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Many lens distortion models exist with several variations, and each distortion model is calibrated by using a different technique. If someone wants to correct lens distortion, choosing the right model could represent a very difficult task. Calibration depends on the chosen model, and some methods have unstable results. Normally, the distortion model containing radial, tangential, and prism distortion is used, but it does not represent high distortion accurately. The aim of this paper is to compare different lens distortion models to define the one that obtains better results under some conditions and to explore if some model can represent high and low distortion adequately. Also, we propose a calibration technique to calibrate several models under stable conditions. Since performance is hard conditioned with the calibration technique, the metric lens distortion calibration method is used to calibrate all the evaluated models. OCIS codes: 150.0155, 150.1135, 150.1488.

In this paper, we analyze the symbol error rate (SER) performance of decode-and-forward (DF) cooperative communications over Nakagami-m fading channels. For the classical three-node cooperation model, the exact SER expressions for both M phase shift keying (PSK) and M quadrature amplitude modulation (QAM) are derived. For easy usage, we also provide asymptotic approximations for the SER. In the analysis, we first consider the cooperation scenario in which all the channels are uncorrelated. In practice, it may happen that a correlation exists between the source-destination and relay-destination channels, e.g., for user cooperation in the uplink of a cellular network. We then examine the SER in this scenario. In addition, by varying the parameters of the Nakagami-m fading channels in the analytical results, we obtain some perceptions of choosing a good relay for enhancing the cooperation and make clear about how the included Nakagami fading figures and channel variances affect the SER performance. In addition, the optimal power allocation is investigated based on the derived asymptotic SER expressions. Simulations are finally provided to verify the correctness of our analysis. Index Terms--Cooperative communications, decode-and-forward (DF) protocol, Nakagami-m fading, optimal power allocation, relay selection, symbol error rate (SER).

One-bit delta-sigma A/D converters were used to analyze the noise caused in a compact, digital delay-and-sum beamformer by applying dynamic delays in a delta-sigma modulated bitstream. The findings from the study could be used to design a new method to remove the distortion without any significant increase in system complexity.

The problem of the charge sensitive preamplifier (CSPA) saturation is considered. It is shown that statistical uncertainty of the CSPA saturation time intervals is small in real measurements and it is possible to apply a periodical programmable external reset of CSPA (as well as programmable protection of other electronic blocks in a spectrometer against distortions caused by the preamplifier reset pulse) without essential increase of the dead time. Index Terms--Charge sensitive preamplifier, high count rate, reset, spectrometry, statistical analysis.

Position-sensitive avalanche photodiodes (PSAPDs) are a promising alternative to photomultiplier tubes for the development of a new generation of gamma imagers. They offer compactness, high gain and superior quantum efficiency. PSAPDs having a sensitive surface of up to 28 x 28 [mm.sup.2] have been fabricated. However, unlike pixellated imaging devices having a similar configuration, each PSAPD can achieve submillimeter position sensing over its surface with only four readout channels. This key feature is obtained by Anger-logic event positioning from the signals of four corner anodes printed on a resistive layer covering one of the PSAPD surfaces. This readout scheme provides high degree of multiplexing for reading position and energy information from the device, but leads to pincushion distortion in the spatial information due to the nonlinear charge sharing pattern associated with the potential across the resistive layer. We have developed a method to reproduce and correct this distortion based on finite-element simulations of the readout configuration. The resistive layer and the anodes are represented by a two-dimensional array of resistors and this circuit is numerically solved to obtain the signal on the four anodes for different current injection nodes. The relation between the injection positions and the resulting Anger positions is modeled and then used to correct experimental data. The algorithm was tested on [sup.99m]Tc flood images of a 16 x 16 array of 0.4 x 0.4 x 4 [mm.sup.3] CsI(T1) crystals and successfully restored the regular pattern. The correction procedure is fast and robust, and constitutes a step toward the realization of a low-cost, high-resolution gamma camera based on PSAPDs. Index Terms--Avalanche photodiodes, biomedical nuclear imaging, position sensitive detectors.

