Signal Peak Power Research Articles

Impact evaluation of conducted UWB transients on loads in power-line networks

Abstract. Nowadays, faced with the ever-increasing dependence on diverse electronic devices and systems, the proliferation of potential electromagnetic interference (EMI) becomes a critical threat for reliable operation. A typical issue is the electronics working reliably in power-line networks when exposed to electromagnetic environment. In this paper, we consider a conducted ultra-wideband (UWB) disturbance, as an example of intentional electromagnetic interference (IEMI) source, and perform the impact evaluation at the loads in a network. With the aid of fast Fourier transform (FFT), the UWB transient is characterized in the frequency domain. Based on a modified Baum–Liu–Tesche (BLT) method, the EMI received at the loads, with complex impedance, is computed. Through inverse FFT (IFFT), we obtain time-domain responses of the loads. To evaluate the impact on loads, we employ five common, but important quantifiers, i.e., time-domain peak, total signal energy, peak signal power, peak time rate of change and peak time integral of the pulse. Moreover, to perform a comprehensive analysis, we also investigate the effects of the attributes (capacitive, resistive, or inductive) of other loads connected to the network, the rise time and pulse width of the UWB transient, and the lengths of power lines. It is seen that, for the loads distributed in a network, the impact evaluation of IEMI should be based on the characteristics of the IEMI source, and the network features, such as load impedances, layout, and characteristics of cables.

Hybrid Visible Light and Power Line Communication for Indoor Multiuser Downlink

Visible light communication (VLC) turns indoor light-emitting diode (LED)-based illumination devices into high-speed network portals that, for example, operate in tandem with existing Wi-Fi networks. Since in this scenario, multiple VLC-equipped luminaires would serve overlapping service areas, we suggest the use of power line communication (PLC) to coordinate and provide data to the VLC transmitters. In particular, in this paper, we propose a hybrid VLC-PLC (HVP) system architecture for the indoor downlink transmission and present the analytical framework for the data rate analysis of the HVP system. In our solution, spatial optical OFDM (SO-OFDM) is applied across multiple luminaires, for which we propose several subcarrier allocation schemes to exploit the frequency selectivity of the VLC and PLC channels. Different possible and meaningful variations of the HVP system, including the choice of optical OFDM transmission, relay, and multiple access schemes, are investigated and compared. The numerical results establish achievable rates for relevant communication scenarios and highlight the advantages of the proposed subcarrier allocation scheme in terms of rate and reduced peak power of optical OFDM signals.

A Trellis Shaping for Peak and Average Power Reduction of BICM-OFDM Signals

One of the major drawbacks of orthogonal frequency-division multiplexing (OFDM) systems is their high peak-to-average power ratio (PAPR) signals, and trellis shaping (TS) is a promising approach for reducing both peak power and average power of OFDM signals. In practice, OFDM should be employed with coded modulation for improving reliability, and bit-interleaved coded modulation (BICM) has been often combined with OFDM to gain robustness against severe fading channels. In this work, we propose a new BICM-OFDM system concatenated with TS for achieving good error performance. To this end, a novel soft-in-soft-out decoder for TS is developed. Optimization of the shaping convolutional code in terms of transmitter performance is also discussed. The effectiveness of our system is demonstrated through the analysis in terms of average mutual information as well as frame error rate (FER) over an additive white Gaussian noise channel. Furthermore, the FER is evaluated over a frequency-selective Rayleigh fading channel and compared with the theoretical outage probability. The simulation results reveal that our system can achieve good frequency diversity effect over such a fading channel while enjoying much lower PAPR.

Theoretical analysis of carrier heating effect in semiconductor optical amplifiers

This paper reports an accurate and simple analytical method to study carrier heating effect in semiconductor optical amplifiers using both Fermi–Dirac integrals of 3/2 and 1/2 orders. Global approximations for Fermi–Dirac integrals of 3/2 and 1/2 orders are adopted to obtain the analytical expression for the carrier temperature. The amplification of a single strong pico-second pulse having different peak powers is studied both with and without carrier heating effect. It has been found carrier heating impose more distortion on the amplified pulse, including suppressing the peak power value, increasing the peak temporal shift and broadening the bandwidth of amplified output signals. Also, when the input signal peak power or the pump current increases because of carrier heating effect the carrier temperature increases too. We have studied the amplification of 80 Gbit/s pico-second pulse sequences and found an increase in the peak value of the amplified output signal due to the pronounced fast gain recovery process induced by the carrier heating effect.

