Signal Peak Power Research Articles

Measurement and Data Correction of Channel Sampling Timing Walk-Off of Photonic Analog-to-Digital Converter in Signal Recovery.

A two-channel, time-wavelength interleaved photonic analog-to-digital converter (PADC) system with a sampling rate of 10.4 GSa/s was established, and a concise method for measuring and data correcting the channel sampling timing walk-off of PADCs for signal recovery was proposed. The measurements show that for the two RF signals of f1 = 100 MHz and f2 = 200 MHz, the channel sampling timing walk-off was 12 sampling periods, which results in an ENOB = -0.1051 bits for the 100 MHz directly synthesized signal, while the ENOB improved up to 4.0136 bits using shift synthesis. In addition, the peak limit method (PLM) and normalization processing were introduced to reduce the impacts of signal peak jitter and power inconsistency between two channels, which further improve the ENOB of the 100 MHz signal up to 4.5668 bits. All signals were analyzed and discussed in both time and frequency domains. The 21.1 GHz signal was also collected and converted using the established two-channel PADC system with the data correction method, combining the PLM, normalization, and shift synthesis, showing that the ENOB increased from the initial -0.9181 to 4.1913 bits, which demonstrates that our method can be effectively used for signal recovery in channel-interleaved PADCs.

METHOD OF MINIMIZATION SIDELOBES LEVEL AUTOCORRELATION FUNCTIONS OF SIGNALS WITH NON-LINEAR FREQUENCY MODULATION

Context. At present, when creating new and upgrading existing radar systems, solid-state generator devices are widely used, which imposes certain restrictions on the peak power of probing signals. To overcome this limitation, longer duration signals with internal pulse modulation are used. The main efforts of the researchers are focused on reducing the maximum level of the side lobes of the autocorrelation function of such signals, which, without taking additional measures, has a significant level, which complicates the work of systems for detecting and stabilizing the level of false alarms. Attention is paid to signals with non-linear frequency modulation, which consist of two and three linearly frequency-modulated fragments. The maximum level of the side lobes of such signals depends significantly on the frequency-time parameters of the fragments, and therefore it is very difficult to obtain its stable value. Searching for signals with minimal side lobe level values by optimizing their time-frequency parameters is a difficult task, because changing the parameters of previous signal fragments leads to changes in the parameters of subsequent fragments
 Objective. The aim of the work is to develop a method for simplifying the search for local minima of the level of side lobes of two- and three-fragment signals with nonlinear frequency modulation by using a modified mathematical model with a whole number of periods of radio oscillations of linear-frequency modulated fragments.
 Method. The developed method is based on the proposed modification of the mathematical model, which corrects the frequencytime parameters of two- and three-fragment signals with non-linear frequency modulation by modifying the values of the frequency modulation speed while providing an integer number of complete periods of radio frequency oscillations for each of the fragments, which simplifies the process of finding local minima of the level of side lobes.
 Results. Modification of the initial mathematical model leads to the expansion of the possible range of values of frequency-time parameters, ratios of durations and frequency deviations of linearly-frequency modulated fragments and ensures stability of the mathematical model with a decrease in the maximum level of side lobes of the autocorrelation function.
 Conclusions. It has been experimentally confirmed that the use of the proposed method of modifying the input frequency-time parameters of signals with non-linear frequency modulation in the vast majority of cases reduces the maximum level of side lobes and simpli-fies the process of finding its local minima. The optimal ratios of durations and deviations of the frequency of the signal frag-ments are determined, subject to these, stable operation of the models is ensured and, in most cases, - less than the value of the maximum level of the side lobes.

