FM Antenna Diversity: Notes

In the F01/F02, an FM antenna diversity is standard equipment.

The FM antenna diversity comprises:

• FM1, FM2 and FM3 antennas
• FM antenna amplifier with diversity module

The FM1 to FM3 antennas route their RF signal to the antenna amplifier in the antenna diversity module.

The signal quality of the currently selected FM antenna (FM1 to FM3) is now evaluated in the antenna diversity module.

The high-frequency signal from the active FM antenna at any particular time is fed by the antenna amplifier and antenna diversity module via a coaxial cable to the tuner module in the head unit.

Fig 1: Tuner Module Input Frequency Graph

Courtesy of BMW OF NORTH AMERICA, INC.

The tuner module in the CIC is now informed of the station selected by the customer using iDrive. As a result, the tuner module in the CIC selects the matching frequency. This is done by setting a bandpass filter. The bandpass filter suppresses all frequencies above and below the selected station frequencies.

Fig 2: Frequency Graph After Station Selection

Courtesy of BMW OF NORTH AMERICA, INC.

The remaining RF signal is then demodulated in the tuner and output in the form of an audio signal through the speakers.

The tuner module in the CIC detects that an antenna diversity module is installed and generates the changeover voltage (Us) and the signal of the intermediate frequency (IF) necessary for diversity operation.