Transmission Formula Research Articles

Use of Safety Light Curtains in Mechatronic Systems

The article describes some of the aspects of how the optosensors and laser scanners can be used in the field of security of protected areas and safety fields. The article presents some of the applied possibilities of measuring on spherical area using transmission formulas for gaining data and actual setting of active elements of the optosensors and laser scanners for the environment in a 3D application mechatronic system.

A spectral analysis of an integrated photomixer/antenna in a homodyne terahertz photomixing system

An analysis has been carried out to estimate the spectral characteristics of an integrated photomixer/antenna in a homodyne photomixing system. The analysis adopts the impedance mismatch factor and Friis power transmission formula used in communication links based on the conventional analysis theory of a terahertz photomixer. The analysis and experimental results have proved that an impedance matching condition between the impedance of a photomixer and the input impedance of an antenna is directly related with photomixing terahertz wave generation. The Friis formula is introduced to calculate the propagation loss of the wave from a transmitter to a receiver in a homodyne photomixing system. A log-periodic antenna was used to ensure a high dynamic range in a broad frequency region. The dynamic range of the homodyne terahertz photomixing system was about 60dB near 100GHz and decreased with an increasing frequency from 10GHz to 1000GHz. The measured results agree well with the theoretically analyzed results and prove that the terahertz photomixing power is closely related to impedance mismatch factor and it could be estimated in the homodyne terahertz photomixing system without a terahertz power detector.

Numerical determination of statistical energy analysis parameters of directly coupled composite plates using a modal-based approach

Statistical energy analysis (SEA) parameters such as average modal spacing, coupling loss factor and input power are numerically determined for point connected, directly coupled symmetrically laminated composite plates using a modal-based approach. The approach is an enhancement of classical wave transmission formula. Unlike most of the existing numerical or experimental techniques, the approach uses uncoupled plate modal information and treats substructure by means of averaged modal impedances. The procedure introduced here is verified using analytical definitions of infinite orthotropic plates which physically resemble to laminated plates for (under) specific conditions, and is tested by performing experimental power injection method (PIM) for an actual, right-angled composite structure. In the development process, force and moment transmissions are individually considered in order to be consistent with analytical formulations. Modal information of composite plates is statistically evaluated by the discrete singular convolution method with random boundary conditions. Proposed methodology not only provides an efficient use of SEA method in high frequency vibration analysis of composite structures, but also enhances SEA accuracy in mid frequency region in which conventional SEA fails. Furthermore, the effect of orientation angles of laminations on SEA parameters are also discussed in mid and high frequency regions.

Characterization of Reverberation Chambers for OTA Measurements of Wireless Devices: Physical Formulations of Channel Matrix and New Uncertainty Formula

The paper deals with reverberation chambers for over-the-air (OTA) testing of wireless devices for use in multipath. We present a formulation of the S-parameters of a reverberation chamber in terms of the free space S-parameters of the antennas, and the channel matrix in the way this is known from propagation literature. Thereby the physical relations between the chamber and real-life multipath environments are more easily explained. Thereafter we use the formulation to determine the uncertainty by which efficiency-related quantities can be measured in reverberation chamber. The final expression shows that the uncertainty is predominantly determined by the Rician K-factor in the reverberation chamber rather than by the number of excited modes, assumed by previous literature. We introduce an average Rician K-factor that is conveniently expressed in terms of the direct coupling between the transmitting and receiving antennas (corresponding to a line-of-sight contribution) and Hill's transmission formula (corresponding to a multipath or non-line-of-sight contribution). The uncertainty is expressed in terms of this average K-factor and geometrical mode stirring parameters, showing strong reduction by platform and polarization stirring. Finally the formulations are verified by measurements, and the new understanding of uncertainty is used to upgrade an existing reverberation chamber to better uncertainty.

