what is dBi、dBd、dB、dBm、dBc?（Definition, Explained，difference）
We see the relevant technical information, it often encounters the concept of dBi、dBd、db、dBm、aBc, is the decibel, is a ten logarithm of the number concept. Note that the decibel is used only to evaluate a physical quantity and another proportional relationship between the physical quantities, which itself has no physical dimension. The ratio between the amount of each of two 10-fold increase, their difference can be expressed as 10 decibels.
For example: A = "100", B = "10", C = "5", D = "1" is
A / D = 20dB; B / D = "10dB"; C / D = "7dB"; B / C = 3dB.
In other words, two poor 10 db is the difference between the amount of 10 times, bad 20 db is 100 times worse, and so on. Usually also need to remember the amount of difference between the two 3 db is twice as bad.
please Click here get our dipole antenna
What is dBi？
The suffix i to dBi is often used to denote antenna gain and for clarity, to distinguish it to antenna gain referenced to a lossless half wave dipole in free space (dBd). To a certain extent, the i suffix is redundant under the definition above of Gain, but is used for clarity in a world confused by those who use gain to mean with reference to a dipole.
dBi = dBd + 2.14
dBd = dBi - 2.14
What is dBd?
Expressed in dBd. Through calculation, it can be found that the gain of the lossless half-wave dipole in the free space is 2.14dB, so there is a fixed offset between dBi and dBd, dBd = dBi-2.14dB. This meaning is used in (ITU 1983) and (FCC OET 2010), for example. Readers may want to know the effectiveness of dBd, because to use gain in most calculations, it must be converted to isotropic gain (dBi or equivalent gain). Some other users are mainly from the ham radio community, and they insist that the definition of dBd is different from the previous quotation in this article. The consensus seems to be that dBd means obtaining half a wave dipole at the same height on the same ground. The discussion under the title of the actual example above shows the stupidity of this definition, which is worse if you consider different heights. Sometimes the variable meaning is assigned to the term dBd, especially Hams, which is the most important reason not to use this term for clarity.
What is dBm?
dBm is a decibel milliwatts meaning. That is, a fixed 1 mW of power of 0dBm, used to determine the system's power. For example, our common reader and the data power mostly 27dBm 30dBm. 27dBm is 500 mW; 30dBm is 1000 mW (1 W). Although only a thin 3dBm, twice as bad as the actual power!
dBm to watt conversion table
|
Power（dBm）
|
Power (watts)
|
|
-3 dBm
|
0.0005W
|
|
-2 dBm
|
0.0006W
|
|
-1 dBm
|
0.0008W
|
|
0分贝
|
0.001W
|
|
1分贝
|
00013W
|
|
2 dBm
|
0.0016W
|
|
3 dBm
|
0.002W
|
|
4 dBm
|
0.0025W
|
|
5 dBm
|
0.0032W
|
|
6 dBm
|
0.004W
|
|
7 dBm
|
0.005W
|
|
8 dBm
|
0.0063W
|
What is dBc?
dBc is the ratio of input signal power vs the carrier signal power. It is known as the decibels relative to the carrier. If the value of ratio is positive then the power of input signal is greater than the carrier signal and if the value is negative then the carrier signal has more power.
dBc is the unit used to measure the level of phase noise and harmonics/spurious signals with respect to carrier power level. For example, in the image below the Phase Noise is calculated to be - 70 dBc
What is GOOD Siqnal Strength dBm?
Typically, a strong outside signal would clock in somewhere around -50 to -70 dBm, while anything below -100 dBm would be considered weak (-110 means no signal at all). The use of an indoor antenna could boost that outside dBm signal exponentially — for example, an indoor antenna that is radiating -20 dBm can effectively cover about 3,000 square feet. According to the logarithm, the signal strength doubles with every third decibel, meaning that a dBm signal strength of something like -70 is actually twice the power of -73 dBm. The numbers may not make it look like a great change has occurred, but in reality, the decibels have grown exponentially.
What is the dBi, dBd, dB, dBm, dBc difference between.
