Decibel (dB) Calculator
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Decibel (dB) Calculator. This calculator can be used to find out the Power Gain and Voltage Gain from the Decibel value.
Definition of dB
First of all, dB (Decibel) is a unit that characterizes the relative value, that is, the ratio of two kinds of electric or sound power or the ratio of two voltage or current values or similar sound quantities. It is also a unit for measuring the relative loudness of sound.
(1) A unit that represents the ratio of two kinds of electric or acoustic power, which is equal to 10 times the common logarithm of the power ratio. dB = 10lgX, often used to calculate the bandwidth by power; -3db means that the power becomes 1/2 of the original, 10lg0.5 = -3, -3dB is equivalent to 0.5 in the decimal system; a drop of 3dB is a power drop the half, -3dB point refers to the half power point. This parameter is mostly used for two-dimensional graphics analysis.
(2) A unit that represents the ratio of two voltage or current values or similar sound quantities (such as sound pressure or particle velocity), equal to 20 times the common logarithm of the voltage or current ratio, if the two voltages or currents are at the same Words measured on the resistance. dB = 20lgX, often used for voltage/current gain; -3db means that the amplitude becomes the original (radix 2)/2, which is 0.707 times, 20lg ((radix 2)/2) = -3.
dB is the unit of power gain and represents a relative value.
The calculation formula is: when calculating how many dB the power of A is larger or smaller than that of B, it can be calculated according to the formula 10 lg A/B.
• If the power of A is twice as large as the power of B, then 10 lg A/B = 10 lg 2 = 3dB;
• If the power of A is 46dBm and the power of B is 40dBm, it can be said that A is 6dB greater than B
The Definition of dB
It couldn't be simpler, that is, a very large (followed by a long string of 0s) or a very small (preceded by a long string of 0s) number is relatively short. The introduction of dB is to change the multiplication and division relationship into an addition and subtraction relationship, which is more convenient for engineering calculations. Such as:
X = 1000000000000000 = 10lgX = 150 dB
X = 0.000000000000001 = 10lgX = -150 dB
What is Decibel Milliwatt (dBm)?
dBm is written as decibel relative to one milliwatt, which is the absolute value of power, and it is only a relative value different from dB. The formula for converting arbitrary power P(mW) to x(dBm) is as follows:
For example, the conversion of 1 milliwatt (1 mW) into dBm is 0 dBm; the conversion of 1 Watt (1 Watt) is 30 dBm.
How to quickly convert dBm to W
30dBm=1W
• +3dBm, the power is doubled;
• -3dBm, the power is multiplied by 1/2
• +10dBm, the power is multiplied by 10 times
• -10dBm, the power is multiplied by 1/10
The Relationship between dBm and W
dBm and W are a unit that represents the absolute value of power.
The calculation formula is: dBm = 10lg (power value/1mW)
If the transmit power is 1mW, the value after conversion in dBm unit should be: 10lg (1mW/1mW) = 0dBm;
If the transmit power is 1W, the converted value in dBm unit should be: 10lg (1000mW/1mW) = 30dBm;
The lg calculation
lg is the log with 10 as the base.
(1) 10lg2 = lg2^10 = lg1024, and because lg1000 = 3, 10lg2≠3, but very close.
(2) lg4=lg(2×2)=lg2+lg2=2lg2≈0.6
(3) lg4=lg(2^2) =2lg2≈0.6
(4) 10lg0.5=10 lg(2^(-1))=-10lg2≈-3
Table of Common Decibel Values
FAQ
1. What is the value of 1 dB?
Decibel (dB), unit for expressing the ratio between two physical quantities, usually amounts of acoustic or electric power, or for measuring the relative loudness of sounds. One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio.
2. What is the dimension of decibel (dB)?
The deciBel as such has no dimension. It is based on the ratio of a variable and a corresponding reference variable. This reference value and the variable in question have the same dimension. For instance, the dimension of the variable in sound is Pascal; the reference value is 20 micro pascals. For sound power the dimension is Watt; the usual reference value is 1 PicoWatt (pW).
3. What is the relationship between hertz and decibels?
The difference is quite large. Hertz is the name given to a number of cycles-per-second or frequency, for instance, human hearing is acknowledged to be 20Hz to 20000Hz. A decibel is a ratio between two voltages or powers and is stated as a logarithmic change, so if a voltage is halved; it has a relative level of -6dB, or double, it has +6dB of gain. Similar for power, except that a doubling of power is +3dB. They are normally stated in specifications of amplifiers, receivers, as sound levels, powers of transmitters, attenuators, etc.
4. How do you calculate dB?
Find the logarithm of the power ratio. log (100) = log (102) = 2 Multiply this result by 10 to find the number of decibels. decibels = 10 × 2 = 20 dB If we put all these steps together into a single equation, we once again have the definition of a decibel.
5. What is dB loss?
In fiber optics, data is transmitted via light pulses sent through thin strands of glass, with the goal of converting those pulses into useful information. Performance is measured in decibels (dB)1, similar to how sound is measured. This indicates how much power the light has as it moves through the cables.
Since the real goal is to transmit 100% of the data, the most useful metric is how much of it gets lost in transit. This is called dB loss.
6. How do you divide dB?
Converting from decibels to number ratios.
First, divide the decibel value by 10 and then use the inverse log function of the calculator to find the number ratio. The rounded-off number method gives 500 as the answer, which is sufficiently accurate for a first approximation.
7. What is the percentage change in intensity represented by one decibel?
26 percent.
It may be calculated from this equation that one decibel corresponds to a 26 percent change in intensity.
8. What is dB in RF power?
dBm (dB milliWatt)
Signal strength or power level. 0 dBm is defined as 1 mW (milliWatt) of power into a terminating load such as an antenna or power meter. Small signals are negative numbers (e.g. -83 dBm). For example, typical 802.11b WLAN cards have +15 dBm (32mW) of output power.
9. What is the difference between dB and dBm?
The Key Differences at a Glance.
dB quantifies the ratio between two values, whereas dBm expresses the absolute power level. dBm is an absolute unit, whereas dB is a dimensionless unit. dBm is always relative to 1mW, while dB is expressed in watts and can be relative to other powers.
10. What is a good SNR dB?
Generally, a signal with an SNR value of 20 dB or more is recommended for data networks whereas an SNR value of 25 dB or more is recommended for networks that use voice applications.
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