scholarly journals A Compact Wideband Active Two-Dipole HF Phased Array

2021 ◽  
Vol 11 (19) ◽  
pp. 8952
Author(s):  
Antonios Constantinides ◽  
Haris Haralambous
Keyword(s):  
Mutual Coupling ◽  
Wide Frequency Range ◽  
Low Noise ◽  
Monitoring Site ◽  
High Input ◽  
Quarter Wavelength ◽  
Passive Antennas ◽  
Compact Design ◽  
Electronic Steering ◽  
Very High

The design and construction of an upgraded HF quarter-wavelength two-dipole active array with 90° difference feed was implemented in the course of a research project to perform a directional (azimuthal) investigation of interference at HF. The lack of affordable compact antennas to meet the project requirements was the incentive to develop a compact unidirectional antenna, with the maximum possible front-to-back ratio at frequencies of 20–30 MHz, where the dimensions of traditional passive antennas are enormous. By installing a low-noise very-high-input impedance amplifier in each dipole of the array, the effect of the mutual coupling between the two dipoles was reduced, improving the front-to-back (F/B) ratio over a wide frequency range. Electronic steering, easy polarization adjustment, and fast and easy deployment were the key requirements for the construction of the antenna. Therefore, a light and compact design was of the utmost importance to meet the space limitations at the monitoring site, which did not allow the deployment of a traditional HF directional antenna that employs a very long boom and elements.

A Low-Noise, High-Gain Quasi-Millimeter-Wave Receiver MMIC with a Very High Degree of Integration Using 3D-MMIC Technology

2011 ◽  
Vol E94-C (10) ◽  
pp. 1548-1556 ◽  
Author(s):  
Takana KAHO ◽  
Yo YAMAGUCHI ◽  
Kazuhiro UEHARA ◽  
Kiyomichi ARAKI
Keyword(s):  
Millimeter Wave ◽  
High Gain ◽  
Low Noise ◽  
High Degree ◽  
Very High ◽  
Millimeter Wave Receiver

scholarly journals Improving Accuracy in Studying the Interactions of Seismic Waves with Bottom Sediments

2021 ◽  
Vol 9 (2) ◽  
pp. 229
Author(s):  
Georgy Mitrofanov ◽  
Nikita Goreyavchev ◽  
Roman Kushnarev
Keyword(s):  
Bottom Sediments ◽  
Seismic Waves ◽  
Wide Frequency Range ◽  
Quality Of Data ◽  
High Quality ◽  
Relative Characteristic ◽  
Seabed Evolution ◽  
Marine Seismic ◽  
Very High

The emerging tasks of determining the features of bottom sediments, including the evolution of the seabed, require a significant improvement in the quality of data and methods for their processing. Marine seismic data has traditionally been perceived to be of high quality compared to land data. However, high quality is always a relative characteristic and is determined by the problem being solved. In a detailed study of complex processes, the interaction of waves with bottom sediments, as well as the processes of seabed evolution over short time intervals (not millions of years), we need very high accuracy of observations. If we also need significant volumes of research covering large areas, then a significant revision of questions about the quality of observations and methods of processing is required to improve the quality of data. The article provides an example of data obtained during high-precision marine surveys and containing a wide frequency range from hundreds of hertz to kilohertz. It is shown that these data, visually having a very high quality, have variations in wavelets at all analyzed frequencies. The corresponding variations reach tens of percent. The use of the method of factor decomposition in the spectral domain made it possible to significantly improve the quality of the data, reducing the variability of wavelets by several times.

Improving Gerotor Pump Performance Trough Design, Modeling and Simulation

2021 ◽  
Author(s):  
Lozica Ivanović ◽  
Miloš Matejić
Keyword(s):  
Low Noise ◽  
Operating Conditions ◽  
Design Parameters ◽  
Pump Efficiency ◽  
Hydraulic Systems ◽  
Wear Process ◽  
Gerotor Pump ◽  
Gerotor Pumps ◽  
Negative Effect ◽  
Compact Design

Gerotor pumps are well known by a compact design, simple structure and low noise level, which makes them suitable for use in the automotive industry, and especially in hydraulic systems for engine lubrication. One of the main disadvantages of gerotor pumps is the inability to adjust to wear, which significantly reduces the pump efficiency. In order to mitigate the negative effect of the inevitable wear process, this paper presents a methodology for determining the optimal combination of trochoid gears design parameters for a defined aspect. An appropriate mathematical model has been developed to analyze the effect of changes in gear design parameters in relation to maximum contact stresses, pressure changes in gerotor pump chambers and wear rate proportional factor (WRPF). Verification of the developed models was performed by realizing physical pairs of gears and laboratory experiments with simulation of pump operating conditions. The results and conclusions presented in this paper, with an emphasis on the actual work processes, bring very important perspectives for the gerotor pumps design with improved performance.

scholarly journals Printed dipole antenna and its arrays for wireless applications

2018 ◽  
Vol 7 (2.7) ◽  
pp. 952
Author(s):  
V Teju ◽  
P V. P. S Nikhil ◽  
A Pranusha ◽  
Ch Divya ◽  
G Bhanuprakash
Keyword(s):  
Reflection Loss ◽  
Mutual Coupling ◽  
Dipole Antenna ◽  
Wide Frequency Range ◽  
Single Element ◽  
Frequency Range ◽  
Scanning Angle ◽  
Wireless Applications ◽  
Element Array

This paper proposes single element of micro-stripe antenna having wider bandwidth and also its arrays which are implemented for wire-less applications. In contemplation of wide frequency range of operation, antenna is fed with integrated balun. The single element antenna works under frequency range of 34GHz to 46GHz where reflection loss is less than -10dB and the obtained gain is 2.1 dBi. The linear 8-element array of antenna has been implemented and to obtain low mutual coupling between the elements of antenna a rectangular stub has been implemented. By enforcing the array methodology the not only the overall gain of the antenna has increased but also results in wider scanning angle.  