In this paper, we address the key problem in real-time video coding, the rate-distortion (R-D) tradeoff. As most video coding applications employ color images, we analyze the R-D modeling problem of the color image sequence. We investigate that the R-D characteristics of color video signal in traditional transform-based video coding systems should be modeled for the luminance and chrominance components separately. So we propose separable R-D models for color video coding. The feedback from the encoder buffer is analyzed by a control-theoretic adaptation approach to avoid buffer overflow and underflow. To achieve smooth video quality and satisfy the delay constraints in real-time applications, a novel R-D tradeoff controller is designed. In the proposed R-D tradeoff framework, both the quality variation and buffer safety are considered. Extensive simulation results demonstrate that the proposed approach can achieve smooth video quality without sacrificing overall quality while efficiently utilize the bandwidth without buffer overflow or underflow. Index Terms--Buffer control, H.264, rate control, rate-distortion (R-D) model, R-D tradeoff, video coding.

This paper presents results from an analysis of voltage stability following severe contingencies in the PJM system. The analyses involved the use of steady-state (OPF) and short- and long-term simulation tools. The results highlight the importance of adequate load modeling in assessing the performance of and solutions to voltage instability. Undervoltage load shedding (UVLS) is shown to be beneficial in arresting instability. Optimal power flow (OPF) analyses (supplemented with dynamic simulation results) provide valuable insight into the best locations and required minimum levels of UVLS. However, UVLS may not be able to address the serious scenarios where fast voltage dynamics develop immediately after an outage. Index Terms--Extreme contingencies, fault, short circuit, under-voltage load shedding (UVLS), voltage stability.

Harmonic state estimation (HSE) is used to locate harmonic sources and estimate harmonic distributions in power transmission networks. When only a limited number of harmonic meters are available, existing HSE methods have limited effectiveness due to observability problems. This paper describes a new system-wide harmonic state estimator that can reliably identify harmonic sources using fewer meters than unknown state variables. Note there are only a small number of simultaneons harmonic sources among the suspicious buses. Traditional observability analysis is extended to general under-determined estimation when considering the sparsity of state variables. It is shown that the underdetermined HSE can become observable with proper measurement arrangements by applying the sparsity of state variables. The HSE is formulated as a constrained sparsity maximization problem based on L1-norm minimization. It can be solved efficiently by an equivalent linear programming. Numerical experiments are conducted in the IEEE 14-bus power system to test the proposed method. The underdetermined system contains nine meters and 13 suspicious buses. The results show that the proposed sparsity maximization approach can reliably identify harmonic sources in the presence of measurement noises, model parameter deviations, and small nonzero injections. Index Terms--Harmonic pollution, meter placement, observability, power system harmonics, sparsity, sparsity representation, state estimation, underdetermined system, waveform distortion, wide-area measurements.

This paper deals with the development and implementation of a current-source-converter-based static synchronous compensator (CSC-STATCOM) applied to the volt-amperereactive (VAR) compensation problem of coal mining excavators. It is composed of a [+ or -] 750-kVAR full-bridge CSC with selective harmonic elimination, a low-pass input filter tuned to 200 Hz, and a [DELTA]/Y-connected coupling transformer for connection to medium-voltage load bus. Each power semiconductor switch is composed of an asymmetrical integrated gate commutated thyristor (IGCT) connected in series with a reverse-blocking diode and switched at 500 Hz to eliminate 5th, 7th, 11th, and 13th current harmonics produced by the CSC. Operating principles, power stage, design of dc link, and input filter are also described in this paper. It has been verified by field tests that the developed STATCOM follows rapid fluctuations in nearly symmetrical lagging and leading VAR consumption of electric excavators, resulting in nearly unity power factor on monthly basis, and the harmonic current spectra in the lines of CSC-STATCOM at the point of common coupling comply with the IEEE Std. 519-1992. Index Terms--Current-source converter (CSC), harmonic elimination, power quality, static VAR compensator (SVC).

