Secondary Harmonics Research Articles

A Novel Three-Phase Power Factor Correction with Digital Control

A new three-phase power-factor-correction (PFC) scheme is discussed using two single phase power factor correction circuit parallel connected. Two phase orthonormal voltage is produced by means of a auto transformer from a three phase input,fluctuation of neutral point by three single phase power-factor-correction circuit parallel connected is canceled,coupling interference is reduced among three phases,digitally controlled Power Factor Correction Boost Converters is adapted,input current wave sine with unity power factor suppress the secondary harmonic of input AC side is realized,voltage and low current stresses across each switch are reduced. Simulation and experimental results prove that it can achieve high power factor,low current,good capability of anti-interference and high reliability.

Flexible transceiver array for ultrahigh field human MR imaging

A flexible transceiver array, capable of multiple-purpose imaging applications in vivo at ultrahigh magnetic fields was designed, implemented and tested on a 7 T MR scanner. By alternately placing coil elements with primary and secondary harmonics, improved decoupling among coil elements was accomplished without requiring decoupling circuitry between resonant elements, which is commonly required in high-frequency transceiver arrays to achieve sufficient element-isolation during radiofrequency excitation. This flexible array design is capable of maintaining the required decoupling among resonant elements in different array size and geometry and is scalable in coil size and number of resonant elements (i.e., number of channels), yielding improved filling factors for various body parts with different geometry and size. To investigate design feasibility, flexibility, and array performance, a multichannel, 16-element transceiver array was designed and constructed, and in vivo images of the human head, knee, and hand were acquired using a whole-body 7 T MR system. Seven Tesla parallel imaging with generalized autocalibrating partially parallel acquisitions (GRAPPA) performed using this flexible transceiver array was also presented.

Microwave dielectric properties of Mg 4Ta 2O 9 ceramics with TiO 2 additions for dielectric resonator oscillator

The microwave dielectric properties of the Mg 4Ta 2O 9 electro-ceramics with TiO 2 addition were investigated and the dielectric resonator oscillator (DRO) was simulated and manufactured. All specimens were prepared by solid-state reaction method and sintered at 1450 °C. From the XRD patterns, the Mg 4Ta 2O 9 phase was observed in (1 − x)Mg 4Ta 2O 9– xTiO 2 ceramics as a main phase. Meanwhile, the MgTi 2O 5 phase appeared by increasing the amount of TiO 2. It was found that MgTi 2O 5 and TiO 2 phases have influence on the microwave dielectric properties of the (1 − x)Mg 4Ta 2O 9– xTiO 2 ceramics. The temperature coefficient of resonant frequency ( τ f) was significantly improved by adding the TiO 2 with x = 0.5. However, the Q × f r value decreased from 116,800 GHz of the pure Mg 4Ta 2O 9 ceramics to 102,100 GHz of the TiO 2 added one with x = 0.5. The dielectric constant, Q × f r value and τ f of (1 − x)Mg 4Ta 2O 9– xTiO 2 ceramics sintered at 1450 °C for 10 h were 11.56–22.5, 24,980–186,410 GHz and −49.82 to +19.72 ppm/°C, respectively, depending on the value of x. Advanced Design System (ADS) as an electro-magnetic simulation tool was used for simulation and design for DR and DRO. The estimated EM characteristics of DR with 0.5Mg 4Ta 2O 9–0.5TiO 2 ceramics showed the operating frequency of 11.97 GHz and S 21 of −35.034 dB. The size of manufactured DRO was 56 mm × 48 mm × 34 mm and the operation frequency was 11.93 GHz. The power output and secondary harmonic of the manufactured DRO were +13.61 dBm and −23.81 dBc at 23.85 GHz, respectively.

