Complete Frequency Range Research Articles

Wideband VCO With Simultaneous Switching of Frequency Band, Active Core, and Varactor Size

As the tuning range of integrated LC-VCOs increases, it becomes difficult to co-design the active negative resistance core and the varactor size optimally for the complete frequency range. The presented VCO design solves this by adjusting the size of the negative resistance transistors with a switched active core, with the additional benefit that this reduces parasitics and hence allows to achieve better phase noise and an even higher tuning range. Also the VCO gain variations are counteracted by employing an analog varactor that can change in size. The implementation in 0.13-mum CMOS shows a tuning range from 3.1 to 5.2 GHz, with a power consumption varying accordingly from 7.7 to 2.1 mA from a 1.2 V supply. The measured phase noise is -118 dBc/Hz at 1 MHz from a 4-GHz carrier.

Non compact single-layers of dielectric spheres electromagnetc behaviour

Single layer of dielectric spheres is a recognized model for the basic understanding of some aspects of photonic crystals. Here we present a systematic study of the effect of compacting in the electromagnetic transmission of dielectric spheres monolayers. Experiments were performed in the microwave domain (from 10 GHz to 30 GHz) with glass spheres of high dielectric permittivity e = 7. Time Domain Finite Integration (TDFI) calculations were also accomplished. Experimental data and TDFI calculations agreement provides a double check on the lack of experimental artefacts and the correctness of simulation settings. Following the evolution of the lower frequency spectral peak with layer compacting ratio, we established three different electromagnetic regimes. For the higher and lower compacting ratio regimes, the peak frequency matches isolated sphere pure resonances, while for intermediate values of compacting, some transition between these two modes takes place. Extending the study to the complete frequency range, we find that sphere single layers transmission spectra become closer to isolated sphere scattering calculations as the compacting ratio is decreased. However as the agreement remains imperfect even for our lowest compacting measurable layer, we conclude that some structure contribution cannot be neglected even for low compact layers.

Ultrabroadband terahertz pulses: generation and field-resolved detection

In this paper, we discuss the latest techniques for the generation and field-resolved detection of tunable femtosecond electromagnetic field transients in a spectral regime covering the complete mid-infrared frequency range. In particular, we review the generation scheme based on phase-matched optical rectification. We also present a novel detection method, exploiting phase-matched electro-optic sampling, which extends the accessible frequency range towards the near-infrared.

Feedback control and nonlinear intensity noise ofNd:YVO4microchip lasers

A fully quantum model is used to derive both the intensity noise of a laser operating with an electronic feedback loop and the nonlinear corrections to the noise of the free-running laser. The implementation of a nonstandard feedback loop on a ${\mathrm{N}\mathrm{d}:\mathrm{Y}\mathrm{V}\mathrm{O}}_{4}$ microchip laser pumped with an amplitude squeezed diode laser permits us to decrease the intensity of the relaxation oscillation noise peak while leaving the low-frequency part of the spectrum unaffected. This procedure also results in a decrease of the noise in the low-frequency region, showing evidence for nonlinear effects in the noise spectrum. The latter are found to be in good agreement with the theoretical predictions. Good agreement between the experimental results and theoretical predictions is also found over the complete frequency range.

Space charge field enhancement in photorefractive materials by applied sinusoidal fields: An approximate analytical solution

The second order temporal differential equation, known to describe the space charge field in the high frequency region, is solved approximately in a closed analytical form. The condition for multiple resonances is found. The maxima and minima in the space charge field are shown to correspond to the roots of the zero and first order Bessel functions respectively. The analytical approximations for the space charge field are compared with numerical results for the complete range of frequencies, and it is shown that there is excellent agreement between the two for the high frequency region which includes all the resonances.

