Showing papers on "Phase noise published in 1983"

Noise in homodyne and heterodyne detection.

Abstract: Quantum-mechanical calculations of the mean-square fluctuation spectra in optical homodyning and heterodyning are made for arbitrary input and local-oscillator quantum states. In addition to the unavoidable quantum fluctuations, it is shown that excess noise from the local oscillator always affects homodyning and, when it is broadband, also heterodyning. Both the quantum and the excess noise of the local oscillator can be eliminated by coherent subtraction of the two outputs of a 50-50 beam splitter. This result also demonstrates the fact that the basic quantum noise in homodyning and heterodyning is signal quantum fluctuation, not local-oscillator shot noise.

Theory of the phase noise and power spectrum of a single mode injection laser

Abstract: Spontaneous emission alters the phase and amplitude of the laser field. The amplitude changes induce relaxation oscillations, which cause additional phase changes while restoring the field amplitude to the steady state value. It was previously shown that the additional phase changes greatly enhance the linewidth. We show here that the additional phase changes also give rise to line shape structure in the form of additional peaks separated from the main peak by multiples of the relaxation oscillation frequency. The calculated mean square phase change and power spectrum are in good agreement with published observations.

Local-oscillator excess-noise suppression for homodyne and heterodyne detection.

Abstract: Semiclassical calculations of the signal-to-noise density ratio for a homodyne/heterodyne receiver utilizing two detectors are made. These calculations show that excess intensity noise in the local oscillator can be canceled and need not degrade the performance of the receiver. An experimental demonstration of excess-noise cancellation is reported.

Noise in relaxation oscillators

Abstract: The timing jitter in relaxation oscillators is analyzed. This jitter is described by a single normalized equation whose solution allows prediction of noise in practical oscillators. The theory is confirmed by measurements on practical oscillators and is used to develop a prototype low-noise oscillator with a measured jitter of 1.5 ppm RMS.

Phase noise and spectral line shape in semiconductor lasers

Abstract: Experimental results concerning the study of phase noise in single-mode semiconductor lasers are reported, which show a strict connection between phase and intensity noise. In particular, phase-noise spectrum is found to present a sharp peak at the same peak frequency of intensity-noise spectrum, a fact which is proven to be responsible for the appearance of satellite peaks in the emission line shape. Direct measurements of the line shape, performed by means of a Fabry-Perot interferometer, are in agreement with the line shape evaluated by using phase-noise spectrum measurements.

Measurement of noise in magnetic media

Abstract: A model for medium noise in thin film and particulate discs is presented. The model is based on both time jitter and spectrum analyzer measurements. Thin metallic film discs have different noise mechanisms from either particulate or sputtered γ-Fe 2 O 3 discs. A signal-to-noise ratio equal to the signal /rms noise measured at the predetection filter output gives accurate prediction of peak jitter only if the noise is measured at the transitlon density giving maximum noise.

Performances of the Delay-Line Multiplier Circuit for Clock and Carrier Synchronization in Digital Satellite Communications

Abstract: This paper is concerned with clock and carrier synchronization in digital satellite transmissions, using the delay-line multiplier circuit. For clock recovery from baseband signal, with random data, a closed form formula is derived which gives the spectrum after multiplication, for any arbitrary pulse shape. This spectrum contains spectral lines at the clock frequency and its harmonics, and a continuous part which is the pattern noise. This pattern noise may be decomposed in noise in phase with the recovered clock, and noise in quadrature whose power spectral density is always zero at zero frequency. The effect of Gaussian noise on the channel is taken into account to calculate signal-to-noise ratio at the clock frequency as a function of the classical parameter E/N_{o} . With a modulated input carrier, the signal at the output of the delay-line multiplier may be separated into two parts: a low frequency signal that contains clock information and a bandpass spectrum signal around twice the carrier frequency that contains carrier information, when possible. Spectrum and signal-to-noise ratio in carrier recovery are studied for BPSK and offset quadrature modulation.

Phase noise in semiconductor lasers: A theoretical approach

Abstract: Noise phenomena in semiconductor lasers have been extensively studied from an experimental point of view because of their importance in designing optical communication systems. Recently, a semiclassical theory of laser noise has been presented [1]. In this paper, following a different and simpler approach, we obtain analytical expressions for the intensity and phase noise power spectra which agree with experimental results.

Effect of excitation on coaxial jet noise

Abstract: Coaxial model jets, including those of high bypass ratio engine exhaust hot gas conditions, were excited internally by tone and broadband noise. Acoustic excitation in the secondary (outer) duct was found to be most effective in jet noise amplification due to the sensitivity of the outer shear layer. Jet noise amplification at the subharmonic of the excitation frequency occurred in a number of cases. An acoustic elliptic mirror was used to observe the noise sources along the jet. It revealed local noise source characteristics in different shear layer regions and noise source location changes from unexcited to excited jets.

