L. Schmidt
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    ABSTRACT: This paper presents a sparse periodic linear array, which is designed using the effective aperture concept and optimized for multi-angle reflection ellipsometry measurements in the W-band (75-90 GHz). The optimization of the array is performed in order to achieve multi angle illumination of the object and high ambiguity suppression in the short range, for accurate phase measurements.
    Wireless Information Technology and Systems (ICWITS), 2012 IEEE International Conference on; 01/2012
  • A. Schiessl, R. Juenemann, L. Schmidt
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    ABSTRACT: Active millimeter-wave imaging systems are increasingly utilized in security, medical and industrial applications. At E-Band frequencies, such systems integrate more than three thousand antennas on 2 m × 1 m aperture. Commercial success of those systems requires cost efficient but precise manufacturing technologies to build highly integrated modular mm-wave front ends. Here, a module for a new sparse imaging array architecture is presented. The module is manufactured using a unique mm-wave chip-on-board technology. It operates from 70 GHz to 80 GHz, and integrates 48 MMICs and several thin film ceramic components.
    Microwave Conference (EuMC), 2012 42nd European; 01/2012
  • S.S. Ahmed, L.-P. Schmidt
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    ABSTRACT: The increasing demand on developing advanced imaging methods for the personnel screening applications has motivated many researchers to explore new techniques suitable to the emerging problem. Among the known methods, the active imaging using multistatic arrays in connection to digital-beamforming proofs efficient imaging with high image quality in terms of dynamic range and resolution. As any active imaging method, the illumination of the imaged object becomes an issue due to specular reflections. The human skin causes relatively strong specular reflections in the millimeter-wave range, and hence hinders the visibility of the body to some extend. Therefore, a consolidated understanding of the geometrical problem is essential for the optimization of the illumination issue. In this work, a simulation model is presented to address the problem precisely; and a measurement verification in the frequency range of 75 to 82 GHz is made to demonstrate the exactness of the proposed model. Additionally, an illumination analysis of a typical screening scenario of a human is presented.
    Antennas and Propagation (EUCAP), 2012 6th European Conference on; 01/2012
  • M. Nezadal, J. Schur, L. Schmidt
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    ABSTRACT: The non-destructive testing (NDT) of glass fibre reinforced plastics (GFRP) becomes more and more important. A test setup using a synthetic aperture radar (SAR) at frequencies of 220 - 325 GHz was set up to detect artificial defects in the probe. The paper will present experimental results and will furthermore address the challenges of imaging GFRP samples in a reflection geometry setup.
    Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2012 37th International Conference on; 01/2012
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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.
    Microwave Conference (EuMC), 2012 42nd European; 01/2012
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    ABSTRACT: Due to the enormous advances made in semiconductor technology over the last few years, high integration densities with moderate costs are achievable even in the millimeter-wave (mm-wave) range and beyond, which encourage the development of imaging systems with a high number of channels. The mm-wave range lies between 30 and 300 GHz, with corresponding wavelengths between 10 and 1 mm. While imaging objects with signals of a few millimeters in wavelength, many optically opaque objects appear transparent, making mm-wave imaging attractive for a wide variety of commercial and scientific applications like nondestructive testing (NDT), material characterization, security scanning, and medical screening. The spatial resolution in lateral and range directions as well as the image dynamic range offered by an imaging system are considered the main measures of performance. With the availability of more channels combined with the powerful digital signal processing (DSP) capabilities of modern computers, the performance of mm-wave imaging systems is advancing rapidly.
    IEEE Microwave Magazine 01/2012; 13(6):26-43. · 1.50 Impact Factor
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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.
    IET Microwaves Antennas & Propagation 01/2012; 6(9):1048-1055. · 0.84 Impact Factor

Publication Stats

149 Citations
18.90 Total Impact Points

Institutions

  • 1999–2010
    • Universitätsklinikum Erlangen
      Erlangen, Bavaria, Germany
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      Erlangen, Bavaria, Germany
  • 2005–2008
    • Technical University Darmstadt
      • Institute of Microwave Engineering and Photonics
      Darmstadt, Hesse, Germany
  • 2003–2008
    • Nuremberg University of Music
      Nuremberg, Bavaria, Germany