scholarly journals Application of Kramers-Kronig transformations to increase the bandwidth of small antennas

2019 ◽  
Vol 17 ◽  
pp. 65-70
Author(s):  
Mostafa Bakry ◽  
Ludger Klinkenbusch
Keyword(s):  
Magnetic Material ◽  
Frequency Domain ◽  
Internal Energy ◽  
Electric Energy ◽  
Wide Frequency Range ◽  
Monopole Antenna ◽  
Stored Energy ◽  
Frequency Range ◽  
Small Antennas ◽  
Monopole Antennas

Abstract. The internally stored electric energy (Q-energy) of a disk monopole antenna increases as compared to a monopole antenna without a top disk. Recently it was shown that the Q-energy can be significantly reduced and the bandwidth increased by shielding the disk monopole antenna using a thin magnetic material. In the present paper we consider the same structure to explain another method to increase the bandwidth by using a shield made of dispersive magnetic material. We apply the Kramers-Kronig transforms to derive physically correct real and imaginary parts of the dispersive magnetic material. We do not aim at a reduction of the internal energy but at a compensation of the electric by a magnetic stored energy for a wide frequency range. Disk monopole antennas with shells consisting of such dispersive permeability are finally numerically evaluated by means of a commercial frequency-domain field simulator.

Modeling of a Fractional Order Element Based on Bacterial Cellulose and Ionic Liquids

2021 ◽  
Vol 143 (7) ◽  
Author(s):  
R. Caponetto ◽  
S. Graziani ◽  
E. Murgano ◽  
C. Trigona ◽  
A. Pollicino ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Frequency Domain ◽  
Bacterial Cellulose ◽  
Fractional Order ◽  
Wide Frequency Range ◽  
Complex Frequency ◽  
Frequency Range ◽  
Time Stability ◽  
Order Element ◽  
Lumped Circuit Model

Abstract In this paper, a novel fractional-order element (FOE) is modeled in a wide frequency range. The FOE is based on a green biopolymer, i.e., bacterial cellulose (BC), infused with ionic liquids (ILs). The modeling is performed in the frequency domain and a lumped-circuit model is proposed. The model is an evolution with respect to a simpler one already introduced by the authors, for a narrower frequency range. Results show that ILs generate a quite complex frequency domain behavior, which can be described in the framework of FOEs. Furthermore, results on the time stability of the device under investigation are given.

LOW FREQUENCY MODES PROBED BY TIME-DOMAIN OPTICAL KERR EFFECT SPECTROSCOPY

1996 ◽  
Vol 10 (11) ◽  
pp. 1229-1272 ◽  
Author(s):  
S. KINOSHITA ◽  
Y. KAI ◽  
T. ARIYOSHI ◽  
Y. SHIMADA
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Kerr Effect ◽  
Low Frequency ◽  
Great Accuracy ◽  
Wide Frequency Range ◽  
Optical Kerr Effect ◽  
Spectroscopic Techniques ◽  
Frequency Range ◽  
Debye Relaxation

The principle and application of ultrafast optical Kerr effect (OKE) spectroscopy have been reviewed. This spectroscopy is shown to be very useful to investigate low frequency modes in disordered materials and the obtained data are directly comparable with frequency-domain light scattering spectroscopy. Experimental study to show the consistency between the time- and frequency-domain spectroscopy has been performed for liquid nitrobenzene and the excellent agreement is attained over three orders of magnitude in frequency range. It is also shown that the result obtained by the OKE measurement is consistent with that obtained by four wave mixing spectroscopy. Combination of these spectroscopic techniques is particularly suited for the investigation of low frequency modes because a wide frequency range is covered with great accuracy. Several remarks concerning the OKE spectroscopy are presented such as the breakdown of Debye relaxation model and various interference effects which may distort the time-domain data.

Frequency Domain Modal Parameter Identification of High Order Systems in a Numerically Stable Way

1997 ◽  
Vol 119 (2) ◽  
pp. 265-270 ◽  
Author(s):  
K. Q. Xu
Keyword(s):  
Parameter Identification ◽  
Frequency Domain ◽  
Narrow Band ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Modal Parameter ◽  
Modal Parameter Identification ◽  
Identification Methods ◽  
The Time Domain ◽  
Experimental Data Analysis