Extended nonlinear parametric process in anomalously pumped linear cavity oscillator

We demonstrate a linear cavity fiber optical parametric oscillator with extended pump-signal separation of 14.3 THz (116 nm). The signal laser is provided by a pair of 1675nm fiber Bragg gratings and a tunable idler from 1456.12 nm to 1462.48 nm is generated by detuning the pump wavelength in the anomalous dispersion regime of a highly nonlinear fiber. At such large pump-signal separation, we are still able to record a parametric conversion efficiency of more than -35 dB and idler optical signal-to-noise-ratio of 50 dB on average. The stability of the lasing signal and idler is examined and result shows both signal and idler peak power fluctuation is less than 1 dB over a period of 30 minutes.

Parasitic Stimulated Amplification in High-Peak-Power and Diode-Seeded Nanosecond Fiber Amplifiers

The broadband parasitic amplification in a diode-seeded nanosecond ytterbium-doped fiber laser amplifier system is numerically and experimentally investigated. The amplification is originated from a weak and pulsed parasitic signal associated with the 1064-nm seed diode laser. Although the average power of the parasitic pulse is less than 5% of the total seed laser power, a significant transient spike is observed during the amplification. In agreement with the simulation, nonlinear effects caused by the transient spike limits the scaling of signal peak power in fiber preamplifiers. With the utilization of a narrow bandwidth filter to eliminate the parasitic pulse, the power and energy scalability of a multistage diode-seeded fiber amplifier laser system has been significantly improved. At 1064 nm, pulses with the peak power of 120 kW and energy of 1.2 mJ have been successfully generated in the multistage Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fiber amplifier with an energy gain of 63 dB and 56% conversion efficiency. In viewing of the parasitic pulse's 8.8-nm bandwidth, it has the potential to become a novel seed source for high-peak-power fiber amplifiers.

Joint-level mechanics of the walk-to-run transition in humans.

Two commonly proposed mechanical explanations for the walk-to-run transition (WRT) include the prevention of muscular over-exertion (effort) and the minimization of peak musculoskeletal loads and thus injury risk. The purpose of this study was to address these hypotheses at a joint level by analysing the effect of speed on discrete lower-limb joint kinetic parameters in humans across a wide range of walking and running speeds including walking above and running below the WRT speed. Joint work, peak instantaneous joint power, and peak joint moments in the sagittal and frontal plane of the ankle, knee and hip from eight participants were collected for 10 walking speeds (30-120% of their WRT) and 10 running speeds (80-170% of their WRT) on a force plate instrumented treadmill. Of the parameters analysed, three satisfied our statistical criteria of the 'effort-load' hypothesis of the WRT. Mechanical parameters that provide an acute signal (peak moment and peak power) were more strongly associated with the gait transition than parameters that reflect the mechanical function across a portion of the stride. We found that both the ankle (peak instantaneous joint power during swing) and hip mechanics (peak instantaneous joint power and peak joint moments in stance) can influence the transition from walking to running in human locomotion and may represent a cascade of mechanical events beginning at the ankle and leading to an unfavourable compensation at the hip. Both the ankle and hip mechanisms may contribute to gait transition by lowering the muscular effort of running compared with walking at the WRT speed. Although few of the examined joint variables satisfied our hypothesis of the WRT, most showed a general marked increase when switching from walking to running across all speeds where both walking and running are possible, highlighting the fundamental differences in the mechanics of walking and running. While not eliciting the WRT per se, these variables may initiate the transition between stable walking and running patterns. Those variables that were invariant of gait were predominantly found in the swing phase.

