Zelder T

Leibniz Universität Hannover, Hanover, Lower Saxony, Germany

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Publications (9)3.95 Total impact

  • Thomas Zelder · Bernd Geck ·
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    ABSTRACT: An introduction to contactless vector network analysis is given for the determination of the scattering parameters of embedded devices. In the measurement setup, contactless probes are connected to a conventional vector network analyzer. Suitable probes are developed for the implementation of a contactless measurement setup, whereas the positioning of the probes is essential for an accurate measurement setup. The contactlessly measured results are compared to results received with a conventional vector network analyzer. These comparisons show that it is possible to characterize embedded devices with the contactless vector network analysis at least up to 6 GHz using the suggested probes.
    IEEE Microwave and Wireless Components Letters 10/2011; 21(9-21):504 - 506. DOI:10.1109/LMWC.2011.2162619 · 1.70 Impact Factor
  • T. Zelder · B. Geck · M. Wollitzer · I. Rolfes · H. Eul ·
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    ABSTRACT: In this paper, an introduction to contactless vector network analysis is given. Furthermore, the implementation of a contactless measurement setup is presented using different printed coupling structures. The coupling structures are connected to a vector network analyzer (VNA) by means of conventional on-wafer probes, as well as planar-coaxial transitions. For the contactless method, conventional calibration algorithms are used to determine the scattering parameters of a device within a complex planar circuit. The contactless measured results are compared to results received with a conventional VNA and to simulation results obtained with a 3-D field simulator. These comparisons show that, especially for small coupling structures of approximately 1 mm, the results correspond well up to 20 GHz.
    IEEE Transactions on Microwave Theory and Techniques 12/2008; 56(11-56):2628 - 2634. DOI:10.1109/TMTT.2008.2005893 · 2.24 Impact Factor
  • Thomas Zelder · Elena Valles Lluch · Bernd Geck · Ilona Rolfes · Hermann Eul ·
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    ABSTRACT: In many applications a directional coupler with a high directivity is needed. Therefore, a tunable directional coupler will be presented in this paper. The tunable coupler consists of a conventional directional coupler and a tuning network. By tuning the network, it is possible to increase the directivity of the conventional coupler. The tuning network can either be realized in software or hardware. In this paper the theoretical derivation and an example for a practical realization of the tunable coupler will be presented.
    Microwave Conference (GeMIC), 2008 German; 04/2008
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    Zelder T · Geck B · Rolfes I · Eul H ·
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    ABSTRACT: The scattering parameters of embedded devices can be measured by means of contactless vector network analysis. To achieve accurate measurement results, the contactless measurement setup has to be calibrated. However, if the substrate material or the planar transmission lines on the substrate changes, a new calibration is necessary. In this paper a method will be examined, which reduces the number of calibration cycles by using a database. Analytical results show that by using this database method, errors occur which depend on the coupling coefficients and on the load impedances of the contactless probes. However, the measurement results show deviations smaller than 7% in comparison to the conventional vector network analysis, which is sufficient for the most pratical applications.
    Advances in Radio Science 01/2008; 6. DOI:10.5194/ars-6-19-2008
  • Thomas Zelder · B. Geek · Michael Wollitzer · Ilona Rolfes · Hermann Eul ·
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    ABSTRACT: In this paper a system for the contactless measurement of the scattering parameters of planar two-port devices is presented. Thereby, loop couplers are used as probes. The system is calibrated with the Thru-Reflect-Line calibration algorithm regarding planar reference planes. This provides the possibility to measure scattering parameters of devices embedded in complex planar circuits. The contactless measured scattering parameters of different devices are compared with results received by a conventional vector network analyzer. This comparison shows that the results are corresponding to each other. Furthermore, it is shown, that a contactless measurement of an embedded DUT is possible.
    Microwave Conference, 2007. European; 11/2007
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    Camp M · Herschmann R · Zelder T · Eul H ·
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    ABSTRACT: This paper shows a new method to determine the input impedance of RFID transponder antennas with a combination of on-wafer-prober and network analyzer. It is shown that the results are in a good agreement with FEM simulations (HFSS) for a large part of the examined antenna structures.
    Advances in Radio Science 06/2007; 5. DOI:10.5194/ars-5-115-2007
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    Zelder T · Rolfes I · Eul H ·
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    ABSTRACT: Contactless vector network analysis based on a diversity calibration is investigated for the measurement of embedded devices in planar circuits. Conventional contactless measurement systems based on two probes for each measurement port have the disadvantage that the signal-to-noise system dynamics strongly depends on the distance between the contactless probes. In order to avoid a decrease in system dynamics a diversity based measurement system is presented. The measurement setup uses one inductive and two capacitive probes. As an inductive probe a half magnetic loop in combination with a broadband balun is introduced. In order to eliminate systematic errors from the measurement results a diversity calibration algorithm is presented. Simulation and measurement results for a one-port configuration are shown.
    Advances in Radio Science 06/2007; 5. DOI:10.5194/ars-5-19-2007
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    Zelder T · Rabe H · Eul H ·
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    ABSTRACT: In this paper, a contactless measuring system for the determination of the S-parameters of planar circuits is presented. With a contactless measuring system it is possible to characterise a device-under-test (DUT) embedded in a planar circuit environment without cutting the planar transmission lines connecting the DUT. The technique utilizes four identical capacitive probes in conjunction with a vector network analyser (VNA). For the usage of electromagnetic probes compared to other coupling techniques like the electro-optic probing, there is no need for expensive and complex equipment in addition to the typical equipment of a common microwave laboratory. The S-parameters are determined accurately using conventional calibration methods. A simple analytical model for the representation of the basic characteristics is developed. Furthermore, the influences on the S-parameters as a result of a variation in the coupling are presented. With the knowledge of the system characteristics, an accurate contactless measurement system is set up. The comparison between conventional and contactless measurements in a frequency range of 1–20 GHz shows a very good agreement with a phase error smaller than 1°.
    Advances in Radio Science 01/2007; 5. DOI:10.5194/ars-5-427-2007
  • T. Zelder · H. Eul ·
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    ABSTRACT: An enhanced contactless measuring system based on a vector network analyzer and three electromagnetic near field probes is presented. The system uses diversity calibration in order to get accurate measurement results. By an efficient combination of the contactless measured complex signals the system dynamic range can be increased significantly. Measurements up to 25GHz show an improvement in system dynamics dependent on frequency up to 30dB
    Microwave Conference, 2006. 36th European; 10/2006