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München, Germany

Walter M.,German Aerospace Center | Gligorevic S.,German Aerospace Center | Detert T.,Rohde and Schwarz GmbH and Co. | Schnell M.,German Aerospace Center
EuCAP 2010 - The 4th European Conference on Antennas and Propagation

This paper presents results of air-to-air channel measurements at a center frequency of 250MHz. Using a test signal of 20MHz bandwidth, a large number of channel transfer functions was recorded and propagation characteristics evaluated in terms of power delay profile, Doppler power profile, delay spread and Doppler spread. According to the results, the channel might be approximated by a two-path channel impulse response whose parameters depend on the aircraft altitudes and on the type of overflown terrain. Source

Huang H.,University of Texas at Arlington | Bednorz T.,Rohde and Schwarz GmbH and Co.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

Scattering parameters (S-parameters) are the most common tools for characterizing microwave devices and high-frequency systems but have not been used for ultrasoundbased structural health monitoring (SHM) so far. In this paper, we present the theory, signal processing algorithms, and experimental results to demonstrate the applications of S-parameters for three common ultrasound-based SHM techniques, i.e., ultrasound pitch-catch, pulse-echo, and impedance/admittance measurements. The concept of the S-parameters is first introduced, followed by the discussions of extracting the time-domain ultrasound signals from the frequency-domain Sparameter measurements. The time-domain signals calculated from the measured S-parameters were compared with the oscilloscope measurements. Excellent agreements between these two sets of measurements were achieved. In addition, time-frequency analysis of the ultrasound inspection system based on the S-parameter measurements has also been performed. This work demonstrated that the S-parameters can serve as a versatile tool for ultrasound-based SHM. © 1986-2012 IEEE. Source

Rossetto F.,Rohde and Schwarz GmbH and Co. | Berioli M.,German Aerospace Center
2012 6th Advanced Satellite Multimedia Systems Conference, ASMS 2012 and 12th Signal Processing for Space Communications Workshop, SPSC 2012

Single Carrier FDMA may offer important advantages for satellite networks, for instance in terms of increased spectral efficiency, compared to classic MF-TDMA multiple access schemes. This work studies the performance of synchronization procedures and provides indications on the system sizing when SC FDMA is employed over the return link of a GEO satellite system. It is shown how a DVB-RCS like closed loop synchronization can yield satisfactory results for stationary users, while it is still challenging to achieve the same results for mobile terminals. © 2012 IEEE. Source

Hermenier R.,German Aerospace Center | Rossetto F.,German Aerospace Center | Rossetto F.,Rohde and Schwarz GmbH and Co. | Berioli M.,German Aerospace Center
IEEE Transactions on Wireless Communications

The existing studies of RObust Header Compression (ROHC) have provided some understanding for memoryless channel, but the behavior of ROHC for correlated wireless channels is not well investigated in spite of its practical importance. In this paper, the dependence of ROHC against its design parameters for the Gilbert Elliot channel is studied by means of three analytical models. A first more elaborated approach accurately predicts the behavior of the protocol for the single RTP flow profile, while a simpler, analytically tractable model yields clear and insightful mathematical relationships that explain the qualitative trends of ROHC. The results are validated against a real world implementation of this protocol. Moreover, a third model studies also the less conventional yet practically relevant setting of multiple RTP flows. © 2013 IEEE. Source

Hrobak M.,Friedrich - Alexander - University, Erlangen - Nuremberg | Stein W.,Friedrich - Alexander - University, Erlangen - Nuremberg | Sterns M.,Rohde and Schwarz GmbH and Co. | Schramm M.,Friedrich - Alexander - University, Erlangen - Nuremberg | Schmidt L.-P.,Friedrich - Alexander - University, Erlangen - Nuremberg
European Microwave Week 2012: "Space for Microwaves", EuMW 2012, Conference Proceedings - 42nd European Microwave Conference, EuMC 2012

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 & Element; [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. © 2012 EUROPEAN MICROWAVE ASSOC. Source

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