Simulation investigation of a 160 Gbit/s all-optical data distributor based on cross-phase modulation in highly nonlinear fiber

Ultrafast-photonic logic circuits are crucial elements to perform ultrafast-optical signal processing functions in the next-generation ultrahigh-speed networks. A 160 Gbit/s all-optical data distributor based on cross-phase modulation in a single highly nonlinear fiber is investigated and demonstrated. The numerical calculation is conducted, and the result shows that the data distributor can be realized in 160 Gbit/s for the data signals of return-to-zero format with logical correctness and high quality. To evaluate the performance of the scheme, the Q-factor of the output signal on signal wavelength, the peak power of signals, the initial delay, and the filter position are calculated and discussed, respectively. The proposed data distributor is suitable for ultrafast applications for the emerging all-optical networks.

A Low PAPR Visible Light Communication System Employing SC-FDMA Technique

White light emitting diode (WLED) technology has been regarded as an environment-friendly lighting in the future. The WLED lighting system is able to provide short range wireless communication while illuminating rooms. The WLED based visible light communication (VLC) systems employing orthogonal frequency division multiplexing access (OFDMA) technique has been investigated in many researches. However, the OFDMA technique has the inherent high peak-to-average power ratio (PAPR). Such a VLC system with high peak power produces flickering light that can be detected by human eyes uncomfortably. In this paper, the application of single carrier frequency division multiplexing access (SC-FDMA) to VLC system is proposed and investigated. Because of the lower PAPR, the VLC system employing SC-FDMA technique outperforms comparable systems employing OFDMA, considered in terms of bit error rate performance under various practical considerations. Moreover, the proposed system also protects LED devices and human's eyes from the over-bright due to peak signal power. Computer simulations corroborate the analysis results in the paper.

Peak-Power Controlling Technique for Enhancing Digital Pre-Distortion of RF Power Amplifiers

In this paper, we present a method to limit the generation of signal peak power at the output of a digital pre-distorter that is applied to a RF power amplifier (PA) operating in strong compression. The method can be considered as a joint crest-factor reduction and digital pre-distortion (DPD). A challenging characteristic of DPD when applied to a PA in strong compression is the generation of relatively high peaks due to the DPD expansion behavior. Such high peaks generation, which may be physically unrealistic, can easily damage the amplification system. Such a phenomenon, referred in this study as DPD-avalanche, is more noticed when the signal exciting the PA is compressed due to crest-factor reduction. The suggested method for controlling such DPD-avalanche is based on shaping the input signal to the DPD in such a way to keep the pre-distorted signal peak power below or near the maximum allowed peak power of the PA. The suggested method is tested experimentally on a Class-AB and a Doherty PA when excited with a wideband orthogonal frequency-division multiplexing (OFDM) signal. Scenarios for an OFDM signal with and without crest-factor reduction are evaluated. Measurement results when using the proposed DPD-avalanche controller show smooth deterioration of the in-band and out-of-band linearity compared to steep deterioration when no controller is used. In addition, the suggested controller offers a higher operating power range of the DPD while fulfilling out-of-band distortion requirements and preserving low in-band error.

Limitation in the intrinsic method of EDFA gain optimization for 32 × 40 Gbit/s WDM systems

The gain flattening of the erbium doped fiber amplifier (EDFA) is one of the most important aspects in the EDFA which the gain is wavelength dependent. For the first time the limitation of EDFA gain optimizing for a 32-channel wavelength division multiplexing (WDM) systems is investigated and reported in this paper. In a 32-channel WDM system the most favorable flatness gain achieved was 23.16±1.51dB with an average noise figure of 5.70dB. This outcome proposes that the method does not achieve a uniform spectral gain in a 32-channel WDM system that incorporates a bandwidth of around 25nm. Based on the simulation results the intrinsic optimization of EDFA causes the poor SNR and peak signal power with great variation over a transmission distance of 480km single mode fiber.

Reducing the peak to average power ratio in OFDM systems

High peak to average power ratio of the transmit signal is a major drawback of OFDM systems. After defining the PAPR and analyzing its statistical properties, some of the most representative PAPR-reduction techniques available in the literature are reviewed in detail. Several methods have been proposed to reduce the peak power of OFDM signals. In this paper the effectiveness of some recently proposed methods has been evaluated. Key words: PAPR, OFDM, amplitude clipping, SLM.