Shaped charges are a warhead technology often applied to rocket propelled grenades and represent a dangerous threat for armored vehicles in combat as well as in peace-keeping operations. Their armor piercing performance rests upon an explosively induced collapse of a metallic liner to a stretching jet with very high particle velocities. A copper jet produced by a shaped charge can be distorted by high electric currents injected into the jet by means of spaced electrode plates connected to a high voltage capacitor. In tests carried out at Fraunhofer EMI, a shaped charge with a well characterized jet was used for the experiments in order to examine the current flow through the jet and its effect on the jet evolution. The measured current flow is related to the jet dynamics and the distortion pattern observed by multiple flash X-ray images. As expected, the current flow starts when the jet tip reaches the back electrode plate. No significant change of the current flow is observed at the characteristic jet break-up time. The current flow continues after the tail of the copper jet has left the electrodes and resembles a damped sinusoidal. A distortion of the jet is observed where the jet particles are not aligned along the jet axis. Instead the particles are stretched orthogonally to the jet axis with increased separation along the jet axis. The tip part of the jet is hardly affected. The jet distortion is analyzed with respect to jet dynamics and current flow which allows formulating criteria for the design of electric armor systems. The current injection effective for jet distortion is limited to a time slot of a magnitude of 60 [micro]s for the 44-mm caliber-shaped charge used in the experiments. To a first approximation, the current flow can be modeled by an electric arc. An electric circuit model can describe the current flow behavior with respect to the electric impedance and allows designing an electrical circuit adequate for the time slot. By the analogy of a wire explosion the necessary current magnitude for an effective jet disruption with respect to the interaction time slot can be estimated to begin at 300 kA. For the tip portion of the shaped charge jet, the time of effective current injection is very short. When the current starts to set in, the jet tip is already passing the back electrode plate. For this reason, an effective distortion of the jet tip represents a challenge that has to be mastered. Index Terms--Electric armor, electromagnetic armor, shaped charge jet disruption.

This paper describes the simulation of a microwave link from the transmitter to the receiver intermediate-frequency ports, by means of a rigorous circuit-level nonlinear analysis approach coupled with the electromagnetic characterization of the transmitter and receiver front-ends. This includes a full electromagnetic computation of the radiated far field which is used to establish the connection between transmitter and receiver. Digitally modulated radio-frequency drive is treated by a modulation-oriented harmonic-balance method based on Krylov-subspace modelorder reduction to allow the handling of large-size front-ends. An artificial neural network model is then developed to allow fast computation of the link driven by long sequences of the order of millions of samples. In this way, a meaningful evaluation of such link performance aspects as the bit-error rate becomes possible at the circuit level. Index Terms--Bit-error rate (BER), distortion, electromagnetic analysis, nonlinear circuits, system analysis and design.

An L/S-band 330-W distortion-cancelled Doherty GaAs field-effect transistor (FET) amplifier has been successfully developed optimizing the main and peak amplifiers load impedance shift. The amplifier employed a pair of 28-V operation 150-W GaAs heterojunction FETs. It demonstrated low third-order intermodulation of -37 dBc with a drain efficiency of 42% at an output power of 49 dBm around 6-dB backoff level under the two-carrier wideband code-division multiple-access (W-CDMA) signals of 2.135 and 2.145 GHz. To our knowledge, these represent the best results ever reported among the simple high-power FET amplifiers for W-CDMA base stations. In addition, we proposed the evaluation techniques to obtain each AM--AM and AM--PM characteristics of the main and peak amplifiers in an operating Doherty amplifier, and have experimentally proven the distortion cancellation effect in the GaAs FET Doherty amplifier. Index Terms--Distortion cancellation, Doherty amplifier, efficiency, heterojunction field-effect transistors (HFETs), high power, wideband code division multiple access (W-CDMA).

We characterize the rate distortion function for the source coding with decoder side information setting when the ith reconstruction symbol is allowed to depend only on the first i + l side information symbols, for some finite look-ahead l, in addition to the index from the encoder. For the case of causal side information, i.e., l = 0, we find that the penalty of causality is the omission of the subtracted mutual information term in the Wyner-Ziv rate distortion function. For l > 0, we derive a computable "infinite-letter" expression for the rate distortion function. When specialized to the near-lossless case, our results characterize the best achievable rate for the Slepian-Wolf source coding problem with finite side information looka-head, and have some surprising implications. We find that side information is useless for any fixed l when the joint probability mass function (PMF) of the source and side information satisfies the positivity condition P(x, y) > 0 for all (x, y). More generally, the optimal rate depends on the distribution of the pair X, Y only through the distribution of X and the bipartite graph whose edges represent the pairs x, y for which P(x, y) > 0. On the other hand, if side information look-ahead is allowed to grow faster than logarithmic in the block length, then H(X | Y) is achievable. Finally, we apply our approach to derive a computable expression for channel capacity when state information is available at the encoder with limited look-ahead. Index Terms--Causal source codes, delay-constrained coding, Gel'fand-Pinsker channel, rate distortion function, Slepian-Wolf coding, Wyner-Ziv coding.

