High Frequency Phase Noise Research Articles

A Spur-and-Phase-Noise-Filtering Technique for Inductor-Less Fractional-N Injection-Locked PLLs

A novel phase-noise-filtering technique based on phase-domain averaging is proposed to suppress the large injection spurs and poor high-frequency phase noise of inductor-less injection-locked phase-locked loops (IL-PLLs). Demonstrated using a 1.2-GHz fractional-N IL-PLL based on a capacitive-ring-coupled ring oscillator, wideband spur-and-phase-noise suppression of up to 20 dB is achieved allowing for phase noise as low as −146 dBc/Hz at 30-MHz offset with a 2-MHz resolution. This allows for an inductor-less alternative to LC-based PLLs in scaled-digital CMOS technologies. The 65-nm CMOS prototype improves 10-MHz phase noise from −115 to −135 dBc/Hz, injection spurs from −40.5 to −57 dB, and integrated jitter from 3.57 to 1.48 ps while occupying an area of 0.6 mm2 and consuming 19.8 mW from a 0.85-V supply, resulting in an FoM and FoMJitter of −163 and −223.6 dB, respectively.

Analysis of a Frequency Acquisition Technique With a Stochastic Reference Clock Generator

This brief presents a theoretical analysis of the stochastic reference clock generator (SRCG), which creates a clock like periodic signal from a random nonreturn-to-zero data sequence. The output of the SRCG can be utilized as a reference clock for frequency acquisition in dual-loop clock-and-data recovery circuits. A frequency-locked loop (FLL) subsequent to the SRCG guides the voltage-controlled oscillator frequency into the pull-in range of the phase-locked loop while suppressing the high-frequency phase noise of the SRCG. The phase noise and frequency offset of the SRCG-FLL pair are analyzed. The validity of the theoretical analysis is supported by results taken from a test chip.

Broadband phase noise suppression in a Yb-fiber frequency comb

We report a simple technique to suppress high-frequency phase noise of a Yb-based fiber optical frequency comb using an active intensity noise servo. Out-of-loop measurements of the phase noise using an optical heterodyne beat with a cw laser show suppression of phase noise by ≥7 dB out to Fourier frequencies of 100 kHz with a unity-gain crossing of ∼700 kHz. These results are enabled by the strong correlation between the intensity and phase noise of the laser. Detailed measurements of intensity and phase noise spectra, as well as transfer functions, reveal that the dominant phase and intensity noise contribution above ∼100 kHz is due to amplified spontaneous emission or other quantum noise sources.

Speckle Noise Reduction in Vibration Measurement by Time-Average Speckle Interferometry and Digital Holography-a Unifying Approach

Time-average electronic speckle pattern interferometry and digital holography are two representative full-field coherent optical techniques used in mechanical vibration measurement. In both techniques, the quantitative data processing is affected by several difficulties. The most important are the weak contrast of Bessel-type fringes and the speckle noise. The greatest obstacle in achieving complete amplitude field estimation comes from the orthogonal components of time-averaged digital holograms or speckle interferograms, where multiplicative, high-frequency phase noise covers the deterministic, vibration-related phase. Several researchers studied these problems in relation with the double-exposure method. In the present paper, the author presents in a single, unifying approach, these double-exposure methods, common to speckle interferometry and digital holography. An important reduction of multiplicative high-frequency phase noise allows obtaining fringe-averaged patterns whose intensity noise is much lower than in classical time-average holography. The analysis allows choosing the most appropriate method leading not only to a higher fringe pattern quality, lower noise and extended measurement range, but also to a method of vibration-related phase estimation, which may include in some stages subpixel precision. The method, based on the mathematical inversion of the Bessel function on monotonic intervals, is equivalent to phase unwrapping, but it only uses time-averaged fringe patterns.

Mechanical vibration measurement by high-resolution time-averaged digital holography

In digital holography, a challenge inherited from speckle interferometry is the quantitative data processing of time-averaged holograms in view of estimating the full field of vibration amplitudes. Fundamentally, the greatest obstacle comes from the orthogonal components of time-averaged digital holograms, corrupted by multiplicative, high-frequency phase noise covering the deterministic vibration-related phase. The paper describes a novel method of obtaining through digital holography high-resolution time-averaged fringe patterns. The three-level approach includes the elimination of the multiplicative high-frequency phase noise by synchronous detection followed by low-pass filtering. The high-frequency information needed by this procedure is taken from the digital hologram of the object at rest. The complete procedure includes an automatic correction of the environmental phase drift introduced by the synchronous detection. The different stages of data processing are illustrated by experimental results.

