Lukasz Greda

Development of Robust Safety-of-Life Navigation Receivers

This paper summarizes the development of safety-of-life receivers for global navigation satellite systems. Two receiver systems have been successfully fabricated, integrated, and tested by means of field experiments. Implementation issues of these two systems are described in this paper. The third generation of this receiving system is based on a dual-band approach with antennas that are able to separate two frequency bands using two outputs. Measured results show that high isolation between the two bands can be achieved.

Smart Antenna Terminals for Broadband Mobile Satellite Communications at Ka-Band

This paper deals with a modular Rx- and Tx- antenna terminal featuring digital beamforming (DBF) at Ka-band frequencies. Background and vision of the project SANTANA II and recent realizations are described. Different system components are outlined covering digital baseband, RF- and IF- level as well as software aspects. An outlook on mobile field tests, which will be reported at the conference, concludes this contribution.

Antenna and RF front end calibration in a GNSS array receiver

The use of spatial-domain signal processing for mitigation of interference signals in receivers of global navigation satellite systems (GNSS) allows for improvement of the overall system performance. To fully benefit from the use of adaptive antenna arrays, the individual signal processing paths in such a multi-antenna system should be thoroughly calibrated. The focus of this paper is on the specifics of such calibration in receivers for satellite navigation systems (e.g. GPS and coming Galileo). The design goals of the antenna and RF front end for GNSS receivers are reviewed. The architecture of a GNSS array receiver for safety-of-life applications with high robustness against radio interference is presented. The practical solutions for the antenna array and RF front-end calibration along with the field test results demonstrating their performance are outlined.

Hybrid analysis of three-dimensional structures by the method of lines using novel nonequidistant discretization

Many microwave structures contain various elements with very big difference in their size. Exact modeling of such structures with equidistant discretization requires considerable numerical effort and large memory capacity. Alternative formulas for nonequidistant discretization are proposed. New difference operators for nonequidistant discretization are given. The accuracy of these operators is compared with the previous ones used with the Method of Lines. Numerical results of two microwave filters are presented to check the accuracy of the new algorithm.

Development of robust safety-of-life navigation receivers at the german aerospace center (DLR)

This paper summarizes the development of safety-of-life receivers for global navigation satellite systems (GNSS) that has been being conducted at the Institute of Communications and Navigation of the German Aerospace Center (DLR). Two receiver systems have already been successfully fabricated, integrated and tested by means of field experiments. Implementation issues of these two systems are described in this contribution. Details about the third generation of DLRs receiving system, which is currently under development, are also briefly discussed.

Efficient analysis of waveguide-to-microstrip and waveguide-to-coplanar line transitions

A general procedure using the Method of Lines (MoL) for the analysis of waveguide-to-microstrip and waveguide-to-coplanar line transitions is described. Using two crossed two-dimensional discretization line systems instead of a full three-dimensional discretization allows to reduce the numerical effort. This concept is combined with the concept of impedance/admittance transformation. The described relations are also useful for other applications. The proposed algorithm is validated by comparison to measured and theoretical results.

Tx-terminal phased array for satellite communication at Ka-band

The concept for an active circularly polarized phased-array terminal antenna for satellite communication at Ka-band is presented. The proposed antenna is based on a modular architecture with sub-arrays of 4times4 elements. Sequential rotation of the antenna elements is implemented to improve the polarization purity. Thermal dissipation problems are addressed.

A simulation tool for design and analysis of planar antenna arrays

For the design and analysis of planar antenna arrays the simulation tool SEQAR based on MATLABreg has been developed. With the help of single element radiation patterns from simulations with commercial software or measurements it offers the possibility of beamforming and beamsteering with arbitrarily rotated elements in a wide range of array configurations. The integrated array editor allows the fast and easy assembly of antenna arrays. Both big arrays and arrays with non-uniform spacing can be efficiently designed and analyzed. Mutual coupling between the antenna elements can be taken into account and its undesired effects alleviated by decoupling plalgorithms.

Modeling of planar microwave filters

An approach for modeling of planar microwave filters by the Method of Lines (MoL) is presented. The algorithm combines 2-D discretization of the cross-section with the numerically stable impedance/admittance transformation. To improve accuracy and efficiency of this approach, edge conditions are examined and the best edge position relative to the discretization lines is derived. The convergence behaviour of the method for different edge positions is examined. To substantiate the proposed formulation three planar microwave filter are modeled.

Demonstrator concept for a satellite multiple-beam antenna for high-rate data relays

This paper describes concept and development of some key components for a demonstrator of a multiple-beam antenna used for high-rate data relays. The demonstrator shall validate the whole antenna concept, showing among others antenna multibeam capability and advantages of the deployed digital beamforming.