Abstract: The method of using Boost type of converter was proposed for a 300W single-phase rectifier in this paper. By designing the necessary techniques and methodology, the overall Power Factor [...]

This paper examines the broadband distortion behavior in flexible filters employing varactor-diode tuning elements. Series- and parallel-resonant varactor-loaded transmission-lines, both commonly used in bandpass and bandstop microwave filters, are analyzed. Nonlinear Volterra-series analysis is employed to determine the second- and third-order distortion ratios dependent on the frequencies of the incident signals. It is shown that in a bandpass filter (employing parallel tuned resonators), maximum distortion occurs in the passband, while in a bandstop filter (employing series tuned resonators), minimum distortion occurs at the minimum-loss passband. The analysis is verified by practical measurement of filters employing the two modes of resonators. Index Terms--Distortion, microwave filters, tunable filters.

Advances in microwave instrumentation now make it feasible to accurately measure not only the magnitude spectrum, but also the phase spectrum of wide-bandwidth signals. In a practical measurement, the spectrum is measured over a finite window of time. The phase spectrum is related to the position of this window, causing the spectrum to differ between measurements of an identical waveform. It is difficult to compare multiple measurements with different window positions or to incorporate them into a model. Several methods have been proposed for determining the phase spectrum such that multiple measurements can be effectively compared and utilized in models. The methods are reviewed in terms of the information required to determine the phase and compared in terms of their robustness in the presence of measurement noise. Index Terms--Intermodulation distortion, measurement uncertainty, nonlinear systems, phase measurement.

This paper investigates the harmonic behavior of three phase power transformers under nonsinusoidal operations. The terminal behavior of the transformer was obtained by coupling the transformer transient finite-element (FE) model and external electric circuits. Such a technique would allow the physical representation of the nonlinear magnetization behavior of the transformer as well as the strong frequency dependence of the transformer parameters. The harmonic behavior of the transformer currents and the dc load current were analyzed using wavelet packet transform algorithm (WPT). The key findings are, uniform frequency bands resulting from WPT decomposition process of the current waveforms can be used for identification of harmonic components. The flattened input voltage distorted by 3rd harmonic component has the highest impact on the dc load current harmonics (with respect to the sinusoidal case). The peaking input voltage distorted by the 5th harmonic component has the highest impact on the transformer secondary current and the magnetizing current harmonics. Index Terms--FE, harmonic behavior, total harmonic band distortion, transformer, wavelet packets transform.

This paper presents an efficient multilevel-synthesis scheme and its application to a 27-level inverter. In the proposed multilevel scheme, this can be realized by an array of switching devices composing full-bridge inverter modules and proper mixing of each transformer terminal voltage. The most different aspect, compared to the conventional approach, in the synthesis of the multilevel output waveform is the utilization of a combination of transformers rather than the accumulation of capacitor voltage sources. A 27-level inverter consists of three full-bridge modules and their corresponding transformers. Quasi-sinusoidal voltage waves can be generated from a suitable selection of the turns ratio of the transformer. The validity of the proposed system is verified by computer-aided simulation and experimental results using a 500-W prototype, which can generate a 110-V ac output voltage from a 12-V dc input. Index Terms--Cascaded transformer, multilevel inverter, total harmonic distortion (THD).

