Phased Noise Research Articles

50 GHz active‐LC CMOS oscillator: Theoretical study and experimental proofs

AbstractA 50 GHz cross‐coupled differential‐pair oscillator with a high‐Q active inductor in the LC tank has been designed and fabricated in 65 nm bulk complementary metal‐oxide semiconductor (CMOS) technology. The principle of operation is explained and a complete theoretical study is carried out. The analytical expressions for the open loop transfer function, oscillation frequency, start‐up condition, tank impedance, and phase noise are derived. The results of the analytical study are compared with those obtained by SpectreRF simulations in the Cadence design environment. Measurement results of the stand‐alone mm‐wave active inductor show an equivalent inductance of 133 pH with a quality factor exceeding 400 at 50 GHz, demonstrating experimentally the implementation of high‐Q active inductors operating at the millimeter waves in CMOS technology. The measurement results of the oscillator show a phase noise of −85 dBc/Hz at 1 MHz frequency offset from the carrier when the active inductor is switched off and −91 dBc/Hz when it is switched on, leading to a phased noise reduction of 6 dB.

Phase Noise Compensation for OFDM Systems

We describe a low complexity method for time domain compensation of phase noise in OFDM systems. We extend existing methods in several respects. First we suggest using the Karhunen-Lo\'{e}ve representation of the phase noise process to estimate the phase noise. We then derive an improved datadirected choice of basis elements for LS phase noise estimation and present its total least square counterpart problem. The proposed method helps overcome one of the major weaknesses of OFDM systems. We also generalize the time domain phase noise compensation to the multiuser MIMO context. Finally we present simulation results using both simulated and measured phased noise. We quantify the tracking performance in the presence of residual carrier offset.

State-of-the-Art Analysis of High-Frequency (Gamma Range) Electroencephalography in Humans

Gamma oscillations (>30 Hz) in the brain are involved in attention, perception and memory. They are altered in various pathological states, as well as by neuropharmaceuticals, so that they are of interest in drug and clinical investigations. However, when the human electroencephalogram is recorded on the scalp, this neural high-frequency signal is buried under a range of other electrical signals such that, without careful handling, recordings of the high-frequency electroencephalogram cannot be considered reliable. The artefacts of concern originate from: power line noise, saccade-associated contraction of the extra-ocular muscles, activity of muscles in the scalp, face and neck, screen refresh artefacts and activity of the muscles associated with blinking. Recent progress in dealing with these artefacts is described, including either noise cancellation or phased noise template subtraction for power line noise, regression or independent component analysis for correcting extra-ocular muscle activity and mathematical modelling for reducing scalp, face and neck muscle activity. If the artefacts are properly addressed, the neural gamma signal can be uncovered.

Large-Scale Silicon Photonic Circuits for Optical Phased Arrays

We review recent advances in integrated large-scale optical phased arrays. The design and fabrication of large-scale optical phased arrays using silicon photonic circuits are discussed from device designs including the directional couplers, thermo-optic phase shifters, and optical nanoantennas, to system studies including phased array synthesis and noise analysis. By taking advantage of the well-developed silicon complementary metal-oxide-semiconductor (CMOS) fabrication technology, several large-scale integrated silicon photonic phased arrays are demonstrated, including two passive-phased arrays (64 × 64 and 32 × 32) with the ability to generate complex holographic images, an 8 × 8 active phased array for dynamic optical beamforming, and an 8 × 8 active antenna array with amplitude apodization. These optical phased array demonstrations, with up to 12 000 integrated optical elements, represent the largest and densest silicon photonic circuits demonstrated to date.

