A self-tuning filter
Self-tuning filter automatically adjusts its center frequency to track signal frequency. This permits the use of a filter with a bandwidth smaller than the range of input signal frequencies.
Deboo, G. J.↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Thermal tuning of organic dye lasers
Non-mechanical method for tuning liquid laser wavelengths involves electrically varying temperature of laser medium. Technique is used to investigate behavior of laser dyes, and may lead to broad, tunable, light source for spectroscopy measurements of long path absorption.
Billman, K. W.↗
System automatically tunes hydrogen masers
Automatic tuning system permits frequency synchronization between two hydrogen masers. System matches spaceborne clock performance with that of ground-based clock to test red shift theory. This system, used in conjunction with radio astronomy for long-baseline interferometer experiments, serves as a tool for investigation of distant universe phenomena.
Levine, M. W.↗
Tuning arrangement for an electron discharge device or the like Patent
Tuning arrangement for frequency control of magnetron-type electron discharge device
Martucci, V. J.↗
Mean square exceedance characteristics of a single tuned system to amplitude modulated random noise
Mean square exceedance characteristics of single tuned system to amplitude modulated random noise of limited duration
Barnoski, R. L.↗
Prediction of the tuning characteristics of an optical parametric oscillator using parametric fluorescence
Tunable CW optical parametric oscillator optimum operating conditions, using barium, sodium and lithium niobate crystals parametric fluorescence tuning curves for comparison
Laurence, C.↗
Electronic tuning of a dye laser using the acousto-optic filter
Dye laser electronic tuning by inserting calcium-molybdenum oxide acousto-optic filter into cavity
Hansch, T. W.↗
Acousto-optic filter for electronic laser tuning
Electronically tunable lithium niobate filter utilizes acoustic-optic diffraction for tuning laser to desired frequencies. Filter placed inside laser cavity diffracts incident optical signal of one polarization into orthogonal polarization by collinearly propagating acoustic beam to desired wavelength.
Harris, S. E.↗
Electronically tuned optical filters
A detailed account is given of efforts to develop a three layer, polychromic filter that can be tuned electronically. The operation of the filter is based on the cooperative alignment of pleochroic dye molecules by nematic liquid crystals activated by electric fields. This orientation produces changes in the optical density of the material and thus changes in the color of light transmitted through the medium. In addition, attempts to improve materials and devices which employ field induced changes of a cholesteric to a nematic liquid crystal are presented.
Castellano, J. A.↗
Active tuning circuit
Low-cost, inductorless, high Q active-tuning circuit can be made by coupling pair of transistors and their supporting circuitry to take advantage of frequency dependent energy storage effects. Circuit may be manufactured by standard micro-electronic techniques; has very low noise factor; and input-output matching networks are not necessary.
Kleinberg, L. L.↗
Avalanche-diode oscillator circuit with tuning at multiple frequencies
Detailed theoretical analysis of three different modes or types of high efficiency oscillation in a PIN diode are presented. For the TRAPATT mode in a PIN diode, it is shown that a traveling avalanche zone is not necessary to generate a dense trapped plasma. An economical computer program for TRAPATT oscillations in a PIN diode is described. Typical results of diode power, dc-to-RF conversion efficiency, and required circuit impedances are presented for several different current waveforms. A semianalytical solution for a second type of high efficiency mode in a PIN diode is derived assuming a rectangular current waveform. A quasi-static approximation is employed to derive a semianalytical solution for the voltage across a PIN diode in a third mode, where avalanching occurs during a major portion of a half cycle. Calculations for this mode indicate that the power increases proportionally to the magnitude of the drive current with a small decrease in efficiency relative to the ordinary TRAPATT mode. An analytical solution is also given for a PIN diode, where it is assumed that the ionization coefficient is a step function. It is shown that the step-ionization approximation permits one to draw possible patterns of avalanche region in the depletion layer as a function of time. A rule governing admissible patterns is derived and an example solution given for one admissible pattern. Preliminary experimental results on the high-efficiency oscillations are presented and discussed. Two different experimental circuits, which used channel-dropping filters to provide independent harmonic tuning, are described. Simpler circuits used to produce high-efficiency oscillations are discussed. Results of experiments using inexpensive Fairchild FD300 diodes are given.
