Number Of Carrier Frequencies Research Articles

Studying the bioeffects of complexly organized electromagnetic impacts of low intensity

Introduction. One of the modern tasks of hygienic assessment of the human environment is the accumulation of data on the bioeffects of electromagnetic fields (EMF), formed by the simultaneous action of several microwave sources. There is virtually no literature on the corresponding comparative analysis of the results of identical in conditions and energy effects on animals and humans. The purpose of this work is to compare bioeffects and analyze possible mechanisms of their formation, as a result of the action of electromagnetic fields (EMF) of one, two and three carrier frequencies, within 0.9-1.4 GHz with equivalent energy and modulation characteristics. Materials and methods. The work was performed in experiments on 11 rabbits (2.5-3 kg) of the Chinchilla breed and clinical- physiological studies involving 14 volunteers - men, aged 40-50 years. Irradiation was subjected mainly to the head of the object. The series differed in the number of carrier frequencies, their specific value and modulation within different EEG ranges, while maintaining an energy flux density (EPR) in the total pulse - 300 μW/cm2. We analyzed a set of indicators related to the functional assessment of central nervous, cardiovascular, respiration and muscular vbody systems. Results. The results on the dependence of the EMF effect of complex organization on the carrier frequency, their number and modulation nature are presented. It was established that each of the observed reactions was within the physiological norm, but along with the gain in the number of carrier frequencies and the specific modulation value, their qualitative and quantitative characteristics increased. Analysis of their phenomenology (of the alpha EEG range only at one carrier; + delta with a reflection of the reaction in other indicators - at two; an increase in the percentage of reactions in a complex of indicators, especially EMG - at three) indicated a different degree of synchronization of the bioelectric activity of the brain and the neurophysiological mechanism of their formation. The information obtained, of course, is limited to specific EMF parameters. It complements the relevant information available by highlighting the need for more research on a case-by-case basis. Limitations. The study of the phenomenology and mechanism of bioeffects of several low-intensity EMFs at the same time is a complex task that requires the involvement of a larger number of electromagnetic sources and a variety of indicators of the body’s response than this work was limited to and which, undoubtedly, is promising in the development of this area of research. Conclusion. In this study, there were no reactions that would go beyond the physiological norm. However, further strengthening of synchronization processes in the central nervous system, according to the analysis of the literature, can lead to such changes. This circumstance dictates the need to take it into account in the formation of the appropriate sanitary and hygienic assessment.

Cross Correction and Chaotic Shape-Forming Filter Based Quadrature Multi-Carrier Differential Chaos Shift Keying Communication

In this paper, an improved Quadrature Multi-carrier Differential Chaos Shift Keying (QMC-DCSK) based on Chaotic Shape-forming Filter (CSF) and Cross Correction (CC) is proposed. The chaotic signal generated by CSF is used as reference spreading sequence in QMC-DCSK. Quadrature multi-carriers are used to carry the reference and multiple information bearing signals simultaneously in order to improve the Bit Transmission Rate (BTR). By this way, the proposed system is able to transmit <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2M-1$</tex-math></inline-formula> bits Traditional Data Stream (TDS) during one traditional DCSK bit duration, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$M$</tex-math></inline-formula> is the number of carrier frequencies. Meanwhile, the reference signal transmits Additional Data Stream (ADS) encoded by CSF together with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2M-1$</tex-math></inline-formula> identical or inverse data stream carried by the rest <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2M-1$</tex-math></inline-formula> channels (information bearing signals). By this system configuration, the channel redundance can be used to improved bit error rate (BER) performance of ADS, after decoding TDS. In turn, the TDS reliability can also be improved by checking most ADS polarity of the corresponding carrier. This process is referred to as CC. The contribution of this work lies in the CC operation, by which the reliability of both TDS and ADS is improved significantly. It is the CSF and multi-carrier that make CC possible. The analytical BER is derived for the proposed method. The merits of the proposed system include, first, it improves the BTR as compared to that of QMC-DCSK, because ADS conveys more information bits; second, the ADS reliability is improved dramatically because the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{2}\,M$</tex-math></inline-formula> duplication can be used to improve the signal to noise ratio; third, the TDS reliability is improved as well because the information bits conveyed by each carrier frequency is enhanced and corrected by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{2}\,M$</tex-math></inline-formula> repetitions. By this way, not only TDS and ADS are transmitted (i.e., the higher BTR is achieved), but also both reliability are improved (i.e. the lower BER is achieved). In order to testify the feasibility and superiority of the proposed method, simulation and wireless open-access research platform (WARP) experiment are conducted. The simulation and experiment results show that the proposed method is superior to other comparison methods.

