Related papers: Spillover and diffraction sidelobe contamination i…
A wide bandwidth, dual polarized, modified four-square antenna is presented as a feed antenna for radio astronomical measurements. A linear array of these antennas is used as a line-feed for cylindrical reflectors for Tianlai, a radio…
The analysis of wireless communication channels at the mmWave, sub-THz and THz bands gives rise to difficulties in the construction of antenna arrays due to the small maximum inter-element spacing constraints at these frequencies. Arrays…
Scattering from objects near an antenna produce correlated signals from strong compact radio sources in a manner similar to those used by the Sea Interferometer to measure the radio source positions using the fine frequency structure in the…
Metasurfaces enable powerful control of electromagnetic waves using subwavelength planar structures, but their deeply subwavelength periodicity typically suppresses propagating diffraction orders, which limits the number of available…
This paper presents a new method to obtain the deformation distribution on the main reflector of an antenna only by measuring the electric intensity on a spherical surface with the focal point as the center of the sphere, regardless of…
Broadband antenna feeds are of particular interest to existing and future radio telescopes for multi-frequency studies of astronomical sources. Although a 1:15 range in frequency is difficult to achieve, the well-known Eleven feed design…
This is the second part in a series of two papers that concern with the quantitative analysis of the electromagnetic field enhancement and anomalous diffraction by a periodic array of subwavelength slits. In this part, we explore the…
We investigate beam scanning by lateral feed displacement in novel metasurface based reflector antennas with extremely short focal distances. Electric field distributions of the waves reflected from the antenna are studied numerically and…
An experimental strong increase of the reflection loss (from 25 up to 35 dBs) and an extension of the absorption bandwidth up to 20% is measured in a set of novel functional bilayer systems. We focus our work on studying the samples in an…
This study explores the use of synchrotron measurements as a nanometrology tool for blazed gratings. In grazing incidence geometry, one can measure both the conical diffraction and the diffuse scattering on the grating simultaneously in a…
A circularly polarized leaky-wave antenna capable of frequency scanning is proposed in this paper. The main objective is to achieve high gain and polarization purity without the need for a complex feed network. The antenna consists of two…
Stray radiation of various origin is a major source of degradation of centimeter to sub-millimeter astronomical observations. This is particularly problematic for the detection of signals such as faint cosmic microwave background…
At relatively high frequencies, highly sensitive grating sidelobes occur in the primary beam patterns of low frequency aperture arrays (LFAA) such as the Murchison Widefield Array (MWA). This occurs when the observing wavelength becomes…
We present the electromagnetic model of a dual circular polarization antenna-feed system, consisting of a corrugated feedhorn, a polarizer and an orthomode transducer. This model was developed for the passive front-end implemented in the…
This paper provides indoor reflection, scattering, transmission, and large-scale path loss measurements and models, which describe the main propagation mechanisms at millimeter wave and Terahertz frequencies. Channel properties for common…
We report the spectral index of diffuse radio emission between 50 and 100 MHz from data collected with two implementations of the Experiment to Detect the Global EoR Signature (EDGES) low-band system. EDGES employs a wide beam…
Spectral measurements of the 21 cm monopole background have the promise of revealing the bulk energetic properties and ionization state of our universe from z ~ 6-30. Synchrotron foregrounds are orders of magnitude larger than the…
The radiation pattern of an antenna array depends on the excitation weights and the geometry of the array. Due to wind and atmospheric conditions, outdoor millimeter wave antenna elements are subject to full or partial blockages from a…
This paper proposes a dual-band frequency scanning meandering microstrip leaky-wave antenna with linear polarization in the Ku-band and circular polarization in the K-band. This is achieved by making use of two spatial harmonics for…
Telescopes for observing the Cosmic Microwave Background (CMB) usually have shields and baffle structures in order to reduce the pickup from the ground. These structures may introduce unwanted sidelobes. We present a method to measure and…