Frequency domain modal parameter identification methods have several attractive properties as compared with the time domain methods except for the limitation of low-order-and-narrow-band per analysis. As rule of thumb, a limit of less than ten modes has been observed for several popular frequency domain algorithms. However, this paper will show, that with a proper and thorough use of the orthogonal polynomials in the frequency domain, the number of modes per analysis can be increased to as high as 75 in a comparatively wide frequency range of interest while still retaining numerical stability. Both numerical example (75 modes in 5–1000 Hz) and experimental data analysis (56 modes in 50–5000 Hz) are presented to demonstrate the effectiveness of this innovative approach.

scholarly journals The Effecting of Human Body on Slotted Monopole Antenna in Wearable Communications

2021 ◽  
Vol 27 (2) ◽  
pp. 27-43
Author(s):  
Aven Rawf Hamza ◽  
Asaad M. Jassim Al-Hindawi
Keyword(s):  
Human Body ◽  
Free Space ◽  
Ground Plane ◽  
Pure Copper ◽  
Relative Dielectric Constant ◽  
Monopole Antenna ◽  
Ultra Wideband ◽  
Frequency Range ◽  
Radiating Element ◽  
Monopole Antennas

In this paper, the characteristics of microstrip monopole antennas are studied firstly in free space. Secondly, the effects of the human body on the studied antenna's performance are investigated for wearable communications. Different patch shapes of microstrip monopole antenna are chosen to operate at two bands: industrial scientific and medical band (ISM) and ultra-wideband (UWB) for wearable applications. The studied antenna consists of a radiating element on one side of the substrate and a partial ground plane on the other side. The antenna is supposed to fabricate on cloth fabric whose relative dielectric constant is Ɛr =1.7. At the same time, the pure copper could be used as the conducting part representing both the radiating monopole and the partial ground plane. The software program of Computer Simulation Technology (CST) for Microwave Studio (MWS) is utilized to simulate the studied antennas. The obtained results have illustrated that in the free space, the proposed antennas of slotted hexagonal, rectangular, and circular shapes can operate from 2-12 GHz and of the bandwidth of 10.31 GHz, 10.19 GHz, and 9.67 GHz, respectively. The hexagonal antenna is selected and proposed to investigate the effects of the human body on its performance. The human body is simulated, and its effects on the performance of the proposed antenna are studied. The reflection coefficient, Voltage Standing Wave Ratio (VSWR), gain, and efficiency are found over that frequency range. The simulated results indicate that the human body effects are significant, and the proposed antenna showed to be a good candidate for wearable communications.

scholarly journals Explicit parallel co-simulation approach: analysis and improved coupling method based on H-infinity synthesis

2021 ◽  
Author(s):  
Weitao Chen ◽  
Shenhai Ran ◽  
Canhui Wu ◽  
Bengt Jacobson
Keyword(s):  
Frequency Domain ◽  
Wide Frequency Range ◽  
Coupling Method ◽  
Sampled Data ◽  
H Infinity ◽  
First Case ◽  
Communication Step ◽  
Coupling Variables ◽  
The Stability ◽  
Stability And Accuracy

AbstractCo-simulation is widely used in the industry for the simulation of multidomain systems. Because the coupling variables cannot be communicated continuously, the co-simulation results can be unstable and inaccurate, especially when an explicit parallel approach is applied. To address this issue, new coupling methods to improve the stability and accuracy have been developed in recent years. However, the assessment of their performance is sometimes not straightforward or is even impossible owing to the case-dependent effect. The selection of the coupling method and its tuning cannot be performed before running the co-simulation, especially with a time-varying system.In this work, the co-simulation system is analyzed in the frequency domain as a sampled-data interconnection. Then a new coupling method based on the H-infinity synthesis is developed. The method intends to reconstruct the coupling variable by adding a compensator and smoother at the interface and to minimize the error from the sample-hold process. A convergence analysis in the frequency domain shows that the coupling error can be reduced in a wide frequency range, which implies good robustness. The new method is verified using two co-simulation cases. The first case is a dual mass–spring–damper system with random parameters and the second case is a co-simulation of a multibody dynamic (MBD) vehicle model and an electric power-assisted steering (EPAS) system model. Experimental results show that the method can improve the stability and accuracy, which enables a larger communication step to speed up the explicit parallel co-simulation.

Installation for testing electronic voltmeters over a wide frequency range

1976 ◽  
Vol 19 (10) ◽  
pp. 1525-1526
Author(s):  
A. M. Fedorov ◽  
V. V. Krestovskii ◽  
V. S. Kiselev ◽  
S. A. Razumovskii ◽  
V. A. Shcheglov
Keyword(s):  
Wide Frequency Range ◽  
Frequency Range
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