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The phase dynamics of bulk (SOA) examined with regard with all-optical switching applications.

Communication over the noncoherent additive white Gaussian noise (AWGN) channel is considered, where the transmitted signal undergoes a phase rotation, unknown to the transmitter and the receiver. The effects of phase dynamics are explicitly taken into account by considering a block-independent model for the phase process: the unknown phase is constant for a block of N complex symbols and independent from block to block. In the first part of the paper, the capacity-achieving input distribution is characterized. In particular, it is shown that the maximizing density has circular symmetry, is discrete in amplitude with infinite number of mass points, and always has a mass point at zero. Furthermore, asymptotic expressions and bounds for the capacity are derived. Based on these results, the capacity is evaluated through numerical optimizations for unconstrained and modulation-constrained input distributions. In the second part of this paper, inspired by the capacity results, two classes of coding and modulation schemes are proposed for fast and moderate phase dynamics. In the case of fast phase dynamics (i.e., small N), optimized modulation alphabets are designed having exponential complexity with N at the demodulator. In the case of moderate phase dynamics (i.e., moderate values of N), specially designed modulation alphabets are utilized that have linear complexity with N. These alphabets are used together with optimized irregular low-density parity-check (LDPC) codes. Simulation results show that these codes can achieve close-to-capacity performance with moderate complexity, and outperform the best known codes so far. Index Terms--Block-independent noncoherent channel, channel capacity, coding for noncoherent channel, noncoherent channel.

Phase dynamics and phase noise of N coupled phase-locked loops (PLLs) with N independent oscillators are analyzed. The phase noise of coupled PLLs with independent oscillators is analyzed by using the signal flow graph and Mason's gain rules. The near-carrier phase noise of PLL elements in the array can be reduced to 1/N that of a single independent (without coupling) VCO oF the PLL element, and return to its free-running phase noise far from the carrier frequency, provided the coupling network is reciprocal, the feedback loop gain of the PLL elements is large, and the Phase detector and amplifier noise are neglected. The phase dynamics and noise improvement of coupled PLL arrays are verified by using two coupled PLLs with independent GaAs MESFET x oscillators operating at X-band. Index Terms--Active antenna array, AM noise, beam control, coupled oscillators, coupled phase-locked loops (PLLs), feedback loop, injection locked, locking range, Mason's gain rule, oscillator, phase locked, phase noise (PM noise), PLL, signal flow graph (SFG).

The analysis and experimental results of an antenna array using injection locked coupled oscillators with self-tuning of oscillator free-running frequencies are presented. With the use of coupled type-II phase locked loops for tuning oscillator free-running frequencies and an external injection signal for stabilizing the array operating frequency, this antenna array can steer its beam through a single control voltage and hold its output frequency at the injection signal frequency in operation. In addition, its beam-pointing error arising from phase errors in coupled oscillators can be reduced and the array works well over a certain frequency band. Phase dynamics and stability are studied and experimentally verified. Experimental results of a three-element injection locked coupled oscillator array show that its uniform phase progression ranges between -16[degrees] and 52[degrees], and the phase errors are less than 5[degrees] at 2.7 GHz. The operation bandwidth is shown from 2.68-2.72 GHz. By loading the injection locked coupled oscillator array with rectangular patch antennas, the beam-steering radiation characteristics are measured at various control voltages. Index Terms--Coupled oscillators, injection locked oscillators, phase locked loops, stability.

The charge pump phase-locked loops with a digital sequential phase frequency detector are analyzed using linear and nonlinear models. Nonlinear analytical maps are derived. The stability analysis results agree with linear analysis results, with higher order corrections. The effects of the loop delay are also discussed. Index Terms--Charge-pump phase-locked loop (PLL), phase dynamics, stability.

A data-driven adaptive neurofuzzy controller is presented for the water-level control of U-tube steam generators in nuclear power plants. This neurofuzzy controller is capable of learning the control action principles from the data obtained using other methods of automatic or manual control. There are four inputs in the neurofuzzy system, yet only eighty fuzzy rules involved. Therefore, the fuzzy system is versatile and moderately compact. The versatility is due to the higher input space dimension that helps to learn more control principles. The compactness is due to the number of rules being not too many. A 10-h evaluation trial of the trained fuzzy controller demonstrated its capability in regulating the water level under random disturbances and reference level changes. Index Terms--Adaptive neurofuzzy system, nonminimum phase dynamics, Takagi-Sugeno fuzzy model, U-tube steam generator.

The paper addresses the problem of output power regulation of fixed-pitch variable-speed wind energy conversion systems. Operation is constrained by practical reasons to the low-speed side of the turbine power--speed curve. Unfortunately, this region is characterized by a nonminimum phase dynamics which is an obstacle to perform the regulation task. A dynamical variable structure controller is developed that accomplishes the control objective despite this limitation. The proposed control strategy presents attractive features such as robustness to parametric uncertainties of the turbine and generator as well as to electric grid disturbances. Index Terms--Power generation control, variable structure systems, wind energy.

