This paper discusses the architecture of an adaptive transmitting microstrip array that allows highly flexible beamsteering and beamshaping. The antenna array is digitally controlled by a field programmable gate array (FPGA) board. The power and phase of the excitation signals delivered to the array elements are optimized using an algorithm based on particle swarm optimization (PSO), which includes all electromagnetic effects such as mutual coupling and installed performance. Further, the efficiency of the proposed approach is validated by synthesizing various beam patterns, including side lobe level control and beam shaping for cosecant squared and isoflux contours. Very good agreement between simulated and measured results is thereby observed. The paper also addresses implementation aspects that are not reported in detail in literature, such as the compensation for the faulty antennas or transmitting channels, as well as the calibration procedure applied for the experimental validation of the proposed architecture.

Reliable and accurate positioning underwater has been the goal of many research activities in the last years. In this paper, we present our design of a self-maintainable underwater navigation system, which provides a simple, low-cost, and flexible solution. In our concept, a set of buoys is equipped with Global Navigation Satellite System (GNSS) receivers as well as underwater pseudolite signal transmitters. Therefore, the buoys are able estimate their position and transmit this information underwater through a pseudolite signal. We particularly designed this signal for underwater ranging for both fresh and salt water. Any suitable underwater receiver is then able to do ranging via these pseudolite signals. In this paper, we theoretically analyze and test our concept using several buoy distributions and diving depths. The optimal arrangement of buoys is determined in terms of accuracy and availability depending on the number of available buoys and targeted water depth for an efficient operation. For example, at a targeted depth of 30 m in fresh water, a maximum horizontal position root-mean-square (RMS) error of less than 3 m can be achieved with a set of five buoys providing a service radius of up to 72 m.

This paper describes the concept and the development of key components of a novel multiple-beam antenna for satellite applications. The antenna is designed to be used in a transparent high-rate data relay system that links several low earth orbit (LEO) satellites to a single ground station via a satellite positioned on a geostationary orbit (GEO). The proposed antenna is based on the concept of an array-fed reflector. The antenna can track LEO satellites by switching between different subarrays of a bigger multifeed array using a reconfigurable switch matrix based on radio frequency micro-electromechanical system (RF MEMS) switches. The radiation characteristic of the antenna is further improved by combining digital beamforming with beam switching. In order to validate the proposed antenna concept and to show its suitability for space applications a demonstrator has been built. Measurements of the antenna's key components and of the demonstration system are given

This paper investigates polarization properties of circularly polarized 4x4 patch arrays at Ka-band for classical arrangement and sequential rotation of elements. The investigations are performed for various values of axial ratio of array elements and different steering angles. The simulated results are validated by measurements of fabricated arrays.