SC-FDMA기술을 적용한 WLED 통신시스템

In this paper, a WLED communication system with SC-FDMA technique is proposed. OFDM is a promising technique to realize high-speed WLED communication system. However, because of the PAPR, the system performance can be significantly compromised by non-linear distortions in the transmission chain. Furthermore, the overload current due to peak signal power lead the WLED equipment over bright which is harmful to equipment life and human‘s eye. The novel WLED communication system proposed in this paper solved these problems by using SC-FDMA technique which has an inherent low PAPR property. The severity of PAPR performances expressed by CCDF curve and the BER performances under different modulation schemes are analyzed in this paper.

High peak power eye-safe intracavity optical parametric oscillator pumped by a diode-pumped passively Q-switched ND:GGG laser

By exploiting the diode-end-pumped Nd:GGG/Cr4+:YAG laser as the pump source, a high peak power gray-trace resistance KTP intracavity optical parametric oscillator at eye-safe wavelength was first demonstrated (to our knowledge). Under the incident diode power of 10 W, the maximum average output power of 320 mW at 1567 nm was obtained with the T = 33% output coupler. The corresponding signal pulse width and repetition rate were respectively 1.4 ns and 5.8 kHz. Due to the greatly reduced pulse repetition rate and short pulse width, the signal peak power was estimated to be as high as 39.4 kW.

Efficiency-Improved High-Voltage Analog Power Amplifier for Driving Piezoelectric Actuators

A novel high-voltage analog power amplifier derived from a well-known complementary class B amplifier is presented in this paper. The amplifier offers improved efficiency when driving capacitive loads such as piezoelectric multilayer actuators, while maintaining a high level of signal quality, peak power and low electromagnetic radiation. The main drawback of a class B amplifier in comparison to other power amplifiers is low efficiency, resulting in extensive power-loss in the two complementary transistors of the amplifier stage. Power-loss can be reduced by minimizing the voltage drop across the collector-emitter path of the transistors when a high collector current occurs. The proposed circuit uses an additional capacitor to recover up to one half of the charge stored in the actuator whenever the actuator is being discharged. The capacitor offers an additional power supply rail next to the positive and negative supply voltage of the amplifier stage. Switching the power supply net of the power transistors between the different supply rails, in order to reduce the voltage drop across the transistors, minimizes power-loss. The development of the amplifier was triggered by the introduction of a new piezoelectric motor and the requirements concerning signal quality and electromagnetic radiation. Therefore, in this paper, the circuit is analyzed using application-specific sinusoidal control signals which are used to drive the motor. Following the analytical investigation of the circuit, the amplifier is tested in an experiment measuring power consumption with a pure reactive load, and the level of distortion caused by the amplifier. In the experiment, a power-loss reduction of 47% was achieved in comparison with a class B stage. The amplifier processed a peak power of 160 W. The proposed amplifier showed total harmonic distortion of THD = 0.60% maximum. Distortions of a pure class B amplifier in the same setup were measured at THD = 0.25% .

Validity of the Additive White Gaussian Noise Model for Quasi-Linear Long-Haul Return-to-Zero Optical Fiber Communications Systems

In this paper, we study the validity and limitations of the additive white Gaussian noise (AWGN) model in quasi-linear, long-haul, return-to-zero, direct-detection optical fiber communications systems. Our approach is to compare bit-error ratios (BERs) computed using the additive white Gaussian noise method to those obtained using standard and multicanonical Monte Carlo (MMC) simulations and to a noise-linearization method, referred to as the noise covariance matrix (NCM) method. We show that the AWGN method provides a very good approximation to the actual system BER for power levels and dispersion profiles that are used in typical modern-day quasi-linear systems. For example, the BER obtained using the AWGN method is within a factor of 4 of the actual system BER computed using MMC simulations for a realistic 10 Gb/s, 6000 km system based on dispersion-shifted fiber in which the peak signal power at the transmitter is 1 mW and the absolute residual dispersion at the receiver is less than 200 ps/nm. However, when the peak power is increased to about 4 mW, or the average map dispersion is zero and the absolute residual dispersion exceeds 200 ps/nm, the AWGN and NCM methods may simultaneously breakdown due to a combination of nonlinear signal-noise and noise-noise interactions during transmission. In addition, for a 5000 km system based on low-nonlinearity <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sub> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sub> fiber with an average map dispersion that is 4% of the dispersion variation within the map, and that operates at a peak power of 5 mW, we find that the BERs obtained using the AWGN and NCM methods are about 500 times smaller than the actual system BER computed using MMC simulations.