Real-time online monitoring technology for sweeping frequency ultrasound (SFU) assisted extraction of amur grape (Vitis amurensis) seed oil

Sweeping frequency ultrasound (SFU) was used to assist extraction of amur grape (Vitis amurensis) seed (AGS) oil. Extraction conditions and physicochemical properties were optimized and analyzed under different extraction methods. Meanwhile, frequency and time domains were online monitored during SFU assisted extraction of AGS oil. PVDF piezoelectric sensor was used in time domain, and the hydrophone in frequency domain, so as to obtain the time–voltage waveform, signal power, spectrum distribution and other visual models. Physical models of the spatial peak acoustic intensity, charge quantity and work done by electric field force under different ultrasonic conditions were derived. The mathematical model between the work done by electric field force and the spatial peak acoustic intensity under the working state of PVDF piezoelectric sensor was constructed. Results show that the content of AGS oil by SFU assisted extraction was higher than that by organic extraction. Furthermore, the optimal single-frequency was 40 kHz and dual-frequency was 28/33 kHz, and SFU extraction time of 30 min was suitable with higher oil yield of 16.70 % and 16.94 %, respectively. In addition, the selection and combination of SFU also affected the oil oxidation degree. The peak voltage, spatial peak acoustic intensity, signal power and work of electric field force at 28/33 kHz were all higher than those at 40 kHz.

A CA and ML approach for M-MIMO optical non-orthogonal multiple access power efficiency

Abstract The non-orthogonal multiple access (NOMA) multiple access approach can be used in future wireless communication systems to support massive connections and increase spectrum efficiency. Because user signal intensities and interference levels vary, precise channel assessment is essential in NOMA. Optimal power allocation and decoding order are made possible by precise algorithms, increasing system effectiveness and performance. However, NOMA can be adversely impacted by high peak-to-average power ratio (PAPR) values, leading to worsened system performance and more complex power amplifiers. In order to solve this issue, this paper recommends PAPR reduction in NOMA using companding methods for 512, 256, and 64 sub-carriers. Nonlinear companding techniques, such as MA and A-law companding, can efficiently reduce the high peak power of NOMA signals while reducing distortion and enhancing overall system dependability. The effectiveness of the proposed companding methods is evaluated using simulations, and the results demonstrate a significant decrease in PAPR, ensuring higher bit error rate (BER) effectiveness and transmission resilience in NOMA-based communication systems. The proposed approach is compared to the traditional Ml (C- Ml) and A-Law (C- A-Law).

Зменшення відношення пікової до середньої потужності за допомогою алгоритму компандування для NOMA сигналу

Майбутні системи бездротового зв’язку можуть підтримувати величезну кількість з’єднань і підвищити ефективність використання спектра завдяки використанню підходу неортогонального множинного доступу NOMA (non-orthogonal multiple access). Однак високі рівні відношення пікової до середньої потужності PAPR (Peak-to-Average Power Ratio) можуть негативно впливати на NOMA, що призводить до зниження продуктивності системи та ускладнення підсилювачів потужності. У цьому дослідженні пропонується зменшити PAPR в NOMA, використовуючи методи компандування для 512, 256 і 64 піднесучих з метою вирішення цієї проблеми. Висока пікова потужність сигналів NOMA може бути ефективно стиснута за допомогою нелінійних методів компандування, таких як ущільнення за μ-законом і A-законом, що зменшує спотворення і покращує загальну надійність системи. Для оцінки ефективності запропонованих методів компандування використано моделювання, результати якого свідчать про значне зменшення PAPR, що забезпечує підвищення ефективності коефіцієнта бітових помилок BER (Bit Error Rate) та стійкості передачі в системах зв’язку на основі NOMA. Запропонований метод порівнюється з традиційними A-законом (C-A-law) та μ-законом (C-μ-law).

Signal strength in FSO communication channels based on directly measured modulated laser with dual drive Mach–Zehnder modulators (MZMs) measured

Abstract The work clarified directly measured modulated laser with dual drive measured Mach–Zehnder modulators for signal strength in free space optics (FSO) channel. Peak power after free space communication channel at various propagation distances is measured in the optical time domain. As well as the signal level amplitude quality and data error rates after light detector at various propagation distances are also measured in the time bit period. The directly measured modulated laser with dual drive measured Mach–Zehnder modulators for signal strength in FSO communication channels is stimulated with optisystem program version 13. Peak signal power after free space communication channel at various propagation distances is measured in the optical time domain. The optimum peak signal power is achieved at 10 km distance with a value of 4.328 W. The signal level amplitude quality and data error rates after light detector at various propagation distances are also measured in the time bit period. The optimum Q level and BER level are clarified at 10 km distance with the values of 23.1164 for signal quality and 1.439 × 10−118 for minimum data error rates.

