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  2. 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.

  3. Frequency-hopping spread spectrum - Wikipedia

    en.wikipedia.org/wiki/Frequency-hopping_spread...

    The frequency band is divided into smaller sub-bands. Signals rapidly change ("hop") their carrier frequencies among the center frequencies of these sub-bands in a determined order. Interference at a specific frequency will affect the signal only during a short interval. [1] FHSS offers four main advantages over a fixed-frequency transmission:

  4. Wavelet packet decomposition - Wikipedia

    en.wikipedia.org/wiki/Wavelet_packet_decomposition

    This approach allows for a detailed examination of the signal at different frequency bands, providing a more comprehensive understanding of the moisture distribution within the material. [13] Researchers employ wavelet packet decomposition to analyze the seismic response of structures, enabling a finer resolution in both time and frequency domains.

  5. Radio spectrum - Wikipedia

    en.wikipedia.org/wiki/Radio_spectrum

    A radio band is a small frequency band (a contiguous section of the range of the radio spectrum) in which channels are usually used or set aside for the same purpose. To prevent interference and allow for efficient use of the radio spectrum, similar services are allocated in bands.

  6. Spectrum (physical sciences) - Wikipedia

    en.wikipedia.org/wiki/Spectrum_(physical_sciences)

    A source of sound can have many different frequencies mixed. A musical tone's timbre is characterized by its harmonic spectrum. Sound in our environment that we refer to as noise includes many different frequencies. When a sound signal contains a mixture of all audible frequencies, distributed equally over the audio spectrum, it is called white ...

  7. Two-tone testing - Wikipedia

    en.wikipedia.org/wiki/Two-tone_testing

    Two signal generators, set to two different frequencies F1 and F2, are fed into a power combiner through circulators. The combiner needs to have good isolation to prevent the signal from one generator being sent to the output of the other. If this happens, intermodulation can occur in the non-linear parts of the generator internal circuit.

  8. Modulation - Wikipedia

    en.wikipedia.org/wiki/Modulation

    This alphabet can consist of a set of real or complex numbers, or sequences, like oscillations of different frequencies, so-called frequency-shift keying (FSK) modulation. A more complicated digital modulation method that employs multiple carriers, orthogonal frequency-division multiplexing (OFDM), is used in WiFi networks, digital radio ...

  9. Radio frequency - Wikipedia

    en.wikipedia.org/wiki/Radio_frequency

    This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies, and also encompasses the microwave range. These are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves, so they are used in radio technology, among other uses. Different sources ...