A theory of diffusion in the ordered alloy I. Tracer correlation effects

Abstract In this study, two and four frequency versions of a model of a long range ordered alloy where the sublattices exist a priori are proposed. This model is a natural extension to the ordered state of the well-known random alloy model. Manning's (1971) formalism for describing tracer correlation effects in the random alloy is adapted and extended to the present model. The model is applicable to any lattice which can be conceived as a combination of two sublattices with the same number of sites and where diffusion requires a vacancy jump from one sublattice to the other. Computer simulation results for the simple cubic lattice from a previous study (Belova, Ivory and Murch 1995) and new ones presented here are used to assess the new analysis. The general trends of the correlation factors across the complete frequency range are described very well. The detailed fit is generally better for the faster moving atomic component.

Unsteady unified hypersonic/supersonic method for aeroelastic applications including wave/shock interaction

A unified unsteady hypersonic/supersonic method using perturbed Euler characteristics (PEC) has been developed for the treatment of stability derivatives and panel flutter of wedgelike profiles. The present PEC method is valid for all supersonic Mach numbers, ranging from the low supersonic shock-attached limit to the Newtonian limit, in the complete frequency range, and for arbitrary body thickness so long as the bow shock remains attached to the body apex. The unsteady lifts, moments, and stability derivatives for oscillating wedge profiles, an oscillating leading-edge flap, and the related panel flutter problem are studied. Our computed results are found to differ with those of piston theory and linear potential theory in their invalid regions as expected. The essential feature of the PEC method lies in that it can fully account for the unsteady Mach wave/shock wave interaction and, hence, the rotationality and thickness effects. In view of its exactness, in terms of the characteristic formulation, and its ease of application, the present (PEC) method should be a promising method for panel flutter applications to hypersonic vehicles such as NASP.

Modelling and analysis of non-linear orifice type damping in vibration isolators

The effects of non-linear orifice type damping on the response of one- and two-degree of freedom (DOF) systems are studied. The damping is formulated through the hydraulic resistance of the fluid path as a function of the frequency of flow oscillation and mean flow velocity for the laminar and turbulent flows. A comparison is made to demonstrate the vibration control capability of linear and non-linear damping models in terms of displacement transmissibility ratios for a 1-DOF system and for a 2-DOF system with an optimally tuned absorber, providing the minimum peak displacement of the isolated mass over the complete frequency range of interest. The results show a significant shift in resonant frequency between the linear and non-linear damping approaches.

TV and TVSAT mixer-oscillator PLL ICs

Two mixer-oscillator PLL ICs were developed to convert the desired TV-RF (45 MHz-1000 MHz) or TVSAT-RF (700 MHz-2500 MHz) to standard IF for TV or TVSAT sets and setstop baseband converters. Only two switched bands cover the complete frequency range of the TV or TVSAT channels. These ICs combine analog (mixer-oscillator) and a complete digital (PLL) functionality.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Quantitative infrared analysis of the stretching peak of SiO2 films deposited from tetraethoxysilane plasmas

Infrared transmission spectra of silicon dioxide (SiO2) thin films (∼4500 Å) prepared by plasma-enhanced chemical-vapor deposition have been quantitatively analyzed. The films were deposited at different substrate temperatures (30–450 °C) using tetraethoxysilane (TEOS)/He, TEOS/He/O2, and TEOS/O2 gas mixtures in a parallel-plate radio-frequency reactor. The infrared transmission fits prove to be very accurate showing evidence of deconvolution into three separated Gaussian profiles to account for the asymmetric line-shape feature of the infrared stretching peak between 950 and 1300 cm−1. The examination of the Fourier transform infrared spectroscopy spectra in the complete frequency range (400–4000 cm−1) and ex situ x-ray photoelectron spectroscopy spectra indicates that some extra structures originate from the incorporation of carbon and hydrogen impurities in the film. As the substrate deposition temperature is increased, impurities are gradually removed from the growing layer. Films deposited at high substrate temperatures reveal a better stoichiometry and present similar deconvolution bands regardless of the gas-phase composition; the corresponding frequencies are shifted to lower energies compared to thermal oxides. In addition, the intensity of the first Gaussian profile, associated with the low-energy asymmetry of the stretching peak, increases with the substrate deposition temperature while the intensity of the third Gaussian profile associated with the presence of the high-energy peak shoulder decreases. The vibrational properties of the film seem to be strongly related to the deposition conditions.