In this paper, we consider iterative detection over bandpass channels that introduce an unknown phase rotation in the transmitted signal. This work focuses on the comparison between two adaptive detection strategies for trellis-based coded modulation: limited-tree-search (LTS) detection, obtained by reducing a tree search to a limited trellis search, and truncated-memory (TM) detection, based on channel-memory truncation, which automatically leads to a trellis search. Both strategies are used to derive trellis-based forward-backward (FB) algorithms. A quantitative analysis based on simulations, with various coding and modulation schemes, is carried out to evaluate and compare the two approaches. The results show that the channel-phase dynamics should significantly influence the choice of the detection strategy: For low-phase variations, LTS algorithms are a simple and reasonable choice, while for moderate to fast phase variations, TM algorithms show a considerable robustness. Index Terms--Adaptive iterative detection, noncoherent detection, truncated-memory detection.

The phase dynamics of double-barrier Josephson junction that is implemented in the rapid-single-flux-quantum (RSFQ) circuits and their current use in voltage standards is discussed. Decreasing the switching time of Josephson elements and reducing the excess wiring are the ways by which microscopic analyses allows optimization of the performance of the double-barrier Josephson junction-based RSFQ

In this paper, design and robustness of rotationally invariant (RI) codes is investigated. In the first part of this paper, RI codes are extended to the case of serially concatenated (SC) trellis-coded modulation (TCM) and several high-rate powerful RI-SCTCM codes are designed over 8-phase-shift keying and 16-quadrature amplitude modulation alphabets. The investigation continues by considering more realistic channels that introduce cycle slips during phase estimation, and thus rotate only part of the transmitted codeword. It is proven that RI codes with small state space are robust in these channels, even when traditional coherent decoders are utilized. Furthermore, it is demonstrated through simulations that the addition of a simple stopping criterion to the coherent iterative decoding algorithm is sufficient for robustness of the more powerful RI-SCTCM codes when partial codeword rotations are considered. Finally, the issue of whether RI codes are useful for transmission in the noncoherent channel is investigated. It is proven that RI codes are as good as any other good codes for this channel when the phase dynamics are low, and optimal decoding is performed. However, it is shown that for a certain class of receivers, RI codes are also robust to partial phase rotations in this channel. Index Terms--Noncoherent channels, rotationally invariant codes, trellis codes, turbo codes.

We describe the effect of phase synchronization of chaotic oscillators. It is shown that phase can be defined for continuous time dynamical oscillators with chaotic dynamics, and effects of phase and frequency locking can be observed. We introduce several tools which characterize this weak synchronization and demonstrate phase and frequency locking by external periodic force, as well as due to weak interaction of nonidentical chaotic oscillators. In the synchronous state the phases of two systems are locked, while the amplitudes remain chaotic and noncorrelated. The intermittency phenomenon at the synchronization transition is considered. The application to the analysis of bivariate experimental data is discussed. Index Terms - Chaotic oscillators, frequency locking, phase dynamics, weak interaction.

This paper presents a simple method for the calculation of the frequency and power variation of an active antenna operated in the presence of a reflecting surface. The situation modeled accounts for interdependent amplitude and phase dynamics and also allows for the extraction of active antenna array coupling coefficients. Analytical and experimental results are presented for both frequency and power variations of an individual element when operated in a strongly coupled imaged array environment. Here the nearest neighbor coupling is shown to be the dominant coupling mechanism.

This paper considers the analysis of an oscillator array with an arbitrary coupling network, described in terms of N-port circuit parameters. A Kurokawa analysis is used to transform the frequency domain network description into a set of equations for the oscillator amplitude and phase dynamics. The results reduce to previous work with 'loosely' coupled Van der Pol oscillators, provided that the coupling network satisfies a broadband condition: the Q-factor of the coupling network must be much smaller than that of the oscillator. The theory is verified using a new coupling structure and a six-element patch oscillator array operating at 4 GHz, which produced a 70 [degrees] scanning range using a phase-shifterless technique.

Theoretical studies involving cross- and time-covariance functions of the variables controlling Langevin noise sources help examine the noise in semiconductor lasers. Analytical expressions represent frequency noise, carrier noise spectrum, the AM and FM noise and the phase change modification. Approximations of the phase dynamics require the inclusion of the shot noise factor in addition to carrier contributions.

Arrays of coupled oscillators can be used for power-combining at microwave and millimeter-wave frequencies, and have been successfully demonstrated with a variety of devices. Such arrays have also recently been mode-locked for pulse generation, and can be configured for phase-shifterless beam-scanning. The nonlinear theory of coupled-oscillator phase dynamics depends crucially on the parameters describing the coupling between oscillators. Methods for experimental characterization of these parameters are described here, and simple models are developed which reproduce the measurements quite well. The models apply to radiative coupling and the effects of external reflectors which are sometimes used for stabilization. The theory is verified with a two-oscillator system.

The ability of two coupled oscillators to synchronize depends critically on the coupling network. Previous analyses have accurately predicted the performance of quasi-optical microwave oscillator arrays for both weak and strong coupling, but have been limited to coupling networks with bandwidths considerably larger than the locking bandwidths of the oscillators. In this paper, the authors develop a method for deriving a suitable system of nonlinear differential equations describing the oscillator amplitude and phase dynamics using a generalization of Kurokawa's method. The method is applied to the case of two Van der Pol oscillators coupled through a resonant network for a wide range of coupling strengths and bandwidths. Simple approximate formulas are developed for the size of the frequency locking region as functions of the basic circuit parameters. Index Terms--Injection locking, oscillators.