Showing papers on "Noise (electronics) published in 1984"

Phase Noise in Signal Sources

Abstract: This book contains a thorough treatment of phase noise, its relationship to thermal noise and associated subjects such as frequency stability. The design of low phase noise signal sources, including oscillators and synthesisers, is explained and in many cases the measured phase noise characteristics are compared with the theoretical predictions. Full theoretical treatments are combined with physical explanations, helpful comments, examples of manufactured equipment and practical tips. Overall system performance degradations due to unwanted phase noise are fully analysed for radar systems and for both analogue and digital communications systems. Specifications for the acceptable phase noise performance of signal sources to be used in such systems are derived after allowing for both technical and economic optimisation. The mature engineer whose mathematics may be somewhat rusty will find that every effort has been made to use the lowest level of mathematical sophistication that is compatible with a full analysis and every line of each mathematical argument has been set out so that the book may be read and understood even in an armchair. Due to a novel approach to the analytical treatment of narrow band noise, the book is simple to understand while simultaneously carrying the analysis further in several areas than any existing publication.

Line narrowing in a single-mode injection laser due to external optical feedback

Abstract: The effect of external optical feedback on the linewidth of a single-mode injection laser is considered theoretically. A set of three rate equations with Langevin noise sources is used to obtain the power spectrum. If the high-frequency structure in the power spectrum is ignored, the line shape is Lorentzian and exhibits broadening or narrowing depending on the external-cavity phase shift. Particular attention is paid to the line narrowing after including the effect of carrrier-induced index changes.

Signal-to-Noise Ratio Advantage of Binaural Hearing Aids and Directional Microphones under Different Levels of Reverberation

Abstract: The signal-to-noise ratio necessary for a constant performance level was determined for normally hearing and hearing-impaired subjects under three levels of reverberation (0.3, 0.6, and 1.2 s) with...

Quantum dynamics of a superconducting tunnel junction

Abstract: Basing our model and method on the microscopic theory we formulate a quantum-mechanical description for the relevant variable in a superconducting tunnel junction, i.e., the phase difference across the junction. The quasiparticle degrees of freedom are responsible for dissipation and noise in the system. Because of the discreteness of the charge-transfer process, the noise is shot noise. The energy gaps in the superconductors lead to further interesting features. We discuss the consequences of these physical effects on macroscopic quantum phenomena.

Composition of 1 f Noise in Metal-Insulator-Metal Tunnel Junctions

Abstract: We have studied the low-frequency conductance fluctuations of very small-area metalinsulator-metal tunnel junctions. We find that the spectral power density at high temperature is typical of $\frac{1}{f}$ noise, but is resolved into a small number of Lorentzian spectra for $T\ensuremath{\lesssim}80$ K. The thermally activated Lorentzians are described by a two-rate kinetics and a broad distribution of activation energies and attempt rates.

Noise in homodyne detection.

Abstract: A simple but rigorous analysis of the important sources of noise in homodyne detection is presented. Output noise and signal-to-noise ratios are compared for direct detection, conventional (one-port) homodyning, and two-port homodyning, in which one monitors both output ports of a 50-50 beam splitter. It is shown that two-port homodyning is insensitive to local-oscillator quadrature-phase noise and hence provides (1) a means of detecting reduced quadrature-phase fluctuations (squeezing) that is perhaps more practical than one-port homodyning and (2) an output signal-to-noise ratio that can be a modest to significant improvement over that of one-port homodyning and direct detection.

Bistable flow driven by coloured gaussian noise: A critical study

Abstract: A one-dimensional bistable flow driven by additive, exponentially correlated Gaussian noise is considered. The small relaxation time Fokker-Planck approximations, widely used in the recent literature, are derived and possible shortcomings of those approximation schemes are discussed. In particular, it is pointed out that higher order non-Fokker-Planck type contributions are generally of the same order as the Fokker-Planck terms. In principle, those contributions cannot be neglected if the global behavior of the probability solutions is to be described accurately. The result for the activation rate (Arrhenius factor), as evaluated from the approximative Fokker-Planck schemes, does not coincide in leading order in the correlation time τ of the noise with a computer simulation of the rate at low noise level. This result indicates that the wings of the stationary probability\(\bar p(x)\) are in leading order in τ not recovered correctly from the approximative Fokker-Planck schemes. Some implications of our study for adiabatic elimination procedures are also discussed.

