scholarly journals Characteristic impedance and propagation of the first higher order microstrip mode in frequency and time domain

2002 ◽  
Vol 50 (5) ◽  
pp. 1370-1379 ◽  
Author(s):  
Shyue-Dar Chen ◽  
C.-K.C. Tzuang
Keyword(s):  
Time Domain ◽  
Characteristic Impedance ◽  
Higher Order

scholarly journals Time-domain Multiple-order Diffraction for Two Wedges of Arbitrary Angles

2019 ◽  
Vol 8 (9) ◽  
pp. 2241-2244
Keyword(s):  
Time Domain ◽  
Higher Order ◽  
Multiple Diffraction ◽  
Double Wedge ◽  
Diffraction Coefficient ◽  
Order Diffraction

Generally, higher order diffraction coefficient is used for the consideration of multiple diffraction. Due to this, the calculation becomes complex as well as not consider all possible order of diffraction among the wedges. In this paper, frequency and time-domain multiple-order diffraction for double wedge has been proposed. Only, single-order diffraction coefficient is used for higher-order diffraction calculation. So the proposed method is very simple and considers all possible order of diffraction. Both the IFFT-FD solution and proposed TD solution has been compared to confirm the accuracy.

Effects of blood volume changes on characteristic impedance of the pulmonary artery

1982 ◽  
Vol 242 (2) ◽  
pp. H197-H202 ◽  
Author(s):  
J. P. Dujardin ◽  
D. N. Stone ◽  
C. D. Forcino ◽  
L. T. Paul ◽  
H. P. Pieper
Keyword(s):  
Pulmonary Artery ◽  
Blood Volume ◽  
Time Domain ◽  
Volume Expansion ◽  
Characteristic Impedance ◽  
Main Pulmonary Artery ◽  
Time Domain Method ◽  
Frequency Domain Method ◽  
Domain Method ◽  
The Time Domain

Experiments were performed on eight anesthetized dogs to study the response of the characteristic impedance (Zc) of the main pulmonary artery to changes in circulating blood volume. Pressure and flow were measured in the proximal main pulmonary artery under control conditions, after hemorrhage (-15% of the estimated blood volume), again under control conditions, and finally after volume expansion (+30% of the estimated blood volume). Two different methods were used to determine Zc from these recordings. With the frequency-domain method values for Zc were obtained by averaging the input impedance moduli between 2 and 15 Hz. With the time-domain method Zc was derived as the slope of the early ejection pressure-flow relationship. The values for Zc obtained with the two methods were not statistically different. In the time-domain method the average increase in Zc with hemorrhage was 30.7 +/- 7.4 (SE) %, and the average decrease with volume expansion was -21.1 +/- 5.0 (SE) %. Because the time-domain method allowed the values of Zc during control conditions and after hemorrhage to be obtained in the same pressure range, it was concluded that the observed changes were caused by a change in the activity of the smooth muscle in the pulmonary arterial wall. Similarly, it was concluded that the decrease in Zc after volume expansion was active in nature.

Modeling near‐field GPR in three dimensions using the FDTD method

Geophysics ◽  
1997 ◽  
Vol 62 (4) ◽  
pp. 1114-1126 ◽  
Author(s):  
Roger L. Roberts ◽  
Jeffrey J. Daniels
Keyword(s):  
Electrical Properties ◽  
Finite Difference ◽  
Time Domain ◽  
Near Field ◽  
Characteristic Impedance ◽  
Fdtd Method ◽  
Three Dimensions ◽  
Field Pattern ◽  
Scattered Fields ◽  
Transmitting Antenna

Complexities associated with the theoretical solution of the near‐field interaction between the fields radiated from dipole antennas placed near a dielectric half‐space and electrical inhomogeneities within the dielectric can be overcome by using numerical techniques. The finite‐difference time‐domain (FDTD) technique implements finite‐difference approximations of Maxwell's equations in a discretized volume that permit accurate computation of the radiated field from a transmitting antenna, propagation through the air‐earth interface, scattering by subsurface targets and reception of the scattered fields by a receiving antenna. In this paper, we demonstrate the implementation of the FDTD technique for accurately modeling near‐field time‐domain ground‐penetrating radar (GPR). This is accomplished by incorporating many of the important GPR parameters directly into the FDTD model. These variables include: the shape of the GPR antenna, feed cables with a fixed characteristic impedance attached to the terminals of the antenna, the height of the antenna above the ground, the electrical properties of the ground, and the electrical properties and geometry of targets buried in the subsurface. FDTD data generated from a 3-D model are compared to experimental antenna impedance data, field pattern data, and measurements of scattering from buried pipes to verify the accuracy of the method.

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