Frequency-independent Characteristics Research Articles

Development and Temperature Correction of Piezoelectric Ceramic Sensor for Traffic Weighing-In-Motion.

Weighing-In-Motion (WIM) technology is one of the main tools for pavement management. It can accurately describe the traffic situation on the road and minimize overload problems. WIM sensors are the core elements of the WIM system. The excellent basic performance of WIMs sensor and its ability to maintain a stable output under different temperature environments are critical to the entire process of WIM. In this study, a WIM sensor was developed, which adopted a PZT-5H piezoelectric ceramic and integrated a temperature probe into the sensor. The designed WIM sensor has the advantages of having a small size, simple structure, high sensitivity, and low cost. A sine loading test was designed to test the basic performance of the piezoelectric sensor by using amplitude scanning and frequency scanning. The test results indicated that the piezoelectric sensor exhibits a clear linear relationship between input load and output voltage under constant environmental temperature. The linear correlation coefficient R2 of the fitting line is up to 0.999, and the sensitivity is 4.04858 mV/N at a loading frequency of 2 Hz at room temperature. The sensor has good frequency-independent characteristics. However, the temperature has a significant impact on it. Therefore, the output performance of the piezoelectric ceramic sensor is stabilized under different temperature conditions by using a multivariate nonlinear fitting algorithm for temperature compensation. The fitting result R2 is 0.9686, the root mean square error (RMSE) is 0.2497, and temperature correction was achieved. This study has significant implications for the application of piezoelectric ceramic sensors in road WIM systems.

Arrayed Photomixers for THz Beam-Combining and Beam-Steering

In this study, generating and enhancing THz continuous/pulsed waves is achieved by fabricating a monolithic InP substrate chip of arrayed photomixers, where each photomixer includes an InP/InGaAs uni-traveling-carrier photodiode (UTC-PD) with integrated 1 × 4 planar slot antennas (PSAs). Through optoelectronic time-aligned and -gradient delays of lightwaves that couple to arrayed photomixers, the radiated THz waves yield both quantitative gain and spatial directional gain. To generate continuous 300 GHz waves, each UTC-PD is excited at a photocurrent of 3 mA to attain −15.79 dBm THz power that exhibits 12 dB combined gain by four arrayed UTC-PDs. Whereas, −17.71 dBm THz pulse generation with a duration of 25 ps can be achieved at the same optical pump power. The results show that the power enhanced gain of THz pulses is around 10 dB, which is less than that of continuous THz waves, because a part of the generated frequency components of the THz pulse is significantly deteriorated by bandwidth-limited PSAs. Furthermore, by means of optoelectronic time-gradient delay with frequency-independent characteristics, we successfully demonstrate steering of continuous and pulsed THz waves repeatedly in a range of 30 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> and 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> , respectively. In conclusion, strengthening directional THz power by beam-combining and -steering with arrayed photomixers is a promising technique for effective generation of continuous/pulsed THz waves.

On frequency-independent horn antenna design for plasma positioning reflectometers, from simulation to prototype testing

Using a new framework for horn antenna optimization, a first frequency-independent horn antenna for a plasma positioning reflectometer (PPR) is designed.This hardware optimization is a new approach aiming on lowering the computational complexity of PPR interpretative models able to extract profiles and fluctuations of electron density and temperature from reflectometry measurements. PPR measurements are a strong candidate to provide real-time feedback for plasma position control in long-discharge fusion tokamaks such as ITER and DEMO, which requires fast interpretative models. Reducing the computational complexity of these models is therefore critical.In this paper, ray tracing simulations in the poloidal plane are used to compare different radiation patterns and evaluate them on multiple performance criteria. An antenna shape leading to a frequency-independent far-field radiation diagram is found with the PROFUSION optimizer and a prototype of this antenna is tested against an unoptimized conical reference antenna.The ray tracing performance criteria indicate that fundamental Gaussian frequency-independent antennas perform well, albeit in general worse than same-sized frequency-dependent antennas. Furthermore, it is seen that the pyramidal ITER gap 6 antenna performs well given the spatial constraints and that more performant antennas could be used, when more space was available.The prototype testing reveals challenges in obtaining frequency-independent characteristics within a tokamak blanket environment, which is additionally complicated by misalignment risks.

Wide Band Antenna with Ultra-smooth Spectral Characteristics

Understanding the evolution of Universe is, in the forefront of, the modern day observational cosmology. It requires precise and accurate measurement of cosmological signal, orders of magnitude weaker than the bright sky background. Detection of such a signal having distinct spectral signature, needs an antenna with frequency independent characteristics over more than an octave bandwidth. A spherical monopole antenna has been designed to operate in the frequency range 50-200 MHz with a spectral smoothness of about few parts in 104. The structure has been modeled and optimized using WIPL-D, to minimize spectral features arising out of abrupt reflections of surface currents and frequency dependent radiation patterns. A prototype has been built to validate the design. This paper presents the methodology adopted in the overall antenna design, experiences in its prototyping and simulation and the measurement results.