Different mode operations based all optical fiber amplifiers with optical differential polarization quadrature phase shift keying transmitter

Abstract This paper simulated the different mode operations based all optical fiber amplifiers with optical differential polarization quadrature phase shift keying transmitter. Gain mode operation, power mode operation and saturation mode operation based all optical fiber amplifiers are employed to measure the signal power, noise power level at both spectral time domain and frequency domain. The peak signal power and signal power amplitude are accurately measured for different mode operations based all fiber optical amplifiers. The performance is enhanced with saturation mode operation based all optical fiber amplifiers.

Tunable narrow-linewidth high-peak-power sub-nanosecond optical parametric generator by injection seeding.

We present an efficient tunable optical parametric generator (OPG) with its linewidth close to the Fourier transform limit by injection seeding a tunable diode laser. Benefitting from high-peak-power sub-nanosecond (426 ps) laser pumping and a high-gain MgO:PPLN (PPMgLN) crystal, the OPG produced signal peak power up to 0.343 MW at 1638 nm and the total conversion efficiency reached 47.9% at 1-kHz pulse repetition rate. Considering the linewidth limit of short signal pulses (∼ 350 ps), a tunable seeder with the linewidth at hundred-MHz level was applicable. The achieved OPG signal tuning range was 1510-1638 nm with linewidth at GHz level, which is two orders of magnitude narrower than the unseeded OPG. Injection seeding a non-resonant OPG device does not introduce extra cavity feedback electronics that are essential for an optical parametric oscillator (OPO), greatly improving robustness and reducing cost. It is believed such a compact, tunable and costless PPMgLN OPG with high peak power, high repetition rate and relatively narrow linewidth has great significance in lidar, spectroscopy, etc.

Efficient MW-peak-power kHz-repetition-rate sub-nanosecond optical parametric generator tunable from near- to mid-infrared

A high-efficiency, high-peak-power, widely tunable optical parametric generator (OPG) based on a multi-period MgO-doped periodically poled lithium niobite (PPMgLN) crystal is presented. Pumped by a passively Q-switched microchip Nd:YAG laser with the pulse duration of 330 ps and repetition rate of 1 kHz, the OPG could be continuously tuned from 1399 nm to 4443 nm by changing the grating period and working temperature. The total output power of the signal and idler waves reached 591 mW, corresponding to the conversion efficiency of 67.2% and slope efficiency of 89.6%, the highest as far as we know. The maximum signal peak power was over 1.6 MW at 1758 nm. The evolution of line width and beam profile of the signal wave during wavelength tuning were also studied and the theoretical models were proposed.

Improved joint subcarrier and power allocation to enhance the throughputs and user fairness in indoor OFDM-NOMA VLC systems.

Orthogonal frequency division multiplexing non-orthogonal multiple access (OFDM-NOMA) is a promising multi-user access scheme in indoor visible light communication (VLC) systems. In this paper, we propose three novel joint subcarrier and power allocation algorithms in OFDM-NOMA-VLC to improve the throughputs and/or user fairness. These three proposed algorithms address the requirements in fairness-throughput-balanced (FTB), fairness-first (FF), and throughput-first (TF) scenarios, respectively. All of them improve the objective function in the previous joint allocation algorithm and ensure the fairness of users in terms of their overall throughput, rather than that in every subcarrier that is tight and redundant. The designs using the proposed algorithms also exhibit reduced peak-to-average power ratios (PAPRs) and so the average signal power can be better used to further enhance the throughput when the system is limited by the signal peak power. Simulations verify that the proposed algorithms are superior to the previous joint subcarrier and power allocation algorithm as well as the conventional fixed power allocation (FPA) and gain ratio power allocation (GRPA) algorithms. The performance improvement of the proposed algorithms is particularly greater for a larger number of multiplexed users per subcarrier or a larger number of OFDM subcarriers, under which the PAPRs of designs using conventional algorithms are higher. When the total user number, the number of the multiplexed users per subcarrier, and the number of subcarriers are 5, 2, and 16, respectively, the throughputs of the three proposed algorithms are 62.17%, 53.35%, and 67.25% higher than the conventional joint allocation algorithm, while the user fairness is improved by 4.64%, 7.87%, and degraded by 20.71%, respectively. Therefore, the three proposed algorithms can address the requirements in FTB, FF, and TF scenarios, respectively.