Investigation on the effect of strong out-of-band signals on global navigation satellite systems receivers

The mitigation of radio frequency interference (RFI) has a fundamental role in global navigation satellite system (GNSS) applications, especially when a high level of availability is required. Several electromagnetic sources, in fact, might degrade the performance of the global positioning system (GPS) and Galileo receivers, and their effects can be either in-band (i.e., secondary harmonics generated by transmitters of other communication systems due to non-linearity distortions) or out-of-band (i.e., strong signals that occupy frequency bandwidths very close to GNSS bands). We investigated the effects of real out-of-band signals on GNSS receivers and analyzed the impact on the overall receiver chain in order to evaluate the impact of the interference source. In particular, the analysis focuses on the spectrum at the front-end output, on the automatic gain control (AGC) behavior, as well as on the digital processing stages (signal acquisition and tracking) at the analog digital converter (ADC) output. This study refers to several experiments and data collections performed in interfered areas of downtown Torino (Italy). The obtained results underline how digital/analog TV transmissions represent a potential interference source for GNSS applications and might be critical for the safety of life services.

Detection of CMOS Open Node Defects by Frequency Analysis

A method to detect open node defects that cannot be detected by the conventional IDDQ test method has previously been proposed employing a sinusoidal wave superposed on the DC supply voltage. The present paper proposes a strategy to improve the detectability of the test method by means of frequency analysis of the supply current. In this strategy, defects are detected by determining whether secondary harmonics of the sinusoidal wave exist in the supply current. The effectiveness of the method is confirmed by experiments on two CMOS NAND gate packages (SSIs).

Contribution from the secondary harmonics of a disturbance to the separatrix map of the Hamiltonian system

The special role of low-frequency secondary harmonics with frequencies that are sums of and differences between primary frequencies entering into the Hamiltonian in explicit form has been already discussed in the literature. These harmonics are of the second order of smallness and constitute a minor fraction of the disturbance. Nevertheless, under certain conditions, their contribution to the amplitude of the separatrix map of the system may be several orders of magnitude higher than the contributions from primary harmonics and, thereby, govern the formation of dynamic chaos. This work generalizes currently available theoretical and numerical data on this issue. The role of secondary harmonics is demonstrated with a pendulum the disturbance of which in the Hamiltonian is represented by two asymmetric closely spaced high-frequency harmonics. An analytical expression for the contribution of the secondary harmonics to the separatrix map amplitude for this system is derived, and the range of very low secondary frequencies not studied earlier is considered using this equation. The domains where the separatrix map amplitude linearly grows with frequency and the chaotic layer size is frequency-independent are indicated. Theoretical predictions are compared with numerical data.

An Experimental Study of Cutting Forces in High-Speed End Milling and Implications for Dynamic Force Modeling

The characteristics of high-speed machining (HSM) dynamic milling forces was investigated. Recent studies in chip segmentation are discussed. A Mikron 700 High-Speed Machining Center was used in the end-milling of AISI H13 tool steel using PVD TiN coated two flute micrograin carbide tools. Dynamic force signals were studied using a real-time data acquisition system for spindle speeds from 3,750 to 31,500 rpm for a 6 mm dia tool. Frequency domain studies were also carried out for a larger tool of 12 mm dia for spindle speeds between 10,000 and 40,000 rpm. The trend and frequency domain aspects of the dynamic forces were evaluated and discussed. The fundamental concept of modeling cutting forces based on chip morphology is revisited. A new basis for modeling dynamic forces from the static component and harmonic contributions is presented. This approach for modeling the dynamic HSM force signal accounts for secondary harmonics.

Chaos in a driven pendulum under asymmetric forcing

An analysis of the stochastic layer in a pendulum driven by an asymmetric high-frequency perturbation of fairly general form is continued. Analytical expressions are found for the amplitudes of secondary harmonics, and their contributions to the amplitude of the separatrix map responsible for onset of dynamical chaos are evaluated. Additional evidence is presented of the previously established fact that the secondary harmonics completely determine the stochasticl-ayer width when the primary frequencies lie in certain intervals. The mechanism of the onset of chaos in the vicinity of zeros of Melnikov integrals is shown to be substantially different as compared to the previously analyzed case of symmetric perturbation.

WITHDRAWN: Secondary Harmonic Imaging Overestimates Left Ventricular Mass Compared to Fundamental Echocardiography.

The publisher regrets that this was an accidental duplication of an article that has already been published in Eur. J. Echocardiogr., 4 (2003) 178-181, . The duplicate article has therefore been withdrawn.

