Marcos Vinicio Thomas Heckler

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.

Dual-band circularly polarized microstrip antenna with two isolated outputs suitable for navigation systems

The geometry and numerical results of a dual-band circularly polarized microstrip antenna with two isolated outputs have been presented in this paper. Good return loss has been obtained for both frequency bands. Moreover, a gain response with a strong suppression in the frequency range located between both Galileo bands has been achieved.

Analysis of Conformal Microstrip Antennas With the Discrete Mode Matching Method

An extension of the discrete mode matching (DMM) method is used to analyze microstrip antennas conformed to cylinders. The structure needs to be discretized only along the azimuthal and the axial directions by sampling the fields and current densities in the interfaces between dielectric layers. The solution in the radial direction is obtained analytically with the dyadic Greens function, which is calculated using the full-wave equivalent circuit (FWEC) in the spectral domain. The structure is truncated in the axial direction by employing absorbing boundary conditions (ABCs). The mathematical formulation is given in this paper, followed by its application to compute the main properties of conformal microstrip antennas, such as resonant frequency, radiation patterns and input impedance. Validation with the commercial software HFSS has been done and good agreement between the results has been observed.

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.

Synthesis of linear antenna array for 4G mobile communication systems

This paper presents the application of optimization methods for the synthesis of a linear array to operate in the frequency range of 4G technology in Brazil. The desired pattern shall exhibit squared-cosecant shape, so as to provide uniform distribution of power inside the base station cell and to reduce co-channel interference. Such an array is well suited to operate as a radio base station of mobile communications systems. The synthesis is performed by a combination of optimization methods: the genetic algorithm, which is used for the initial global search, and the sequential quadratic programming, which is applied for local refinement of the solution. This approach allows faster convergence than using only one kind of optimization method. The technique is demonstrated for a linear array of isotropic elements and, subsequently, for an array of E-shaped microstrip antennas.

Analysis of cylindrical microstrip lines using the discrete mode matching method

This letter presents an extension of the discrete mode matching (DMM) method to analyze microstrip lines conformed on cylinders. The DMM is well suited to the analysis of multilayered structures, since the fields must be only sampled at the interfaces between the dielectric layers. For the case of cylindrical microstrip lines, the structure is discretized only along one direction, whereas the analytical solution is obtained in the other with the Greens functions calculated using a full-wave equivalent circuit. The mathematical formulation of the present extension is given in this letter, followed by its application to compute the propagation constants for cylindrical microstrip lines

Synthesis of linear antenna arrays for radio base stations

This paper presents the application of optimization methods for the synthesis of a linear array for radio base stations of mobile communications systems. The desired pattern shall exhibit squared-cosecant shape, so as to provide uniform distribution of power inside the base station cell and to reduce co-channel interference. The synthesis is performed by a combination of optimization methods: the genetic algorithm is used for the initial global search, then the sequential quadratic programming is applied for local search. This approach allows faster convergence than using only one kind of optimization method. The technique is demonstrated for a linear array of isotropic elements and, subsequently, for an array of microstrip antennas.

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.