Achim Dreher

Analysis of planar waveguides with the method of lines and absorbing boundary conditions

The method of lines is extended to analyze planar waveguides with open boundaries. The efficiency of using absorbing boundary conditions is demonstrated by the calculation of the effective permittivity of a single microstrip line. The results show that the boundaries may be placed closer to the guiding structure whereby the discretized area and the corresponding matrices become smaller.<<ETX>>

Antenna and receiver system with digital beamforming for satellite navigation and communications

To demonstrate and investigate the possibilities of active antennas with digital beamforming, a compact breadboard model operating in C-band with planar patches as radiators is fabricated and measured. It was originally designed as a technology demonstrator for navigation purposes, but will be extended for future use in combined navigation and communication systems. Several parameters for beam position, sidelobe reduction, and nulling are set and controlled by a suitable user interface. A special calibration and error-correction procedure is developed to compensate for drift of active elements, mutual coupling of the patches, and finite-ground plane effects. The excellent results demonstrate the versatile features of digital beamforming for satellite navigation and communication systems.

Full-wave analysis of radiating planar resonators with the method of lines

The method of lines (MoL) is extended to analyze radiating planar resonators by the use of absorbing boundary conditions. For stratified layers, an equivalent network is derived to set up a system equation by simple multiplication of hybrid matrices. As an example, the complex resonant frequency of a microstrip patch is computed and compared to results achieved with the integral equation method in spectral domain. The radiation in the near-field region is depicted by a vector plot of the energy flow, given by the real part of the Poynting vector. >

Dual polarized wide-band stacked microstrip antenna with aperture coupling for SAR applications

The design and experimental results of a C-band dual polarized aperture-coupled stacked patch microstrip antenna are presented. The antenna is capable of operating over a bandwidth of 26% with improved front-to-back ratio. The patches are excited through crossed slots. The feed lines are separated by a thin substrate to enhance the port decoupling. The measured impedance and the radiation pattern of the antenna at C-band are presented.

A new approach to dyadic Green's function in spectral domain

A new method is proposed to derive the dyadic Greens function for stratified dielectric layers from the wave equation in spectral domain. The result is a clear equivalent circuit of the whole structure which combines the TE and TM modes by hybrid block matrices. It is simple to apply and evaluate. The relation to the conventional immittance approach is shown by means of a similarity transform which diagonalizes the submatrices. The simplicity of the method is demonstrated in the application to the well-known example of a single microstrip patch on a grounded dielectric layer as well as structures with multiple layers and metallizations in arbitrary interfaces. >

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.

New aspects of the method of lines

A re-examination of the fundamentals of the method of lines (MoL) shows its close relation to the mode-matching technique, on which it is merely a variant with further approximations. It is obvious that the discretization of the differential operators should be avoided, because it has no advantage, and in fact only leads, to additional errors. This effect is demonstrated for a partially filled waveguide. >

A unified approach to the analysis of radial waveguides, dielectric resonators, and microstrip antennas on spherical multilayer structures

This paper presents a uniform procedure to analyze radial waveguides, dielectric resonators, dielectric resonator antennas, and microstrip antennas on spherical structures. It can be applied to any type of spherical multilayer closed and sector structures, which also include hemispherical structures. The arbitrary layers may be airgaps or dielectric substrates with or without metallizations in the interfaces. The inner layer can be a metallic or dielectric core. The kernel of this approach is the derivation of the spectral- and space-domain dyadic Greens function of multilayer spherical structures by using an equivalent circuit and simple network analysis techniques. The relations between the spectral and space domains are derived using the vector-Legendre transformation. For the demonstration of the applicability of this approach, the dyadic Greens functions and the system equations of some commonly used spherical structures are presented, among which the system equation of a two-layer dielectric resonator is verified analytically with the literature. As an example, the resonant frequencies of a spherical resonator with two dielectric layers covering a metallic inner layer are calculated and verified with commercial software.

Planar digital-beamforming antenna for satellite navigation

A planar digital-beamforming (DBF) antenna for user terminals in future satellite navigation systems has been developed to improve the overall system performance. A C-band breadboard model including aperture coupled patches, receiver and signal-processing unit has been designed, manufactured and tested.