The Improvement of Temperature Coefficient of Frequency in Thin Film Bulk Acoustic Wave Resonator using Secondary Harmonics

ABSTRACTWe have succeeded in making an 870MHz-range thin film bulk acoustic wave (BAW) resonator that has a small temperature coefficient of frequency (TCF) using secondary harmonics. The 870MHz-range BAW resonator has been requested to have nearly zero TCF, because it will be used in an oscillator for remote keyless entry systems. The BAW resonator has composite structure that consists of Al electrodes and ZnO/SiO2. We directed our attention to the fact that ZnO and Al have negative TCF, and SiO2 has a positive one. It is theoretically possible to make zero TCF BAW resonators by optimizing the thickness ratio of ZnO and SiO2. However, using fundamental resonance, TCF is so sensitive to the thickness ratio that it cannot be easily controlled by MEMS techniques. We founds in finite element method simulation and confirmed by experiment that the TCF of secondary harmonics has a local minimum when changing the ZnO/SiO2 thickness ratio. As the result, a nearly zero TCF resonator without strict control of ZnO/SiO2 thickness ratio has been realized by adopting Al/ZnO/SiO2/ZnO/Al/SiO2 structure and combining thermal oxidized Si and sputtered SiO2. The resonator has the TCF of -1.86ppm/degree in the range of −40 to 85 degrees centigrade.

Stress Adjustment and Characteristics Improvement in a 1.8GHz Range Film Bulk Acoustic Wave Resonator by Using Multi-layer Structure of ZnO/A12O3/SiO2

ABSTRACTStress adjustment and improvement of electrical characteristics in film bulk acoustic wave resonator (BAW) have been successfully carried out in 1.8GHz range by using a multi-layer structure of ZnO / Al2O3 / SiO2. The BAW resonator, designed on secondary harmonics at about 1.8GHz, has Al / ZnO / Al / Al2O3 / SiO2 structure. ZnO and SiO2 thin films have a negative and a positive temperature coefficient of sound velocity, respectively. So temperature coefficient of frequency (TCF) of the BAW resonator can be controlled by the thickness ratio of ZnO and SiO2 thin films. Since both ZnO and SiO2 have compressive stress, and Al2O3 has tensile one, the stress of the membrane is reduced by combining these thin films so that the membrane can avoid deformation. The BAW resonator, with thickness of ZnO / Al2O3 / SiO2=1.2 /0.45/1.25 microns, was designed by finite element method (FEM) simulation and fabricated. The value of quality factor (Q factor) and the TCF of the BAW resonator were realized over 1000 and −20 ppm/degree C, respectively. The Q of ZnO / Al2O3 / SiO2 structure was higher than that of ZnO / SiO2 one with keeping small TCF.

Chaotic layer of a nonlinear resonance driven by quasiperiodic perturbation

We present the numerical and analytical evidences are given of the fact that the formation of a chaotic layer of a nonlinear resonance under the action of multifrequency perturbation is qualitatively different from the case of a single-frequency perturbation which is well studied by now. The new effect of appearance in the separatrix mapping of the system of low-frequency secondary harmonics is discussed and the conditions under which just these harmonics play the dominant role in the formation of chaos are found. Theoretical estimates of the secondary harmonic amplitudes are compared with the results of numerical calculations. Invariants of the first two orders of separatrix mapping enabling one to produce an approximate picture of resonance overlapping on the edge of the chaotic layer and to get its size value are introduced.

Low frequency audio conversion circuit

A low frequency audio conversion circuit for converting the frequency of low frequency audio components. An input audio signal includes a low frequency audio component lower than the frequency a speaker can reproduce. The low frequency audio component is filtered and extracted by a low pass filter and full-wave rectified to generate even-numbered harmonics of the low frequency audio component. Secondary harmonics are extracted from the even-numbered harmonics and added to the input audio signal after being amplified to an appropriate level. When a speaker whose low frequency sound reproduction characteristics are poor is used, and a low frequency component lower than the frequency the speaker can reproduce is supplied, the low frequency audio component is reproduced as secondary harmonics which fall within the frequency range of the speaker. Thus, the low frequency audio component is compensated, and a powerful sound is reproduced at a low cost without degrading the sound.