Additional noise reduction with diffracting elements on barriers: experimental testing

2021 ◽  
Vol 263 (4) ◽  
pp. 2654-2664
Author(s):  
Wout Schwanen ◽  
Mark Mertens ◽  
Ysbrand Wijnant ◽  
Willem Jan van Vliet
Keyword(s):  
Noise Reduction ◽  
Experimental Testing ◽  
Low Noise ◽  
Motor Vehicles ◽  
Additional Element ◽  
High Noise ◽  
Quarter Wavelength ◽  
Noise Barrier ◽  
Sound Reduction ◽  
Development And Validation

The noise reduction of a (low) noise barrier can be enhanced by using an additional element with quarter-wavelength resonators with varying depths. The so-called WHISwall or WHIStop deflects sound upwards for specific frequencies creating an additional sound reduction. Different experiments on the WHISwall and WHIStop are performed as input for model validation. The development and validation of the model are described in a separate paper. In this paper the measurement campaign and its results are presented. We performed measurements on two setups. The first setup consists of a 1.1 meter high WHISwall, a 1.1m high noise barrier and a reference section (without noise measure). Measurements have been conducted with both an artificial sound source and pass by measurements with light and heavy motor vehicles. In a second test setup, the WHIStop was placed on top of a 4 meter high noise barrier and the diffraction was determined according the European standard EN 1793-4.

An Overview of EEG and MEG

2017 ◽  
pp. 38-44
Author(s):  
Riitta Hari ◽  
Aina Puce
Keyword(s):  
Visual Inspection ◽  
Low Noise ◽  
Clinical Diagnostics ◽  
Brain Disorders ◽  
Clinical Environment ◽  
Single Trial ◽  
Eeg Activity ◽  
Technical Developments ◽  
Very High ◽  
Made In

This chapter discusses the rather different histories of MEG and EEG. EEG has been used as a tool of clinical diagnostics since the 1930s with visual inspection of spontaneous EEG activity in patients suffering from various brain disorders, particularly epilepsy. For MEG, the evolution of applications has been the opposite: the first recordings were made in research laboratories and the recordings started by averaging a very high number of single trials, and it took some time before low-noise MEG equipment became available to allow single-trial analyses. Only with recent technical developments, especially with the advent of whole scalp–covering devices, has MEG become increasingly popular in the clinical environment. We discuss the evolution of both techniques with respect to the measurement of brain rhythms and evoked and event-related responses.

scholarly journals A 1 to 32 GHz broadband multi-octave receiver for monolithic integrated vector network analyzers in SiGe technology

2018 ◽  
Vol 10 (5-6) ◽  
pp. 717-728
Author(s):  
Marco Dietz ◽  
Andreas Bauch ◽  
Klaus Aufinger ◽  
Robert Weigel ◽  
Amelie Hagelauer
Keyword(s):  
Noise Figure ◽  
Gain Control ◽  
Wide Frequency Range ◽  
Low Noise ◽  
Vector Network Analyzer ◽  
Ultra Wideband ◽  
Network Analyzer ◽  
Active Mixer ◽  
Input Matching ◽  
Better Than

AbstractA multi-octave receiver chain is presented for the use in a monolithic integrated vector network analyzer. The receiver exhibits a very wide frequency range of 1–32 GHz, where the gain meets the 3 dB-criterion. The differential receiver consists of an ultra-wideband low noise amplifier, an active mixer and an output buffer and exhibits a maximum conversion gain (CG) of 16.6 dB. The main design goal is a very flat CG over five octaves, which eases calibration of the monolithic integrated vector network analyzer. To realize variable gain functionality, without losing much input matching, an extended gain control circuit with additional feedback branch is shown. For the maximum gain level, a matching better than −10 dB is achieved between 1–28 GHz, and up to 30.5 GHz the matching is better than −8.4 dB. For both, the input matching and the gain of the LNA, the influence of the fabrication tolerances are investigated. A second gain control is implemented to improve isolation. The measured isolations between RF-to-LO and LO-to-RF are better than 30 dB and 60 dB, respectively. The LO-to-IF isolation is better than 35 dB. The noise figure of the broadband receiver is between 4.6 and 5.8 dB for 4–32 GHz and the output referred 1-dB-compression-point varies from 0.1 to 4.3 dBm from 2–32 GHz. The receiver draws a current of max. 66 mA at 3.3 V.

scholarly journals An Hα Survey of the Galactic Plane

1998 ◽  
Vol 179 ◽  
pp. 179-181
Author(s):  
Q.A. Parker ◽  
S. Phillipps
Keyword(s):  
Galactic Plane ◽  
Narrow Band ◽  
Interference Filter ◽  
Low Noise ◽  
Magellanic Clouds ◽  
Coverage Depth ◽  
Ionized Gas ◽  
Fine Grain ◽  
The Galaxy ◽  
Very High

We describe a major new Anglo-Australian proposal for a U.K. Schmidt Telescope (UKST) Hα survey of the Southern Galactic plane, Magellanic clouds and selected regions. The agreed survey will use a new 12 × 12 inch monolithic Hα interference filter of very high specification in combination with Tech Pan film. Tech Pan offers significant advantages for this work due to an inherent sensitivity at Hα and its extremely fine grain, high resolution, exceptional DQE, excellent imaging and low noise (e.g., Parker et al. 1994). The combination of Tech Pan and a narrow band Hα filter will provide a survey of unprecendented area coverage, depth and resolution, superior to any previous optical survey of ionized gas in the galaxy. It should to lead to exciting new discoveries and avenues of research.

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