Volume 73, Issue 11-12 - Special Issue: GeMiC 2019

This paper presents the design and characterization of linearly polarized low-cost transmitarray antennas with ± 70° azimuth beamforming range in V-band in order to add beam steering functionality to existing radar front ends. The transmitarray antennas are composed of 13 × 13 planar unit-cells. The unit-cells consist of two layers of RO4350B laminate and provide a one bit phase resolution. The desired unit-cell behavior has been validated by simulations and measurements. Eight transmitarrays with different phase distributions have been designed and fabricated to realize different beam steering angles in azimuth. The experimental characterization of the radiation patterns shows the desired performance in the frequency range from 59 GHz to 63 GHz. Additionally, steering angle combinations in azimuth and elevation up to 40° have been realized and successfully demonstrate by measuring the 2D radiation pattern.

This paper presents an overview of fully dielectric antenna arrays with integrated dielectric power dividers developed at Technische Universität Darmstadt as an extension of previous work. The power dividers are based on the principle of multimode interference and offer one- and two-dimensional power division in a single step, which allows the realization of small and lightweight devices. In order to prove the concept, 1  ×  4 and 4  ×  4 fully dielectric antenna arrays with integrated power dividers milled from Rexolite are designed, realized and characterized, operating between 90 GHz and 105 GHz. To assess miniaturization and beamsteering capabilities, three 1  ×  4 arrays composed of different materials, Rexolite, Preperm L300 and Preperm L440, are compared regarding gain, size, weight and element spacing. Depending on array size and material, gain is between 12.5 dBi and 22 dBi, accompanied with sidelobe levels below - 7.5. All demonstrators are realized by milling, but the designs show the potential to be 3D printed or injection molded for large scale manufacturing.

In this paper the realization of multiple additional transmission zeros in folded W-band waveguide filters is discussed. The transmission zeros (TZs) can be placed symmetrically as well as asymmetrically in the near passband region of the filter and arise due to a resonant coupling between source and / or load. Third and fourth order filter set-ups are presented, showing in total between three and six TZs. These zeros can be used to improve the selectivity of the filter without increasing the overall order. The filter design and realization process is discussed. Subsequently, the measurement results are compared with simulation, showing good agreement. As the filters are designed for the W-band, the manufacturing process is connected with some difficulties which are addressed within this paper as well.

The performance of polarimetric imaging radar systems depends greatly on how well they are calibrated. The complexity of the calibration procedure scales with the number of send and receive antennas, i. e. the size of the antenna array. This article proposes a practical and effective approach for calibrating a polarimetric near field MIMO imaging radar using only two simple passive targets. The calibration requires four measurement steps: An empty space measurement for suppressing direct mutual coupling between the channels. An offset short calibration with the specular reflection of a planar metal plate for the co-polarized channels. Two measurements with a dihedral reflector inclined at different angles for the cross-polarized calibration.

Fully autonomous driving, even under bad weather conditions, requires use of multiple sensor systems including radar imaging. Microwave photonics, especially the optical generation and distribution of radar signals, can overcome many of the electronic disadvantages. This article will give an overview about several photonic components and how they could be incorporated into a photonic synchronized radar system, where all the complexity is shifted to a central station. A first proof-of-concept radar experiment with of the shelf telecommunication equipment shows an angular resolution of 1.1°. Furthermore an overview about possible photonic electronic integration is given, leading to comprising low complexity transmitter and receiver chips.