The system allows more frequency overlap/shorter pulse duration. In this mode the beams inside the fan are separated in frequency by a factor of 0.58. Except for the two neighbouring beams, in space, at the bottom of the V-shape. For these the beam separation is set to 0.85. The same applies at the top of the inverse V shape.
Reference beams inside the band are separated from their neighbouring fan beams, in frequency, by a factor of 1 (as the reference
beams may be located identically in space as their frequency neighbours.
In both cases the frequencies (except those frequencies allocated to reference beams) are allocated to the beams in the fan. This allocation is performed in the V or inverse V manner according to the Frequency/Space Distribution parameter.
The figure shows the default mode of a 7 beam fan, covering 70 to 120 kHz. Two reference beams have been added at 70 and 120 kHz respectively. With optimized frequency spacing, the shortest allowable pulse duration is 448 us without reducing the signal separation.
The vertical bars show the bandwidth of each beam. The beams at the bottom of the V-shape are allowed to slightly overlap. The other neighbour beams in frequency are steered in opposite directions, and a larger overlap is allowed. The reference beams are not allowed to overlap at all.