scholarly journals Archimedean Spiral Antenna Calibration Procedures to Increase the Downrange Resolution of a SFCW Radar

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
Ioan Nicolaescu ◽  
Piet van Genderen
Keyword(s):  
Time Domain ◽  
Continuous Wave ◽  
Phase Variation ◽  
Antenna System ◽  
Spiral Antenna ◽  
Multiple Reflections ◽  
Archimedean Spiral ◽  
Wave Radar ◽  
Time Domain Response ◽  
The Time Domain

This paper deals with the calibration procedures of an Archimedean spiral antenna used for a stepped frequency continuous wave radar (SFCW), which works from 400 MHz to 4845 MHz. Two procedures are investigated, one based on an error-term flow graph for the frequency signal and the second based on a reference metallic plate located at a certain distance from the ground in order to identify the phase dispersion given by the antenna. In the second case, the received signal is passed in time domain by applying an ifft, the multiple reflections are removed and the phase variation due to the time propagation is subtracted. After phase correction, the time domain response as well as the side lobes level is decreased. The antenna system made up of two Archimedean spirals is employed by SFCW radar that operates with a frequency step of 35 MHz.

An antenna system of a continuous wave radar

2004 ◽  
Author(s):  
S.D. Andrenko ◽  
I.A. Vyazmitinov ◽  
Y.B. Sidorenko
Keyword(s):  
Continuous Wave ◽  
Antenna System ◽  
Wave Radar

Ladder structure in the time-domain response of Landau levels to a shock electromagnetic pulse

1998 ◽  
Vol 245 (3-4) ◽  
pp. 329-333 ◽  
Author(s):  
I.G. Lang ◽  
V.I. Belitsky
Keyword(s):  
Time Domain ◽  
Electromagnetic Pulse ◽  
Landau Levels ◽  
Ladder Structure ◽  
Time Domain Response ◽  
The Time Domain

scholarly journals Tailoring of multi-pulse dynamics in mode-locked laser via optoacoustic manipulation of quasi-continuous-wave background

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Ki Sang Lee ◽  
Chang Kyun Ha ◽  
Kyoung Jun Moon ◽  
Dae Seok Han ◽  
Myeong Soo Kang
Keyword(s):  
Information Processing ◽  
Time Domain ◽  
Continuous Wave ◽  
Single Pulse ◽  
Laser Cavity ◽  
Temporal Position ◽  
Optical Information ◽  
Pulse Dynamics ◽  
Mode Locked Laser ◽  
The Time Domain

Abstract Various nonequilibrium multi-pulse states can emerge in a mode-locked laser through interactions between the quasi-continuous-wave background (qCWB) and pulses inside the laser cavity. While they have been regarded as unpredictable and hardly controllable due to the noise-like nature of qCWB, we here demonstrate that the qCWB landscape can be manipulated via optoacoustically mediated pulse-to-qCWB interactions, which alters the behaviors of multi-pulse dynamics. In this process, impulsive qCWB modulations are created at well-defined temporal locations, which act as the point emitters and attractive potentials for drifting pulse bunches and soliton rains. Hence, we can transport a single pulse bunch from a certain temporal position to another, and also make soliton rains created and collided exclusively at specific temporal locations. Our study opens up possibilities to control the nonequilibrium multi-pulse phenomena precisely in the time domain, which would offer a practical means of advanced optical information processing.

Improving the time domain response of fractional order digital differentiators by windowing

2015 ◽  
Vol 107 ◽  
pp. 282-289 ◽  
Author(s):  
Chengyan Peng ◽  
Xiaochuan Ma ◽  
Geping Lin ◽  
Min Wang
Keyword(s):  
Fractional Order ◽  
Time Domain ◽  
Time Domain Response ◽  
The Time Domain

scholarly journals Transmission compensated primary reflection retrieval in the data domain and consequences for imaging

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. Q27-Q36 ◽  
Author(s):  
Lele Zhang ◽  
Jan Thorbecke ◽  
Kees Wapenaar ◽  
Evert Slob
Keyword(s):  
Thin Layer ◽  
Time Domain ◽  
Velocity Model ◽  
Original Data ◽  
Transmission Losses ◽  
Multiple Reflections ◽  
Data Set ◽  
Numerical Examples ◽  
The One ◽  
The Time Domain

We have developed a scheme that retrieves primary reflections in the two-way traveltime domain by filtering the data. The data have their own filter that removes internal multiple reflections, whereas the amplitudes of the retrieved primary reflections are compensated for two-way transmission losses. Application of the filter does not require any model information. It consists of convolutions and correlations of the data with itself. A truncation in the time domain is applied after each convolution or correlation. The retrieved data set can be used as the input to construct a better velocity model than the one that would be obtained by working directly with the original data and to construct an enhanced subsurface image. Two 2D numerical examples indicate the effectiveness of the method. We have studied bandwidth limitations by analyzing the effects of a thin layer. The presence of refracted and scattered waves is a known limitation of the method, and we studied it as well. Our analysis indicates that a thin layer is treated as a more complicated reflector, and internal multiple reflections related to the thin layer are properly removed. We found that the presence of refracted and scattered waves generates artifacts in the retrieved data.

scholarly journals Scattering of an Impact Wave by a Crack in a Composite Plate

1992 ◽  
Vol 59 (3) ◽  
pp. 596-603 ◽  
Author(s):  
S. K. Datta ◽  
T. H. Ju ◽  
A. H. Shah
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Impact Load ◽  
Near Field ◽  
Boundary Integral ◽  
Transition Elements ◽  
Element Discretization ◽  
Crack Tips ◽  
Time Domain Response ◽  
The Time Domain

The surface responses due to impact load on an infinite uniaxial graphite/epoxy plate containing a horizontal crack is investigated both in time and frequency domain by using a hybrid method combining the finite element discretization of the near-field with boundary integral representation of the field outside a contour completely enclosing the crack. This combined method leads to a set of linear unsymmetric complex matrix equations, which are solved to obtain the response in the frequency domain by biconjugate gradient method. The time-domain response is then obtained by using an FFT. In order to capture the time-domain characteristics accurately, high-order finite elements have been used. Also, both the six-node singular elements and eight-node transition elements are used around the crack tips to model the crack-tip singularity. From the numerical results for surface responses it seems possible to clearly identify both the depth and length of this crack.

Improved analysis of the time domain response of scanning force microscope cantilevers

2000 ◽  
Vol 88 (12) ◽  
pp. 7321-7327 ◽  
Author(s):  
Brian A. Todd ◽  
Steven J. Eppell ◽  
Fredy R. Zypman
Keyword(s):  
Time Domain ◽  
Scanning Force Microscope ◽  
Scanning Force ◽  
Time Domain Response ◽  
The Time Domain
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