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Results for “PHASE LOCK”

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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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Pulsed phase locked loop strain monitor

A pulse phase locked loop system according to the present invention is described. A frequency generator such as a voltage controlled oscillator (VCO) generates an output signal and a reference signal having a frequency equal to that of the output signal. A transmitting gate gates the output frequency signal and this gated signal drives a transmitting transducer which transmits an acoustic wave through a material. A sample/hold samples a signal indicative of the transmitted wave which is received by a receiving transducer. Divide-by-n counters control these gating and sampling functions in response to the reference signal of the frequency generator. Specifically, the output signal is gated at a rate of F/h, wherein F is the frequency of the output signal and h is an integer; and the received signal is sampled at a delay of F/n wherein n is an integer.

Froggatt, Mark E.↗
NASA NTRS1973

All-digital phase-lock loops for noise-free signals

Bit-synchronizers utilize all-digital phase-lock loops that are referenced to a high frequency digital clock. Phase-lock loop of first design acquires frequency within nominal range and tracks phase; second design is modified for random binary data by addition of simple transition detector; and third design acquires frequency over wide dynamic range.

Anderson, T. O.↗
NASA NTRS1982

A coupled phase-locked loops system for carrier tracking improvement

A system that couples several phase-locked loops to improve carrier tracking performance is considered. It coherently combines the received carrier signals at geographically separated ground antennas to increase the total effective aperture. The received carrier's phases are automatically aligned to enhance the received carrier signal-to-noise ratio. The system's tracking performance is assessed in terms of rms phase jitter. It is shown that the phase-locked loop in the first receiver, where the carrier arraying is performed, tracks the received carrier phase using the received carrier power from all receivers.

Divsalar, D.↗
NASA NTRS1986

Phase-locked laser array having a non-uniform spacing between lasing regions

A phase-locked semiconductor array wherein the lasing regions of the array are spaced an effective distance apart such that the modes of oscillation of the different lasing regions are phase-locked to one another. The center-to-center spacing between the lasing regions is non-uniform. This variation in spacing perturbs the preferred 180.degree. phase difference between adjacent lasing regions thereby providing an increased yield of arrays exhibiting a single-lobed, far-field radiation pattern.

Ackley, Donald E.↗
NASA NTRS1966

Theory and Practical Design of Phase-locked Receivers, Volume I

This is Volume I of a two-volume work on the theory, of phase-locked receivers, with pertinent reference material on practical receiver design. Volume I is primarily devoted to the performance of carrier-tracking loops, including a rigorous treatment of narrow-band systems having IF limiters. The bulk of the work is based on a theoretical linear model, but a nonlinear method is also presented to predict behavior near the threshold. The emphasis throughout the work is toward completeness, simplicity, and internal consistency of the material assembled. Part I of this Volume is an exposition of the theory, the resulting equations, and the design philosophy that have enabled the phase-lock concept to evolve into the basic principle underlying the most sensitive receivers il, the world today. Part II is a condensed version of Part I, intended as a quick reference to formulas, definitions, and salient design considerations.

RECEIVER↗
NASA NTRS1984

Rate equations analysis of phase-locked semiconductor laser arrays under steady state conditions

Rate equations analysis of phase-locked semiconductor laser arrays has been carried out. It was found that for given (laser) current densities, the photon density distribution in the array elements is that particular one which maximizes the total photon density. The results of this analysis were then combined with the waveguide properties of the laser array waveguide, yielding a basic model of phase-locked diode laser arrays. This model explains the effects of the variation of the current combination through the array elements on its mode structure that were observed recently.

Katz, J.↗
NASA NTRS1974

On first cycle slip time of phase-locked loops in cascade

Precise measurement and spacecraft tracking are obtained by using phase-locked loops in cascade in two-way communications links. Statistics on cycle slip time are of vital importance in system planning and design. This paper presents: (1) results of a computer simulation study of the mean time to first cycle slip of cascade phase-locked loops preceded by bandpass limiters, and (2) the determination of probability distributions of cycle slip. Numerical results are obtained for a typical coherent communication system.

Yuen, J. H.↗
NASA NTRS1974

On the performance of digital phase locked loops in the threshold region

Extended Kalman filter algorithms are used to obtain a digital phase lock loop structure for demodulation of angle modulated signals. It is shown that the error variance equations obtained directly from this structure enable one to predict threshold if one retains higher frequency terms. This is in sharp contrast to the similar analysis of the analog phase lock loop, where the higher frequency terms are filtered out because of the low pass filter in the loop. Results are compared to actual simulation results and threshold region results obtained previously.

Hurst, G. T.↗
NASA NTRS1961

A Threshold Theory for Phase-Locked Loops

A model of a phase-locked loop has been developed which is valid for all signal-to-noise ratios. The model is in the form of a nonlinear feedback system with randomly time-varying parameters. The analysis considers two operating regions. In low signal-to-noise ratio regions, the important consideration is stability. We want to study the asymptotic stability in the mean of a nonlinear system. It follows directly that a necessary condition for asymptotic stability of any nonlinear system is that a linearized model about some equilibrium point be asymptotically stable. By considering all possible equilibrium points, we can find an upper bound on the value of noise density which makes the system unstable. This upper bound represents a threshold value for system operation. In high signal-to-noise ratio regions, our results provide an exact statistical. description of system behavior. Therefore, knowledge of the spectrum of the signal and noise may be used to optimize the system configuration.

Van Trees, H. L.↗