시스템 추가장착을 위한 항공기의 안정성 해석

본 연구에서는 외부 장착물이 존재하는 항공기의 안정성 검증을 위해 진동 및 구조해석을 수행하였다. 외부 장착물이 존재하는 경우, 외부 장착물 자체의 정확성 및 안정성을 위한 요구조건이 주어지며, 이와 동시에 외부 장착물이 항공기에 장착되도록 개조된 항공기 구조물의 안정성 문제가 중요하다. 따라서 본 연구에서는 정적 상태에서의 고유주파수 계산을 통한 공진 여부를 조사하고 발사기를 장착하기 위해 개조된 구조물에 작용하는 진동하중을 구하였다. 또한 로컬 모델링 방법을 이용하여 추가 장착 구조물의 구조적 안정성을 검토하였으며 지상 및 비행시험을 통하여 이를 검증하였다. This paper presents the stability analysis of UH-60 helicopter with external store such like chaff/flare dispenser. An external store can affect the natural frequency of the aircraft and induce the resonance, which cause the failure of structures. In this paper, therefore, Rayleigh method is used to investigate the resonance with aircraft and external store, and transmission formula is used to determine the vibration load. Structural analysis with local modeling method are performed to present the robust design of aircraft with external store. The ground and flight test are also done to verify the stability of the aircraft.

Exact Gaussian-Beam Theory for Outgoing and Standing Spherical Waves: Application to Transmitting and Receiving Antennas

Outgoing spherical vector-wave functions are expressed in terms of Gaussian beams (also called complex source-point beams) radiating in all directions. By use of a vector-wave expansion, the electromagnetic field of an arbitrary source of finite extent is thus expressed in terms of Gaussian beams with weights determined directly from the spherical expansion coefficients of the source. These outgoing-wave formulas allow the field of any transmitting antenna to be expressed in terms of Gaussian beams. Elementary Gaussian-beam receivers are introduced as the electromagnetic field at complex points in space. The outputs of elementary Gaussian-beam receivers pointing in all directions determine the spherical expansion coefficients in a standing-wave expansion. These standing-wave formulas allow the output of any receiving antenna to be expressed in terms of the outputs of elementary Gaussian-beam receivers. Combining the formulas for outgoing and standing waves produces a new antenna-antenna transmission formula based solely on Gaussian beams. The theory is exact and validated through numerical examples.

高透光率感性网栅膜的电磁屏蔽

This paper studies the influencing factors on the electromagnetic shielding of an inductive metallic mesh when the infrared transmission reduction of optical window caused by the mesh is less than 5%.The infrared transmission formulas of the inductive mesh are summarized,then,the electromagnetic field integral equation for the periodic structure of metallic mesh is built based on Galerkin's method in the spectral domain.The transmission and reflection coefficients are derived by the Moment of Method(MOM).After that,the electromagnetic shield effectiveness of the mesh is calculated and the effects of different line widths,periods,substrate materials,substrate thicknesses on the electromagnetic shielding of the transparent conductive optical window(with metallic mesh) are calculated and analyzed.Finally,metallic mesh samples with a line width of 12 μm,a period of 360 μm×360 μm and the surface resistance of 13 Ω,25 Ω are fabricated on a ZnS substrate by the laser direct writing figure,vacuum coating,et al..The electromagnetic shield effectiveness from 2 GHz to 18 GHz is tested by a free space method.Results indicate that the average electromagnetic shield effectiveness is more than 20 dB when the infrared transmission reduction caused by the metallic mesh is less than 2% in 8-10 μm.Experiments indicate that the optical and electrical performance of metallic mesh film is inconsistent.The main solution method is to select a thinner line width and smaller period and to reduce the surface resistance value of the mesh as low as possible at the same time.

Bloch wave deafness and modal conversion at a phononic crystal boundary

We investigate modal conversion at the boundary between a homogeneous incident medium and a phononic crystal, with consideration of the impact of symmetry on the excitation of Bloch waves. We give a quantitative criterion for the appearance of deaf Bloch waves, which are antisymmetric with respect to a symmetry axis of the phononic crystal, in the frame of generalized Fresnel formulas for reflection and transmission at the phononic crystal boundary. This criterion is used to index Bloch waves in the complex band structure of the phononic crystal, for directions of incidence along a symmetry axis. We argue that within deaf frequency ranges transmission is multi-exponential, as it is within frequency band gaps.