Phase Noise in Signal Sources: Theory and applications

Abstract: * Chapter 1: Introduction * Chapter 2: Review of modulation theory * Chapter 3: The relationship betweenphase jitter and noise density * Chapter 4: Noise induced frequency modulation * Chapter 5: Noise in oscillators * Chapter 6: Frequency multiplier chains * Chapter 7: The use of phase lock loops * Chapter 8: Frequency synthesisers * Chapter 9: The reciprocal relationships between phase noise and frequency stability * Chapter 10: System phase noise requirements * Appendix 1: Summary of important formulae * Appendix 2: Noise figure review * Appendix 3:The quadrature representation of narrowband noise * Appendix 4: The Q of varactor tuned oscillators * Appendix 5: The phase noise performance of Gunn oscillators

Effect of noise on time-dependent quantum chaos

Abstract: The dynamics of a time-dependent quantum system can be qualitatively different from that of its classical counterpart when the latter is chaotic. It is shown that small noise can strongly alter this situation.

Estimating Fried’s parameter from a time series of an arbitrary resolved object imaged through atmospheric turbulence

Abstract: A method to obtain an estimate of Fried’s seeing parameter r0 from time series of an arbitrarily shaped, resolved structure that exhibits degradation resulting from atmospheric turbulence is presented. The basic idea is to evaluate the ratio of the observed squared modulus of the average Fourier transform and the observed average power spectrum. The theory of the method is developed, and the influence of noise on the ratio is discussed. The method has been applied to five consecutive time series of observations of solar granulation under different seeing conditions. The power spectra, which are reconstructed with appropriate theoretical modulation transfer functions, converge.

Detuned loading in coupled cavity semiconductor lasers—effect on quantum noise and dynamics

Abstract: We derive the modulation and noise properties of a semiconductor laser consisting of an active cavity loaded by a passive cavity. The results indicate that under certain conditions the direct modulation bandwidth can be doubled with simultaneous phase noise reduction as compared to a conventional laser.

Technique for elimination of polarisation fading in fibre interferometers

Abstract: A technique is described in which polarisation fading of the output of an interferometer is eliminated. The optical output of the interferometer is projected onto three (or more) polarisation states, detected and combined. The maximum variation in signal and in signal/noise ratio is 6 dB.

Noise in Receiving Systems

Abstract: A systematic and unified treatment of thermal noise from an engineering viewpoint. This reference presents the methods used for characterizing and measuring thermal noise in RF communication systems and components. Defines power gain and its applicability to noise problems, shows how to calculate the final signal-to-noise ratio in RF systems using the known gains and noise temperatures of individual system building blocks, and discusses the dependence of dynamic range on the noise factor and noise temperature of a given transducer.

Adaptive smoothing of spectroscopic data by a linear mean-square estimation

Abstract: An adaptive smoothing method based on a least mean-square estimation is developed for noise filtering of spectroscopic data. The algorithm of this method is nonrecursive and shift-varying with the local statistics of data. The mean and the variance of the observed spectrum at an individual sampled point are calculated point by point from its local mean and variance. By this method, in the resultant spectrum, the signal-to-noise ratio is maximized at any local section of the entire spectrum. Experimental results for the absorption spectrum of ammonia gas demonstrate that this method distorts less amount of signal components than the conventional smoothing method based on the polynomial curve-fitting and suppresses noise components satisfactorily. The computation time of this algorithm is rather shorter than that of the convolution algorithm with seven weighting coefficients. The a priori information for the estimation of the signal by this method are: the variance of noise, which can be attainable in the experiment; and the window function which gives the local statistics. The investigation of various types of window functions shows that the selection of the window function does not directly affect the performance of adaptive smoothing.

Stochastic processes driven by dichotomous Markov noise: Some exact dynamical results

Abstract: Stochastic processes defined by a general Langevin equation of motion where the noise is the non‐Gaussian dichotomous Markov noise are studied. A non‐Fokker–Planck master differential equation is deduced for the probability density of these processes. Two different models are exactly solved. In the second one, a nonequilibrium bimodal distribution induced by the noise is observed for a critical value of its correlation time. Critical slowing down does not appear in this point but in another one.

Monolithic Silicon Bolometers

Abstract: A new type of bolometer detector for the millimeter and submillimeter spectral range is described. The bolometer is constructed of silicon using integrated circuit fabrication techniques. Ion implantation is used to give controlled resistance vs temperature properties as well as extremely low 1/f noise contacts. The devices have been tested between 4.2 and 0.3 K. The best electrical NEP measured is 4 x 10 to the -16th W/Hz to the 1/2 at 0.35 K between 1- and 10-Hz modulation frequency. This device had a detecting area of 0.25 sq cm and a time constant of 20 msec at a bath temperature of 0.35 K.

Carrier-induced phase noise in angle-modulated optical-fiber systems

Abstract: Phase noise in angle-modulated optical-fiber communication systems arising from optical power fluctuations is analyzed. The nonlinear refractive index of silica is the physical mechanism which converts power fluctuations into phase fluctuations. The effects of self-phase modulation (an optical wave acting on itself) and cross-phase modulation in wavelength-division multiplexed (WDM) systems (one optical wave modulating a channel at a different wavelength) have been calculated. The phase noise generated in single-channel systems is negligible for laser fluctuations less than 1-mW rms. In WDM systems containing as few as four channels the phase noise exceeds tolerable levels (0.15 rad) for power fluctuation of 1 mW in each channel.