Many ancient rhythmic hemipelagic sequences have been interpreted to record orbital variations, but the exact nature of the climatic and depositional transfer functions responsible for this link remains poorly understood. Two- dimensional numerical simulations were used to explore selected aspects of orbital signal distortion in linked siliciclastic and hemipelagic systems. The models suggest that transfer of multiorder (e.g., 20, 100, and 400 k.y.) oscillations in relative sea level into the hemipelagic record produces an inherent amplitude distortion of the shorter-period (e.g., 20 k.y.) cycle. This distortion gives rise to amplitude modulation (AM), which is qualitatively similar to AM of orbitally driven changes in insolation (e.g., eccentricity modulation of precession-driven cycles). However, unlike the orbitaily driven AM, synthesized AM is distinctly phase shifted relative to the stratigraphic record of the long-period (e.g., 100 k.y., 400 k.y.) cycle as a result of sealevel-driven changes in the storage capacity of nearshore through alluvial parts of the source siliciclastic system. Hence, multiorder changes in sea level can leave a distinct AM signature in dilution-affected hemipelagic records, thus making hemipelagic rhythms due to eccentricity-forced sea-level changes distinguishable from other types of orbitally driven hemipelagic cyclicity. Keywords: amplitude distortion, hemipelagic sedimentation, sea level, cycles, modeling, spectral analysis.

Byline: Y. Kim (1), R. M. Braun (1) Keywords: predistorter; COFDM; TTCM; equalization; HPA Abstract: We present an improved channel equalizing scheme to be used in Coded OFDM systems over an ISI channel. The scheme uses TurboTrellis Coded Modulation (TTCM) which retains a powerful errorcorrection capability while elegantly incorporating turbo codinginto the Trellis Coded Modulation (TCM).In OFDM over wireless communications, M-ary Quadrature AmplitudeModulation (M-QAM) schemes have been widely used to achieve highbandwidth efficiency. However, M-QAM signals require linearamplification to avoid spectral regrowth and severe performancedegradation due to their large envelope fluctuations. Moreover,the OFDM transmitter shapes the signal with a linear pulse shapingfilter. The combination of a linear filter with a High PowerAmplifier (HPA) forms a nonlinear system with memory, whichseverely degrades performance.We propose an efficient one-tap-equalizer using a modified LMSalgorithm and a novel adaptive predistortion technique tocompensate for the nonlinear distortion caused by the high poweramplifier cascaded with a linear filter in TTCM-OFDM systems. Theperformance of this method is compared with methods that have beenused previously with OFDM. A computer simulation confirms that theproposed approach is superior to the conventional methods. Author Affiliation: (1) Telecommunications Engineering, Faculty of Engineering, University of Technology, Sydney Article History: Registration Date: 11/10/2004

The large-characteristics of GaN-A1(sub x)Ga(sub 1-x)N high-electron mobility transistors (HEMTs) with particular emphasis on intermodulation distortion (IMD) and the third-order intercept point are analyzed. GaN system has the potential for microwave and RF applications at elevated temperatures.

This paper investigates the operation of four space vector-based synchronized pulse-width modulation (PWM) strategies in the overmodulation zone using three different overmodulation algorithms. It is shown that the symmetries in the PWM waveforms generated can be preserved in the overmodulation zone also. With any given overmodulation algorithm, the voltage control characteristics (i.e., fundamental voltage versus control variable) are found to vary with PWM strategy, pulse number and type of clamping. The inverse of the appropriate voltage control curve is used during premodulation to maintain the modulator gain constant. The differences in the nature of the voltage control characteristics with the different overmodulation algorithms are brought out. These characteristics are compared and contrasted against those at high switching frequencies. The harmonic distortion in the different cases is evaluated and compared. It is shown that the bus clamping strategies perform better than the conventional strategy with any given overmodulation algorithm employed. These strategies, which exploit the flexibilities in the space vector approach, are useful in high power drives on account of their superior waveform quality at low switching frequencies and high dc bus utilization. Index Terms--Harmonic distortion, induction motor drives, inverters, overmodulation, pulse-width modulation, space vector, vectors, voltage control.

The neutron powder diffraction data of deuterated clatharate hydrates of CO2 and Xe are measured to investigate the effects of the motion of guest molecules on the structure of the surrounding hydrogen-bonded network. Rietveld analysis revealed that the magnitude of the thermal parameters of the host atoms of the CO2 clathrate hydrate depends strongly on the crystallographic site, while those of the Xe clathrate hydrate do not depend on the site.

