Shulou(Shulou.com)06/01 Report--

This time we write something purely theoretical, but this is the foundation. We have clarified the contents of this section, and the calculation is involved later, and it is not a problem at all.

Unit of measurement:

Absolute units:

Watt: the symbol "W" is the power unit of the international system of units. Watts are defined as 1 joule per second (1 J beat s), that is, the rate at which energy is converted, used or dissipated (measured in amperes) per second

Milliwatt: the symbol "mW". 1 milliwatt equals 1/1000 watts.

Milliwatt decibel: symbol "dBm", power, relative to 1 milliwatt. When the power is 1 mW, the dBm value is 0. DBm = 10 X log10 (PmW) so 100mW power is equivalent to + 20 dBm.

Relative units:

Decibel: the symbol "dB" is a unit that measures the proportion of two identical units. Describe the change in power

DBi: decibels relative to an isotropic radiator (dBi), which is generally used to measure the antenna gain, that is, the relative output strength of the antenna signal.

DBd: that is decibels relative to a half-wave dipole antenna (dBd), 0 dBd = 2.15dBi

10s and 3s rules:

For every 3 dB of gain (relative), double the absolute power (mW). 3 dB gain = mW * 2

Every time the signal increases 3dB, the signal strength doubles (mW).

For every 3 dB of loss (relative), halve the absolute power (mW). 3 dB loss = mW / 2

Every time the signal decreases 3dB, the signal strength doubles (mW).

For every 10 dB of gain (relative), multiply the absolute power (mW) by a factor of 10. 10 dB gain = mW * 10

Every time the new number increases 10dB, the signal strength increases tenfold (mW).

For every 10 dB of loss (relative), divide the absolute power (mW) by a factor of 10. 10 dB loss = mW / 10

Every time the signal decreases 10dB, the signal strength decreases tenfold (mW).

Table:

0dBm = 1mW

3dBm = 2mW

6dBm = 4mW

9dBm = 8mW

10dBm = 10mW

13dBm = 20mW

20dBm=100mW

30dBm=1000mW

-3dBm=0.5mW

-6dBm=0.25mW

-9dBm=0.125mW

-10dBm=0.1mW

-13dBm=0.05mW

-20dBm=0.01mW

-30dBm=0.001mW

-40dBm=0.0001mW

Calculation formula: n = (x) * 3 + (y) * 10, that is, all dBm can be calculated according to the combination of 3 and 10.

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