Photonically synchronized large aperture radar for autonomous driving.

Fully autonomous driving, even under bad weather conditions, can be enabled by the use of multiple sensor systems including 5D radar imaging. In order to get three dimensional, high resolution images with Doppler and time tracking of the target, the radar needs to utilize a large number of transmit/receive modules. For proper beam forming, all of them demand synchronization. Here a new concept for the optical distribution of radar signals, comprising low complexity integrated transmitter and receiver chips and a complex central station, will be introduced. Unavoidable temperature drifts due to environmental influences were compensated to maintain a continuous electrical output power. Within a proof-of-concept radar experiment an angular resolution of 1.1° has been achieved

Large Minimum Redundancy Linear Arrays: Systematic Search of Perfect and Optimal Rulers Exploiting Parallel Processing

Minimum Redundancy Linear Arrays (MRLAs) are special linear arrays that provide the narrowest main lobe in the radiation pattern possible for a given number of antennas. We found that the calculation of MRLAs is the same as for the mathematical problem of perfect sparse rulers. Finding perfect rulers (or MRLAs) is a hard problem, as there is no proven mathematical rule to design them. They can only be found by constructing ruler candidates via an exhaustive search while ensuring that no ruler with less redundancy exists. We revisited the problem of sparse ruler construction and used two exhaustive search algorithms to compute longer rulers than previously published. Further, we present an approach to accelerate the execution by distributing the recursive search algorithms over multiple computers. Our compute cluster found perfect rulers with all lengths up to 244 in 443 years of combined CPU time. All found rulers are provided to the research community. Additionally, we confirm previously known Low Redundancy Linear Arrays being MRLAs. Our results show that larger perfect rulers do not always require equal or more marks (antennas) but can sometimes be constructed with fewer marks than the previous ruler

A Systematic Comparison of Near-Field Beamforming and Fourier-based Backward-Wave Holographic Imaging

In this paper we show the equivalence of near-field beamforming and backward-wave reconstruction algorithm. The proof is carried out analytically with two different approaches, using the principle of stationary phase from a signal processing point of view and the angular spectrum representation as an electromagnetic point of view. A comparison of the time complexity of the near-field beamforming and backward-wave reconstruction algorithm is given. A detailed discussion of the constraints required for a digital implementation is presented, leading to limitations for the chosen system parameters, especially for the backward-wave reconstruction approach. An exemplarily scenario is simulated and processed, confirming the found equivalence between the two very different approaches of image reconstruction. An additional measurement with a 120 GHz radar showcases the capabilities of both algorithms and validates our findings

Independently Tunable Triband Patch Antenna with Band-Notched Characteristics for X-Band Applications

This paper presents a triband antenna with a simple design for X-band applications. The proposed antenna is designed based on a patch with a truncated corner slot and complementary split-ring resonators in the ground plane. In this way, the antenna exhibits three operating bands and its resonant frequencies can be controlled independently by changing dimensions of the slot in the patch and the resonator structures in the ground plane. In addition, due to the antiresonant behavior of the complementary split-ring resonator structures, the antenna exhibits a notch-band characteristic at 10.7 GHz. A parametric study is performed to provide a detailed understanding of the independent resonance tuning behavior of the antenna. Both simulated and measured results of the proposed antenna are presented, which are in good agreement. The proposed antenna shows three operating bands in the X-band including (with absolute and relative bandwidths) 9.4–9.7 GHz (300 MHz, 3.14%), 10.3–10.6 GHz (300 MHz, 2.86%), and 11.05–11.32 GHz (297 MHz, 2.66%). In addition to that, a notched band of 10.6–11.05 GHz is introduced to exclude operation in the frequency bands of radiometric observation systems (10.6–10.7 GHz). To the best of our knowledge, this work is unique in its combination of independent tuning of three frequency bands of operation with single-layer implementation in the X-band. Such a structure provides additional degrees of freedom to the antenna design, customizing operation in the required bands while avoiding operation in other bands

Independently tunable triband patch antenna with band-notched characteristics for X-band applications

Abstract This paper presents a triband antenna with a simple design for X-band applications. The proposed antenna is designed based on a patch with a truncated corner slot and complementary split-ring resonators in the ground plane. In this way, the antenna exhibits three operating bands and its resonant frequencies can be controlled independently by changing dimensions of the slot in the patch and the resonator structures in the ground plane. In addition, due to the antiresonant behavior of the complementary split-ring resonator structures, the antenna exhibits a notch-band characteristic at 10.7 GHz. A parametric study is performed to provide a detailed understanding of the independent resonance tuning behavior of the antenna. Both simulated and measured results of the proposed antenna are presented, which are in good agreement. The proposed antenna shows three operating bands in the X-band including (with absolute and relative bandwidths) 9.4–9.7 GHz (300 MHz, 3.14%), 10.3–10.6 GHz (300 MHz, 2.86%), and 11.05–11.32 GHz (297 MHz, 2.66%). In addition to that, a notched band of 10.6–11.05 GHz is introduced to exclude operation in the frequency bands of radiometric observation systems (10.6–10.7 GHz). To the best of our knowledge, this work is unique in its combination of independent tuning of three frequency bands of operation with single-layer implementation in the X-band. Such a structure provides additional degrees of freedom to the antenna design, customizing operation in the required bands while avoiding operation in other bands