We analyze distortions in analog VLSI arrays for linear image filtering due to component mismatch and nonlinearity. The analysis can be used to evaluate different circuit architectures implementing the same computation for both one-dimensional (1-D) and two-dimensional (12-D) rectangularly and hexagonally sampled arrays. In addition, it can determine which elements within a given architecture are most critical for accurate computation of the output. Based upon the concept of equivalent input sources, it offers both mathematical and intuitive explanations of the responses of the networks to mismatch and nonlinearity. Index Terms: Analog integrated circuits, cellular neural networks, image processing, filtering, nonlinear distortion, sensitivity.

One of the origins of harmonic distortion in current mirrors is the inevitable mismatch between the mirror transistors. In this brief, we examine both single current mirrors and complementary class-AB current mirrors, and develop analytical expressions for the mismatch-induced harmonic distortion. The expressions are verified through simulations and are used for a discussion of the impact of mismatch on harmonic distortion properties of CMOS current mirrors. The distortion model is combined with well-known statistical models for the device mismatch in order to establish a relation between geometrical parameters, distortion, and production yield. It is found that distortion levels somewhat below 1% can be attained by carefully matching the mirror transistors, but ultra-low distortion is not achievable. Index Terms - Current mirror, distortion analysis, harmonic distortion.

This paper describes a novel solution to the problem of bandwidth-efficient digital signal transmission in the presence of dynamic multipath distortion. A burst transmission is comprised of two consecutive data blocks with Identical data that have been processed differently. The two data blocks are transmitted adjacent to each other In time so that the time-variable transmission channel will apply approximately the same linear distortion to each block. At the receive site, the two blocks are captured and processed together to cancel the effects of the linear distortion, while adding the signal energy from each block.

This article describes the measurements of composite second order (CSO), composite triple beats (CTB) frequency spectrum and time-varying distortion in basic bandwidth (BB) (0 - 4 MHz) of the 64-QAM digital channels by multichannel AM/64QAM both optical and coaxial transmission systems. For any regular standard frequency plans (Europe, USA NCTA etc.) there is, for I and Q components in BB of the QAM channels, harmonic series of CSO/CTB with first harmonic [f.sub.1]. It has been showing that for all the same laser-optics or coaxial transmission systems CSO/CTB distortions spectrum form in QAM BB the 60-80[[micro]seconds] duration bursts of series pulse with pulse periode T = 1/[f.sub.1] and the pulse duration [Tau] [approximately equal to] 0.4/[f.sub.m], where [f.sub.m] is the CSO/CTB harmonic with max. amplitude in BB of QAM. The bursts result in the essential unevenness of error bits in time domain distribution. These bursts can deteriorate essential of Error Correction by Interleaver-Deinterleaver and Reed-Solomon (RS) Forward Error Correction (FEC) Code of the transmission systems also with a relative low. Bit Error Rate (BER) about [10.sup.-5] before FEC. There is, white Gaussian noise like, intermodulations .distortion from interaction of digital-, digital-analog channels too, that have summed with white Gaussian noise. Indexing terms: CATV, Distortion, Noise, Optical communication, CNR, CSO, CTB, QAM.

This paper investigates the harmonic amplification problems in a plastic plant and the appropriate mitigation methods. Four single-tuned filters (LC filters) were installed to eliminate the harmonic currents from three 6-pulse rectifiers. However, after the capacitance reduction of some filter capacitors, the driving point impedance at the frequency of 8th order harmonic increased severely and the harmonic current of this order was amplified. There were many failures about the capacitors of filters. Field measurements and computer simulations are used to verify the disturbance problems. Finally, two high-pass damped filters are recommended to replace the original single-tuned filters. The amplification problems at some even-order harmonics can be avoided. keywords: harmonic distortion, filters, resonance, capacitance reduction.

This paper presents the applications of regression models to predict the future growth trend of total harmonic distortions (THD) of 40 power transformers from field measurement data. The prediction values are important and can be used for transformer planning. Those transformers which feed different types of customers reveal different harmonic characteristics. While the linear regression model is suitable for harmonic voltage distortion, the nonlinear exponential regression model is better for current. All transformers' harmonic voltage distortions follow with harmonic current distortions, that is, feeder loads are harmonic sources. The prediction harmonic values of regression analysis are lower than that from the method of average spread rate. Keyword: Harmonics, power transformer, regression analysis, prediction, statistics

Research was conducted to examine the generation of second-order cumulative waves (SOCWs) that accompany the fundamental modes in a two-dimensional hard-walled waveguide of semi-infinite length using second-order perturbation. SOCW analytical expressions were obtained through appropriate boundary and initial conditions of excitation. Results demonstrate SOCW field distortion very clearly.