Ionic structure and plasmon response in sodium clusters

The linear and nonlinear optical response of sodium clusters is studied using fully three-dimensional electronic dynamics with frozen ionic positions. The detailed ionic structure produces more spectral fragmentation than a comparable jellium model, and the fragmentation patterns come close to measured spectra, even at low temperatures. The nonlinear response shows the same trends as found in former, symmetry restricted, investigations, namely that the plasmon resonance is a very harmonic mode showing no trace of nonlinear effects as secondary harmonics or spectral diffusion.

Optical Density Dependence of Write/Read Characteristics in Photon-Mode Photochromic Memory

When photobleaching reactions are used for writing in a photochromic optical memory, the initial optical density in the recording layer plays an important role in the various write/read characteristics; i.e., secondary harmonics, repeatedly readout characteristics, and crosstalks in a multi-wavelength recording. Better characteristics, that is, lower secondary harmonics, higher readout repeatability and lower nonlinear component of crosstalks, were obtained for media with higher optical density.

Formation of a chaotic layer of nonlinear resonance by a two-frequency perturbation

A new effect [V. V. Vecheslavov, Zh. Eksp. Teor. Fiz. 109, 2208 (1996) (JETP 82, 1190 (1996)]—the appearance of low-frequency secondary harmonics in the separatrix mapping of a system—is discussed in detail for the example of a pendulum with a two-frequency perturbation. It is shown that there exist regions of values of the perturbation parameters where these harmonics make the main contribution to the formation of the chaotic layer of the fundamental resonance. The results of analytical and numerical determinations of the amplitudes of the secondary harmonics are compared.

Redox, photochemical and optical activity in molybdenum chemistry: Towards molecular electronics

Compounds containing the [Mo(NO)]3+ group are redox-active. Incorporation into tris(3,5-dimethylpyrazolyl)borato (L*) systems, e.g. [MoL*(NO)XY] where X, Y = halide, alkoxide, aryloxide, amide, anilide, thiolate, etc. affords a variety of species which undergo one-electron reduction. The factors influencing this behaviour are described. Attachment of the molybdenum redox centre to macrocyclic polyethers and the effect of added cation is discussed. The group {MoL*(NO)X} can be attached to the periphery of tetra-aryl porphyrins, and the electrochemistry and photochemistry of the extra-ring metallated species is reported. A series of ferrocenyl compounds, [(η5-C5H5)Fe(η5-C5H4) C6H4E{ML*(NO)X}] and trans-[(η5-C5H5)Fe(η5-C5H4)C6H4ZZC6H4E{ML*(NO)X}] (where Z = CH or H, E = O or NH, M = Mo or W, X = Cl or I) have been prepared, their electrochemistry investigated and several compounds identified as having non-linear optical (Secondary Harmonic Generation) properties.

SIMULATION OF TIME‐DOMAIN, AIRBORNE, ELECTROMAGNETIC SYSTEM RESPONSE

The response of a time‐domain electromagnetic system over a thin conducting sheet may be simulated by purely electronic means and without recourse to scale model experiments. The simulation is based on the similarity between the frequency domain response function for a thin sheet and the transfer function of certain RC active networks. Since this type of experiment employs actual field equipment, the proposed technique also constitutes a valid means of data quality control. It is difficult to carry out an analog simulation for conductors which do not resemble a thin sheet. If, however, the frequency domain response function for the situation in question is known, the simulation may be carried out on a digital computer. The digital simulation process involves a numerical Fourier decomposition of the primary field waveform (as seen by the receiver), the calculation of the effect of the ground on each harmonic component, and the recombination of the secondary field harmonics to form the observed transient. The technique is illustrated with some calculations of theoretical responses for an EM system over a homogeneous ground and over a thin horizontal conducting sheet. The digital simulation technique is more useful than the analog.

Checking heat treatment of ferromagnetic components by the eddy current method

1. Equations were formulated for the field within a cylindrical ferromagnetic test-piece in a weak alternating field (Rayleigh region). 2. Solution of this equation formed the basis of formulae for calculating the amplitude and phase of the secondary emf first and third harmonics. 3. Analysis of the formulae shows that the third E2 harmonic is the most suitable for controlling heat treatment of ferrous metal components. This theoretical conclusion was confirmed by experiment.