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We report the intermediate results on a novel slotted waveguide antenna for point-to-point communications at Ka band. The antenna adopts an aperiodic layout with uniformly-excited elements capable of meeting the ETSI class II radiation pattern envelop in all planes with high aperture efficiency. A total of 16 regular waveguide subarrays with an aperiodic inter-column spacing along the E-plane are...
The design of a push-broom multi-beam radiometer for future ocean observations is described. The radiometer provides a sensitivity one order of magnitude higher than a traditional conical scanning radiometer, and has the big advantage of being fully stationary relative to the satellite platform. Thanks to a dense focal plane array and a dedicated optimization procedure, the instrument can accurately...
Design considerations concerning a scanning as well as a push-broom microwave radiometer system are presented. Strict requirements to spatial and radiometric resolution leads to a multiple-beam scanner achieving good sensitivity through integration over many beams, or to a push-broom system where sensitivity is not a problem. Strict requirements to land contamination leads to a dense feed array system...
Novel antenna architectures for real aperture multi-beam radiometers providing high resolution and high sensitivity for accurate sea surface temperature (SST) and ocean vector wind (OVW) measurements are investigated. On the basis of the radiometer requirements set for future SST/OVW missions, conical scanners and push-broom antennas are compared. The comparison will cover reflector optics and focal...
A dual-mode antenna design, utilizing a combination of differential- and common-mode excitations, is presented. This antenna offers the possibility to complex-combine both modes in order to obtain a near-hemispherical Field of View (FoV) coverage. A Single-Ended (SE) to Mixed-Mode (MM) transformation model is introduced to determine the MM radiation characteristics of this antenna from SE scattering...
A novel beam expansion method is proposed for the fast and accurate prediction of antenna radiation patterns. Only a few physics-based entiredomain vector basis functions — called Characteristic Basis Function Patterns (CBFPs) — are employed for modeling each far-field beam. To determine the beam expansion coefficients, it suffices to measure the unknown beam for a few angular directions only, after...
A computationally efficient numerical procedure has been developed and used to analyze the mutual interaction effects between an electrically large reflector antenna and a phased array feed (PAF). The complex electromagnetic behavior for such PAF systems is studied through a few simple and didactical examples, among which a single dipole antenna feed, a singly-excited antenna in an array of 20 dipoles,...
This paper presents some new topics that will be lectured in the December 2011 course within European School of Antennas course on Reflector and Lens Antennas. The new material is mainly related to characterization of wideband feeds for reflector antennas for future radio telescopes, such as for SKA and VLBI 2010. The lectures will contain details of how to design decade bandwidth log-periodic antenna...
This work has studied and successfully demonstrated the ability of patch-array covers placed over PAF feeds comprising waveguide elements for achieving improved coupling and aperture efficiencies of singly-steered as well as multiple-overlapping beams, as compared to those of uncovered PAF feeds. Future work would be to include dielectric losses into the studies. Preliminary results are expected to...
Upgrading the Multi-Frequency-Front-Ends of the Westerbork Synthesis Radio Telescope (WSRT) by multiple-beam phased array feeds will improve its survey speed by a factor 20. The present paper describes two design steps of the dual-polarized tapered slot antenna (TSA) array required for this upgrade. Redesign of the TSA element, integration of the Low Noise Amplifier on the feed line substrate and...
This paper presents some results of a numerical modeling study of a focal plane array (FPA) comprising of 144 Vivaldi antenna elements, and complements the results which were earlier reported in. In the present study, we consider two EM-problems of different complexity, namely, (i) the free-standing FPA with a finite ground plane that was modeled to evaluate the accuracy of the simulated patterns...
This article describes the design of a radio telescope front-end system with a focal plane array (FPA) and an RF beamforming section. The multi-beam capability of the FPA will increase the field of view and the survey scanning speed of the telescope. The system performance is related to the different components and a model for the complexity is derived. We address the number of beams and elements...
The 8??9 element dense tapered slot array operating over 1-7 GHz range is used to synthesize a dual-band (2.215-2.375 GHz and 4.770-5.020 GHz) feed for a F/D=0.35 reflector. Only 25 elements are excited in a concentric ring manner to simulate a conventional coaxial feed. Not only experiments, including mutual coupling effects, but also array simulations using the cos2 element power pattern give a...
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