Brightness enhancement in a high-peak-power cladding-pumped Raman fiber amplifier

We demonstrate a cladding-pumped Raman fiber amplifier (CPRFA) whose brightness-enhancement factor depends on the cladding-to-core diameter ratio. The pump and the signal are coupled independently into different input arms of a pump-signal combiner, and the output is spliced to the Raman amplifier fiber. The CPRFA generates 20 microJ, 7 ns pulses at 1100 nm at a 2.2 kHz repetition rate with 300 microJ (25.1 kW peak power) of input pump energy. The amplified signal's peak power is 2.77 kW, and the brightness-enhancement factor is 192--the highest peak power and brightness enhancement achieved in a CPRFA at any wavelength, to our knowledge.

Compact low threshold Cr:YAG passively Q-switched intracavity optical parametric oscillator

We report a compact KTP-based intracavity optical parametric oscillator (IOPO) driven by a diode-end-pumped passively Q-switched Nd:YVO4/Cr:YAG laser. For the first time, we take the thermal lens effect of the Cr:YAG into consideration and discuss its impact on the signal output. Diode pump threshold as low as 0.52W has been achieved, which is the lowest result reported to date. At the incident diode pump power of 4W, we obtained the maximum signal average and peak power of 358mW and 12.5kW, respectively, corresponding to a diode-to-signal conversion efficiency of 9%. Moreover, cavity-dumping characteristic and pulse transforming process from 1064 to 1573nm are qualitatively analyzed.

A Compact 6.5-W PHEMT MMIC Power Amplifier for Ku-Band Applications

A compact 6.5-W AlGaAs/InGaAs/GaAs PHEMT monolithic microwave integrated circuit (MMIC) power amplifier (PA) for Ku-band applications is proposed. This two-stage amplifier with chip size of 8.554mm2 (3.64mmtimes2.35mm) is designed to fully match 50-Omega input and output impedance. Under 8V and 2000mA dc bias condition, the PA deliver 38.1dBm (6.5W) saturated output power, 10.5-dB small signal gain and peak power added efficiency of 24.6% from 13.6 to 14.2GHz. This MMIC also achieved the best power densities (760mW/mm2) at Ku band reported to date

Grating-based 40-Gbit/s optical code-division multiplexing system incorporating a nonlinear amplifying loop mirror

Abstract. A seven-chip, 280-Gchip/s OCDM system incorporating qua-ternary phase coding and decoding is experimentally demonstrated. Theencoder and decoder, consisting of superstructured fiber Bragg gratings,are fabricated using the equivalent-phase-shift method; only ordinaryphase masks and submicrometer precision in control are required. Inter-channel interference noise is also considered and evaluated; 40-Gbit/s2-channel multiplexing is demonstrated. In addition, a nonlinear ampli-fying loop mirror NALM within the receiver is introduced to improve thesystem performance under two-channel operation. Switching is obtainedfor peak signal power less than 10 mW. We show that the NALM can actas a nonlinear processing element capable of reducing both the pedestalassociated with conventional matched filtering and the width of the as-sociated code recognition pulse. © 2007 Society of Photo-Optical InstrumentationEngineers. DOI: 10.1117/1.2424917 Subject terms: optical code-division multiplexing; superstructured fiber Bragggrating SSFBG ; all-optical encoding and decoding; equivalent phase shift; non-linear amplifying loop mirror .NALMPaper 060430R received Jun. 6, 2006; revised manuscript received Jul. 18, 2006;accepted for publication Jul. 20, 2006; published online Jan. 5, 2007.