Synthesis and characterization of (1 − y) [0.996Na0.475K0.475Li0.05Sb0.05Nb0.95O3–0.004Bi0.95Nd0.05FeO3] + (y) [Co0.50Cu0.15Zn0.35Fe1.95Mn0.05O4] composites

In this study, polycrystalline (1 − y) [0.996Na0.475K0.475Li0.05Sb0.05Nb0.95O3–0.004Bi0.95Nd0.05FeO3] (NKLNSO–BNFO) + (y) [Co0.50Cu0.15Zn0.35Fe1.95Mn0.05O4] (CCZMFO) (where y = 0.0–1.0) composites were prepared via the solid-state sintering route at 1273 K and 1323 K. The XRD and FTIR analyses asserted that the individual phases belong to the orthorhombic and cubic spinel structure, respectively, and additionally confirm the coexistence of the individual phases. The dielectric constant was decreased while the dielectric loss increased with increasing CCZMFO content. The grain size was decreased with increasing CCZMFO content due to the pinning effect. The $$\left( {\varepsilon^{\prime}_{\max } \left( \omega \right) - \varepsilon^{\prime}_{\min } \left( \omega \right)} \right)/\varepsilon^{\prime}_{\max } \left( \omega \right) $$ ratio was increased with increasing CCZMFO content and tanδ exhibits suitable value at x = 0.4 and x = 0.3 at 1273 K and 1323 K. The complex impedance and electric modulus studies revealed a significant benefaction from the grain boundary contribution to the electrical conduction and exhibited non-Debye relaxation. The AC conductivity study asserted that the small polaron hopping is ascribed to electrical conduction. The permeability exhibits almost frequency-independent characteristics. A maximum magnetoelectric voltage coupling coefficient of ~ 1.35 V cm−1 Oe−1 was observed with 80% CCZMFO at 1323 K.

Experimental work on mechanical, electromagnetic and microwave shielding effectiveness properties of mortar containing electric arc furnace slag

It is well known that one of the widely used structural materials is ordinary cement mortar. Whereas the mechanical properties are sufficient as structural materials, its shielding effectiveness and prevention properties of microwave signal is insufficient due to the lack of electromagnetically conductive components. Electric Arc Furnace Slag (EAFS) is a by-product which is produced after the melting and the primary acid refining of liquid steel. It has potential to improve both mechanical and electrical properties of cement. In this study, ordinary cement mortar specimens with Electric Arc Furnace Slag are investigated. The EAFS used in this study takes part in the mortar specimens as aggregate. Electrical properties are measured by a vector network analyzer in the frequency range of 3–18 GHz. Both the reflection and transmission of the proposed specimens exposed to EM wave are evaluated by free space measurement techniques at the same frequency range. The compressive strength, flexural tensile strength and shielding effectiveness of mortars are also tested, respectively. The real part of permittivity increases with the increased EAFS content of the mortars up to dielectric constant of 40. Nearly constant and frequency independent characteristics of specimens have potential applications. Furthermore, the effective dielectric constant of permeability of the mortars is explicitly improved in the related frequency ranges with the addition of the EAF slags. The transmission prevention of the EAF slag mortars tend to increase significantly with the increasing ratio of EAF slag content. The minimum transmission is around −70 dB and the transmission below −10 dB for 40% EAF aggregate ratio in mortar which has the best mechanical properties in the entire frequency range and averagely and it is −10 dB lower than that of the cement without EAF aggregates. The shielding effectiveness is in excellent level for 80% and 100% EAFS aggregate levels and that of 40% aggregate ratio is still in a good level with a value varying between 15 dB and 20 dB. Besides, the mortars with 40% EAF slag content exhibit approximately 7 MPa higher compressive strength value and 0.9 MPa higher flexural tensile strength.

두 개의 팔을 가진 초광대역 자기상보형 시뉴어스 안테나

본 논문에서는 Cellular/GSM800, GSM900, ISM, GPS, DCS/GSM1800, PCS/GSM1900, WCDMA/UMTS/IMT2000, WiBro, WLAN, WiMax의 주파수 대역(0.824~5.85 GHz) 전체를 포함하는 초광대역 시뉴어스 안테나를 제안하였다. 제안한 시뉴어스 안테나는 두 개의 팔(arm)로 이루어져 있으며, 자기상보(self-complementary) 구조로 설계하여 주파수 무관 특성을 나타내도록 하였다. 안테나는 클로펜스타인 테이퍼(Klopfenstein taper) 구조의 광대역 발룬(balun)을 사용하여 <TEX>$50{\Omega}$</TEX>에 정합시켰다. 측정 결과, 제안한 안테나의 대역폭은 반사손실 -10 dB를 기준으로 할 때 0.76~6 GHz까지 5.24 GHz로, 목표 주파수 대역을 모두 포함하는 것을 확인하였다. 방사패턴은 E-plane과 H-plane 모두에서 전체 동작 주파수 대역에 걸쳐 거의 변화 없이 양방향성 브로드사이드 빔을 보였으며, 최대 이득은 2.32~6.01 dBi로 측정되었다. This paper presents a ultra-wideband sinuous antenna that operates in a whole frequency range (0.824~5.85 GHz) of Cellular/GSM-800, GSM900, ISM, GPS, DCS/GSM1800, PCS/GSM1900, WCDMA/UMTS/IMT2000, WiBro, WLAN and WiMax. The proposed antenna, which is composed of two sinuous arms, is designed as a self-complementary structure in order to have frequency-independent characteristics. It also uses a wideband balun of Klopfenstein taper structure to match to <TEX>$50{\Omega}$</TEX>. Experimental results show that the -10 dB return loss bandwidth of the proposed antenna is 5.24 GHz that ranges from 0.76 to 6 GHz, which covers all the frequency bands of the various wireless services. Within the entire operating frequency range, the measured radiation patterns in both E-plane and H-plane show nearly constant bidirectional broadside beams and the maximum antenna gain is measured to fall between 2.32~6.01 dBi.