Experimental optical fan beam tomography.

Abstract: Optical tomography is used to map the iodine vapor density in a plane. Two-dimensional images are obtained with 1-cm spatial resolution using a fan beam geometry with a 28-cm radius fan source circle. The images are reconstructed using the convolution backprojection algorithm with data collected in 0.1 sec from 90 detectors on a full circle using 90–360 fan source positions. Experimental results quantitatively confirm a theoretical analysis of the noise in the reconstructed image, including the effects of correlated noise, position within the image, and spatial resolution. The noise amplitude–absorption length product for a 2-cm pixel size is 6 × 10−4 which is equivalent to an iodine concentration of 6 ppm.

Continuous Thermal Measurement of Cardiac Output

Abstract: A thermal-dilution technique for the continuous measurement of cardiac output has been developed. It employs pulmonary-artery sensing of low-level periodic thermal signals generated in the right ventricle of the heart. A resistive element in a modified Swan Ganz®catheter is energized with a periodic electrical waveform. The resulting thermal signal is diluted by blood flow and attenuated by mixing within the heart. Sensed by a thermistor in the pulmonary artery, the thermal signal is processed by a microprocessor-based instrument using a suitable mathematical model. With multiple signal frequencies, separate estimates of the flow-dependent and mixing-dependent attenuation components become possible, allowing continuous monitoring of cardiac output. This technique works well in anesthetized, mechanically ventilated animals, even with average power levels as low as 4 W and corresponding temperature increases of a few hundredths of a degree centigrade. Based on measurements of pulmonary artery thermal noise spectra in humans, we infer that similar performance levels should be attainable with mechanically ventilated human subjects. However, noise spectra from spontaneously breathing critically ill patients suggest that signal-to-noise ratios would be less than satisfactory in that group unless increased signal power is allowed or improved algorithms are developed.

Optimum MSK-type receivers for CPM on Gaussian and Rayleigh fading channels

Abstract: Power efficient schemes with excellent power spectra are contained among the continuous phase modulation (CPM) schemes. This is a constant envelope digital modulation technique, which in general requires a maximum-likelihood sequence detector (Viterbi detector) for efficient detection. This optimum receiver is sometimes complex. In this paper a parallel MSK-type receiver is studied. It is useful for binary schemes with modulation index h = 1/2. We consider coherent detection of signals transmitted over an additive white Gaussian noise channel and also over a Rayleigh fading channel. The MSK-type receiver can be implemented with only two filters and simple decision logic. Error probability formulas are given both for the nonfading and the fading channel. A simple algorithm giving the optimum filter for the Gaussian channel for high signal/noise ratios is presented. The optimum filter for low signal/noise ratios is also derived. For intermediate signal/noise ratios numerical optimisations are presented, both for the Gaussian and the Rayleigh fading channels. We have also considered diversity schems with ideal two-branch maximal ratio combining and selection combining. The optimum receiver filters are given for some selected schemes. It is shown that also, for the more complex CPM schemes, the loss compared to the optimum receiver is moderate.

Spectral induced polarization parameters as determined through time‐domain measurements

Abstract: A method for the extraction of Cole-Cole spectral parameters from time-domain induced polarization data is demonstrated. The instrumentation required to effect the measurement and analysis is described. The Cole-Cole impedance model is shown to work equally well in the time domain as in the frequency domain. Field trials show the time-domain method to generate spectral parameters consistent with those generated by frequency-domain surveys. This is shown to be possible without significant alteration to field procedures. Cole-Cole time constants of up to 100 s are shown to be resolvable given a transmitted current of a 2 s pulse-time. The process proves to have added usefulness as the Cole-Cole forward solution proves an excellent basis for quantifying noise in the measured decay.

Semiconductor position-sensitive detectors

Abstract: Basic concepts for position sensing in particle and photon semiconductor detectors are summarized. Signal and noise criteria are discussed, particularly in view of the trends toward monolithic integration of charge sensing and position readout circuits with the detector.

On the Probability Density of Signal-to-Noise Ratio in an Improved Adaptive Detector. Part 1

Abstract: : Document describes an approximate probability distribution for the SNR (signal-to-noise ratio) of an improved adaptive detector in near rank-1 gaussian noise where the filter weights are computed using the principal eigenvectors of the estimated noise covariance matrix. The noise consists of two components, a strong rank-1-covariance interference component plus white noise. Computer simulation is used to verify the approximating SNR distribution and show that it is accurate even for small sample size and low interference-to- noise ratios.