Electromagnetic characterization of substrated metasurfaces

In this paper we present a macroscopic model of a metasurface—optically dense grids of resonant scatterers located on a refracting interface. Similar models were previously built for the case when the scatterers are non-resonant electric dipoles and for the case when there is no substrate. In the present case scatterers are resonant, can have magnetic response, and for substrates with large refraction index acquire also substrate-induced bianisotropic properties. Representing the homogenized response of a metasurface to incident electric and magnetic fields through surface susceptibilities we derive the reflection and transmission formulas for semi-infinite and finite-thickness substrates. We develop a robust algorithm of the retrieval of the characteristic surface parameters from the reflection and transmission coefficients measured or exactly calculated for three different incidence angles. With numerical examples we show that the retrieved susceptibilities of metasurfaces are independent on the incidence angle and can be really called characteristic parameters.

Hydrodynamic Characteristics of a Free-Surface Semicircular Breakwater Exposed to Irregular Waves

A free-surface semicircular breakwater (SCB) has been developed for protecting coastal and marine infrastructures against ocean waves. The hydrodynamic characteristics of the breakwater are investigated in irregular seas through an experimental program. A test model of the semicircular breakwater has been constructed with front wall porosity varied at 0 (i.e., no perforations), 9, 18, and 27%. The wave surface elevations are measured at different locations upstream and downstream of the models, and the coefficients of wave transmission, reflection, and energy dissipation are evaluated. Wave climate in the vicinity of the breakwater models and horizontal wave force on them are also measured. On the basis of the measured data, empirical models are proposed to provide design formulas for wave transmission, wave reflection, and horizontal wave force. The proposed empirical models show good agreement with the measured data; however, sensible engineering judgment must be taken while using these because the equa...

Design of Yb Fiber High Power Amplifier through 915nm Pumping

Analyze the fiber amplified theory and obtain the transmission formula of pump and signal for the use of rate equation. In the experiment, take the Yb-doped double cladding fiber based on phosphor silicate as gain medium, high power single emitter in 915nm as pump source. According to gain fiber length obtained by the theory analyses, the output power achieves 20W above. Apply the cladding power stripper at the output end for stripping the remained pump power.

A 60-GHz Millimeter-Wave CMOS Integrated On-Chip Antenna and Bandpass Filter

This paper presents a first reported 60-GHz millimeter-wave integrated on-chip antenna and bandpass filter fabricated with a standard 0.18-μm complementary metal-oxide-semiconductor (CMOS) process. The on-chip coplanar waveguide (CPW) bandpass filter utilizes a backed-side half-wavelength resonator integrated with a CPW-fed Yagi antenna. A finite-element-method-based 3-D full-wave electromagnetic solver, i.e., the High-Frequency Structure Simulator, is used for design simulation. A detailed on-wafer measurement methodology for the on-chip antenna is presented. The Friis power transmission formula is used to determine the radiation power gain and antenna pattern. The possible effect of the probe radiation, which may affect the accuracy of the antenna measurement, is also investigated. The proposed integrated on-chip antenna-filter can be very useful for the integrated design of the 60-GHz CMOS single-chip radio-frequency transceiver.

Throughput and delay limits of chirp spread spectrum-based IEEE 802.15.4a

The IEEE 802.15.4 standard is designed to provide a low-power, low data rate protocol offering a high reliability. As an amendment to this standard, IEEE 802.15.4a introduces new options for physical layer to enable precision ranging. In this work, we analyzed the theoretical throughput and delay bounds of the unslotted version of chirp spread spectrum PHY-based 802.15.4a. The formulae for transmission between one sender and one receiver for an ideal channel with no transmission errors are given. The throughput and delay bounds are derived for different frequency bands and data rates. Additionally, to measure spectral utilization, we measured the bandwidth efficiency for both the standards. We also compared our results with IEEE 802.15.4. The comparative analysis concludes that the performance of 802.15.4a exceeds 802.15.4 in terms of throughput and delay. The analytical results of throughput are verified by computer simulations. Copyright © 2011 John Wiley & Sons, Ltd.

Bistable switching in the lossy side-coupled plasmonic waveguide-cavity structures

We show numerically that the lossy side-coupled plasmonic resonators can be used as bistable switches without compensation. While the internal loss imposes on the bistable characteristics by reducing the transmission contrast and raising the input power requirement, it makes the switching more available by enlarging the width of the hysteresis loop. We also correct the nonlinear transmission formula of the resonators to adapt the lossy condition. Both the theoretical and simulation results are in good agreement.