Demodulation scheme fibre interferometric sensors employing laser frequency switching

Abstract: A demodulation technique suitable for use with fibre interferometric sensors is described The scheme employs a frequency switched diode laser and an unbalanced Mach-Zehnder interferometer Minimum phase sensitivity ≈ 2× 10-5 rad is obtainable, and can be shown to be limited by the laser phase noise

Disciplined oscillator system with frequency control and accumulated time control

Abstract: A disciplined oscillator system having a standard oscillator which is automatically corrected for both frequency errors and time error accumulation to a constant frequency signal which is derived from the WWVB carrier frequency and the WWVB TIME CODE to maintain overall frequency accuracy within one part in 10 9 notwithstanding oscillator aging and in spite of jitter and distortion due to propagation delays and noise which may cause loss of, or time jitter in, the WWVB signals. Frequency errors are detected through the use of a counter (24) having a measurement accuracy greater than one part in 10 10 . An error detector (26) derives correction signals by averaging a plurality of frequency variances obtained in successive measurement cycles. Timing errors are corrected by dividers (34, 40) controlled by a timing discriminator (36) which responds to timing variance between signals from the standard oscillator and from the WWVB reference which are phase locked to those TIME CODE signals which are substantially free of noise and jitter. The timing correction is inhibited after the standard oscillator is corrected. Frequency correction is applied continuously.

Excess Noise in Quartz Crystal Resonators

Abstract: : Frequency and phase noise in quartz crystal resonators are studied as a function of the driving power. At low power, where the crystal behaves linearly, 1/f fluctuations of the resonance frequency are observed. At medium power the nonlinearities of the crystal significantly increase the phase fluctuations at low Fourier frequencies. At high power, thermal instabilities and chaotic behavior occur characterized by the generation of high level white noise.

V-band Low-noise Integrated Circuit Receiver

Abstract: A compact low-noise V-band integrated circuit receiver has been developed for space communication systems, The receiver accepts an RF input of 60-63 GHz and generates an IF output of 3-6 GHz. A Gunn oscillator at 57 GHz is phaselocked to a low-frequency reference source to achieve high stability and low FM noise. The receiver has an overall single sideband noise figure of less than 10.5 dB and an RF to IF gain of 40 dB over a 3-GHz RF bandwidth. All RF circuits are fabricated in integrated circuits on a Duroid substrate.

A theory of noise in GaAs FET microwave oscillators and its experimental verification

Abstract: A theory has been developed which provides an entirely analytical approach to the calculation of AM and FM noise in free-running GaAs FET microwave oscillators. The theory is based on the model that low-frequency device noise is mixed with the carrier signal via the nonlinearity of the FET and upconverted to microwave frequencies. Because of the analytical nature of the theory, all the important device and circuit parameters on which the noise generation depends are explicitly given. Two GaAs FET oscillators have been fabricated and used to investigate the FM noise. The theory predicts well both the spectral dependence and the absolute magnitude of the FM noise in both oscillators. The noise performance of the oscillators differs by 19 dB. The theory indicates that no single factor is responsible for this, and moreover that attention should be given to the optimization of many device and circuit features in the design of a low noise FET oscillator.

Near-Carrier Noise in FET Oscillators

Abstract: An exhaustive study is presented of the relation of near-carrier FM noise of FET oscillators to baseband noise, gate technology, surface passivation, channel formation, and traps. FM noise performance of an FET oscillator will be presented which is over 20 dB better than heretofore reported.

Individual Characterization of an Oscillator by Means of Cross-Correlation or Cross-Variance Method

Abstract: Two new methods using the concepts of cross correlation and cross variance are proposed for comparing three oscillators. They allow one to characterize individually each oscillator and they reduce the influence of the measurement system noise if the noise sources on each channel are independent. Therefore, better resolution can be obtained in the spectral purity and frequency stability measurements.

1/f Noise in GaAs MESFETs

Abstract: The origin of low frequency noise in GaAs MESFETs was experimentally investigated. Traps in a depletion region of the MESFET were found to be primarily responsible for the low frequency noise. The observed dependence of the low frequency noise on the gate length supports this conclusion.

RF Local oscillator with low phase noise

Abstract: An RF local oscillator, particularly useful in connection with phase shift key modulation in satellite communications systems, provides a low phase noise signal by use of a phase locked loop having a phase stable oscillator to provide frequency conversion of a frequency synthesizer output signal.

Theory of FM noise of single-mode injection lasers

Abstract: The FM noise of single-mode injection lasers is studied in terms of the root-mean-square frequency deviation Δfrms against the angular modulation frequency ωm off-carrier. Spontaneous emission causes phase fluctuations of the laser wave. Enhanced FM noise may occur due to radiation-induced fluctuations of the carrier density. The influence of the coupling between laser field and active region on this modulation noise is investigated.

Laser phase noise effects in fiber-optic signal processors with recirculating loops.

Abstract: The power spectrum laser of the optical intensity at the output of a single-mode-fiber recirculating delay line driven by a multimode semiconductor laser is shown to exhibit a spectral structure with notches at zero frequency as well as at other multiples of 1/(loop delay). A theoretical model based on laser phase noise is suggested to explain the experimental data.

