Antenna diversity increases the received signal strength by taking advantage of the natural properties of radio WAVES.

There are two primary diversity methods: space diversity and polarization diversity.

Space Diversity: Increased received signal strength at the BTS may be achieved by mounting two receiver antennae instead of one. If the two Rx antennae are physically separated, the probability that both of them are affected by a deep fading dip at the same time is low. At 900 MHz, it is possible to gain about 3 dB with a distance of five to six meters between the antennae. At 1800 MHz the distance can be SHORTENED because of its decreased wavelength.

By choosing the best of each signal, the impact of fading can be reduced. Space diversity offers slightly better antenna gain than polarization diversity, but requires more space.

Polarization Diversity: With polarization diversity the two space diversity antennae are replaced by one dual polarized antenna. This antenna has normal size but contains two differently polarized antenna arrays. The most common types are vertical/horizontal arrays and arrays in 45 DEGREE slant orientation. The two arrays are connected to the respective Rx branches in the BTS. The two arrays can also be used as combined Tx/Rx antennas. For most applications, the difference between the diversity gain for space diversity and polarization diversity is negligible, but polarization diversity reduces the space required for antenna.

Antenna diversity increases the received signal strength by taking advantage of the natural properties of radio waves.

There are two primary diversity methods: space diversity and polarization diversity.

Space Diversity: Increased received signal strength at the BTS may be achieved by mounting two receiver antennae instead of one. If the two Rx antennae are physically separated, the probability that both of them are affected by a deep fading dip at the same time is low. At 900 MHz, it is possible to gain about 3 dB with a distance of five to six meters between the antennae. At 1800 MHz the distance can be shortened because of its decreased wavelength.

By choosing the best of each signal, the impact of fading can be reduced. Space diversity offers slightly better antenna gain than polarization diversity, but requires more space.

Polarization Diversity: With polarization diversity the two space diversity antennae are replaced by one dual polarized antenna. This antenna has normal size but contains two differently polarized antenna arrays. The most common types are vertical/horizontal arrays and arrays in 45 degree slant orientation. The two arrays are connected to the respective Rx branches in the BTS. The two arrays can also be used as combined Tx/Rx antennas. For most applications, the difference between the diversity gain for space diversity and polarization diversity is negligible, but polarization diversity reduces the space required for antenna.