Gaussian Pulse Characterization of RF Power Amplifiers

This work presents a new RF power amplifier characterization technique based on a Gaussian pulse, which is shown to approximate the envelope of a multicarrier signal with 0.5% error around the peaks. The standard deviation of the Gaussian pulses is inversely proportional to the I/Q signal bandwidth. This test signal is shown to accurately capture nonlinear memory effects that result in gain dispersion after the peak power is reached. As an example, it is shown that the gain amplitude and phase can vary up to 2.3 dB and 6° for a 10-W 3.75-GHz GaN power-amplifier evaluation board, depending on the I/Q signal bandwidth and peak power level.

A PAPR Reduction Technique for Fast Touch Sensors Adopting a Multiple Frequency Driving Method on Large Display Panels.

The multiple frequency driving method (MFDM) capacitive touch system (CTS), which drives transmit (TX) electrodes in parallel, has been developed to improve the touch-sensitivity of large touch screens at high speed. However, when driving multiple TX electrodes at the same time, TX signals are merged through the touch panel, which results in increasing the peak-to-average power ratio (PAPR) of combined signals. Due to the high PAPR, the signal is distorted out of the power amplifier’s linear range, causing a touch malfunction. The MFDM CTS can avoid this problem by reducing the drive voltage or partially driving the TX electrodes in parallel. However, these methods cause a significant performance drop with respect to signal-to-noise ratio (SNR) in the MFDM systems. This paper proposes a stack method which reduces PAPR effectively without the performance degradation of MFDM and achieves real-time touch sensitivity in large display panels. The proposed method allocates a suitable phase for each TX electrode to reduce the peak power of combined signals. Instead of investigating all of the phases for the total number of TX electrodes, the optimal phase is estimated from the highest frequency to the lowest one and fixed one by one, which can reduce the required time to find a suitable phase considerably. As a result, it enables high-speed sensing of multi-touch on a large touch screen and effectively reduces PAPR to secure high signal-to-noise-ratio (SNR). Through experiments, it was verified that the proposed method in this paper has an SNR of 39.36 dB, achieving a gain of 19.35 and 5.98 dB compared to the existing touch system method and the algorithm used in the communication system, respectively.

ПОВЫШЕНИЕ ПОМЕХОЗАЩИЩЕННОСТИ ПЕРЕДАЧ ДЕКАМЕТРОВЫХ РАДИОКАНАЛОВ В УСЛОВИЯХ НЕПРЕДНАМЕРЕННЫХ ПОМЕХ

The transmission of messages is a complex process, which is largely determined by the properties of the radio channel used. Decameter radio channels are the most difficult for organizing communication, since the ionospheric propagation of radio waves is associated with their significant attenuation, due to the significant length of the paths, as well as the presence of Rayleigh fading in the channel. However, the possibility of transmitting information over long distances without serious resource costs stimulates further research to improve the reliability of decameter radio communication. In this paper, we investigate the possibility of increasing the noise immunity of frequency-shift keying transmissions of decameter radio channels in conditions of unintentional interference due to the use of broadband signals. An analytical expression of the dependence of the probability of a bit error on the level of the ratio of the peak signal power to the peak interference power is considered; a graph of this dependence is presented. It is shown that the plot is consistent with the overall noise immunity estimate for Rayleigh fading channels using double FSK signals. The rationality of methods for obtaining the required reception quality in decameter radio channels is analyzed. It is shown that the most rational direction for increasing the noise immunity of FM-2 transmissions in decameter radio channels with Rayleigh fading in conditions of unintended interference is the use of broadband signals. In this case, for expansion, it is advisable to choose a value kf = 7, which makes it possible to increase the noise immunity by 9 dB. The conclusions are illustrated by graphs.

Fabry Perot laser properties with high pump lasers for upgrading fiber optic transceiver systems

Abstract The work has outlined the Fabry Perot laser properties with high pump lasers for upgrading fiber optic transceiver systems. The physical structures of the light source are taken into account such as active layer length and active layer width. High pump laser is used for providing strength to the signal through the transmission/reception stages. Peak and minimum signal power levels are measured in the spectral frequency domain and time domain. Signal amplitude level margin is also measured with the optimum physical parameters of the light source. The optimum operation system performance efficiency is achieved with an active layer length of 0.06 cm, and active layer width suitable is 1.5 × 10−4 cm.