Generation of tunable high power far-infrared radiation by stimulated Raman scattering in gaseous methylhalides

This paper is a review on the generation of far-infrared (FIR) radiation via stimulated Raman scattering in methylhalides by the use of a frequency tunable 20 atm CO 2 laser as pump source. A survey on the properties of the methylhalide molecules was achieved by studying the seven gases 12CH 3F, 13CH 3F, 12CD 3F, 13CD 3F, CH 3Cl, CH 3Br and CH 3I. All these gases turned out to be well suitable media for generation of tunable FIR radiation with the lightest of them having the most favourable emission characteristics. With the pump laser applied, frequency tunable FIR radiation was obtained from the seven gases for more than 600 Raman tuning ranges covering almost the complete frequency range from 8 to 72 cm −1. It is also demonstrated that the broad tuning ranges and the high maximum quantum efficiencies up to 0.1 can be used for generation of intense FIR pulses with subnanosecond duration.

Threshold of hearing (0.125-20 kHz) in children and youngsters.

Pure-tone air-conduction audiometry has been performed in three groups of children and youngsters aged 10, 14 and 18 years old. The complete frequency range of 0.125 to 20 kHz was measured, and number of different questions were raised. Firstly, the hearing threshold in the conventional frequency range was compared to the international standard ISO 389. Significant differences from ISO zero were found for all groups and at all frequencies of 0.125 to 8 kHz. Secondly, possible noise damage, shown as dips in the audiograms at 3, 4 or 6 kHz was examined; and thirdly, high-frequency (8-20 kHz) sensitivity between groups was compared. Only a few audiograms, the majority being in the youngest age group, were found to be a result of possible noise damage, and in the extra-high-frequency range, a systematic decrease in sensitivity was found for the two older groups compared to the 10-year-old children at frequencies higher than 14 kHz.

Phonon-order parameter coupling in YBa2Cu3O7- delta as observed by infrared absorption spectroscopy

Infrared absorption spectroscopy has been used to investigate the complete phonon frequency range (20 cm-1-700 cm-1) at temperatures between 10 K and 300 K. A direct coupling of bulk phonon modes in YBa2Cu3O7- delta with the superconductor order parameter is deduced from the critical temperature dependence in the superconducting low temperature phase (Tc approximately 92 K). The excess intensity and the frequency shift of the mode near 580 cm-1 are shown to be proportional to the square of a BCS-like order parameter in agreement with the predictions of Hard Mode Spectroscopy.

Dynamic response of submerged layered composites

The dynamic interaction between elastic and homogeneous two-phase periodically layered bodies and a surrounding acoustic fluid has been studied. The plane-strain elastodynamic behavior of the composite has been modeled on the basis of Floquet's theory for periodic structures. This approach consists of solving the equations of motion for a cell that repeats periodically, and then applying Floquet's theorem to extend the solution to the entire body. The dispersion spectrum exhibits the classical Brillouin structure of stopping and passing bands. Even though Floquet's theory applies essentially to infinite regions, it is nevertheless possible to adapt the scheme for finite boundaries and to formulate interface conditions with an acoustic fluid. Qualitative and quantitative results are presented for harmonic motions of two geometries, namely, a layered half-space with an overlying acoustic fluid and a submerged infinite laminated plate. Special attention is paid to the energy partition between the layered solid and the fluid for the complete range of frequencies. [Work supported by ONR.]