Spectral Dispersion of Modulated Signals Due to Oscillator Phase Instability: White and Random Walk Phase Model

Abstract: This paper considers the modeling of oscillator phase instability and the resulting spectral dispersion. A phase covariance matrix method is developed for determining the autocorrelation function and the power spectral density of the oscillator sinusoidal RF signal when corrupted by a superposition of a white phase random process and a random walk phase random process. By limiting the discussion to phase covariance matrices, it is shown that the direct use of a certain class of nonstationary phase random processes leads to stationary RF signal autocorrelation functions and associated power spectral densities. This is so despite the nonstationary phase driving force. The procedures provided here are also applied towards the determination of the average autocorrelation function and the average spectrum when the cisoidal oscillator signal undergoes modulation. Modulating waveforms used as examples include the CW, the infinite pulse train, and the finite pulse train.

A Structure Function Representation Theorem with Applications to Frequency Stability Estimation

Abstract: Random processes with stationary nth differences serve as models for oscillator phase noise. The theorem proved here allows one to obtain the structure function (covariances of the nth differences) of such a process in terms of the differences of a single function of one time variable. In turn, this function can easily be obtained from the spectral density of the process. The theorem is used for computing the variance of two estimators of frequency stability.

Influence of semiconductor-laser phase noise on coherent optical communication systems.

Abstract: Several authors have recently investigated phase noise in semiconductor lasers and the related problems that arise when such lasers are employed in coherent optical communication systems. We report accurate measurements of high-frequency phase noise in single-mode injection lasers that show the presence of a peak in the phase-noise spectrum at the same frequency as that of the amplitude-noise peak. This peculiar phenomenon must be taken into account when one studies the characteristics of coherent optical communication systems.

Noise Generation in a Forward DC-to-DC Converter

Abstract: The mechanism of switching-noise generation is examined for the most popular power converter, i.e. the forward dc-to-dc converter. Particularly the output noise voltage generated during the transistor's turnoff is analyzed by dividing the turnoff time into four sequent states and deriving the corresponding high-frequency equivalent circuits. In these circuits the parameter of transistor's fall time is also introduced. As the result, not only the influence of the inductive or capacitive parasitic elements on the noise generation but also the relationship between the transistor's switching speed and the noise voltage are quantitatively clarified.

Low Noise Design of Dielectric Resonator FET Oscillators

Abstract: Experimental comparison has been made between different ORO circuits with FET's of various origins and size around 11 GHz. Details of the most pertinent conclusions are given together with theoretical explanations of the observed results. A ?105 dBc/Hz figure has been achieved at 10 KHz off carrier.

Influence of an external cavity on semiconductor laser phase noise

Abstract: Investigation of phase noise in semiconductor lasers allows one to understand the physical processes that influence both the width and the shape of the emission line. Furthermore, the limitations associated with phase noise have to be taken into account when semiconductor lasers are employed in coherent optical communication systems. In this letter we report phase‐noise measurements on single‐mode semiconductor lasers in the presence of optical feedback. We are able to observe, besides the expected linewidth reduction, a peculiar behavior in the high‐frequency region not yet reported in the literature, strongly dependent on the external cavity length.

Arrival time determination using iterative signal reconstruction from the phase of the cross spectrum

Abstract: A situation encountered in such applications as seismics, ocean acoustics, radar, sonar and others, is that of an unknown wavelet propagating nondispersively in a reverberatory or multipath environment. Two receivers placed in such an environment will each record the arrival of this wavelet numerous times and each time with a different attenuation factor. In this paper, we demonstrate that if 1) there is no noise, 2) the interreceiver delays are distinct, and 3) the arrival sequence at each receiver has no zero phase convolutional component, then the arrival times and attenuation factors at each receiver can be determined as well as the wavelet itself. We show this via the construction of a finite length sequence whose phase equals that of the cross spectrum of the two received signals. This reconstructed signal, under the conditions above, can then be "inverted" to recover the desired arrival time and attenuation information at each receiver. An example using synthetically generated data is provided.

Demodulation circuit for a digitized chrominance signal having a sampling signal oscillator coupled to a chrominance signal oscillator

Abstract: In a digital demodulation circuit for a chrominance signal of a color television signal having a first digital oscillator (35) for producing reference signals and a phase control loop (29, 17, 19, 49, 43) therefor, there is added in the phase control loop a signal combination (at 56) which is obtained from a phase control loop (67, 63, 59) of a second digital oscillator (77). This second digital oscillator derives the sampling frequency for sampling the chrominance signal from a signal source (83) of a constant frequency and couples this sampling frequency to the horizontal deflection frequency. By the addition in the phase control loop of the first oscillator, variations in the horizontal deflection frequency cannot lead to the undesired phenomenon of the first digital oscillator being pulled to a side-band frequency of the color subcarrier wave.