Conversion of power units MW and dBm

The RF signal of the radio transmitters output is transmitted to the antenna via a feeder (cable) and radiated out by the antenna in the form of electromagnetic waves. Electromagnetic
When the wave arrives at the receiving location, it is received by the antenna (only a small fraction of the power is received) and sent to the radio receiver via the feeder.
Therefore, it is very important to calculate the transmitting power of the transmitting device and the radiation ability of the antenna in the project of wireless network.

TX is the abbreviation for emission (transmits). The transmitting power of radio waves refers to the energy in the range of a given frequency band, which is usually measured in two ways
or measurement criteria:

1, Power (W): relative to the linear level of 1 watts (Watts). For example, a WiFi wireless card typically emits 0.036W of power, or
36mW, said the speaker.

2, Gain (DBM): proportional to 1 MW (Milliwatt). For example, the WiFi wireless card has a transmit gain of 15.56dBm.
Conversion of power units MW and dBm:

1, dBm = ten x Log [power MW]

2, MW = 10 [Gain DBM/10DBM]

In wireless systems, antennas are used to convert current waves into electromagnetic waves, and in the process of transmitting and receiving signals can be "put
The metric of this energy amplification becomes "gain (Gain)". The unit of measure for antenna gain is "dBi". Because the power in the wireless system
The magnetic wave energy is generated by the transmitting energy of the transmitting device and the amplification and superposition of the antenna, so the measurement of emission energy is best the same metric-gain
(DB), for example, the power of the transmitting device is 100mW, or 20dBm, and the gain of the antenna is 10dBi, then:

Total transmit energy = transmit power (dBm) + antenna gain (dBi)

= 20dBm + 10dBi = 30dBm

Or: = 1000mW = 1W

Each db is important in a "small power" system, such as a wireless local area network device, especially when you remember the "3 DB rule." Each additional
adding or lowering 3 DB means increasing the power by one or less half:

-3 DB = 1/2 Power

-6 DB = 1/4 Power

+3 DB = 2x Power

+6 DB = 4x power

Power is increased by one times and the level value increases by 3dBm