Parker, D.↗
Dynamic errors in a tuned flexure-mounted strapdown gyro
Motion induced errors in a tuned, flexure-mounted strapdown gyro are investigated. Analytic expressions are developed for errors induced by linear vibrations, angular motion, and detuning. Sensor-level errors (gyro drift rate) and system-level errors (navigation errors) that are stimulated by an actual dynamic motion environment are computed.
Bortz, J. E., Sr.↗
Dye laser tuning with pellicles.
Thin nitrocellulose membranes (pellicles) are shown to exhibit properties which make them suitable for intracavity tuning elements in high-energy pulsed dye lasers. Uncoated pellicles of 2-micron and 8-micron thickness with surface figures of lambda/1 are shown to closely approximate the properties of low-finesse etalons with wide free spectral ranges. Pellicles of 8-micron thickness, coated on both surfaces with 50% reflectivity multilayer dielectrics, are shown to be effective as spectral narrowing elements with peak transmission greater than 80% and resultant laser linewidths of 0.57 nm full width at half-maximum.
Mumola, P. B.↗
An automatic data system for vibration modal tuning and evaluation
A digitally based automatic modal tuning and analysis system developed to provide an operational capability beginning at 0.1 hertz is described. The elements of the system, which provides unique control features, maximum operator visibility, and rapid data reduction and documentation, are briefly described; and the operational flow is discussed to illustrate the full range of capabilities and the flexibility of application. The successful application of the system to a modal survey of the Skylab payload is described. Information about the Skylab test article, coincident-quadrature analysis of modal response data, orthogonality, and damping calculations is included in the appendixes. Recommendations for future application of the system are also made.
Salyer, R. A.↗
Nonlinear analysis of a family of LC tuned inverters
Four widely used self-oscillating dc-to-square-wave parallel inverters which employ an inductor-capacitor tuned network to determine the oscillation frequency are reduced to a common equivalent RLC network, The techniques of singular-point analysis and state-plane interpretations are employed to describe the steady-state and transient behavior of these circuits and to elucidate the three possible modes of operation: quasi-harmonic, relaxation, and discontinuous. Design guidelines are provided through a study of the influence of circuit parameter variations on the characteristics of oscillation and on frequency stability. Several examples are provided to illustrate the usefulness of this analysis when studying such problems as transistor emitter-to-base junction breakdown during oscillations and the design of starting circuits to insure self-excited oscillations in these inverters.
Lee, F. C. Y.↗
Feasibility study of a digital rebalance loop for a dry tuned TDF gyro
A two degrees-of-freedom (TDF) rate integrating gyro in the strapdown mode is a candidate for attitude sensing in a spacecraft navigation system, since it provides an additional axis of information for a relatively small increase in hardware complexity. A type of gyro which has not been fully exploited is of the dry, tuned, TDF design, in which the spring constant of the suspension system is effectively cancelled by the dynamic antispring of a swiveling, rotating, gimbal. The use of this unconventional gyro in a digital rebalance loop was investigated.
Coffman, D. E.↗
Methods of reducing low frequency cabin noise and sonically induced stresses, based on the intrinsic structural tuning concept
Control of low frequency interior noise has been difficult in all commercial and general aviation aircraft, since the existing sound attenuation techniques are less effective at these frequencies. Therefore low frequency cabin noise and sonically induced stresses can be reduced mainly by a proper design of the fuselage structure. For this purpose, a concept based on intrinsic tuning and damping of fuselage structural elements has been under development at Boeing for the past three years. This paper describes the results of some laboratory and field tests that were conducted for evaluation of the concept.
Sengupta, G.↗
Low frequency cabin noise reduction based on the intrinsic structural tuning concept: The theory and the experimental results, phase 2
Low frequency cabin noise and sonically induced stresses in an aircraft fuselage may be reduced by intrinsic tuning of the various structural members such as the skin, stringers, and frames and then applying damping treatments on these members. The concept is also useful in identifying the key structural resonance mechanisms controlling the fuselage response to broadband random excitation and in developing suitable damping treatments for reducing the structural response in various frequency ranges. The mathematical proof of the concept and the results of some laboratory and field tests on a group of skin-stringer panels are described. In the so-called stiffness-controlled region, the noise transmission may actually be controlled by stiffener resonances, depending upon the relationship between the natural frequencies of the skin bay and the stiffeners. Therefore, cabin noise in the stiffness-controlled region may be effectively reduced by applying damping treatments on the stiffeners.
Sengupta, G.↗