Structural, optical and dielectric studies of NixZn1−xFe2O4 prepared by auto combustion route

NixZn1−xFe2O4 (0≤x≤1) powders were synthesised by the auto combustion method. The derived samples show well defined peaks of cubic spinal structure with space group Fd3m. The lattice parameter calculated increased from 0.8372nm to 0.8429nm with raise of Zn content. The average crystallite sizes were determined by using Debye-Scherer method and found to be in the range of 18–23nm. Microstructural analyses show the regular and uniform grain morphology. Raman analyses demonstrated that the peaks have symmetric and asymmetric stretching as well as symmetric bending. Fourier transform infrared spectroscopy was used to investigate the structure and shows the changes in the tetrahedral and octahedral bond stretching. Photoluminescence measurements indicated intense emission in the wavelength range lie in blue-green region. The composition with x=0.2 showed highest intensity and explained on the basis of disordered cluster model. Dielectric analyses showed frequency sensitive behaviour in the low frequency region and frequency independent characteristics at high frequency side. The composition with x=0.2 showed highest dielectric constant and lowest dielectric loss in the studied frequency range. The ac conductivity showed a power law behaviour and conduction is explained on the basis of hoping mechanism.

Extraction of Substrate Resistance in Bulk FinFETs Through RF Modeling

A new method to extract substrate resistance (Rsub) for small-sized nano-scale metal oxide semiconductor field effect transistors (MOSFETs) including bulk FinFETs is proposed and compared with conventional method. The Rsub's extracted from small-size MOSFETs by using the proposed method are shown to have frequency independent characteristics, unlike those from the conventional method. Proposed equivalent circuit explains well the Rsub behavior with body width. The proposed model showed very good agreement (error in Y22~3%) with three-dimensional device simulation

Circular fractal antenna approaches with descrates circle theorem for multiband/wideband applications

The multiband and wideband performances of innovative fractal antennas constructed with circular patterns are proposed in this paper. By using the Descartes circle theorem and self-similar iteration design, the circular fractal antennas exhibit frequency-independent characteristics and multiband spectra. The simulated and experimental results with multiband/wideband spectra and radiation patterns are presented and discussed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 404–408, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20649

An ultra-broad-band reflection-type phase-shifter MMIC with series and parallel LC circuits

An ultra-broad-band reflection-type phase shifter is proposed. Theoretically, the proposed phase shifter has frequency-independent characteristics in the case of 180/spl deg/ phase shift. The phase shifter is composed of a 3-dB hybrid coupler and a pair of novel reflective terminating circuits. The reflective terminating circuit switches two states of series and parallel LC circuits. Using an ideal circuit model without parasitic circuit elements, we have derived the determining condition of frequency independence of circuit elements. Extending the concept, we can also obtain a broad-band phase shifter for other phase difference as well. In this case, for a given phase difference and an operating frequency, we also derive a condition to obtain minimum variation of phase difference around the operating frequency. This enables the broad-band characteristics for arbitrary phase difference. The fabricated 180/spl deg/ reflective terminating circuit monolithic microwave integrated circuit (MMIC) has achieved a phase difference of 183/spl deg/ /spl plusmn/ 3 over 0.5-30 GHz. The 180/spl deg/ phase-shifter MMIC has demonstrated a phase shift of 187/spl deg/ /spl plusmn/ 7/spl deg/ over 0.5-20 GHz. The 90/spl deg/ reflective terminating circuit MMIC has performed a phase difference of 93/spl deg/ /spl plusmn/ 7/spl deg/ over 4-12 GHz.

A cross LPD array antenna on a conducting cone

A cross LPD array antenna on a conducting cone has been designed and tested. The frequency-independent characteristics of the LPD array antenna were maintained by coinciding the virtual tip of the LPD array and that of the conducting cone. It was found that the radiation pattern and the input impedance of this antenna are not significantly deteriorated by the presence of the conducting cone.