Correct self-assembling of spatial frequencies in super-resolution synthetic aperture digital holography

Synthetic aperture enlargement is obtained, in lensless digital holography, by introducing a diffraction grating between the object and the CCD camera with the aim of getting super-resolution. We demonstrate here that the spatial frequencies are naturally self-assembled in the reconstructed image plane when the NA is increased synthetically at its maximum extent of three times. By this approach it possible to avoid the use of the grating transmission formula in the numerical reconstruction process, thus reducing significantly the noise in the final super-resolved image. Demonstrations are reported in 1D and 2D with an optical target and a biological sample, respectively.

Determination of probe receiving coefficients for near‐field to far‐field transformation

AbstractWhen the field radiated by an antenna is measured in the near‐field region, this must be transformed into far‐field. If a spherical wave expansion is used for this transformation, the transmission formula must be solved, and hence the probe receiving coefficients must be known. Normally, the electric Hertzian dipole coefficients can be applied; however, sometimes this approximation is not possible, and even though the antenna under test and probe are far away, the correct probe receiving coefficients are necessary. In this letter, an algorithm for determining these coefficients using the gain parameter of the probe is proposed. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51:2826–2829, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24797

Experimental comparison of different dead-time correction techniques in single-channel counting experiments

For single-channel counting, the dead-time correction method using transmission formulae was compared experimentally with the live-time technique. Agreement is within 4×10 −4 for count rates up to 10 4 s −1 when the formulae for dead times in series are used and the dead-time value related to the analogue pulse width is adjusted for the BIPM modules. At higher count rates, a bias of 2×10 −3 is observed. Two different live-time modules were compared and it was demonstrated that the live-time correction is also sensitive to the analogue pulse width and to the duration or rise time of the clock pulses. When these effects are taken into account, the two modules differ by only 5×10 −4.

Investigation of strain transmission of surface-bonded FBGs used as strain sensors

Bonding an FBG on a substrate as a sensor using an adhesive, the strain transferred from the substrate through the bonding layer to FBG is smaller than that on the substrate. The strain transmission loss becomes large when the substrate is thin and/or made by a low-modulus material, e.g. the polyimide film used in lithium battery and chip on film manufacturing industry. Moreover, the FBG and the bonding layer affect the original strain distribution on the thin and low-modulus substrate. As a result, the substrate strain sensed by the FBG is underestimated and thus required to be corrected. Based on elasticity, an analytical model is proposed to characterize the strain transmission of an FBG used as a strain sensor when it is surface-bonded on a structure using an adhesive. The proposed strain transmission formula takes the influences caused by the stiffness of substrate and FBG as well as the bonding layer characteristics, i.e. the length, thickness and shear lag parameter into consideration. Validated respectively by numerical simulations using finite element method and experiments, this formula provides a simple but accurate correction for the bonded FBG to reflect the true structural strain.

Simultaneous Measurement of Antenna Gain and Complex Permittivity of Liquid in Near-Field Region Using Weighted Regression

As a technique for calibrating electric-field probes used in standardized SAR (Specific Absorption Rate) assessment, we have studied the technique using the Friis transmission formula in the tissue-equivalent liquid. It is difficult to measure power transmission between two reference antennas in the far-field region due to large attenuation in the liquid. This means that the conventional Friis transmission formula cannot be applied to our measurement so that we developed an extension of this formula that is valid in the near-field region. In this paper, the method of weighted least squares is introduced to reduce the effect of the noise in the measurement system when the gain of the antenna operated in the liquid is determined by the curve-fitting technique. And we examine how to choose the fitting range to reduce the uncertainty of the estimated gain.

Diffraction transfer function and its calculation of classic diffraction formula

In scalar diffraction theory, Kirchhoff formula, Rayleigh–Sommerfeld formula, and angular spectrum transmission formula are classic formulas that express diffraction correctly. But as complex calculation, Fresnel diffraction integral, which is the paraxial approximate solution to these formulas, is used widely. This paper presents diffraction transfer function corresponding to each classic diffraction formula, gives discussion on methods when using fast Fourier transform to calculate these formulas, derives conditions each formula must meet when it is calculated correctly based on sampling theorem, and finally real examples are finished to certify the results.