Topic
Very low frequency
About: Very low frequency is a research topic. Over the lifetime, 1540 publications have been published within this topic receiving 24233 citations. The topic is also known as: VLF.
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the traveling wave tube amplification process proposed by Gallet and Helliwell is considered in greater detail, and it is shown that narrow band bursts of hiss can be generated by weak electron streams of even very broad velocity and pitch distribution.
Abstract: The traveling wave tube amplification process proposed by Gallet and Helliwell is considered in greater detail. Account is taken of the spiral motion of particles traveling in the magnetic field, the interaction distance for which amplification at any one frequency can occur, and the slowing down of the stream particles by the wave amplification process. It is shown that narrow band bursts of hiss can be generated by weak electron streams of even very broad velocity and pitch distribution. The center frequency of such a band is characteristic of the terminating latitude of the line of force of generation. Stronger streams produce an overload effect giving rise to wide and very wide bands. Narrow bands can be produced at other frequencies by streams of narrow velocity and pitch distribution.
18 citations
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03 Apr 2011
TL;DR: In this paper, the authors present measurements of actual power line noise and argue that the cyclostationary model is unnecessarily restrictive and that VLF PLC channel may be modeled as having a non-trivial wide-sense periodic component.
Abstract: Very low frequency (VLF) power line communications (PLC) presently has widespread use in AMR/AMI deployments and may also be useful for smart grid applications, largely due to its excellent propagative properties. However, noise within the VLF band is more energetic than at higher frequencies and without effective mitigation algorithms degrades channel capacity, possibly to the point of making the band impractical. Recent work has demonstrated that PLC noise in the low frequency band (LF) and above is effectively modeled as a cyclostationary random process. We present measurements of actual power line noise and argue that the cyclostationary model is unnecessarily restrictive and that VLF PLC channel may be modeled as having a non-trivial wide-sense periodic component. We demonstrate the preponderance of periodic noise in this band by means of constrained covariance estimation from power line noise measurements. This has important ramifications for receiver design and when employed appropriately will increase the post-processed SNR, making VLF PLC a more attractive prospect for smart grid communications.
18 citations
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TL;DR: In this paper, a floating sensor system is provided to detect very low frequency pressureignals (down to 0.01 Hz) in the presence of unwanted pressure signals generated by surface wave induced motion.
Abstract: A floating sensor system is provided to detect very low frequency pressureignals (down to 0.01 Hz). This system detects pressure fluctuations or pressure signals of interest in the ocean or other body of water in the presence of unwanted pressure signals generated by surface wave induced motion. A drifting sensor surface float follows the surface waves and in turn moves a suspended pressure sensor vertically, such that it detects the wave motion as a change in static pressure which then constitutes a noise source. A correlation circuit and a logic circuit discriminate between a first composite signal, comprised of the pressure signals of interest and wave motion noise, and a second reference signal, comprised only of the wave motion noise to provide an output signal transmitted to a monitoring station.
18 citations
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TL;DR: In this paper, the generation of ELF and VF waves by ionospheric heating using powerful high-frequency (HF) radio waves is reviewed, where most attention is given to natural current modulation using modulated HF heating.
18 citations
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25 Feb 2014TL;DR: In this paper, a method and device for cancelling, from a radio signal received by a radio device in a first frequency band, the interference generated through a nonlinearity of the radio device when the radio devices transmits radio signal on at least a second frequency band simultaneously with the received radio signal, the at least one second frequency bands being different from the first frequency bands, the transmitted radio signal being obtained from digital signal.
Abstract: The invention discloses a method and device for cancelling, from a radio signal received by the radio device in a first frequency band, the interference generated through a nonlinearity of the radio device when the radio device transmits a radio signal on at least a second frequency band simultaneously with the received radio signal, the at least one second frequency band being different from the first frequency band, the transmitted radio signal being obtained from digital signal.
18 citations