A half-sinusoidally driven class-A harmonic-control amplifier (hHCA) combines the advantage of high gain of class A with the advantage of high drain efficiency of class F. Consequently, power-added efficiency is increased as compared with state-of-the-art high-efficiency amplification techniques. As this innovative amplifier concept consists of a pulse-forming class-B amplifier stage followed by a class-A power-amplifier stage, intermodulation distortion is low even in saturation. The realization of such a two-stage hHCA offers 71% overall efficiency, 27.9-dBm output power, and 22.4-dB gain at 1.62 GHz. Two-tone measurements at 1-dB-gain compression, where the amplifier's single-carrier (SC) overall efficiency is still 64%, has demonstrated third- and fifth-order intermodulation distortion of -29 and -21 dBc, respectively. Index Terms - Class F, efficiency, harmonic control, linearity, microwave, power amplifier.

We investigate the problem of guessing a random vector X within distortion level D. Our aim is to characterize the best attainable performance in the sense of minimizing, in some probabilistic sense, the number of required guesses G(X) until the error falls below D. The underlying motivation is that G(X) is the number of candidate codewords to be examined by a rate-distortion block encoder until a satisfactory codeword is found. In particular, for memoryless sources, we provide a single-letter characterization of the least achievable exponential growth rate of the pth moment of G(X) as the dimension of the random vector X grows without bound. In this context, we propose an asymptotically optimal guessing scheme that is universal both with respect to the information source and the value of p. We then study some properties of the exponent function E(D, p) along with its relation to the source-coding exponents. Finally, we provide extensions of our main results to the Gaussian case, guessing with side information, and sources with memory. Index Terms - Fidelity criterion, guessing, rate.distortion theory, side information, source coding, source coding error exponent.

We discuss the quantitative location of objects from holographic images when the reconstruction wavelength differs from the recording wavelength. The holographic image equations are interpreted in a way that clarifies the meaning of stereo pairs of holographic images and indicates how backprojection methods can be used in holography to locate objects. Alternative methods involving the production of distortion-free regions in the holographic image field during reconstruction, the use of self-calibrating objects in the object field during recording, and triangulation can be used to locate objects. OCIS codes: 090.0090, 100.0100, 129.3940.

An analytical model of intermodulation distortion and chirp in cable television (CATV) distributed feedback laser diodes was presented. Longitudinal spatial hole burning was compared to gain compression over the CATV band. Results showed that the effects of longitudinal spatial hole burning on chirp and distortion were significant in actual lasers. In addition, the entire CATV band was affected by the nonhomogenous distribution of the photon along the cavity.

We apply Golay complementary sequences for measuring the dipulse response and transfer functions of a digital magnetic-saturation-recording channel. Our experimental channel suffers from nonlinear distortion caused by a magnetoresistive (MR) sensor. The measured-channel characteristics are compared with the same characteristics obtained by the dipulse-response measurement technique by using feedback-shift register sequences. based on a practical nonlinear Volterra model of a digital magnetic-saturation-recording channel, we analyze the artifacts caused by second- and third-order nonlinear distortion, which do occur in the Golay dipulse responses and transfer functions. We show that with either of the considered dipulse-response measurement techniques, the artifacts caused by even-order nonlinear distortion, which occur in the measured-channel characteristics, can easily be removed. The measured-channel characteristics obtained show excellent performance for either of the considered excitation sequences. Index Terms- Channel characterization, Golay complementary sequences, magnetic recording, nonlinear distortion.

In this paper, we consider the problem of separate coding for two correlated memoryless Gaussian sources. We determine the rate-distortion region in the special case when one source provides partial side information to the other source. We also show that the previously obtained inner region of the rate-distortion region is partially tight. A rigorous proof of the direct coding theorem is also given. Index Terms - Correlated Gaussian sources, partial side information, rate-distortion region, separate coding.

