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  2. Extremely low frequency - Wikipedia

    en.wikipedia.org/wiki/Extremely_low_frequency

    Because of the difficulty of building antennas that can radiate such long waves, ELF have been used in only a very few human-made communication systems. ELF waves can penetrate seawater, which makes them useful in communication with submarines, and a few nations have built military ELF transmitters to transmit signals to their submerged ...

  3. Time–frequency analysis - Wikipedia

    en.wikipedia.org/wiki/Time–frequency_analysis

    Light is an electromagnetic wave, so time–frequency analysis applies to optics in the same way as for general electromagnetic wave propagation. Similarly, it is a characteristic of acoustic signals, that their frequency components undergo abrupt variations in time and would hence be not well represented by a single frequency component ...

  4. Signal processing - Wikipedia

    en.wikipedia.org/wiki/Signal_processing

    In geophysics, signal processing is used to amplify the signal vs the noise within time-series measurements of geophysical data. Processing is conducted within either the time domain or frequency domain, or both. [14] [15] In communication systems, signal processing may occur at:

  5. Electromagnetic spectrum - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_spectrum

    A diagram of the electromagnetic spectrum, showing various properties across the range of frequencies and wavelengths. The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band.

  6. Electromagnetic radiation - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_radiation

    Electromagnetic radiation is commonly referred to as "light", EM, EMR, or electromagnetic waves. [2] The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves of different frequency are called by different names since they have ...

  7. Modulation - Wikipedia

    en.wikipedia.org/wiki/Modulation

    Categorization for signal modulation based on data and carrier types. In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a separate signal called the modulation signal that typically contains information to be transmitted. [1]

  8. Extremely high frequency - Wikipedia

    en.wikipedia.org/wiki/Extremely_high_frequency

    Millimeter waves are used for military fire-control radar, airport security scanners, short range wireless networks, and scientific research. In a major new application of millimeter waves, certain frequency ranges near the bottom of the band are being used in the newest generation of cell phone networks, 5G networks. [6]

  9. Radio spectrum - Wikipedia

    en.wikipedia.org/wiki/Radio_spectrum

    The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz).Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication.