Pseudorandom Amplitude Research Articles

Network authentication by close-loop synchronized chaotic lasers

We numerically study a new hardware method for network authentication, using a pair of chaotic lasers subject to the same optical injection from a third chaotic laser, in a close-loop configuration. One laser is in the secure environment, the other is in the unsecure environment, and if their parameters are matched (i.e., they are ‘twins’), in suitable operating conditions they synchronize and generate the same pseudo-random amplitude modulation. Access to the secure environment is authorized only if the two responses are found equal. As in other schemes based on Physical Unclonable Functions (PUFs), security relies on unavoidable small differences between nominally identical but physically separate devices: due to the strong sensitivity of chaos to laser parameter dispersion, finding a suitable laser to synchronize is a very difficult task for the Adversary, while the laser of the Authorized user can be selected as a twin of the one in the secure environment.

Специфика применения оконных функций при обработке сигналов с псевдослучайным законом амплитудно-фазовой манипуляции

Window functions are used in the radar signal processing to reduce the undesirable effect of masking a weak signal of a moving target with powerful reflections from stationary or slow-moving objects. The effectiveness of window functions weakens in radars which transmit and receive signals with pseudo random amplitude and phase-shift keying on common aerial. The article shows that pseudorandom pauses between phase-manipulated pulses of pseudo random duration affect the result of window weighted processing. The best parameters of the probing signal for weighing them by window functions during fasttime and slow-time processing are determined. An algorithm for normalization and interpolation of compressed segments of the signal with pseudorandom amplitude and phase-shift keying is proposed. The results obtained are confirmed by modeling the processing of an additive mixture of echo signals with different Doppler frequencies.

Saccadic initiation biased by fixational activity

Both the gap and overlap paradigm may reveal the interaction between fixating and moving the eyes, but the effects of the overlap paradigm have not been fully characterized yet. Here we present a series of experiments probing how an overlap paradigm, combined with the manipulation of stimuli durations, saliency and transient changes might modulate saccadic reaction time distributions.We recorded saccadic reaction time in four participants in six experiments in which a saccade-target appeared at a pseudo-random amplitude after a fixation period. First, we parametrically manipulated the duration of the overlap using a range of intervals (from 0 to 200 ms). In a second experiment we probed the interaction of various foreperiod intervals (i.e. the duration of the fixation period prior to saccade-target onset) and overlap using two overlap intervals (20 or 140 ms). In two additional experiments we manipulated either the stimuli sizes or their contrast ratio in overlap paradigms (20 or 140 ms). Lastly, we introduced a visual transient during the overlap interval via two manipulations (both with a range of SOA): either a distractor ring appeared around the fixation-target, or a dynamic random noise patch replaced the fixation-target.Results show reliable modifications in the latency distributions depending on the overlap interval as well as idiosyncratic differences. Additional experimental manipulations also affected the latency distributions revealing strong interacting inhibitory processes. We conclude that the effects of overlap intervals may combine with the influence of other stimuli properties affecting decision process.

Numerical modeling and verification of room impulse response inference from the coherence properties of speech and music signals

In previous work, we presented theory and motivating examples to demonstrate that the coherence properties of the harmonic partials of speech and music signals recorded in an acoustic space give information about the impulse response of the space. By analyzing auto- and cross-correlations between pairs of harmonics of the signal, we may “blindly” obtain the frequency-dependent reverberation time of the acoustic space. Assuming that the signal contains harmonically related partials with mutually correlated amplitude and phase modulations, a reasonable assumption for sources such as musical instruments or the human voice, this approach allows inference of information about the impulse response of an acoustic space. In this work, we verify this method for a variety of signals with different coherence times and amounts of pseudo-random amplitude and frequency modulations.

On the reinforcement of thin-walled cold-drawn C-channel beams

The paper considers the problem of stability of a thin-walled channel. Options for increasing the stability of the channel by changing its cross-section are proposed. Stiffness increased by adding triangular folds, as well as by adding stiffeners. The influence of initial imperfections of geometry in the channel model on the critical load of stability loss and postcritical behavior of the model is investigated. Imperfections were defined as deviations of the geometry of the pseudo-random amplitude.

Pseudorandom amplitude-phase-shift keyed signals with irregular bi-level amplitude spectrum for moving target detection

This paper considers the target locating against the clutter background in radars with quasi-continuous mode of transmission and reception on common aerial of signals with pseudorandom amplitude- and phase-shift keying. Pseudorandom amplitude-phase-shift keyed signals with irregular bi-level amplitude spectrum are proposed for use. The high-level spectrum components of returns from the moving and stationary targets can be partially overlapped. It is proposed to perform the frequency rejection of high-level components of the stationary targets before the correlation signal processing. As a result, significant part of the energy of interfering reflections is cut out and just a small part of the energy of the useful signal is lost. The signal-to-clutter ratio increases. The synthesis method of pseudorandom amplitude-phase-shift keyed signal with irregular bi-level amplitude spectrum is considered. The spectrum of the synthesized signals is analyzed. Increase of the signal-to-clutter ratio was obtained in the processing of signals with frequency interference rejection. The result of detection modeling of a moving target against the background of reflections from a stationary object is presented.