A GA-based Autofocus Technique For Correcting High-frequency Sar Phase Error

The presence of a space-invariant sinusoidal phase error in the azimuth SAR (synthetic aperture radar) signal history causes paired echoes to appear in the system impulse response [1]. These high peaksidelobes may be interpreted erroneously as separate targets by conventional autofocus algorithms. In this paper, a new approach to solve the high-frequency phase noise problems in SAR imaging is presented. The phase error is formulated as a nonlinear optimization problem for continuous variables. The optimum solution is obtained by minimizing the entropy of the signal. The proposed algorithm utilizes a real-coded genetic algorithm (GA) in the first stage to direct the search towards the global optimum region and a local search method in the second stage to do fine tuning. The algorithm is tested on simulated point targets and the results show significant improvement in the target response, as compared to the conventional autofocus and optimization algorithms. Thus the efficiency and the success rate of the algorithm are placed in sharper focus to minimize high frequency phase noise. Furthermore, the complexity of the problems solved clearly demonstrates the usefulness of this novel approach in solving such nonlinear systems.

Short-term frequency stability of clock generators for multigigahertz rapid-single-flux quantum digital circuits

Superconducting digital systems based on Josephson junctions have generally used a synchronous timing strategy. A master clock signal is used to delimit a data window during which the system changes state and data is transferred from one block to the next. The temporal stability of the clock signal has a profound effect on the performance of rapid single flux quantum (RSFQ) digital systems. In particular, short-term clock fluctuations, or clock jitter, can degrade system performance due to the hazard of timing constraint violations. The successful development of large-scale RSFQ digital systems will require highly stable multigigahertz on-chip clock sources. To meet this need, methods for characterizing and measuring the short-term stability of such sources are required. We identify the relevant figure of merit to characterize and compare various clocks: the cycle-to-cycle standard deviation of the clock periods. We present experimental techniques for the measurement of this figure of merit and apply them to the measurement of jitter in a clock generator used often in RSFQ systems, the ring oscillator. High-frequency phase noise measurements found the jitter of a 9.6-GHz clock to be in the range from 0.6% to 0.36% of the clock period. The measured values of clock jitter fell within the 95% confidence interval of our stochastic circuit simulations. This was sufficient evidence to conclude that thermal noise from the resistors in the circuit may be the dominant source of jitter in the ring oscillator.

Phase noise characteristics associated with low-frequency noise in submicron SOI MOSFET feedback oscillator for RF IC's

Phase noise in silicon-on-insulator (SOI) MOSFET feedback oscillators for RF IC applications is investigated. The observed correlation between the oscillator's high frequency phase noise and the transistor's low-frequency noise characteristics demonstrates that the phase noise overshoot still exists in partially-depleted (PD) floating body SOI nMOS Colpitts oscillators. These results suggest that kink-induced effects associated with low-frequency components of the signal are upconverted into the ideally kink-free high frequency domain operation mode of PD floating body SOI oscillators.

Actively mode-locked semiconductor lasers

Measurements of actively mode-locked semiconductor lasers are described and compared to calculations of the mode-locking process using three coupled traveling-wave rate equations for the electron and photon densities. The dependence of pulse width on the modulation current and frequency are described. A limitation to minimum achievable pulse widths in mode-locked semiconductor lasers is shown to be dynamic tuning due to gain saturation. Techniques to achieve subpicosecond pulses are described, together with ways to reduce multiple pulse outputs. The amplitude and phase noise of linear- and ring-cavity semiconductor lasers were measured and fond to be tens of dB smaller than YAG and argon lasers and limited by the noise from the microwave oscillator. High-frequency phase noise is only measurable in detuned cavities, and is below -110 dBc (1 Hz) in optimally tuned cavities. The prospects for novel ways to achieve even shorter pulses are discussed. >

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

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.