DFT-Spread OTFS Communication System with the Reductions of PAPR and Nonlinear Degradation

The orthogonal time frequency space (OTFS) system with two-dimensional (2-D) modulation technique is an attractive technology to show the better performance than the conventional orthogonal frequency division multiplexing (OFDM) system, particularly in the high-speed vehicle communications and high-level dimensions of multiple-input multiple-output systems. However, the OTFS system has high peak-to-average power ratio (PAPR), like OFDM system. In this paper, we analyze the PAPR characteristics of the OTFS signal and propose a concept of discrete Fourier transform (DFT)-Spread OTFS system to reduce the PAPR efficiently. The key idea of the DFT precoding technique is to spread the energy of a subcarrier throughout the subcarriers. Therefore, the PAPR is decreased. In the practical wireless communication systems, the power efficiency could become worse, or the bit error rate (BER) is seriously degraded by the high peak signal power in a high power amplifier (HPA). So, by reducing the PAPR, the efficiency of the HPA can be significantly improved and the nonlinear distortion caused by HPA can be decreased, too. We evaluate the spectrum characteristics of conventional OFDM and OTFS schemes and the proposed DFT-Spread OTFS scheme according to the different nonlinear conditions of HPA. Simulation results demonstrate that the power spectrums of the proposed system are less sensitive than the conventional schemes in HPA nonlinear environments. In addition, we compare the uncoded BER performance among the different schemes over the AWGN and delay-Doppler channels according to the several HPA nonlinear conditions for the different mobility speeds of user equipment. The BER performance of the conventional OFDM system breaks down completely in high-mobility scenarios for both HPA linear and nonlinear conditions. The proposed scheme improves the BER performance over AWGN and delay-Doppler channels in HPA nonlinear environments, as compared to the conventional OTFS system. In high-mobility scenarios and at BER of $$1 \times 10^{ - 3}$$ , simulation results verify that the OTFS and our proposed scheme can achieve a gain of 12.8 dB compared to OFDM scheme. Moreover, the proposed DFT-Spread OTFS scheme can be reduced PAPR by 2.2 dB and 1.8 dB compared to OFDM and OTFS schemes, respectively.

An Iterative Deconvolution-Time Reversal Method with Noise Reduction, a High Resolution and Sidelobe Suppression for Active Sonar in Shallow Water Environments

Matched filtering is widely used in active sonar because of its simplicity and ease of implementation. However, the resolution performance generally depends on the transmitted waveform. Moreover, its detection performance is limited by the high-level sidelobes and seriously degraded in a shallow water environment due to time spread induced by multipath propagation. This paper proposed a method named iterative deconvolution-time reversal (ID-TR), on which the energy of the cross-ambiguity function is modeled, as a convolution of the energy of the auto-ambiguity function of the transmitted signal with the generalized target reflectivity density. Similarly, the generalized target reflectivity density is a convolution of the spread function of channel with the reflectivity density of target as well. The ambiguity caused by the transmitted signal and the spread function of channel are removed by Richardson-Lucy iterative deconvolution and the time reversal processing, respectively. Moreover, this is a special case of the Richardson-Lucy algorithm that the blur function is one-dimensional and time-invariant. Therefore, the iteration deconvolution is actually implemented by the iterative temporal time reversal processing. Due to the iterative time reversal method can focus more and more energy on the strongest target with the iterative number increasing and then the peak-signal power increases, the simulated result shows that the noise reduction can achieve 250 dB in the “ideal” free field environment and 100 dB in a strong multipaths waveguide environment if a 1-ms linear frequency modulation with a 4-kHz frequency bandwidth is transmitted and the number of iteration is 10. Moreover, the range resolution is approximately a delta function. The results of the experiment in a tank show that the noise level is suppressed by more than 70 dB and the reverberation level is suppressed by 3 dB in the case of a single target and the iteration number being 8.

