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Moreover, for a given noise power spectral density (PSD), spread-spectrum systems require the same amount of energy per bit before spreading as narrowband systems and therefore the same amount of power if the bitrate before spreading is the same, but since the signal power is spread over a large bandwidth, the signal PSD is much lower — often ...
Numerous individuals suffering from auditory hallucinations, delusional disorders, [18] or other mental illnesses have claimed that government agents use forms of mind control technologies based on microwave signals to transmit sounds and thoughts into their heads as a form of electronic harassment, referring to the alleged technology as "voice ...
Chirp spread spectrum is ideal for applications requiring low power usage and needing relatively low data rates (1 Mbit/s or less). In particular, IEEE 802.15.4a specifies CSS as a technique for use in low-rate wireless personal area networks (LR-WPAN). However, whereas IEEE 802.15.4-2006 standard specifies that WPANs encompass an area of 10 m ...
In some sources, the term chirp is used interchangeably with sweep signal. [1] It is commonly applied to sonar, radar, and laser systems, and to other applications, such as in spread-spectrum communications (see chirp spread spectrum). This signal type is biologically inspired and occurs as a phenomenon due to dispersion (a non-linear ...
Subvocal recognition (SVR) is the process of taking subvocalization and converting the detected results to a digital output, aural or text-based. [1] A silent speech interface is a device that allows speech communication without using the sound made when people vocalize their speech sounds.
In the US, FCC part 15 on unlicensed spread spectrum systems in the 902–928 MHz and 2.4 GHz bands permits more power than is allowed for non-spread-spectrum systems. Both FHSS and direct-sequence spread-spectrum (DSSS) systems can transmit at 1 watt, a thousandfold increase from the 1 milliwatt limit on non-spread-spectrum systems.
Direct-sequence spread-spectrum transmissions multiply the symbol sequence being transmitted with a spreading sequence that has a higher rate than the original message rate. Usually, sequences are chosen such that the resulting spectrum is spectrally white. Knowledge of the same sequence is used to reconstruct the original data at the receiving ...
Sound from an array spreads less than sound from a point source, by the Huygens–Fresnel principle applied to diffraction. While a large loudspeaker is naturally more directional because of its large size, a source with equivalent directivity can be made by utilizing an array of traditional small loudspeakers , all driven together in-phase.