Used to indicate the impedance matching condition of the reflection loss, the unit is dB. Its mathematical formula can be written:
Loss =-20log|r| (RL) Return (dB)
The gamma is the reflection coefficient between WIFI antenna input and output of the transceiver, can WIFI antenna input impedance and output impedance of Za transceiver Zt to indicate the:
Gamma = (Za-Zt) (Za+Zt)
From the above two can be easily learned that the relationship between RL, Za and Zt three. For example, when the WIFI antenna input RL reached -10dB, that there will be 10% because of impedance mismatch between the antenna and transmitter and the formation of energy loss of WIFI antenna fed by the transmitter energy; assume that output impedance is 50 ohm Zt at the transmitter, it can be said that the WIFI Za input impedance of the antenna is 96 ohm thus, WIFI can verify the impedance between the antenna and transmitter does not match.
The operating frequency and bandwidth (Operating Frequency) (Bandwidth, BW)
The operating frequency of WIFI antenna is required to cover all possible use of system bandwidth, and all difference between the highest operating frequency band of fU scale with the lowest operating frequency of fL is the WIFI antenna operating bandwidth. In general, the size of the antenna bandwidth WIFI as a percentage of that:
/fC (fU-fL) BW= * 100%
In the meantime, fC is the base operating frequency. With Bluetooth as an example, it is shown that the WIFI antenna for minimum operation bandwidth of 83.5 MHz, which is 3.4%.
In the understanding of the definition of the WIFI antenna operating bandwidth, also need to know how the size of the operating frequency resolution of WIFI antennas. The most commonly used is the voltage in Bobbi (VSWR) 2:1 standard frequency scale thus formed by a series of VSWR is less than 2 of the frequency is the WIFI antenna operating bandwidth. The general standard is used to determine the operation bandwidth with different communication system will be different, for example, VSWR must be less than 1.5 of the standard. But for Bluetooth, VSWR less than 2 of the conditions are now able to fit the needs of the system.