Arne F. Jacob

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.

Vertical feedthroughs for millimeter-wave LTCC modules

This paper reports on novel types of vertical interconnects to be incorporated inside highly integrated LTCC Modules (Low Temperature Co-fired Ceramics). RF-transitions vertically interconnecting the top and bottom side of the LTCC are studied using alternatively CPW (coplanar waveguide) or microstrip feedlines. Vertical DC supply and control lines with integrated RF blocking capacitors are also demonstrated. LTCC test modules were fabricated and the performance of all feedthroughs successfully validated by scattering parameter measurements up to 40 GHz.

Accelerated Simulation of Planar Circuits by Means of Wavelets

A simple and computationally efficient method to a priori evaluate the magnitude of reactions in wavelet Galerkin schemes is presented. This avoids the calculation of unnecessary impedance matrix elements. Computational savings in matrix filling and inversion time are demonstrated for two microstrip circuits.

A priori size estimation of wavelet-based Galerkin matrices [planar microwave circuits]

The use of wavelets in Galerkin scheme moment methods significantly reduces computation time and memory requirements. An a priori estimation of the number of entries of the system matrix is presented. The wavelet scheme is particularly advantageous when analyzing electrically small but complex structures. While normally O(N/sup 2/) elements need to be stored, wavelets allow a reduction to O (N log N) with N the number of unknowns.

Wavelet-based Simulation of Arbitrarily Shaped Planar Circuits

A wavelet analysis of arbitrarily shaped planar circuits is presented. A simple algorithm is implemented for the step approximation of such structures. This study represents a generic step towards the simulation of more complex circuits.

Non-Uniform Wavelets on Adapted Grids for Modelling Edge Singularities

Moment method simulations of microwave planar circuits are more effective with optimum varidistant bases for modelling field singularities. Novel close to optimum knot sequences are developed and compared to existing schemes. The complexity of the underlying matrices is further reduced by means of especially constructed non-uniform wavelets.

Planar Multiresolutional Antenna for Automotive Radar

High resolution and wide angle surveying capability are combined within a single planar antenna system using a modified Rotman-lens. While narrow beam mode is achieved by feeding the beamports of the lens, broad beams are realized by distributed sidewall feeding with secondary lenses. A Fresnel-lens-like delay network is introduced in the design to reduce the sidelobe level. Effects of fabrication tolerances are assessed. The concept is validated experimentally.

Nonlinear surface impedance of Y-Ba-Cu-O films in a DC magnetic field

We study the microwave power dependence of the surface impedance of YBCO epitaxial films in a DC magnetic field up to 0.7 T. We demonstrate that the surface impedance of our films in the linear regime is dominated by weak links at low DC field and by vortices at high DC field. However, the microwave power dependence of the surface impedance arises mostly from the hysteretic RF vortex penetration.

Stabilized Fin-Line FET-Oscillators

The design and realization of stable fin-line FET-oscillators is described. Several examples of fundamental mode oscillators through X-band and Ku-band are given. A Ka-band second harmonic FET-oscillator is reported.

On the Modeling of Small Wire Scatterers with Core

Summary A simple model for chiral wire scatterers with core is presented. The model reduces the (isotropic) core of the scatterer to its dipole moments. The resulting description of the electromagnetic problem allows a simple calculation of the complete dipole polarizability tensors of the scatterer. For spherical cores the theoretical results obtained from the model are compared with the exact solution. Measurements performed on single helices without and with spherical or cylindrical core show that the model allows a reliable characterization of scatterers with arbitrarily shaped core.