Identification of nonminimum phase linear stochastic systems

Abstract: We consider the identification of time-invariant, nonminimum phase, stochastic systems driven by non-Gaussian white noise, given only the noisy observations of the system output A two-step procedure is proposed In the first step a spectrally equivalent minimum phase (SEMP) system is estimated using a standard technique that exploits only the second order statistics of the measurements In the second step partial, 4th order cumulants of the measurements are exploited to resolve the location of the system zeros Knowledge of the probability distribution of the driving noise is not required Strong consistency of the proposed estimator is proved under certain mild sufficient conditions Simulation results are also presented in support of the theory

Simulation and optimization of a dc SQUID with finite capacitance

Abstract: This paper deals with the calculations of the noise and the optimization of the energy resolution of a dc SQUID with finite junction capacitance. Up to now noise calculations of dc SQUIDs were performed using a model without parasitic capacitances across the Josephson junctions. As the capacitances limit the performance of the SQUID, for a good optimization one must take them into account. The model consists of two coupled nonlinear second-order differential equations. The equations are very suitable for simulation with an analog circuit. We implemented the model on a hybrid computer. The noise spectrum from the model is calculated with a fast Fourier transform. A calculation of the energy resolution for one set of parameters takes about 6 min of computer time. Detailed results of the optimization are given for products of inductance and temperature ofLT=1.2 and 5 nH K. Within a range of β and β c between 1 and 2, which is optimum, the energy resolution is nearly independent of these variables. In this region the energy resolution is near the value calculated without parasitic capacitances. Results of the optimized energy resolution are given as a function ofLT between 1.2 and 10 mH K.

Characterization of GaAs FET's in Terms of Noise, Gain, and Scattering Parameters through a Noise Parameter Test Set

Abstract: A method for the complete characterization of GaAs FET's in terms of noise parameters (F/sub o/,Gamma/sub on/, R/sub n/), gain parameters (G/sub ao/, Gamma /sub og/, R/sub g/), and of those scattering parameters ( S/sub11/, S/sub22/|,S/sub12/| S/sub21|, /spl angle/S/sub 12/S/sub 21/ ) that are needed for low-noise microwave amplifier design is presented. The instrumentation employed, i.e., a noise-figure measuring system equipped with a vectorial reflectometer, as well as the time consumption, are the same required for the determination of noise parameters only through conventional methods. The measuring setup and the experimental procedure are described in detail. Considerations about the computer-aided data processing technique are also provided. As an experimental result, the characterization of a sample device versus frequency (4-12 GHz) and drain current is reported. A comparison between the scattering parameters provided by the method and those measured by means of a network analyzer is also included.

Asymptotic analysis of P.D.E.s with wide–band noise disturbances, and expansion of the moments

Abstract: We present an asymptotic analysis -in the “ white-noise limit”- of a linear parabolic partial differential equation, whose coefficients are perturbed by a wide-band noise. After having studied some ergodic properties of a class of diffusion processes, we prove the convergence in law towards the solution of an Ito stochastic P.D.E. We then establish an expansion in powers of Δ ( 1/Δ being a measure of the bandwith of the driving noise) of the first moment of the solution

Low Noise High Electron Mobility Transistors

Abstract: Sub-half-micron gate length High Electron Mobility Transistors (HEMT) were fabricated by direct-write electron beam lithography for low noise EHF amplifiers. Modulation-doped epitaxial structures were grown by molecular beam epitaxy having 8,000 cm/sup 2// V-sec room temperature and 77,600 cm /sup2// V-sec liquid nitrogen Hall mobility for 10/sup12/ electrons/cm/sup 2/ . Gate lengths as narrow as 0.28 micron were defined in a recess etched through the n/sup +/ GaAs contact layer. The dc transconductance of 0.4 micron gate length depletion mode devices exceeded 260 mS/mm. Preliminary measurement of noise figure and associated gain made at room temperature yielded 2.7 dB noise figure and 5.9 dB associated gain at 34 GHz for devices having 0.37 micron gate length. Enhancement mode devices were also fabricated having 240 mS/mm dc transconductance. These devices yielded 1.5 dB noise figure and 10.5 dB associated gain at 18 GHz for 0.35 micron gate length. These results are comparable to the best quarter-micron gate length GaAs MESFET noise figures yet reported.

Derivation of the Spectral Width of a 0.8μm AlGaAs Laser Considering 1/f Noise

Abstract: The spectral profile of a CSP-type 08 µm AlGaAs laser and its spectral width (FWHM) were estimated from experimental results on the lasers FM noise at room temperature The power-independent spectral width was also derived from the recently-reported power-independent 1/f noise The result was 20 MHz, which agrees well with previous experimental results The power-dependent width Δν was also derived as 20 MHz<Δν88 MHz for 0<(I/Ith-1)-17, where I and Ith represent the injection current and its threshold value, respectively