What is the antenna diversity

Antenna diversity is a technique used to restore signal integrity. Antenna diversity in the product has a 90o antenna rack with another antenna, so the polarization/directivity effect will not degrade the quality of the potential radio communication links. Also, each antenna in the product to realize antenna diversity is positioned at a distance of at least 1/4 wavelength, to ensure that at least one antenna is in the wave peak of the waveform.

While antenna diversity can be useful in restoring signal integrity and maintaining link boundaries from environmental impacts, significant sacrifices must be made in other areas, meaning an increase in the overall cost of microcontrollers (MCUS), which must be on call for long periods to evaluate antenna signals. The added microcontroller functionality will lead to the need for higher-specification and more expensive microcontrollers, which must be “on call at all times” and lead to shorter battery life. In other cases, a two-antenna solution would add additional space requirements or require additional coding expertise, which limits designers to single antenna design.

Coding an antenna diversity system will increase the coding burden on the design. Many antenna diversity systems are optimized to operate synchronously. The microcontroller on the receiver has a timing function that lets the receiver know when to start receiving data. In these cases, the microcontroller can immediately start evaluating the signals from both antennas. To assess this Signal, the microcontroller switches the antennas and evaluates the Received Signal Strength Indication level. In other products where the receiver does not use a timer, radio communications must detect the start of packaging because the lead signal may be misinterpreted as noise (or vice versa), and unfortunately, strong noise in a particular antenna may cause the start of packaging to be missed.

To ensure that the antenna switches frequently enough to capture the packaging of one of the antennas, a timer is activated each time the algorithm enters the “measure SQ” function.

From：http://www.hj-antenna.com/what-is-the-antenna-diversity/