Jet-Surface Interaction Test: Far-Field Noise Results

Many configurations proposed for the next generation of aircraft rely on the wing or other aircraft surfaces to shield the engine noise from the observers on the ground. However, the ability to predict the shielding effect and any new noise sources that arise from the high-speed jet flow interacting with a hard surface is currently limited. Furthermore, quality experimental data from jets with surfaces nearby suitable for developing and validating noise prediction methods are usually tied to a particular vehicle concept and, therefore, very complicated. The Jet-Surface Interaction Tests are intended to supply a high quality set of data covering a wide range of surface geometries and positions and jet flows to researchers developing aircraft noise prediction tools. The initial goal is to measure the noise of a jet near a simple planar surface while varying the surface length and location in order to: (1) validate noise prediction schemes when the surface is acting only as a jet noise shield and when the jet-surface interaction is creating additional noise, and (2) determine regions of interest for future, more detailed, tests. To meet these objectives, a flat plate was mounted on a two-axis traverse in two distinct configurations: (1) as a shield between the jet and the observer and (2) as a reflecting surface on the opposite side of the jet from the observer. The surface length was varied between 2 and 20 jet diameters downstream of the nozzle exit. Similarly, the radial distance from the jet centerline to the surface face was varied between 1 and 16 jet diameters. Far-field and phased array noise data were acquired at each combination of surface length and radial location using two nozzles operating at jet exit conditions across several flow regimes: subsonic cold, subsonic hot, underexpanded, ideally expanded, and overexpanded supersonic. The far-field noise results, discussed here, show where the jet noise is partially shielded by the surface and where jet-surface interaction noise dominates the low frequency spectrum as a surface extends downstream and approaches the jet plume.

Cumulative probability noise analysis in geophysical spectral records

The technique of rank ordering of spectral energy density samples was applied to high frequency (HF) ocean backscatter radar spectra to examine the properties of signal and noise in the record. HF ocean backscatter spectra have characteristic Bragg scatter lines and bands of energy with random phasing, and it is known that spiky noise from sferics and anthropogenic sources contribute to the observed energy density. Rank ordering of the spectral density data revealed three main features: (i) first-order Bragg scattering; (ii) continuum of randomly phased energy; and (iii) the underlying noise floor of the system. It is shown that the technique of rank ordering of spectral amplitude samples provides better insights and an improved algorithm for differentiating between bands of randomly phased sea echoes and system noise. The analysis reveals a constant offset in the spectral energy density data from the Ocean Surface Current Radar (OSCR) HF radar system, which should be removed before algorithms are applied to extract significant wave height information. The rank ordering of spectral energy density samples is a useful tool for differentiating between system noise and wide-band incoherent energy often obtained in a wide range of geophysical remote sensing.

Quantum-state diffusion with adaptive noise

We present a scheme for stochastic quantum-state diffusion (QSD) with adaptive noise to calculate the time evolution of an arbitrary observable of an open system. The method is based on the fact that the observable is much less sensitive to adaptive noise than to noise with a random phase. Hence, the individual realisations of the expectation value of the observable stay closer to the average evolution and fewer realisations are required to obtain the ensemble average. This is illustrated by applying QSD to a driven two-level system using both randomly phased and adaptive noise. Applying QSD with adaptive noise to an undriven two-level system enables us to derive a deterministic Schrodinger equation that produces the exact evolution of an arbitrary observable.

Phased array active noise controller for ducts

The phased array active noise controller offers a cost‐effective solution to noise control in ducts at frequencies below “cutoff.” The system consists of an array of loudspeakers phased to generate a downstream propagating wave that is an inverted replicate of an incident sound wave. The signal to be controlled is sensed by a microphone or microphones upstream of the array. Each element of the array provides a fraction of the overall cancellation signal, a feature making the system a robust one. Furthermore, detrimental upstream signals arrive out of phase, and the destabilizing positive feedback paths are virtually eliminated. There are, however, installation effects, a consequence of the relative positions of the transducers in the duct. It can be shown that the bandwidth of operation as well as the maximum attenuation is governed by the relative loudspeaker‐microphone separations. Analysis provides some insight and “optimum” relative positions can be found. The other installation effect is due to the radiation impedance seen by the array. Measurements of relevant impedances are presented. The overall system performance is documented for the case of a rectangular duct with and without air flow. [Work supported by the Natural Sciences and Engineering Research Council of Canada.]

Phased treatment noise suppressor for acoustic duct applications

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