TV VHF/Hyperband Tuner ICs

Two monolithic tuner circuits were developed to convert the desired TV-RF input channel of a VHF/ Hyperband to standard television IF for TV sets and set-top baseband converters. Not more than two switched bands are required for covering the complete frequency range of the 64 channels. Tracking is improved and local oscillator leakage is also reduced. The performance of CATV up/down converters is also improved if these ICs are used in the down-converter section.

Continuous measurement of complex modulus from 10–30 kHz

The paper describes a technique which measures the complex modulus of materials in the range 10–30 kHz. The apparatus measures the input impedance of a sample of the material which is approximately 0.25 in. long and 0.7 in. in diameter. A shaker with an impedance head is used to drive one end of the sample which has a large mass at the other end. A noise drive and analysis by a dual channel spectrum analyzer connected to a desktop computer, gives a continuous frequency spectrum of the real and imaginary parts of the modulus. The method has been used over a frequency range of 10–30 kHz to measure moduli from 107–1010 Pascals with loss factors as low as 0.02 and it is felt that these ranges could be extended. The technique enables a measurement over the complete frequency range to be made in less than 5 min and the results are repeatable.

Hydrogen-Bond Spectroscopy of Water by Neutron Scattering

We obtain a series of incoherent-inelastic-neutron-scattering spectra covering the complete frequency range of vibrations of hydrogen atoms in water over a temperature range of -15 to 80\ifmmode^\circ\else\textdegree\fi{}C and also in ice at 20 K for reference. Comparison of these frequency spectra with those generated by computer molecular dynamics with flexible water molecules indicates that the proton motion in a free water molecule is substantially affected by formation of hydrogen bonds in the condensed phases.

Seismic response of structures by the response spectrum method

The problems of the acceleration profile at the lower elevations of cantilever structures and the response of relatively rigid structures are explored. It is shown that the use of the conventional methods for the above problems provide very approximate results. An alternate combination of the modal responses is proposed that not only resolves the above problems but also provides better estimates of response for the complete range of structure frequencies. The procedure treats the relative and rigid body responses separately and then appropriately combines the two results. For the rigid range of frequencies (fundamental frequencies greater than about 2 Hz), the proposed procedure does not encounter any numerical difficulties because of the additive nature of the component responses; however, the application of the proposed procedure for very flexible structures causes accuracy problems since the rigid body effects tend to be subtractive from the flexural response of about equal magnitude. For this latter class of problems, the conventional approach of modal combination provides adequate results and avoids the above mentioned numerical difficulties.

Ring–disc electrodes. Part 18.—Collection efficiency for high frequency a.c.

By using contour integration to invert the Laplace transforms, an analytical expression for the first order kinetic collection efficiency for a ring–disc electrode can be obtained for values of κ > 3. One can then obtain analytical results for the phase shift and amplitude of the ring current with respect to the disc current when an alternating current is passed through the disc. Hence, theoretical results for the complete frequency range can now be obtained. Theory and experiment are found to be in good agreement.

Partial Discharge Measurements over the Frequency Range 0.1 Hz to 50 Hz

The need for partial discharge (corona) measurements at very low frequencies is explained, and the results of tests on epoxy resin and polyethylene samples are given for the frequency range 0.1 Hz to 50 Hz. As no suitable commercial generator was available, a new type of low-frequency low-noise generator has been developed. The discharge detection system includes a pulse discrimination system for eliminating unwanted pulses from outside the test component. This was particularly useful when measuring discharges in a short length of cross-linked polyethylene cable and in a stator bar sample, in the presence of discharges over the ends. Traditional display methods are not suitable at low-frequency and the paper describes possible alternative recording techniques. One of these is a multi-channel pulse height analyzer, which facilitates the comparison of results over the complete frequency range. Discharge characteristics have also been recorded on a storage oscilloscope. The results obtained show that the inception voltage is virtually constant over the frequency range 0.1 Hz to 50 Hz, and also indicate how the partial discharge characteristics are affected by frequency, void size, temperature and humidity.