Suppression of Frequency Modulation to Amplitude Modulation Conversion with Modified Group Velocity Dispersion Compensation Device in the Front End of High-Power Lasers

The group velocity dispersion (GVD) occurring in the front end of high-power lasers is one of the primary factors leading to the conversion of frequency modulation (FM) to amplitude modulation (AM). In this paper, we propose a modified, active, closed-loop feedback compensation device for GVD-induced FM–AM conversion, using a two-dimensional, electric, adjustable mirror mount and parallel grating pair to improve the long-term stability, efficiency of adjustment, and accuracy of compensation. Experimental results of a 12 h FM–AM depth test revealed that the depth varied between 2.28% and 5.22%. Moreover, we formulated a mathematical relationship between the dispersion parameters and temperature in optical fibers to analyze the intrinsic effect of temperature on FM–AM. The related simulation and experimental results consistently validated the quantitative relationship between the temperature and FM–AM depth.

Vocal traits of shorebird chicks are related to body mass and sex

Acoustic communication is critical during early life phases in precocial birds. For example, adult alarm calls can elicit antipredator behaviour in young, and chick vocalisations can communicate information to parents about chick identity, condition, location, sex, or age. We investigated whether chick calls of two species of Australian Charadriidae vary with sex or body mass. We handled Red-capped Plover Charadrius ruficapillus and Southern Masked Lapwing Vanellus miles novaehollandiae chicks for purposes of measurement, blood sampling, and banding. We opportunistically recorded their distress calls while in the hand, and analysed the calls to determine whether call structure is related to sex or body mass (a proxy for age). We measured five traits per call, plus time intervals between successive calls, for 26 plover chicks (2600 calls) and 95 lapwing chicks (6835 calls). In plovers, inter-call intervals were shorter in males and both inter-call interval and the dominant frequency range of calls decreased with increasing body mass. In lapwings, frequency modulation (computed as the range in the rate of change of the dominant frequency) was lower in male calls. The dominant frequency range of lapwing calls decreased with mass in both sexes, but the decline was greater in males, resulting in a lower dominant frequency range in males. Frequency modulation and entropy of lapwing calls also decreased with increasing body mass. Minimum dominant frequency did not change with body mass or sex in either species. Our study provides the first evidence for charadriid chicks of (a) a sexual difference in call structure and rate and (b) gradual growth-related changes in call structure and rate, across chicks. Studies on calls from a greater range of chick ages and from more species within this large and diverse family would be valuable. We provide a foundation for further studies of shorebird vocalisations during growth, which may elucidate the development and functional significance of such vocalisations.

CHARACTERISTICS OF Μ-RHYTHM FREQUENCY MODULATION UNDER IMAGINARY MOVEMENTS

The aim of the paper is to assess the phenomena of EEG frequency modulation while performing real and imaginary movements necessary for BCI control. Materials and Methods. The study enrolled a group of 30 volunteers of both sexes, aged 17 to 23. The subjects had to execute four commands and to run them randomly following the program instruction. The experiment was carried out in two ways: physically and mentally. Firstly, each command corresponded to a certain subject’s movement. Secondly, the same commands were not performed, they were only imaginary. The command was considered successfully executed if a volunteer was able to follow the program instruction and to hold the position for 2 seconds. The analysis of the results was carried out for five frequency ranges: 7–10 Hz, 9–12 Hz, 12–15 Hz, 15–20 Hz, 20–25 Hz. Results. Correlation analysis and exploratory statistics (namely, correspondence analysis and cluster analysis) were used to process the generated electroencephalographic parameters. The actually performed subjects’ movements were associated with a high number of low-frequency modulations in the 12–20 Hz range in the absence of modulating influences in the range below 12 Hz. Pronounced patterns of high-frequency modulation were peculiar for unexecuted commands. Conclusion. The results of the correlation analysis demonstrate a positive relationship between the number of cases of high-frequency modulation in the range of 9–12 Hz with the number of cases of low-frequency modulation in all other studied signal ranges in case of successful command execution. Key words: brain-computer interface, μ-rhythm, frequency modulation, EEG. Цель – оценка феноменов частотной модуляции ЭЭГ в условиях выполнения реальных и воображаемых движений, необходимых для управления ИМК. Материалы и методы. Для получения данных была сформирована группа из 30 добровольцев обоих полов в возрасте от 17 до 23 лет. Участники эксперимента должны были выполнить четыре команды и повторить их в неизвестном для них порядке, заданном программой. Эксперимент проводился двумя способами: физически и мысленно. То есть при первом способе каждая команда соответствовала определенному движению человека, при втором те же команды выполнялись воображаемо, движение представлялось мысленно. Команда считалась успешно исполненной, если добровольцу удавалось повторить и удержать заданное программой положение в течение 2 с. Анализ результатов проводился для пяти частотных диапазонов: 7–10 Гц, 9–12 Гц, 12–15 Гц, 15–20 Гц, 20–25 Гц. Результаты. Сгенерированные электроэнцефалографические показатели обрабатывались методом корреляционного анализа и методами разведочной статистики, такими как анализ соответствий и кластерный анализ. Реально выполняемые движения испытуемых связаны с высоким количеством низкочастотных модуляций в диапазоне 12–20 Гц при отсутствии модулирующих влияний в диапазоне ниже 12 Гц. Для случаев невыполнения команд характерны выраженные паттерны высокочастотной модуляции. Выводы. Результаты корреляционного анализа демонстрируют положительную связь между числом случаев высокочастотной модуляции в диапазоне 9–12 Гц с числом случаев низкочастотной модуляции во всех других исследуемых диапазонах сигнала в случае успешного выполнения команд. Ключевые слова: интерфейс «мозг – компьютер», μ-ритм, частотная модуляция, ЭЭГ.

