Dynamic Correction of the Influence of Long Measuring Path Irregularity in Antenna Tests

This article investigates the influence of random microwave discontinuities on the characteristics of long transmission paths. This is most important for dynamic measuring stands, accompanied by multiple space movement of long transmission paths with their bending or twisting during the measurement process. In modern active electronically scanned arrays this issue also becomes relevant, due to increased requirements for the accuracy of beam shaping. The aim of this study is to develop a theoretical background and perform experimental verification for taking into account the effect of random microwave discontinuities on the transmission path characteristics. A method for correcting the effect of such irregularities is considered based on electrical length control by measuring the input reflection coefficient. Relations for the magnitude and phase of the path’s input reflection coefficient depending on the S-parameters of a long four-terminal network terminated with mismatched load are obtained and plotted. Using theory of sensitivity, the mathematical expressions of conditions were obtained to achieve maximum accuracy of measuring the electrical length of a long microwave path. The possibility of dynamic error correction in antenna measurements with a long test path caused by random microwave irregularities along it has been experimentally proved.

Method of localization of agricultural robotic vehicles using AESA established by an UAV complex

This paper considers a relevant method to ensure communication and object location in vast agricultural areas. To solve this problem an operational scenario was proposed, an approach, involving a complex of several UAVs, which establish an AESA; an algorithm for building an optimal path, along which the UAV complex moves, formulas for calculating AESA direction pattern for linear and flat formations of UAV groups, formulas for calculating time, required for terrain scanning with various areas. In such complex on each UAV an antenna with phase shifter is mounted. The paper also considers modeling and comparison of different approaches to motion of an UAV complex for terrain scanning. Due to application of active electronically scanned arrays, the proposed localization method is characterized by high noise immunity, is better shielded from noise, less dependent on weather conditions and appliable at night time. Unlike other methods, it supports wide-range transmission and reception of data. Thereby, application of AESA makes this method robust and practical for localization and communication establishment, whereas the proposed algorithm for building of optimal path, along which the robotic complex moves, enables to reduce time, required for area scanning. Consequently, this method allows achieving the shortest distance that the UAV complex has to cover.

APAR: The Next Generation of Airborne Polarimetric Doppler Weather Radar

<p>A novel, airborne phased array radar (APAR) is currently under design at the NCAR Earth Observing Laboratory. This novel airborne radar is to be carried by the NSF/NCAR C-130 aircraft. The APAR system will consist of four removable C-band active electronically scanned arrays (AESA), strategically placed on the fuselage of the aircraft. Conceptually, the radar system is divided into the front-end, the backend, and the aircraft-specific section. The front-end primarily consists of AESAs, the backend of the signal processor, and the aircraft specific section includes a power system and a GPS antenna.</p><p>APAR, with dual-Doppler and dual polarization capabilities at a lesser attenuating C-band wavelength, is designed to enable further advancement in understanding of in-cloud microphysical and dynamical processes within a variety of precipitation systems. Such unprecedented observations, in conjunction with the advanced radar data assimilation systems, is anticipated to significantly improve understanding and predictability of hazardous weather events.</p><p>At present, and with funding from both the National Science Foundation and the National Oceanic and Atmospheric Administration, NCAR is engaged in the risk reduction and APAR preliminary design activities. In this talk, we will provide an update on the status of these activities for various system components as well as the system-level design. For the final design and development of APAR, NCAR plans to apply for the NSF Mid-scale Research Infrastructure funds in 2021. It is anticipated that the APAR final design and development will be a five-year effort.</p>

Airborne Phased-Array Radar (APAR): The Next Generation of Airborne Polarimetric Doppler Weather Radar

<p>This paper presents a configuration of a novel, airborne phased array radar (APAR) motivated by major advances in cellular technology, component miniaturization, and radar antenna simulation software. This has paved the way for a next-generation radar being designed by NCAR/EOL to be installed on the NSF/NCAR C-130 aircraft. The APAR system will consist of four removable C-band active electronically scanned arrays (AESA) strategically placed on the fuselage of the aircraft. Each AESA measures approximately 1.5 x 1.5 m and is composed of 2368 active radiating elements arranged in a total of 37 line replaceable units (LRU). Each LRU is composed of 64 radiating elements that are the building block of the APAR system.</p><p> </p><p>Polarimetric measurements are not available from current airborne tail Doppler radars. However, APAR, with dual-Doppler and dual polarization diversity at a lesser attenuating C-band wavelength, will further advance the understanding of the microphysical processes within a variety of precipitation systems<em>. </em>Such unprecedented observations, in conjunction with the advanced radar data assimilation schema, will be able to address the key science questions to improve understanding and predictability of significant weather.</p><p>A Mid-scale Research Infrastructure proposal is submitted to the National Science Foundation to request the implementation cost. The development is expected to take ~5 years after the funding is in place. It adopts a phased approach as an active risk assessment and mitigation strategy. At the present time, both the National Science Foundation and the National Oceanic and Atmospheric Administration are funding the APAR project for risk reduction activities. The APAR Team is actively seeking partners in industry and in the university community. An APAR science and engineering advisory panel has been organized.</p><p> </p><p>The authors will review the overall design and current progress of APAR and outline ambitious future development work needed to bring this exceptional tool into full operation.</p>

Rotman lens design and optimization for 5G applications

The next generation of wireless networks (5G) employs directional transmission at millimeter wave (mmW) frequencies to provide higher bandwidth and faster data rates. This is achieved by applying antenna arrays with proper beam steering capabilities. Rotman lens has long been used as a lens-based beamformer in electronically scanned arrays and its efficient design is important in the overall performance of the array. Minimizing the phase error on the aperture of the antenna array is an important design criterion in the lens. In this paper, a 7 × 8 wideband Rotman lens is designed. Particle swarm optimization is applied to minimize the path length error and thereby the phase error. The optimized lens operates from 25 to 31 GHz, which covers the frequency bands proposed by the Federal Communications Commission for 5G communications. The proposed optimized lens shows a maximum phase error of <0.1°. The proposed Rotman lens is a good candidate to be integrated with wideband microstrip patch antenna arrays that are suitable for 5G mmW applications.