Signal-Noise Interaction in Optical-Fiber Communication Systems Employing Nonlinear Frequency-Division Multiplexing

We address the properties of nonlinear-Fourier-transform (NFT)-based fiber-optic communications systems and, particularly, study how the presence of noise deteriorates the performance of these systems. Similarly to the case of linear Fourier modes evolving independently under the action of chromatic dispersion alone, NFT-based systems employ so-called ``nonlinear modes,'' forming a nonlinear spectrum, as data carriers, and these nonlinear modes evolve independently in an uncoupled manner under the joint action of nonlinearity and dispersion. However, the influence of amplified-spontaneous-emission (ASE) noise on these nonlinear modes is still relatively poorly studied. In this paper, dealing with a continuous nonlinear spectrum, we scrutinize the properties of the effective noise emerging in the nonlinear Fourier domain. We also show that in the transmission stages, where the signal peak power is relatively high (e.g., at the receiver, in back-to-back transmission, or at short distances), the performance of an NFT system is mostly degraded not by the inline ASE noise, but by the imperfections of the digital sampling and the forward and backward NFT algorithms, i.e., by the NFT processing noise.

Design of an Efficient Pulsed Dy3+: ZBLAN Fiber Laser Operating in Gain Switching Regime

A time-dependent numerical model of a dysprosium-doped ZBLAN glass fiber is developed in order to design a pulsed laser emitting at about 3 $\mu \text{m}$ wavelength, by employing an in-band pumping scheme. A number of design parameters are changed to optimize the laser performance. Gain-switching regime with an output signal peak power close to 59 W and a full width at half maximum pulse duration shorter than 184 ns is simulated for a fiber with dopant concentration of 2000 ppm, by employing a pulsed input pump with a peak power of 5 W and a repetition rate of 100 kHz at the wavelength of 2.8 $\mu \text{m}$ . These characteristics are very promising and theoretically predict the feasibility of a laser, which can find application in many areas such as chemical, biological, and environmental monitoring.

All-optical logic NOR gate using a single quantum-dot SOA-assisted an optical filter

We thoroughly explore the characteristics of an ultrafast all-optical NOR gate for 160 Gb/s return-to-zero Gaussian data signals using a single quantum-dot semiconductor optical amplifier (QD-SOA) and an optical filter (OF). In this proposed scheme, we employ an optical clock signal as a probe in addition to data signals as pumps between which the Boolean NOR function is executed. By conducting numerical simulations, we investigate and evaluate the effects of various critical factors on the extinction ratio and Q2-factor. This enables us to specify the margins of clock wavelength, peak power of data and clock signals, current density, electron relaxation time from the excited state to the ground state, linewidth enhancement factor, small signal gain of QD-SOA, OF bandwidth and order, the permissible extent of arrival time difference between data signals and clock, and the effect of amplified spontaneous emission. Moreover, we demonstrate that the proposed device can be applied to a multiple-input NOR gate. The results show that the proposed NOR gate can be achieved with both logical correctness and high quality when the specified conditions are satisfied.

On the skilled plantar flexor motor action and unique electromyographic activity of ballet dancers.

The study aimed to compare the ability of dance and non-dance subjects to perform fine control of a simple heel-raising/lowering movement, and to determine if there are any differences in motor unit activity in the primary plantar flexor muscles during the movement. Subjects were instructed to accurately track a sinusoidal trace with a heel-raising and lowering movement at four controlled frequencies (1, 0.5, 0.25, and 0.125Hz). The ankle joint angle was used to characterize movement errors from the target. Surface electromyography was recorded from the soleus and medial gastrocnemius muscles. One trial including five sinusoidal traces was divided into two phases: an up phase and a down phase. To characterize motor unit activity of the plantar flexor muscles, a wavelet transform was applied to electromyographic signals recorded in each phase. For both phases, errors in movement accuracy were lower in dancers than in controls (8.7 ± 4.6 vs. 11.5 ± 6.8%, P < 0.05) regardless of the frequency of the sinusoidal wave traced. During the down phase, peak power of soleus electromyographic signals at ~ 10Hz was statistically larger in control subjects than in dancers (10.4 ± 0.7 vs. 6.3 ± 0.4% total power, P < 0.05). These results indicate that dancers have a higher degree of motor skill in a heel raise tracking task and exhibit adaptations in the motor unit activity during skilled dynamic movements.