Detection and measurement of hypersonic target radial velocity in pulse Doppler radar

В работе предложен алгоритм обнаружения и однозначного измерения радиальной скорости воздушных объектов (ВО), летящих с абсолютной скоростью, превышающей скорость звука в несколько раз (гиперзвуковых целей). Область применения алгоритма – импульсно-доплеровские РЛС с линейно-частотно модулированным (ЛЧМ) зондирующим сигналом (ЗС). Приведено описание, обоснование использования и результаты моделирования обработки пачки принятых радиоимпульсов разработанным алгоритмом на модели современной импульсно-доплеровской РЛС. An algorithm for the detection and unambiguous measurement of the radial velocity of supersonic air objects is proposed. The scope of the algorithm is pulse-Doppler radars with a linear frequency modulation (LFM). The description, justification of the use and the results of modeling the processing of a packet of received radio pulses by the developed algorithm on a model of a modern pulse-Doppler radar are presented.

A Truncated Matched Filter Method for Interrupted Sampling Repeater Jamming Suppression Based on Jamming Reconstruction

Interrupted sampling repeater jamming (ISRJ) is becoming more widely used in electronic countermeasures (ECM), thanks to the development of digital radio frequency memory (DRFM). Radar electronic counter-countermeasure (ECCM) is much more difficult when the jamming signal is coherent with the emitted signal. Due to the intermittent transmission feature of ISRJ, the energy accumulation of jamming on the matched filter shows a ‘ladder’ characteristic, whereas the real target signal is continuous. As a consequence, the time delay and distribution of the jamming slice can be obtained based on searching the truncated-matched-filter (TMF) matrix. That is composed of pulse compression (PC) results under matched filters with different lengths. Based on the above theory, this paper proposes a truncated matched filter method by the reconstruction of jamming slices to suppress ISRJ of linear frequency modulation (LFM) radars. The numerical simulations indicate the effectiveness of the proposed method and validate the theoretical analysis.

Energy Storage Economic Optimization Scheduling Method for Multi-Scene Demand of Peak and Frequency Modulation

energy storage (ES) only contributes to a single-scene (peak or frequency modulation (FM)) control of the power grid, resulting in low utilization rate and high economic cost. Herein, a coordinated control method of peak modulation and FM based on the state of ES under different time scales is proposed. Firstly, for monotone peak and FM control scenarios, the ES configuration and scheduling model is constructed with the goal of maximizing net profit. Secondly, to further improve the ES utilization rate and optimize the operating cost of ES, a cooperative control method of peak modulation and FM is proposed. This method can realize the switch between peak modulation and FM control of ES and improve the ES utilization rate and system economy. Finally, the simulation results show that, compared with that of mono-peak and single-FM control, the ES efficiency of the peak-FM multiscenario optimization scheduling method is improved by 16.25% and 37.29%, respectively. The annual net income is increased by €28,021.50, the investment recovery period is shortened by 0.27 years, and the ES configuration economy is effectively improved.