An Estimation Method for number of carrier frequency

This paper proposes a method that utilizes AR model power spectrum estimation based on Burg algorithm to estimate the number of carrier frequency in single pulse. In the modern electronic and information warfare, the pulse signal form of radar is complex and changeable, among which single pulse with multi-carrier frequencies is the most typical one, such as the frequency shift keying (FSK) signal, the frequency shift keying with linear frequency (FSK-LFM) hybrid modulation signal and the frequency shift keying with bi-phase shift keying (FSK-BPSK) hybrid modulation signal. In view of this kind of single pulse which has multi-carrier fre- quencies, this paper adopts a method which transforms the complex signal into AR model, then takes power spectrum based on Burg algorithm to show the effect. Experimental results show that the estimation method still can determine the number of carrier frequencies accurately even when the signal noise ratio (SNR) is very low.

Characterizing the Spectral Properties and Time Variation of the In-Vehicle Wireless Communication Channel

To deploy effective communication systems in vehicle cavities, it is critical to understand the time variation of the in-vehicle channel. Initially, rapid channel variation is addressed, which is characterized in the frequency domain as a Doppler spread. It is then shown that, for typical Doppler spreads, the in-vehicle channel is underspread, and therefore, the information capacity approaches the capacity achieved with perfect receiver channel state information in the infinite bandwidth limit. Measurements are performed for a number of channel variation scenarios (e.g., absorptive motion, reflective motion, one antenna moving, and both antennas moving) at a number of carrier frequencies and for a number of cavity loading scenarios. It is found that the Doppler spread increases with carrier frequency; however, the type of channel variation and loading appear to have little effect. Channel variation over a longer time period is also measured to characterize the slower channel variation. Channel variation is a function of the cavity occupant motion, which is difficult to model theoretically; therefore, an empirical model for the slow channel variation is proposed, which leads to an improved estimate of the channel state.

A novel invariable carrier frequency multi-level inverter PWM for balancing switching transitions and better distribution of harmonic power

The number of switching per modulation cycle at each level in a multi-level inverter depends on the carrier frequency and the duration that the reference waveform dwells within the level. The variable carrier frequency band (VFCB) approach creates as many clusters as the number of carrier frequencies and consequent deterioration of the harmonic spectrum. Therefore, a new pulse width modulation (PWM) strategy, with the view to ensure that the power devices at all the levels are switched equal number of times, is proposed in this paper. It is designed such that the frequency of the carrier waves is allowed to remain constant for the chosen application while maintaining the number of switching for all devices is same. The MATLAB-based simulation response and its experimental validation are included to highlight the fact that there is a significant enhancement in harmonic power distribution besides contributing to reduce the switching losses and improve the efficiency.

Architecture of a multifrequency synthesizer with a high spectral efficiency on the basis of a dispersive surface-acoustic-wave filter

New possibilities of creating a wideband parallel multifrequency synthesizer with a high spectral efficiency are investigated. The synthesizer is based on a dispersive filter using surface acoustic waves (SAWs). Discrete spectrally distinguishable frequencies are synthesized with the help of derived theoretical relationships. SAW-based synthesizer characteristics (bandwidths, the number of carrier frequencies generated, frequency pulse durations, and efficiency parameters) have been analyzed.

A dynamic channel assignment method for TDMA/FDMA packet transmission cellular system

AbstractIn the packet transmission cellular system using TDMA/FDMA with a small number of carrier frequencies, the assignment of the carrier frequency to the cell, as well as the assignment of the slot, are crucial issues regarding efficient use of the frequency resources. In the micro‐cellular system, it is difficult to assign the frequency beforehand, and a procedure is desired for each base station whereby the channel is assigned dynamically by an autonomous and distributed process. In the method proposed herein, the channel is assigned dynamically in each base station by an autonomous and distributed process, not only for the time‐division channel, but also for the frequency‐division channel. It is shown by a computer simulation that the proposed system can efficiently utilize the channels on both the time and the frequency axis. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(6): 25–32, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10046

Bayesian analysis of generalized frequency-modulated signals

General frequency-modulated (GFM) signals can be used to characterize many vibrations in dynamic environments, with applications to engine monitoring and sonar. Most work into parameter estimation of such signals assumes knowledge of the number of carrier frequencies. In this paper, we make no such assumption and use Bayesian techniques to address jointly the problem of model selection and parameter estimation. Following the work of Andrieu and Doucet (see ibid., vol.47, p.2667-76, 1999), who addressed the problem for nonmodulated sinusoids, a posterior distribution for the parameters and model order is obtained. This distribution is too complicated for analytical extraction of moments and to sample from directly; therefore, we use a reversible jump Markov chain Monte Carlo (RJMCMC) algorithm to draw samples from the distribution. Some simulated examples are presented to illustrate the algorithm's performance.