Phase characteristic and information transmission of laser signals through plasma in shock tube

Laser communication is a promising way of achieving effective communication during reentry. This paper focuses on the phase characteristics and information transmission of laser signals in plasma sheaths. First, propagation of the laser signals through the sheaths is analyzed theoretically. Next, phase characteristics of the periodic laser signals are studied by ground simulation experiments in shock tube. Further, experiments of the pseudorandom amplitude and phase modulated signals are conducted. Finally, information transmission is tested. This paper is the basic research of laser transmission characteristics in plasma sheaths and has experimentally realized successful information transmission in the plasma generated by shock tube. The results could provide reference for the future ground and flight experiments.

Clutter clipping in radars with quasicontinuous mode of transmission and reception of signals with pseudorandom amplitude- and phase-shift keying

This paper considers the target locating against the clutter backgroundin radars with quasicontinuous mode of transmission and reception of signals with pseudorandom amplitude- and phase-shift keying. The clutter clipping is proposed to increase the signal-to-clutter-plus-noise ratio (SCNR). The mathematical model of the time-distributed clutter clipping is presented. The modelling example of a pinpoint target locating using correlation processing of a return signals is given with and without clutter clipping. Given example shows the effectiveness of clutter clipping. The estimation of SCNR in presence of clutter clipping is derived using the distribution histogram of the received signal amplitudes. The clutter clipping efficiency depending on the parameters of the probe signal is investigated.

Digital Model of Fourier and Fresnel Quantized Holograms

Some models schemes of Fourier and Fresnel quantized protective holograms with visual effects are suggested. The condition to arrive at optimum relationship between the quality of reconstructed images, and the coefficient of data reduction about a hologram, and quantity of iterations in the reconstructing hologram process has been estimated through computer model. Higher protection level is achieved by means of greater number both bi-dimensional secret keys (more than 2128) in form of pseudorandom amplitude and phase encoding matrixes, and one-dimensional encoding key parameters for every image of single-layer or superimposed holograms.

Random changes in envelope of AM tones and their detection.

The aim of this investigation was to determine the detection thresholds of sinusoidal and random changes in envelope of amplitude modulated (AM) signals. The envelope changes were obtained as a result of modulation of a pure-tone carrier by chosen types of modulators, which gave either sinusoidal, pseudorandom, or random (Gaussian) amplitude modulation. For pseudorandom and random modulation, the detection thresholds were determined when only modulation depth (m) of AM signals was changed randomly (fm const) or when both modulation depth and modulation frequency (fm) were changed randomly (fm random). The data showed that for low modulation frequency (fm≤64Hz) the detection thresholds for sinusoidal amplitude modulation (SAM), pseudorandom amplitude modulation (PAM) and random amplitude modulation (RAM) overlapped one another in the limit of the standard deviation (SD). However, for higher modulation frequencies, the average threshold for the RAM (fm, const) was about 3dB lower (around fm=128Hz) than that for sinusoidal amplitude modulation. In this case the PAM threshold was similar, within the limit of SD, to the SAM threshold. However, when random changes in amplitude were combined with random changes in frequency, the PAM (fm, random), and RAM (fm random) thresholds decreased about 5 dB relative to the SAM threshold.

Spread spectrum signals with low probability of chip rate detection

Spread-spectrum signals that use spreading codes chosen to give a low probability of chip rate detection are examined. Pulse shaping and pseudorandom amplitude weighting are used to defeat the interceptor who uses a nonlinear circuit to generate a tone at the chip rate of the signal. The case of low input signal-to-noise ratio (SNR) is considered. Under this assumption, the detector output spectrum is found, and the output SNR is then used as a measure of detectability. The effect of signal pulse shape, i.e., band-limiting, on performance is studied. It is shown that a combination of band-limiting and correctly chosen amplitude weightings can, ideally, defeat any such circuit. The performance of a fourth-power envelope detector is analyzed with a combination of signal pulse shape and amplitude weighting. The amplitude distributions are binary, Gaussian, and quantized Gaussian.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pseudo-random analog noise generation

An n-input D/A converter fed from an n-bit pseudorandom noise (PN) generator will generate a pseudorandom amplitude noise uniformly distributed and periodic with period N = 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> - 1. By either permuting the D/A inputs or building a longer PN generator, a sequence of length n! (2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> - 1) is obtained. The resulting autocorrelations are given.