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The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a power ratio of 10 1/10 (approximately 1.26) or root-power ratio of 10 1/20 (approximately 1.12). [1] [2]
Since a lossless dipole antenna has a gain of 2.15 dBi, the relation between these units is () (). For a given frequency, the antenna's effective area is proportional to the gain. An antenna's effective length is proportional to the square root of the antenna's gain for a particular frequency and radiation resistance .
Excel maintains 15 figures in its numbers, but they are not always accurate; mathematically, the bottom line should be the same as the top line, in 'fp-math' the step '1 + 1/9000' leads to a rounding up as the first bit of the 14 bit tail '10111000110010' of the mantissa falling off the table when adding 1 is a '1', this up-rounding is not undone when subtracting the 1 again, since there is no ...
For very low-power systems, such as mobile phones, signal strength is usually expressed in dB-microvolts per metre (dBμV/m) or in decibels above a reference level of one milliwatt . In broadcasting terminology, 1 mV/m is 1000 μV/m or 60 dBμ (often written dBu).
The ideal dipole antenna could be further replaced by an isotropic radiator (a purely mathematical device which cannot exist in the real world), and the receiver cannot know the difference so long as the input power is increased by 2.15 dB. The distinction between dB d and dB i is often left unstated and the reader is sometimes forced to infer ...
dBc (decibels relative to the carrier) is the power ratio of a signal to a carrier signal, expressed in decibels.For example, phase noise is expressed in dBc/Hz at a given frequency offset from the carrier. dBc can also be used as a measurement of Spurious-Free Dynamic Range between the desired signal and unwanted spurious outputs resulting from the use of signal converters such as a digital ...
The actual result is 34.6380 dBi, just shy of the ideal 35.0745 dBi we expected. [7] Why the difference from the ideal? If the spacing in the x and y dimensions is λ {\displaystyle \lambda } , then the spacing along the diagonals is λ 2 {\displaystyle \lambda {\sqrt {2}}} , thus creating tiny regions in the overall array where photons are ...
Such a difference can exceed 100 dB which represents a factor of 100,000 in amplitude and a factor 10,000,000,000 in power. [ 4 ] [ 5 ] The dynamic range of human hearing is roughly 140 dB, [ 6 ] [ 7 ] varying with frequency, [ 8 ] from the threshold of hearing (around −9 dB SPL [ 8 ] [ 9 ] [ 10 ] at 3 kHz) to the threshold of pain (from 120 ...