The 'charge pump' electronic ballast circuit, which employs a charging capacitor and a high-frequency ac source to implement the power factor correction (PFC), has become an attractive topology for ballasting the fluorescent lamp. However, the basic 'charge pump' electronic ballast circuit has the problems of high total harmonic distortion (THD) of the input current, and high crest factor (CF) of the lamp current. This paper analyzes the origin of the problems and proposes a novel solution. With the addition of two small clamping diodes, good input current (PF > 0.99, THD < 5%) and lamp current (CF < 1.6) can be obtained with the open-loop control. The experimental results are provided for verification. Index Terms - Ballast, lamp, power-factor correction (PFC).

In pulse-width-modulation (PWM) ac inverters, the duty-cycle modulator transfer function must be highly linear to achieve low distortion. Current-mode (CM) control, inherently nonlinear, is needed to actively 'damp' otherwise high-Q LC noise-reduction filters. A novel CM control approach is proposed, which tailors external ramp characteristics to achieve 'perfect' transfer-function linearity regardless of duty cycle and guarantee subharmonic stability. Supporting mathematical analysis and prototype measurements are included. The method, when applied to dc/dc converters, provides fixed gain bandwidth in the continuous conduction mode over a broad line and load range. Index Terms - Harmonic distortion, inverters, modeling, MOSFET amplifiers, power control, power conversion harmonics, pulse-width-modulated inverters.

A design method was developed designing near-perfect-reconstruction (NPR) nonuniform integer-decimated filter banks with integer sampling. A linear-phase spectral factor of the 2Mth band filter served as the prototype filter. It was found that the distortion and aliasing of the resulting nonuniform NPR filter bank was comparable to the the stopband attenuation of the prototype filter.

The M-channel maximally decimated filter bank is considered, where, except in the ideal case of perfect reconstruction, aliasing distortion, magnitude distortion, and phase distortion are present. It is shown how these can be controlled if the filter bank is designed by a method that optimizes the gain of an error system. Index Terms - Distortion, filter banks.

It is shown that in a class of SC circuits using correlated double sampling the harmonic distortion caused by nonlinear op-amps is greatly reduced. Hence, these circuits are very useful in applications such as input stages in high-linearity amplifiers or in delta-sigma converters. Index Terms - Correlated double sampling, linear amplifiers, low-distortion amplifiers, nonlinear distortion.

Measured pulse transmission through human breast specimens was utilized to develop correction methods for ultrasonic wavefront distortion. Backpropagation, matched filtering, phase conjugation and time-delay compensation were used to reconstruct one-way point spread functions. Results show that compensation methods are enhanced by a novel amplitude compression technique that approaches inverse filtering.

A compensation technique for nonlinearities is usually necessary in QAM digital satellite links. Analog waveform compensation has the advantage of reducing out-of-band spectral emissions with respect to end-to-end digital predistortion, in addition to its easy realization. Nevertheless, it has been often neglected in the literature because of its lack of adaptivity; we propose making the predistorter fully adaptive. In this paper, different control schemes applied to fifth-order IF predistortion with different optimization criteria have been investigated. A simulation-based analysis shows that adaptive IF compensation achieves excellent performance if compared with static predistortion of the same order. Comparisons with upper bounds related to digital predistortion with memory, moreover, denote that IF analog predistortion can be truly considered an alternative approach, especially for narrow pulse shaping.

Traditional subband coding, where each subband is encoded independently, has been shown by Fischer to be suboptimum for encoding Gaussian sources in the rate-distortion sense. We show here that if we use prediction across subbands when encoding Gaussian sources, the resulting coder is asymptotically rate-distortion-optimum at high rate. We also show for Gauss-Markov sources that although the crossband prediction filter in this case is of infinite impulse response, the filter can be implemented very efficiently to high accuracy due to the fast decay of the filter coefficients. Index Terms - Source coding, subband coding, wavelets, rate-distortion theory, linear prediction, crossband prediction.

The disadvantage of progressive transmission, compared to transmission in a single step, is analyzed for the high-rate case using a polytope that is self-similar under binary subdivision. This disadvantage is calculated to be 0.3424 dB or 0.057 bit compared to scalar quantization, obtained with a step size of 1 bit per ensemble. Index Terms - Progressive transmission, quantization, space filling advantage, high rate assumption, squared-error distortion, bintree, rate distortion.