A: They are the power gain of the unit, the difference is as follows:
dBi and dBd is the power gain of the unit, both of which are relative values, but the reference point is not the same. a reference to dBi omni-directional antenna; dBd reference point for the dipole. DBi and dBd is generally believed that the same gain, the value represented by dBi dBd than that of the larger 2.15 dBi. For example: for a gain of 16 dBd antenna, which converted into units of dBi gain when compared 18.15dBi, generally ignore the decimal places, as 18dBi.
dB power gain of the unit is that a relative value. A calculation of the power when compared to large or small number of B dB, according to the formula 10 lg A / B calculation. For example: A power doubled power than B, then 10 lg A / B = 10 lg 2 = 3dB. In other words, A's power over B, high power 3dB; if the A's power is 46dBm, B's power of 40dBm, you can say, A over B-6dB; if A antenna 12dBd, B antenna 14dBd, it can be said A smaller than B 2dB.
dBc is a relative value of said power unit, and dB is calculated exactly the same. In general, dBc relative to the carrier (Carrier) in terms of power. In many cases, used to measure the relative value of carrier power, as measured interference (co-channel interference, intermodulation interference, crosstalk, with outside interference, etc.) as well as coupling, stray and so the relative value. Place in the use of dBc, in principle, can also use dB instead.
Useful Information - Practical application:
in order to effectively improve communication effectiveness and reduce the antenna input power, the antenna will be made with the radiation of the structure to focus directional radiated power, which would come out of "antenna gain" concept. Simply put, refers to an antenna gain of the antenna input of RF power to the degree of concentration of radiation, apparently, the antenna gain pattern of relationships with large, the narrower the main lobe, the smaller the antenna side lobe, the higher the gain, and different structures of the antenna, its pattern is a big difference.
In communications technology, power and other considerations, the parameter value equal the same power, antenna gain and also the use of relatively simplified logarithmic law to represent the specific calculation method: a location in a certain direction to produce the same radiation field strength, the loss of non-ideal reference antenna input power and antenna input power to be considering taking the logarithm of the ratio multiplied by 10 (G = 10lg (Reference Pin / considerations Pin)), which is called the antenna in the point the direction of the gain. Unit of measure commonly used is dBi antenna gain and dBd. For the dBi, the benchmark for the ideal point source antenna, that is, a true sense of the "point" for the antenna gain compared to baseline. Ideal point source of radiation is omni-directional antenna, and its pattern is the perfect ball, all point the same sphere of electromagnetic radiation are the same; for dBd, the benchmark was the ideal dipole antenna. Is due to dipole antenna with a directional, so both have a constant difference of 2.15 is fixed 0dBd = "2" .15 dBi.
It should be noted that, commonly referred to as "omni-directional antenna" is not strictly to say, omni-directional antenna should refer to the full three-dimensional space, but the engineering is often the picture of a plane direction of the circumference of the antenna as omnidirectional antenna, such as whip antennas, it is the main lobe in the radial circle, but there is still axial sidelobes.Common antenna gain: whip antenna 6-9dBi, GSM base station with a Yagi antenna 15-17dBi, directional parabolic antenna is very easy to do 24dBi.
How do I take dBm measurements on my phone?
When the strength of your cell phone signal matters most, skip the bars on your screen and opt for the master precision of dBm signal strength measurements. Whether it’s choosing the strength of your cell phone signal booster or figuring out where to install it for optimal efficiency, apps like Network Cell Info or inPocket Software make it easy to monitor and measure the dBm in real-time, everywhere you go. Android phones offer a decibel-reading function in their settings, while most iPhones can access decibel information by turning on “test mode”. Simply “call” the number *3001#12345#* from the keypad, and the dB reading will either appear in the top left corner, or can be found by sliding down from the top edge.
An accurate reading of your dBm signal strength will not only optimize the performance of your cell phone booster antennas and amplifiers, but you’ll also sound like a true tech wizard the next time your friends are flailing their phones around in search of those elusive bars.
Our other product:
